Medical Sciences Notes - Introduction to Infections, Diagnostic Tests

Introduction to Medical Sciences 1 Viruses, fungal and parasitic infections Diagnostic tests in infectious diseases Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, fungal and parasitic infections Dr William Lynn 2024 Version 3 willi...

Introduction to Medical Sciences 1 Viruses, fungal and parasitic infections Diagnostic tests in infectious diseases Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, fungal and parasitic infections Dr William Lynn 2024 Version 3 [email protected] Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, fungal and parasitic infections Diagnostic tests in infectious diseases Copyright © Brunel University London v.3 2024. All rights reserved. In this session We will review the tests available for the diagnosis of infectious diseases These tests complement our clinical skills and are vital in targeting appropriate therapy This will include tests used for bacteria as well as those for viruses, fungi and parasites This will illustrate the use of tests with some specific clinical examples Copyright © Brunel University London v.3 2024. All rights reserved. Why is it important to try and identify the organism? Improve patient outcome Public Health Making the correct diagnosis Regional and global surveillance Appropriate antimicrobial therapy Emergence and spread of high Best antibiotic choice risk or new pathogens Reduce risks of antimicrobial Contact tracing resistance Meningitis, tuberculosis Awareness of complications eg: Surveillance Involvement of the eye in Salmonella gastroenteritis cytomegalovirus infection in linked to a restaurant immunocompromised host Copyright © Brunel University London v.3 2024. All rights reserved.  What samples can we take easily Urine Swabs Wounds, skin, Blood throat, urethra etc Stool Pus draining from an abscess Sputum Image: Swab blood-stained pus from an infected wound. Reuben Strayer, CC BY-SA via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Examples of invasive samples from more complex cases Samples from deep in the lungs Via a bronchoscope Cerebrospinal fluid Lumbar puncture Bone marrow Bone marrow biopsy Deep tissue or abscess samples Image-guided aspiration or biopsy Image A: Bronchoscopy. Cancer Research UK, CC BY-SA 4.0 via Wikimedia CommonsImage Image B: Lumbar puncture. Medical gallery of Blausen. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436., via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved. What types of tests can we do? Microscopy Antigen detection Direct visualisation of microorganisms Identify antigens specific to organisms Culture Grow microorganisms in Nucleic acid detection laboratory Amplify and identify sequences of Immunological tests RNA or DNA specific to individual organisms Measure the immune response to specific antigens Copyright © Brunel University London v.3 2024. All rights reserved.  Light microscopy – bacteria, fungi and parasites Direct visualisation of microorganisms Unstained or stained preparations Suggested identification from the morphology and staining characteristics Sensitivity limited Need specimen containing sufficient microorganisms for detection Specificity limited Non-pathogenic organisms in samples from non-sterile body sites Rapid Not a definitive identification No antimicrobial sensitivity data Image A: Rhodamine fluorescent stain showing Mycobacteria. CDC Public Health Image Library available at www.phil.cdc Image B: Normal upper respiratory flora in Gram stained sputum smear. Ajay Kumar Chaurasiya, CC BY-SA 4.0 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Electron microscopy – can visualise viruses Electron microscopes Expensive, specialised interpretation For many years only available method for rapid diagnosis No longer in routine clinical use Image A: Electron microscopy of smallpox virions CDC/ Dr. Fred Murphy; Sylvia Whitfield, Public domain, via Wikimedia Commons Image B: Electron microscopy of herpes virus. CDC/Dr. Erskine Palmer, Public domain, via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Immunostaining – used in specialised settings Technique that uses antibodies against specific antigens to identify pathogens in cellular samples A sample from the base of a genital ulcer has been exposed to an antibody against a herpes simplex antigen A fluorescein (FITC) conjugated immunoglobulin staining technique reveals an epithelial cell fluorescing under ultraviolet light Confirms herpes simplex virus type-2 (HSV-2) infection Image: Herpes simplex immunostaining. Dr. Craig Lyerl. CDC Public health image library. Available at www.phil.cdc.gov Copyright © Brunel University London v.3 2024. All rights reserved.  Culture – a brief overview Culture can be used on any fresh clinical specimen Added to culture media designed to encourage growth in vitro Appearance of bacterial colonies useful More detailed diagnostic tests Identify the organism based on metabolic and biochemical phenotype Anti-microbial sensitivity testing can be performed Image A: Streptococcus pneumoniae colonies (arrows) on agar. CDC public image library. Available at www.phil.cdc Image B: Blood culture bottles. Red for anaerobes, green for aerobes. James Heilman, MD, CC BY-SA 3.0 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Culture – the path to antibiotic sensitivity testing Bacteria from a positive culture have been spread over agar Paper discs containing antibiotics are added and incubated at 37oC The bacteria on the left are sensitive to all of the antibiotics compared to the one on the right which is resistant to 4 and partially resistant to the one in the middle Image: Antibiotic disk sensitivity testing. Dr Graham Beards. Dr Graham Beards at en.wikipedia, CC BY-SA 4.0 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Antigen detection An antigen is any molecule or Advantages particle that can be recognised by a specific Rapid and specific immunoassay antibody Easy to perform Point of care tests available Antigens may remain Not affected by antibiotics attached or may be ‘shed’ by the organism Disadvantages Looked for in clinical samples Can only detect one organism per test or to identify bacterial cultures Sensitivity less than molecular techniques No antimicrobial sensitivity data Copyright © Brunel University London v.3 2024. All rights reserved.  Antigen detection example – COVID 19 A nasal and/or pharyngeal swab is placed in fluid solubilising the viral antigens The fluid is added to the sample well and moves up the testing chamber by capillary action Antigens are captured by specific antibodies embedded in the substrate of the testing chamber floor A colour change allows rapid visualisation with control and test lines Sensitivity – 70-75% Specificity - 98-99% Image: Positive lateral flow test for COVID 19. Courtesy of Dr William Lynn. Copyright © Brunel University London v.3 2024. All rights reserved. Serological tests in infection Serological tests Measure immunoglobulin– IgM, IgG, IgA and IgE Evidence that an individual has mounted an immune response Does not necessarily indicate active infection Negative early in infection before antibody is detectable ‘Window period’ May be difficult to interpretate Cross reacting antibodies between similar organisms/species Distinguishing active infection from past infection or immunisation Poor antibody responses in severely immunocompromised individuals Copyright © Brunel University London v.3 2024. All rights reserved.  