Fungi and Protozoa Lecture 3b PDF

Microbiolog y Lecture 1: FUNGI & PROTOZOA BSc Podiatry (Hons) Program – Year 1 Pathology Sophie Hartfield, Lecturer in Podiatry WELCOME TO MICROBIOLOGY 2  MICROBIOLOGY » Micro-organisms play a large role in maintaining health and influencing various health processes. » Bacteria,...

Microbiolog y Lecture 1: FUNGI & PROTOZOA BSc Podiatry (Hons) Program – Year 1 Pathology Sophie Hartfield, Lecturer in Podiatry WELCOME TO MICROBIOLOGY 2  MICROBIOLOGY » Micro-organisms play a large role in maintaining health and influencing various health processes. » Bacteria, fungi, viruses, archaea can be found in the body with largest colonisation areas in the gut, skin, mouth and respiratory areas (mostly bacteria). Collectively these colonies of microorganisms are called the “microbiota” and the genetic material they carry or provide is known as the “microbiome.” » When we refer to “normal flora” we are referring to the diverse microorganisms that are present and live harmoniously within and on the human body. The majority of these microbes are beneficial or at least do not affect health negatively. Some are also essential for human 3  TERMINOLOGY: PATHOGENIC VS NON-PATHOGENIC » Key terms to point out. These terms will continue to be used within your career. » BUT what do these terms mean? » What is a pathogen? » What do we mean by pathogenic? » What does non-pathogenic mean? 4  TERMINOLOGY: PATHOGENIC VS NON-PATHOGENIC A pathogen refers to any organism (typically micro- organism/microbe) that has the potential of causing a disease. The term pathogenic refers to any organism/microorganism that has/can cause disease. E.g. HPV can cause verrucae/herpes, but its manifestations are different in each person or may not even manifest, but it is still a microorganism that has the potential to cause disease. By the above definitions, the term non-pathogenic means the opposite, an organism/microorganism that 5  MICROBIOLOGY » Normal Flora is important within several physiological functions including; » Digestion and metabolism processes - Microbes especially within the gut (mainly bacteria) help break down complex carbs, fibre and other substances that the body is unable to digest solo. They also assist with delivering energy to cells within gut and intestinal lining via production of short chain fatty acids. This also assists with anti-inflammatory properties and synthesising of some vitamins. » Immune system regulation and development - Having a normal and healthy microbiome assists with the 6 bodies defence of harmful pathogens and helps to distinguish  MICROBIOLOGY » Normal Flora is important within several physiological functions including; » Protection against pathogens - Normal flora competes with harmful microbes for resources and space on body surfaces. A process called “competitive exclusion” can assist in stopping any pathogens from disrupting normal processes. In addition, some microbes also produce antimicrobial compounds which can further inhibit growth of any problematic pathogens » Barrier function - Skin and mucosal areas are typically colonised by beneficial bacteria (e.g. staphylococcus epidermidis & Propionibacterium 7 acnes) that help to provide some protective form against  MICROBIOLOGY » Disruptions to normal flora can be caused by several factors including: - Antibiotic use: Antibiotics are known to cause some disruption to gut microbiome and can also predispose risk of fungal infections. Although antibiotics are often necessary, they should be used as required and not issued without reason and signs of infection. (i.e. distinguish inflammation vs infection) - Diet: Diets that are high in saturated fats, sugars and low in fibre can disrupt gut flora balance leading to propensity of obesity, IBD, HTN, Diabetes etc. - Lifestyle factors: Stress, lack of sleep and poor hygiene can also affect microbiome and its composition. 8  MICROBIAL GROWTH AND TRANSMISSION » All microbes require a suitable environment to thrive in, broken down these factors can include; - Appropriate moisture and temperature – many microbes thrive in damp, moisture rich environments and many grow best at body temperatures around 37°C - Appropriate pH level – dependant upon the microbe… some prefer acidic conditions (e.g. candida), some prefer neutral conditions (e.g. staphylococcus) - Adequate nutrients and/or energy source – e.g. mycology related – many fungi of the skin/nails such as dermatophytes like Trichophyton Rubrum thrive on keratin BUT a basic principle for most microbes = no host  no source  no spread  no survival 9  MICROBIAL GROWTH AND TRANSMISSION » Transmission can generally be distinguished into 2 main categories or modes of spread: DIRECT & INDIRECT DIRECT INDIRECT » Direct skin contact » Contact with direct » Vehicle-bourne » Animal to person contaminants e.g. transmission i.e. (e.g. animal waste » Sexual contact contamination or