Dynamics of antibody responses Situation Pattern Acute or recent IgM positive infection IgG rising Past infection or IgM negative immunisation IgG positive Chronic infection IgM - positive or negative IgG positive Primary antibody responses. Adapted from Figure : 21.24a in Anatomy & Physiology by Queensland University of Technology. Available at https://qut.pressbooks.pub/anatomyandphysiology/chapter/chapter-21-the-lymphatic-and-immune-system/ Public domain via Creative Commons Attribution 4.0. Copyright © Brunel University London v.3 2024. All rights reserved.  Nucleic acid detection – the way forward? Direct hybridisation of RNA or DNA lacks sensitivity PCR amplification is the most common technique Practicalities Uses of nucleic acid tests Used with many biological specimens Rapid accurate diagnosis Detect multiple pathogens from Detection of antimicrobial resistance same specimen High Specificity and Sensitivity Improved clinical decision making Technology improving allowing rapid turnaround and becoming Public health more cost effective Identify new and emerging pathogens Genomic information PCR; polymerase chain reaction Copyright © Brunel University London v.3 2024. All rights reserved. Which tests are best for different types of organisms? Copyright © Brunel University London v.3 2024. All rights reserved.  Viruses Antigen detection Diagnosis of acute infection COVID 19 Microscopy and Culture Detect early infection Viruses not visible on light microscopy HIV antigen positive before antibody Viruses must be cultured inside cells Distinguish active from past infection No longer in routine use Hepatitis B Nucleic acid amplification - PCR Serology Diagnosis Diagnosis of some acute viral infections Respiratory viruses Screen for chronic infections such as HIV Dengue (travel-related) or viral hepatitis CMV in immunocompromised Confirm immunity from past infection or Monitoring the response to therapy immunisation HIV Antiviral resistance CMV, hepatitis B and HIV CMV; cytomegalovirus, HIV; Human immunodeficiency virus Copyright © Brunel University London v.3 2024. All rights reserved.  Bacteria Microscopy Antigen detection Urine, CSF, other body fluids and pus Diagnosis of some bacterial infections Positive blood culture Streptococcus pneumoniae, Limited value on sputum Legionnaires disease Culture Nucleic acid amplification - PCR Mainstay of diagnosis, identification and Not routine for most infections anti-microbial sensitivity testing Standard of care in tuberculosis Increased sensitivity compared to Serology microscopy Diagnosis of some bacterial infections Faster identification and sensitivity Syphilis testing than culture CSF; cerebrospinal fluid Copyright © Brunel University London v.3 2024. All rights reserved. Fungi Microscopy Antigen detection Able to recognise fungal elements in Fungal antigens are useful in the diagnosis clinical specimens – yeasts or moulds of some invasive fungal infections Galactomannan in aspergillus infection Culture Beta-glucan in aspergillus and candida Mainstay of diagnosis and identification Anti-microbial sensitivity testing technically Nucleic acid amplification - PCR more difficult than for bacteria May detect multiple types of fungi Increasingly used in specimens from Serology immunocompromised host Diagnosis of some fungal infections Very sensitive and may be difficult to distinguish colonisation from infection Copyright © Brunel University London v.3 2024. All rights reserved. Parasites Microscopy Most commonly used test for diagnosis examples include: Antigen detection Blood – malaria Rapid diagnosis of malaria on blood Urine- schistosomiasis samples – standard of care Stool – Amoebae and parasitic worms Available or in development for a range of other parasites but not in common use Culture Parasites cannot be cultured in vitro Nucleic acid amplification - PCR Not widely available Serology Increasing use in specialist centres Diagnosis of some parasitic infections Hard to interpret in endemic areas due to previous infections Copyright © Brunel University London v.3 2024. All rights reserved. Summary Many infections are diagnosed clinically and treated empirically Striving to achieve a definitive diagnosis by using tests to identify the organism has significant benefit to the patient and public health Microscopy, culture, serology, antigen detection and nucleic acid amplification are the tests most commonly used to identify organisms and their antimicrobial sensitivity patterns Copyright © Brunel University London v.3 2024. All rights reserved. Glossary Amoebae Candida Single celled free-living organisms. Can cause Yeast which is a common cause of minor gastrointestinal and liver infection infections but can also cause serious invasive disease in some settings Aspergillus Cerebrospinal fluid Fungal mould that causes a number of different Fluid that surrounds the brain and spinal cord illnesses in humans Cytomegalovirus Beta-glucan Virus from the herpes group. Infection is very Component of the fungal cell wall common and usually causes no or very mild symptoms. Serious invasive disease seen im Bone marrow the severely immunocompromised Found in the centre of long bones where blood Galactomannan cells are made. The bone marrow can be the site of a number of unusual infections Component of the fungal cell wall Herpes virus Bronchoscope Family of viruses that cause a number of Fibreoptic flexible device which is used to human illnesses visualise and take samples from within the bronchi in the lungs Copyright © Brunel University London v.3 2024. All rights reserved. Glossary Human immunodeficiency virus (HIV) Legionnaires disease Infects CD4 positive lymphocytes leading to Caused by a gram-negative bacteria, Legionella damage to the immune system. HIV was identified pneumophila. Causes pneumonia following as the cause of the acquire immunodeficiency inhalation of water containing legionella syndrome (AIDS) in the early 1980’s Malaria Immunoassay Illness cause by protozoal parasites (species of A technique that uses the highly specific binding of Plasmodia) transmitted by mosquitos. Mainly antibodies to antigens to identify substances found in tropical and sub tropical zones including microorganisms Meningitis Lumbar puncture Infection of the protective membranes, meninges, A technique which enable sampling of around the brain and spinal cord cerebrospinal fluid. A needle is passed between the vertebrae into the spinal canal below the level where the spinal cord ends. Copyright © Brunel University London v.3 2024. All rights reserved. Glossary Mycobacteria Streptococcus pneumoniae Group of bacteria including the organisms that Gram-positive diplococcus. Some strains are cause tuberculosis and leprosy highly virulent associated with sepsis, pneumonia and meningitis as well as infection at other body Neisseria meningitidis sites Gram-negative diplococcus that is one of the bacterial causes of meningitis. It can also cause Syphilis sepsis and infection at other body sites Sexually transmitted bacterial infection caused by a spirochaete – treponema pallidum Schistosomiasis Complex infection caused by parasitic worms – Tuberculosis species of schistosoma Pulmonary and systemic illness caused by Mycobacterium tuberculosis Smallpox Caused by the variola virus smallpox is a highly Window period transmissible and lethal infectious disease. The time between acquiring a pathogen and the Feared for millennia Smallpox is the first infectious presence of detectable antibody against that disease where vaccination has eradicated global organism transmission Copyright © Brunel University London v.3 2024. All rights reserved. To contact me: email: [email protected] Copyright © Brunel University London v.3 2024. All rights reserved.  Introduction to Medical Sciences 1 Viruses, fungal and parasitic infections Viral structure and replication Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, fungal and parasitic infections Dr William Lynn 2024 Version 3 [email protected] Copyright © Brunel University London v.3 2023. All rights reserved. Viruses, fungal and parasitic infections Viral structure and replication Copyright © Brunel University London v.3 2024. All rights reserved. Key features of viruses Too small to be seen by light microscopy 20 – 400 nm in size Incapable of replication outside of a living host cell Cannot grow on culture media Can grow in cell culture Ubiquitous Infect all organisms including plants, vertebrates, invertebrates, fungi and bacteria Image from: Virology. Korsman, Stephen. Churchill Livingston, Elsevier, 2012. Available through ClinicalKey. Copyright © Brunel University London v.3 2024. All rights reserved. Minimal virus structure Genome - nucleic acid core RNA or DNA Capsid Protein shell formed of repeating subunits known capsomeres Geometrical symmetry Image from: Virology. Korsman, S. Churchill Livingston, Elsevier, 2012. Available through ClinicalKey. Copyright © Brunel University London v.3 2024. All rights reserved.  Complex virus structure Generic virus structure. Image adapted from: Viruses characteristics and structure. Virology. Korsman, S. Churchill Livingston, Elsevier, 2012. Available through ClinicalKey. Copyright © Brunel University London v.3 2024. All rights reserved.  Examples of viral morphology A: Smallpox virion CDC via Wikimedia commons B: Herpes simplex virions. CDC via Wikimedia Commons C: Schematic diagram of parvovirus virion. Swiss Institute of Bioinformatics CC BY via Wikimedia Commons D: SARS-CoV-2 (COVID-19). NIAID-RML CC BY 2.0 via Wikimedia Commons E: Ebola virion. CDC/Cynthia Goldsmith, Public domain, via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Steps in viral replication Cell entry by Uncoating with Attachment to membrane fusion or Replication of the release of the cellular receptors receptor-mediated genome genome endocytosis Translation of non- Incorporation of the Release from the Transcription of structural and new genomes into cell by budding, cell mRNA structural proteins new virions during lysis, or cell-to-cell (or polyproteins) assembly spread Image: Scanning electron micrograph of Lassa virus budding off a cell. NIAID, CC BY 2.0 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Viral replication Image: Scanning electron micrograph of Lassa virus budding off a cell. NIAID, CC BY 2.0 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Baltimore system of virus classification Organised according to genome and replication path Encompasses all known viruses that infect humans VP; Viral Proteins, RT: Reverse transcriptase, HIV; human immunodeficiency virus Image adapted from: Antiviral drugs by Ritter. Ch 53 in Rang & Dale's Pharmacology Copyright © Brunel University London v.3 2024. All rights reserved.  Examples of viral entry through cellular receptors Virus Viral surface protein Cell receptor Human Immunodeficiency Virus GP120/41 complex Chemokine receptor type 5 on macrophages SARS-COV-2 (COVID-19) Spike protein Angiotensin converting enzyme type 2 (ACE-2) receptor on respiratory epithelia Influenza Haemagglutinin Sialic acids on the surface of respiratory epithelial cells Epstein Barr Virus Viral surface CD21 (complement receptor 2) found on B glycoprotein 350 lymphocytes Copyright © Brunel University London v.3 2024. All rights reserved.  Examples of Viral replication cycles Hepatitis C Negative sense SS RNA Replicates in cytoplasm Hepatitis C replication cycle. L.B.Dustin et al CC BY-SA 4.0 < via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Examples of Viral replication cycles Herpes simplex ds DNA replicates in nucleus Herpes simplex replication. Graham colm. Via wikimedia commons Copyright © Brunel University London v.3 2024. All rights reserved. Summary Viruses are small mobile genetic elements with an RNA or DNA core surrounded by a protein capsid and in some cases an outer lipid membrane. Viruses can only replicate inside host cells and are classified according to their nucleic acid and replication processes Viruses enter cells through surface receptors, followed by uncoating which releases the RNA or DNA. The nucleic acid is transcribed, translated and new virus particles are assembled utilising host enzymes and structures These processes act as immunologic and therapeutic targets Copyright © Brunel University London v.3 2024. All rights reserved. Glossary Ebola Measles Viral haemorrhagic fever endemic to central Highly infectious from the paramyxovirus family. and western sub-Saharan Africa. Respiratory tract infection with systemic spread Epstein Barr Virus causing rash. Complications include brain and One of the herpes viruses. Causes glandular heart involvement fever. Oncogenic (cancer causing) virus, infects Parvovirus B cells and can lead to lymphoma Many strains in animals. Only one parvovirus Herpes simplex infects humans – Parvovirus B 19. most One of the herpes viruses. Skin and mucosal infections are in childhood and mild. infections. Cold sores and genital herpes. SARS-COV-2 (COVID-19) Hepatitis C Coronavirus with significant risk of respiratory Transmitted by blood or sex. High rate of failure an/or multiorgan failure. Emerged in late chronic infection leading in a proportion of 2019 with rapid pandemic spread people to liver cirrhosis or liver cancer Smallpox Influenza Caused by the variola virus smallpox is a highly Respiratory virus, highly transmissible. Capable transmissible and lethal infectious disease. of genetic recombination with emergence of Feared for millennia Smallpox is the first new strains infectious disease where vaccination has eradicated global transmission Copyright © Brunel University London v.3 2024. All rights reserved. To contact me: email: [email protected] Copyright © Brunel University London v.3 2024. All rights reserved.  Introduction to Medical Sciences 1 Viruses, viral, fungal and parasitic infections Viruses that cause human disease Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, fungal and parasitic infections Dr William Lynn 2024 Version 3 [email protected] Copyright © Brunel University London v.3 2023. All rights reserved. Viruses, viral, fungal and parasitic infections Viruses that cause human disease Copyright © Brunel University London v.3 2024. All rights reserved. In this session We will summarise the more Some important viruses are important human diseases covered in detail elsewhere in caused by viruses your course and are light blue in This talk is not meant to be the tables that follow comprehensive but to give you Respiratory viruses – BCR an overview of the extent and Travel-related viruses – IMS-2 nature of viral infections Human immunodeficiency Some viruses we will discuss virus – IMS-2 in more detail and these are in Hepatitis viruses – IMS-2 bold in the tables that follow Monkeypox – IMS-2 Copyright © Brunel University London v.3 2024. All rights reserved.  