bite/scratch) - Soil or water » Oral contact from known to be » Zoonotic object/surface » Direct touching of containing (zoonosis) e.g. the manifested contaminants » Droplet (may be anthrax, rabies, condition (e.g. direct also) plague - Sharing an verrucae » Airbourne » Vector bourne infected tool, pedis/tinea pedis) clothing, food » Contaminants » Environmental » Mother to child (salivary) (food, water – can reservoirs (e.g. transmission » Iatrogenic (medical be direct and e.coli from soil) (vertical and procedures) indirect) transmammory) 10 » Needle sharing  MICROBIAL GROWTH AND TRANSMISSION » Hand washing plays a large role in the spread of many pathogens. » Something as simple as handwashing is known to largely reduce the multiplication of microbes which helps to reduce infection risk. » Targeted hygiene for health professionals is an evidence-based policy and is employed in every health field as a priority. » But hygiene isn’t just limited to health professionals. As we know, poor hygiene can contribute to spread of pathogens in any human, same as animals alike (e.g. 11  MICROBIAL GROWTH AND TRANSMISSION » Pathogens thrive in areas where poor sanitation is rife, with crowded conditions and poor hygienic practices – pathogens spread much faster and they become part and parcel of the environment… a haven of infection. Lack of resources such as clean water is also a big concern. » BUT » Further consideration should also be made for those with immunosuppression. » Even with safer precautions some people like those with immune compromise are at an increased risk of pathogenic infection and these infections could cause worsened health complications or disease/illness manifestation may be chronic. 12  LEARNING OBJECTIVES » Introduction to mycology » Describe the structure of fungi » Consider factors surrounding fungal reproduction and replication » Discuss types of fungal infection and involvement including: Localised (cutaneous), Subcutaneous and Systemic » Define protozoa 13 INTRODUCTION TO MYCOLOGY »Mycology is the study of fungi; inclusive of dermatophytes, yeasts, mushrooms and moulds. »Fungi are eukaryotic organisms, capable of causing superficial, cutaneous, subcutaneous and systemic disease 14  INTRODUCTION TO MYCOLOGY » Podiatry/Health related: The term mycoses and mycosis refers to fungal infection, as too does tinea. Within podiatry, these terms are used for nail and skin infections involving fungi, respectively. i.e. onychomycosis and tinea pedis » If you have an interest in etymology; both mycosis and tinea are primarily modelled on latin and greek terminology– mycosis derived from “mykēs” and “mycos” 15  INTRODUCTION TO MYCOLOGY »It is thought that there are over 5 million different species of fungus however only around 100,000 have been identified. » A mushroom is a clear example of fungi, but this is only the fruiting body of this organism 16 FUNGAL CLASSIFICATION Moulds Filamentous fungi and moulds Yeasts Dimorphic fungi MYCOLOGICAL LY CLINICALLY Dermatophytes Yeasts Microsporum Yeast-like fungi Trichophyton Epidermophyton 17  FUNGUS AND THE ENVIRONMENT » Fungi are important for decomposition of organic matter e.g. cellulose; they play a major role in this decomposition process and are one of the most significant organisms relating to this » Without fungi, ecosystems would struggle to break down dead organisms » Plants and fungi typically have a symbiotic relationship e.g. mycorrhiza » BUT » Fungi also cause about 70% of all major crop diseases 18  FUNGUS AND THE ENVIRONMENT » Generate many commercial products e.g. ethanol, organic acids, enzymes, antibiotics » May generate extremely potent toxins that affect human and animal health e.g. aflatoxins Found in agricultural crops e.g. corn, peanuts etc. Produced by moulds such as Aspergillus Associated with liver cancer » With the rise in transplant surgery & immunosuppressive conditions, fungi could play a significant role in morbidity rates 19  SOURCES OF FUNGAL INFECTION » Dermatophytes may originate from a variety of sources » Main sources of fungal infection include: » Animals (Zoophilic fungi) – e.g. Microsporum Canis (ringworm in cats and dogs) » Soil (Geophilic fungi) – e.g. Microsporum Fulvum (has the potential to cause dermatophytosis i.e. ringworm, typically non-systemic infections) » Humans (Anthrophilic fungi) – many types spread via infected surfaces or direct transmission and very common 20  FUNGAL STRUCTURE » Fungi are eukaryotic i.e. cells that have organelles & a cell wall » Eukaryotes obtain food by absorption » The fungi excrete hydrolytic enzymes to break down complex organic molecules into simple ones that can be more easily absorbed » Fungi is typically multicellular (most fungi) but some like yeasts may be unicellular » All fungi reproduce by asexual mechanisms BUT most produce by sexual processes too » This replication and reproduction process occurs through sporous dispersion of almost infinite amounts, 21  FUNGAL STRUCTURE » Some species of fungi have single cells (yeasts) » Most species, however, consist of multiple thread-like cells called hyphae » The hyphae are organised into a network of fibres called a mycelium (i.e. the same structure as a mould that becomes apparent on decaying food) » Fungi have a cell wall consisting of the polysaccharide chitin. 