Medically important DNA viruses Genome Structure Family Examples dsDNA Enveloped Poxviridae Smallpox virus, monkeypox, Brick-shaped capsid molluscum contagiosum Enveloped Herpesviridae Herpes simplex virus 1 and 2, varicella-zoster Icosahedral capsid virus, Epstein-Barr virus, cytomegalovirus, human herpesviruses (HHV) 6, 7, and HHV 8 Nonenveloped Papillomaviridae Human papillomavirus - HPV Icosahedral capsid Nonenveloped Adenoviridae Adenovirus Icosahedral capsid Nonenveloped Polyomaviridae JC virus, BK virus, SV40 Icosahedral capsid ssDNA Nonenveloped Parvoviridae Parvovirus B19, adeno-associated virus Icosahedral capsid dsDNA - RT Enveloped Hepadnaviridae Hepatitis B virus RNA intermediate Icosahedral capsid Adapted from: Chapter 36. Medical Microbiology. 9th Edition. Ed. Murray, P. 2021 Elsevier inc. Available on ClinicalKey Copyright © Brunel University London v.3 2024. All rights reserved.  Herpes virus group Disease Key features Primary infection is often asymptomatic or dsDNA viruses mild Human infection very common Reactivation of the virus may occur may Primary illness which resolves with an years after infection effective immune response More severe in the severely Virus becomes latent with viral DNA immunocompromised remaining in long lived cells Some herpes viruses are oncogenic Latency is where a microorganism remains in the host after initial infection with no Potential links to autoimmune disease replication Anti-viral agents are available Copyright © Brunel University London v.3 2024. All rights reserved.  Herpes virus group Virus Primary disease Site of latency Secondary disease HHV 1 and 2: Mucocutaneous – Sensory neurons Reactivation at the original site Herpes simplex 1 and 2 oral and genital sites innervating the primary site Rare cases of More common and severe in encephalitis immunocompromised HHV-3: varicella zoster Primary varicella Sensory nerve ganglia Reactivation along a peripheral virus (VZV) (chickenpox) around the brain and nerve – shingles (zoster) spinal cord HHV-4: Epstein-Barr Infectious Memory B cells, B lymphocyte malignancies virus (EBV) mononucleosis oropharyngeal epithelial Burkitt’s lymphoma (glandular fever) cells Non-Hodgkins lymphoma Nasopharyngeal carcinoma Link to multiple sclerosis Copyright © Brunel University London v.3 2024. All rights reserved.  Herpes virus group Virus Primary disease Site of latency Secondary disease HHV-5: Infectious Widely disseminated in May disseminate in severe Cytomegalovirus mononucleosis many cells including immunocompromise – eye, (CMV) (glandular fever) monocytes brain, gut and lungs most common sites HHV-6 Roseola infantum – self Salivary glands, other cells Possible links to cancer and limiting febrile illness types autoimmune diseases HHV-7 Febrile illness similar to CD4 + lymphocytes Uncertain roseola HHV-8: Kaposi Not identified Lymphocytes Kaposi sarcoma – endothelial Sarcoma Herpes cell cancer seen in severe Virus (KSHV) immunocompromise Copyright © Brunel University London v.3 2024. All rights reserved.  Herpes virus group A: Herpes simplex ‘cold sore’. CDC Public health image library. Available at www.phil.cdc.gov B: Primary varicella. F malan, CC BY-SA 3.0 via Wikimedia Commons C: Varicella zoster. CDC Public health image library. Available at www.phil.cdc.gov D: Cytomegalovirus in the retina. National Eye Institute, National Institutes of Health Public domain, via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Human papillomavirus - HPV Key features dsDNA virus Human infection very common with multiple strains Chronic persistent replication may occur Disease Very common cause of viral warts Hands, feet, genitalia and larynx Some strains are oncogenic through integrating into the host genome HPV 16 and 18 in 70-90% of cases Cervical, Vulval, Anal and penile cancer Oropharyngeal cancer Image A: Plantar wart (verruca). Marionette, CC BY-SA 3.0 via Wikimedia Commons Image B: Cervical Intraepithelial neoplasia (pre malignant lesion on cervix) Haeok Lee et al. CC BY 4.0. via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Disease Most infection mild Parvovirus B19 Fifth disease with facial ‘slapped cheek’ rash in children Key features ss DNA virus Can cause severe anaemia in situations Multiple strains infect animals where high red cell turnover needed – for B19 main cause of human infection examples sickle cell anaemia Parvovirus spreads systemically and Can cause severe anaemia in unborn child infects cells in the bone marrow reducing red cell production Image: Acute parvovirus B19. Fifth disease (slapped cheek). Kardelen Yangın, CC BY-SA 4.0 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Medically important RNA viruses Genome Structure Family Examples dsRNA Nonenveloped Reoviridae Rota virus Wheel like Enveloped Arenaviridae Lassa fever virus Spherical ssRNA positive Enveloped Coronaviridae SARS-COV 1 and 2, MERS sense Helical symmetry Nonenveloped Calciviridae Calciviruses, Norwalk virus, hepatitis E Icosahedral Nonenveloped Picornaviridae Rhinoviruses, poliovirus, echoviruses, Icosahedral coxsackievirus, hepatitis A virus Nonenveloped Flaviviridae Yellow fever virus, dengue virus, West Nile Icosahedral virus, hepatitis C virus Enveloped Togaviridae Rubella virus, chikungunya virus Icosahedral Adapted from: Chapter 36. Medical Microbiology. 9th Edition. Ed. Murray, P. 2021 Elsevier inc. Available on ClinicalKey Copyright © Brunel University London v.3 2022. All rights reserved.  Medically important RNA viruses Genome Structure Family Examples ssRNA negative Enveloped Paramyxoviridae Parainfluenza, measles, mumps, respiratory sense Spherical syncytial virus (RSV) Enveloped Orthomyxoviridae Influenza types A, B, C Spherical Enveloped Rhabdoviridae Rabies Bullet shaped Enveloped Filoviridae Ebola Filamentous Enveloped Bunyaviridae California encephalitis virus, La Crosse virus, Spherical sandfly fever virus, hantavirus Enveloped 'Satellite agent' Hepatitis D ssRNA Enveloped Retroviridae Human T-cell leukaemia virus (HTLV) 1 and 2 Cone shaped Human immunodeficiency virus (HIV) 1 and 2 DNA intermediate Adapted from: Chapter 36. Medical Microbiology. 9th Edition. Ed. Murray, P. 2021 Elsevier inc. Available on ClinicalKey Copyright © Brunel University London v.3 2024. All rights reserved.  Disease Polio virus – a picornovirus More than 95% of cases very mild or asymptomatic Acquired faecal orally and replicates in the gastrointestinal tract ‘enterovirus’ Poliomyelitis is the result of the virus Spreads through the blood (viraemia) infecting and destroying motor neurones Invades the central nervous system Flaccid paralysis of affected areas Wasting of muscles Effective vaccine Death from respiratory failure No antiviral therapy World Health Organisation aim is for global eradication Problems with vaccine coverage linked to COVID pandemic and conflict in some areas Polio continues to occur in some countries Virus identified in sewage in London and New York in 2022 Image: Poliomyelitis resulting in paralysis and wasting of the right leg. Photo CDC. Barbara Rice, Public domain, via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Measles – has not gone away and may well come back Key features Disease ssRNA Paramyxovirus Febrile illness The most infectious microorganism known Respiratory symptoms Transmitted through respiratory route Rash Vaccine preventable Serious complications Infects respiratory epithelial cells through Respiratory tract, brain and heart interaction of viral haemagglutinin with May affect unborn child CD46 Neurological and eye damage Infects lymphocytes via CD150 leading to relative immunosuppression Mortality in high income countries 0.1 – 0.3% Disseminates with viraemia Mortality in low income countries much higher Copyright © Brunel University London v.3 2024. All rights reserved.  Disease Febrile illness Mumps Classically have swollen parotid glands Key features ssRNA Paramyxovirus Complications Highly transmissible through respiratory Central nervous system – meningitis or route encephalitis Pancreas – pancreatitis Vaccine preventable Testes - orchitis Immunity wanes after vaccination leading to sporadic outbreaks in adults particularly in university settings Surface spike proteins bind respiratory epithelial cells Spread to salivary (parotid glands) and regional lymph nodes before disseminating Disease pathogenesis poorly understood Image: Mumps with swollen left parotid gland. Afrodriguezg, CC BY-SA 3.0 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved. Summary Many viruses are capable of causing human disease All organs may be affected by viruses An understanding of how viruses infect humans and the types of disease that they cause is essential for all clinicians Copyright © Brunel University London v.3 2024. All rights reserved. Glossary B cell lymphoproliferative disease Infectious mononucleosis Condition characterised by rapid division and Also known as glandular fever is an acute amplification of B lymphocytes due to Epstein febrile illness with swollen lymph glands and Barr virus. Most common in the severely sore throat. Complications may include immunocompromised particularly following hepatitis. Caused by Epstein-Barr virus or transplantation. High associated mortality. cytomegalovirus Burkitt’s lymphoma Kaposi sarcoma Type of B-cell lymphoma (lymphoma is cancer Endothelial cell malignancy seen in significant of lymphocytes) immunocompromise such as advanced HIV or after transplantation. Caused by herpes virus Encephalitis type 8 which is oncogenic Infection or inflammation of the brain substance Latent virus Flaccid paralysis Latency refers to viral DNA being present in the Paralysis where there is no tone or resistance cell but without any viral replication in the affected part of the body Copyright © Brunel University London v.3 2024. All rights reserved. Glossary Meningitis Pancreatitis Infection of the meninges which are Infection or inflammation of the pancreas which membranes surrounding the brain and spinal can lead to leakage of pancreatic enzymes into cord the peritoneal cavity Multiple sclerosis Peripheral nerve Autoimmune central nervous disease. Linked to Nerve linking the central nervous system (brain Epstein Barr virus and possibly human herpes or spinal cord) to peripheral tissues such as virus-6 skin and muscles Non-Hodgins lymphoma Sensory nerve ganglia B-cell malignancy a proportion of which are Swelling located along the course of a caused by Epstein-Barr virus. Increased risk in peripheral sensory nerve. Contain the cell severely immunocompromised patients due to bodies of sensory neurons. Along the spinal a high rate of EBV replication cord the sensory ganglia are located on the dorsal roots as the nerves exit the spinal cord. Orchitis Infection or inflammation of testicular tissue Copyright © Brunel University London v.3 2024. All rights reserved. To contact me: email: [email protected] Copyright © Brunel University London v.3 2024. All rights reserved.  Introduction to Medical Sciences 1 Viruses, viral, fungal and parasitic infections How do viruses cause disease Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, viral, fungal and parasitic infections Dr William Lynn [email protected] Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, viral, fungal and parasitic infections How do viruses cause disease Copyright © Brunel University London v.3 2024. All rights reserved. Viral factors affecting transmission Survival outside of Nature of Virulence the host exposure Increased replication Resistance to drying Route of transmission Adhesion to surfaces Resistance to alcohol Exposure dose which Entry into target cells cleaning agents depends on the amount of Mechanisms to avoid host virus in the transmission defences medium For example Enteroviruses Length of time during which resist degradation by exposure can occur stomach acid Copyright © Brunel University London v.3 2024. All rights reserved. Host Factors affecting exposure and infection risk Intrinsic Behavioural Environmental Genetic variation Poor personal Poor sanitation Immunodeficiency hygiene Unsafe drinking Damage to Smoking water surface defences IV drug use Enclosed poorly Immunity Sexual risk ventilated spaces Natural Travel Vaccination Copyright © Brunel University London v.3 2024. All rights reserved.  Virally induced cell death Direct cell lysis Via apoptosis How does viral Inflammation-mediated infection lead Immune recognition and killing of infected cells to disease? Unintended damage to uninfected cells Organ failure Secondary effects on other organs from hypoxia, cardiac, liver or renal failure Copyright © Brunel University London v.3 2024. All rights reserved.  COVID-19 Pathogenesis Copyright © Brunel University London v.3 2024. All rights reserved.  Viral mutations (variants) enhance transmission? Viruses generate many mutations Copyright © Brunel University London v.3 2024. All rights reserved.  Viral evasion of innate immunity Getting a foothold Copyright © Brunel University London v.3 2024. All rights reserved. Examples of avoiding Pattern Recognition Receptors Flaviviruses, hepatitis C and dengue, enter a cytoplasmic endosome and alter the membrane to prevent recognition Enteroviruses have enzymes that cleave cytoplasmic viral pattern recognition proteins HIV DNA binds to a cytoplasmic protein, cyclophilin A, preventing exposure of HIV-1 cDNA to pattern recognition receptors SARS COV-2 has several genes which lead to shielding of viral RNA  Viral evasion of the complement pathway Complement can be activated by antiviral immunoglobulin using the Expression of surface classical pathway proteins that mimic host RCA Complement/antibody complex Incorporation of host RCA binds viral antigens expressed by into the viral outer membrane infected cells leading to cell lysis Secretion of complement Uninfected host cells are protected by cell surface complement control proteins activation regulators (RCA) Copyright © Brunel University London v.3 2024. All rights reserved.  Evasion of Interferon (IFN) Inhibit IFN release Blocking IFN signalling after Influenza A non structural protein 1 receptor binding reduces IFN synthesis and release Multiple mechanisms by many viruses including SARS-COV2 Preventing IFN from binding to its receptor Mitigating the inhibitory effects of IFN Some viruses, for example poxviruses, Gene mutations resulting in resistance to produce soluble IFN homologues which IFN bind and inactivate secreted IFN A single amino acid change in non- structural protein 1 of H5N1 influenza confers resistance to IFN and other antiviral cytokines Copyright © Brunel University London v.3 2024. All rights reserved.  Evasion of Natural killer cells Upregulating host cell MHC-1 expression Expression of MHC-1 like molecules which engage the inhibitory NK receptor Inhibiting expression, functioning or signalling of NK cell activating receptors Image source: Cellular and Molecular Immunology, Tenth Edition Ed. Abbas, A K.2024: Elsevier. Available via ClinicalKey. Copyright © Brunel University London v.3 2024. All rights reserved. Viral evasion of adaptive immunity Strategies for success Copyright © Brunel University London v.3 2024. All rights reserved.  Hide in a sequestered site Antibody and immune cells have difficulty reaching some sites Sites include nervous system, eye and testes Ebola virus in brain, testes and eye Viral hide Rabies virus in neurons and seek Herpes simplex and zoster in sensory neurons Hide inside the genome HIV integrates its DNA into the genome of macrophages and CD4+ T cells Copyright © Brunel University London v.3 2024. All rights reserved.  Mutation in surface antigens escapes neutralising antibody COVID-19 variants Influenza viruses Be a moving target Mutation in antigen epitopes that are recognised by cell mediated immunity Evolves over time in many chronic viral infections for example HIV and hepatitis C Copyright © Brunel University London v.3 2024. All rights reserved.  Antigenic change - Influenza A Structure of influenza A Haemagglutinin (H) mediates binding and entry into respiratory epithelia Neuraminidase facilitates influenza release from an infected cell Both are targets for neutralising antibodies Strains of influenza A are classified by these antigens e.g: H1N1- pandemic 1918 and 2009 Hi Eun Jung and Heung Kyu Lee, CC BY 4.0 H5N1 – 'bird flu' , via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Influenza A - why is it still a problem despite effective vaccines? Outbreaks – antigenic drift Gradual change in H and N antigens Erodes existing immunity Pandemics – antigenic shift Sudden and dramatic change due to nucleic acid recombination No existing herd immunity Abuahmam, CC BY-SA 4.0 , via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved. Origin of the H1N1 2009 influenza pandemic Copyright © Brunel University London v.3 2024. All rights reserved. Mess with your opponent – downgrade immune responses Interfere with antigen presentation and processing eg: Influenza A and B​ down regulate MHC-1 molecules EBV releases a protein (EBNA1) which directly inhibits epitope generation by antigen processing cells HSV has a protein which inhibits presentation of viral peptides by MHC-1 Viruses may express genes that moderate cytokine function Probably originally acquired from host cells Eg: viral homologs of cytokines or cytokine receptors Copyright © Brunel University London v.3 2024. All rights reserved.  All out attack HIV kills CD4 positive helper T cells COVID-19 infection reduces B cells, T Damage or kill immune cells and NK cells effector cells Many viral infections are Measles virus kills T cells and B cells associated with reduction in one or more lymphocyte lineage Some examples are given here Dengue virus reduces all lymphocytes Cytomegalovirus reduces CD4+ and CD8+ T cells and NK cells Copyright © Brunel University London v.3 2024. All rights reserved. Summary Innate immunity is critical in controlling the early phase of viral infection to limit severity and transmission Adaptive immunity provides antigen specific potent immune control of viral infection and memory immunity can prevent reinfection Viruses have evolved multiple strategies to evade both innate and adaptive immunity Copyright © Brunel University London v.3 2024. All rights reserved. Glossary ACE2 receptor Epitope Angiotension converting enzyme type 2 Specific region of an antigen that is recognised receptor. Expressed in a variety of tissues but by an antibody or T-cell receptors particularly in the lung Hypoxia Apoptosis Low oxygen levels Death of a cell through normal pathways. Sometimes called programmed cell death Microvascular thrombus Blood clots forming in small blood vessels Cyclophilin A Cyclophilin A (CyPA) is a ubiquitously Neurons distributed protein belonging to the Nerve cells immunophilin family. CyPA regulates protein folding and trafficking. Copyright © Brunel University London v.3 2024. All rights reserved. To contact me: email: [email protected] Copyright © Brunel University London v.3 2024. All rights reserved.  Introduction to Medical Sciences 1 Viruses, viral, fungal and parasitic infections Fungal structure and immune response Copyright © Brunel University London v.3 2024. All rights reserved. Viruses, fungal and parasitic infections Dr William Lynn 2024 Version 3 [email protected] Copyright © Brunel University London v.3 2023. All rights reserved. Viruses, viral, fungal and parasitic infections Fungal structure and immune response Copyright © Brunel University London v.3 2022. All rights reserved.  What are fungi? Free living organisms Found throughout the environment Vary from single cell organisms through to complex structures A very small number of species cause serious human disease From Mims' Medical Microbiology and Immunology, Sixth Edition. Only fungi capable of growth and spread at Goering, Richard V. 2019, Elsevier Limited. Available on Clinical body temperature of 37oC Key. Copyright © Brunel University London v.3 2024. All rights reserved. Basic fungal cell Eukaryotic Similar composition to protozoal and animal cells Nucleus Organelles Enclosed by a plasma membrane Unlike other organisms they have very tough and unique cell wall Yeast cell: James De La Rosa, CC BY-SA 4.0 , via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved. Features of the fungal cell wall Controls cell Composition and antigenic permeability, protects Interacts with structure key to fungal from osmotic and environment mechanical stress pathogenicity Main target for host Cell wall is a target for immune response antifungal therapy Copyright © Brunel University London v.3 2024. All rights reserved. Schematic of the fungal cell wall Image Dr William Lynn Copyright © Brunel University London v.3 2024. All rights reserved.  Key fungal components Glucans Mannans Polysaccharides of linked D-glucose monomers Polymers of the sugar mannose Up to 60% of the cell wall Recognised by mannose binding lectin Possible immunomodulatory effects pathway – part of innate immune response Fungal glucan can be detected in body fluids Fungal mannan can be detected in body fluids during invasive fungal infection during invasive fungal infection Glucan synthesis anti-fungal drug target Mannan synthesis anti-fungal drug target Structure of glucan: Edgar181, Public Structure of mannan. Smokefoot, Public domain, via Wikimedia Commons domain, via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Key fungal components Chitin Melanin Ergosterol N-acetylglucosamine polymer High molecular weight, Main lipid of the cell Structural strength to hyphae negatively charged, membrane in contrast to Found in some insect cells hydrophobic cholesterol in human cells Recognised by innate Complex structure Antifungal drug target immune receptors Protect fungi from physical and environmental stress Antioxidant Protects from UV light Mechanical strength Virulence factor in fungal infection Structure of ergosterol. Mysid, Public domain, via Wikimedia Commons Structure of Chitin. Dschanz, Public domain, via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Fungal morphology - moulds Multicellular filamentous hyphae Septated or hollow Grows by the tip elongating Hyphae form a dense mat-like structure known as a mycelium Colonies are hairy or woolly A from Microrao, CC BY-SA 4.0 , via Wikimedia Commons B from: Jankaan, CC BY-SA 3.0 , via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Conidia Moulds release spores Conidiophore Moulds produce multiple spores by asexual reproduction Septated Hyphae Released from structures such as conidiophores Aerosolise and easily inhaled Germinate in respiratory tract and can invade epithelium Aspergillus spores at tip of a conidiophore Image A from: Medical Microbiology, Murray, Patrick R., PhD. 2018 by Elsevier. Available via ClinicalKey Image B from: Medmyco, CC BY-SA 4.0 , via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved. Fungal morphology - yeast Reproduce by fission/budding The bud may remain attached forming chains known as pseudo-hyphae Yeasts are unicellular Round mucoid colonies on agar A from: Medical Microbiology, Murray, Patrick R., PhD. 2018 by Elsevier. Available via ClinicalKey B from: CDC/Dr. William Kaplan, Public domain, via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Candida albicans A: Candida albicans showing a budding yeast developing B: Candida albicans in blood culture: pseudohyphae A from: Y tambe, CC BY-SA 3.0 , via Wikimedia Common B from: Basic Medical Microbiology, Murray, Patrick R., PhD. 2022. Elsevier. Available via ClinicalKey Copyright © Brunel University London v.3 2024. All rights reserved.  Dimorphic fungi Exhibit both mould and yeast morphology Form hyphae at environmental temperatures At body temperature they switch to yeast form Coccidioides immitis A: Yeast form Yeasts form causes disease and B: Branching hyphae in culture can be identified in clinical samples From Comprehensive Review of Infectious Diseases. Spec, Escota, Chrisler and. Bethany. 2020. Elsevier. Available via ClinicalKey Copyright © Brunel University London v.3 2024. All rights reserved.  Fungi and the immune system Exposure Immunocompetent Fungi are ubiquitous throughout the Innate and adaptive immune effective environment at preventing most systemic invasion Immune continually challenged Superficial infections are common Immunocompromised Fungi present in the microbiome Fungi are common opportunistic Risk of ‘autoinfection’ infections Disruption of microbiota significantly Defects in innate immunity - increases the risk of fungal infection neutropaenia For example antibiotics used to treat Defects in adaptive immunity – cell bacterial infections mediated immunodeficiency states Copyright © Brunel University London v.3 2024. All rights reserved.  Example of fungal infection leading to systemic spread Aspergillus invading through the lung. Adapted from: Scott G. Filler, Donald C. Sheppard, CC BY 2.5 via Wikimedia Commons Copyright © Brunel University London v.3 2024. All rights reserved.  Innate immune response to fungi Involvement of soluble elements Recognition of fungal PAMPS including complement, collectins and Pattern recognition receptors on mannose binding lectin epithelial cells, dendritic cells, neutrophils and macrophages Recruitment and activation of immune effector cells including neutrophils, Release of cytokines, macrophages, natural killer cells chemokines and other proinflammatory mediators Activation of adaptive immune responses PAMPS; pathogen associated molecular patterns Copyright © Brunel University London v.3 2024. All rights reserved. Examples of fungal pattern recognition receptors PRR Ligands Cell surface Lectin receptors eg: Glucans Dectin 1-3, Macrophage mannose receptor Mannans CD36 – membrane glycoprotein ‘scavenger receptor’ Mannans Toll like receptors - TLR1,2,4 and 6 Mannans and glucans Intracellular - cytoplasm Inflammasome Glucans, mannans, chitin Nucleotide-binding and oligomerisation domain (NOD) Fungal DNA and RNA receptors Toll like receptors – TLR 3,7 and 9 Fungal DNA and RNA Copyright © Brunel University London v.3 2024. All rights reserved. Neutrophils: key in anti-fungal response Recruited and activated by inflammatory mediators Degranulate releasing proteolytic and other substances into the extracellular space to kill fungi Phagocytose leading to intracellular killing of fungi Lack of neutrophils – neutropenia Increased invasive fungal infection with high associated mortality Risk linked to the severity and duration of neutropenia Chronic Granulomatous Disease – a primary immunodeficiency Failure in oxidative killing of intracellular pathogen Fungal infection common and persistent Copyright © Brunel University London v.3 2024. All rights reserved. Adaptive immune response Processing and presentation of fungal antigens Dendritic cells and macrophages Trigger humoral and cell-mediated immune responses Cytotoxic T cell response can kill funghi CD4 T helper cell function and gamma interferon are central to control of invasive fungal infections Copyright © Brunel University London v.3 2024. All rights reserved.  Examples of fungi avoiding immune responses Mechanism Effect on immune response Examples Cell wall mannans Shielding from pattern recognition receptors Candida, histoplasmosis Melanin Impedes phagocytosis partly due to strong negative Cryptococcus charge Outer capsule Impedes phagocytosis Cryptococcus Asteroid bodies Star shaped calcified intracellular structures that Candida, aspergillus, shield fungal cells histoplasma Fungal enzymes Modify surface antigens reducing recognition by Histoplasma immune responses Mycotoxins Fungal enzymes that destroy leucocytes Aspergillus Release of proteins Neutralise anti-fungal peptides Candida Intracellular survival Surviving inside phagocytes shields from immune Cryptococcus mechanisms and helps dissemination Biofilm Hide away from innate and adaptive immunity Candida, aspergillus Copyright © Brunel University London v.3 2024. All rights reserved. Summary Fungi are found throughout nature. They are We have a strong and usually effective eukaryotic cells with a unique cell wall immune response to fungi through innate setting them apart from animal and plant and adaptive pathways eukaryotes Pathogenic fungi have evolved multiple Fungi are classified as yeasts, moulds and strategies to evade host immune responses dimorphic fungi where the organism switches between forms in response to environmental changes The fungal cell wall is composed of chitin, glucans, mannans, melanin and glycoproteins. The cell wall protects the fungus, interacts with the immune system and is a target for antifungal drugs Copyright © Brunel University London v.3 2024. All rights reserved. Glossary Blastoconidia Dectin Outpouching from a fungus undergoing asexual Small glycoprotein which acts as a cell surface reproduction. The bud arises from a yeast receptor with a lectin like binding domain. Pattern recognition receptor for fungi Budding Method of asexual reproduction employed by Degranulate yeasts Process by which a phagocyte releases antimicrobial cytotoxic molecules from Chronic Granulomatous Disease preformed secretory granules Diverse group of inherited disorders where phagocytes are unable to properly form reactive Galectin 3 oxygen radical to kill ingested pathogens. Beta-galactoside-binding protein family that Affected individuals suffer from serious bacterial plays an important role in cell-cell adhesion and and fungal infections from early infancy adhesion to the extracellular matrix Conidia Hyphae Spores arising from a mould and are a form of Branching filaments produced by moulds asexual reproduction Copyright © Brunel University London v.3 2024. All rights reserved. Glossary Inflammasomes Mycotoxins Cytosolic multiprotein oligomers of the innate Toxins secreted by fungi. Some are virulence immune system responsible for the activation of factors facilitating local infection or inflammatory responses dissemination. Some environmental fungi contain powerful mycotoxins with serious health Lectin consequences when ingested in large Carbohydrate binding proteins quantities including causing some cancers Macrophage mannose receptor N-acetylglucosamine Also known as CD206 this macrophage N-Acetylglucosamine (GlcNAc) is an amide receptor will recognise mannose molecules derivative of the monosaccharide glucose within fungal mannan residues. Also recognises bacteria which may express mannose moieties Pseudohyphae on pili Describes the appearance of a chain of yeast cells, linked to each other, which resemble Mycelium hyphae Network of branching hyphae to form a root like structure. In nature the mycelium of fungi may spread for large distances in the soil. During active human infection the mycelium may matt together to form large solid mass lesions Copyright © Brunel University London v.3 2024. All rights reserved. To contact me: email: [email protected] Copyright © Brunel University London v.3 2024. All rights reserved.  Introduction to Medical Sciences 1 Viruses, viral, fungal and parasitic infections Human disease from fungi Copyright © Brunel University London v.3 2023. All rights reserved. Viruses, fungal and parasitic infections Dr William Lynn 2024 Version 3 [email protected] Copyright © Brunel University London v.3 2023. All rights reserved. Viruses, viral, fungal and parasitic infections Human disease from fungi Copyright © Brunel University London v.3 2024. All rights reserved. In this session We will look at the most common and important fungal pathogens Yeasts, moulds and dimorphic fungi cause a range of infections from mild to life threatening disease Antifungal therapy will be covered in year 2 of your course Copyright © Brunel University London v.3 2023. All rights reserved. Transmission of fungi Inhalation of Ingestion of fungal spores yeasts or fungal spores Contact with the general environment Fungi form part of the normal human microbiota Skin and hair Inoculation Mouth, sinuses and pharynx Intestine Vagina Human contact Copyright © Brunel University London v.3 2023. All rights reserved.  Where in the body do we see fungal disease? Type Sites involved Examples Superficial Hair shaft, superficial and dead layers of skin Dandruff Athletes foot Epidermis, scalp Trichophyton - Tinea (ringworm) Nails Onychomycosis Mucocutaneous Mucosal – mouth and genital Candidiasis Subcutaneous Deeper tissues and bone Unusual fungi found in soil Systemic Opportunistic infection – mainly in Invasive candidiasis immunocompromised and critically ill patients Aspergillosis Cryptococcal meningitis Pneumocystis pneumonia Dimorphic fungi (endemic) mycoses Disease in Histoplasmosis immunocompetent Coccidioidomycosis More severe in immunocompromised Adapted from Mims' Medical Microbiology and Immunology, Sixth Edition. Goering, Richard V. 2019, Elsevier Limited. Available on Clinical Key. Copyright © Brunel University London v.3 2023. All rights reserved.  Tinea versicolor - Malassezia furfur – annoying yeast Up to 90% of people are colonised One of a group of organisms – known as dermatophytes Releases keratinase and other enzymes to digest and invade upper dermis Do not invade deeper or disseminate Hypopigmented lesions of Superficial infection of dermis Tinea versicolor Cannot grow at body temperature Common presentation in primary care Image : Sarahrosenau CC BY-SA 2.0 via Wikimedia Commons Copyright © Brunel University London v.3 2023. All rights reserved.  Mucosal candida – common Present in normal flora Asymptomatic Mouth, gut, vagina Minor infections common Oral or vaginal candidiasis commonly triggered by antibiotics Increased in diabetes, poor local hygiene and mild immunocompromise Mucosal disease more severe in significant immunodeficiency A oral candida: CDC, Public domain, via Wikimedia Commons B severe oesophageal candida image courtesy of Dr William Lynn Copyright © Brunel University London v.3 2023. All rights reserved.  Disseminated candida – life threatening yeast Major risk groups Neutropenia Intravenous drug use Central venous line infections Critical illness in intensive care Dissemination via bloodstream Eye, skin, kidney, liver, heart, lungs A Candida in blood culture: Basic Medical Microbiology, Murray, Patrick R., PhD. 2024. Elsevier. Available via ClinicalKey B Candida in the retina (arrows): Comprehensive Review of Infectious Diseases. 2020. Elsevier. Available via ClinicalKey Copyright © Brunel University London v.3 2023. All rights reserved.  Cryptococcus neoformans – uncommon but deadly yeast Found in birds Humans infected by inhaling cryptococcus from dried guano Enters through lung Invades blood and crosses brain barrier to cause meningitis Almost exclusively in severe cell- mediated immunodeficiency such as advanced HIV Image: Cryptococcus neoformans. Comprehensive Review of Infectious Diseases. 2020. Elsevier. Available via ClinicalKey Copyright © Brunel University London v.3 2023. All rights reserved.  Aspergillus – most commonly encountered mould Organism Transmission Disease spectrum Aspergillus species Inhalation of fungal Allergic bronchopulmonary aspergillosis – spores hypersensitivity reaction to aspergillus in airways Aspergilloma – fungal growth inside a lung cavity caused by another illness. Immune system unable to get to the fungal ball in the cavity Invasive aspergillosis – immunocompromised patients, invasive lung or sinus disease. Dissemination to other organs. Copyright © Brunel University London v.3 2023. All rights reserved.  Disease from aspergillus Aspergilloma Allergic bronchopulmonary aspergillosis A: Serological testing demonstrating antibody against aspergillosis. adapted from Medical Mycology, 2015, 53, 417–439. Available at: https://academic.oup.com/mmy/article/53/5/417/1746744 (Accessed 25th March 2024) B: Fungal ball growing in old lung cavity. Courtesy of Dr William Lynn Copyright © Brunel University London v.3 2023. All rights reserved.  Invasive aspergillosis Most disease due to Aspergillus fumigatus or niger Most common mould to cause invasive disease Neutropaenia Severe cell mediated immunodeficiency Critically ill patients in intensive care Chest X ray (A) and computerised tomography (B) of invasive pulmonary aspergillus Images from Mims' Medical Microbiology and Immunology. 6 th Edition by Elsevier. Available via ClinicalKey Copyright © Brunel University London v.3 2023. All rights reserved.  Madurella – locally invasive mould Found in soil and vegetation Unable to invade through intact surface defences Penetrating trauma eg: thorn Immune system prevents dissemination but cannot eradicate local infection Chronic progressive local infection of connective tissue and bone Image courtesy of Dr William Lynn Copyright © Brunel University London v.3 2023. All rights reserved.  Examples of medically important di-morphic fu