22  FUNGAL STRUCTURE » Like human cells, fungal cells also contain a nucleus, endoplasmic reticulum (ER), mitochondria and other organelles » BUT most fungal cells possess a rigid cell wall containing polysaccharides such as chitin and glucan » The plasma membrane does however differ from humans in the type of sterol present Ergosterol, instead of cholesterol is the primary component of the cell membrane in fungi The function of ergosterol is to modulate membrane 23 24  FUNGAL SPORES » Many types of fungi create seed-like structures during reproduction also named spores » Many of these spores are less than 5 µm aerodynamic diameter and are therefore able to enter the lungs. » Spores may contain significant mycotoxins (secondary metabolites produced by microfungi) Toxic pneumonitis » Diseases Chronic associated with spore inhalation fatigue syndrome include; Hypersensitivity pneumonitis Kidney failure Tremors Cancer » In Britain >20 moulds are known to cause allergic reactions including hayfever & rhinitis 25  FUNGAL VS HUMAN CELLS » Unique cell wall using chitin as the main structural polymer » Cell membrane contains unique fungal sterols » Some unique cytoplasmic membrane enzymes in some species » Note: these aspects may all be targeted by anti-fungal therapies 26  FUNGAL BY PRODUCTS » Fungi produce a wide range of secondary metabolites - which play no role in the normal, basic metabolic pathways used for growth and energy production etc. » Some of these secondary metabolites have antibiotic properties. » Others are potent toxins that are dangerous when eaten by humans or other animals e.g. aflatoxins » Others include pigments inserted into the fungal walls or released into the surrounding environment, or flavour and odorous components of toadstools 27  PENICILLIN » The antibacterial effect of penicillin was discovered by Alexander Fleming in 1929. » It was noted that a fungal colony had grown as a contaminant on an agar plate which had been streaked with the bacterium Staphylococcus aureus the bacterial colonies around the fungus were lysing » The substance was named penicillin, because the fungal contaminant was identified as Penicillium notatum » Fleming found that this fungal contaminant was effective against many Gram-positive bacteria in laboratory conditions » He even used makeshift preparations of this substance, from culture filtrates, to control eye infections. 28  PENICILLIN » 2 other British scientists, Florey and Chain, working in the USA during the 2nd World War, produced the antibiotic on an industrial scale » All three scientists shared the Nobel Prize for their work with Penicillin which saved millions of lives and continues to today. » Penicillin is still a front-line antibiotic which is used today » BUT » The development of penicillin-resistance in several pathogenic bacteria has limited the effectiveness, and is also a rising 29  PENICILLIN - ACTION »Penicillin prevents the cross- linking of small peptide chains in peptidoglycan, the main wall polymer of bacteria. »Pre-existing cells are unaffected, but all newly produced cells grow abnormally  Cells are unable to maintain wall rigidity and are therefore susceptible to osmotic lysis. 30  FUNGAL INFECTIONS IN HUMANS » Fungi can cause a variety of diseases and can be divided into 3 main categories; 1. Allergies 2. Toxicity reactions 3. Fungal infections » Allergic reactions to fungi are typically caused by sensitivity to the inhaled fungal proteins e.g. inhaled spores » Toxicity reactions result usually from the consumption of fungal toxins in contaminated food or poisonous fruited fungi (mushrooms) » Both allergies and toxicity reactions are important 31  FUNGAL INFECTIONS IN HUMANS » Fungal infections also known as mycoses are the result of fungus invading living tissue » There are many recognised species of fungi but less than 200 are known to infect humans  90% of fungal infections are linked to only a dozen fungi » Some species of fungi, called primary pathogens, cause infection and disease regardless of the health status of the individual » Others which are referred to as opportunistic fungi primarily affect individuals with a weaker immune system » Therefore, fungal infections may be: Superficial, 32  FUNGAL INFECTIONS IN HUMANS » 4 main groups which relate to the tissue and/or body site the fungus invades; » Superficial- affect the hair shaft and the outermost, non-living layer of the skin e.g tinea nigra (Exophiala werneckii) & piedra (Piedraia hortae) » Cutaneous - involve infection of the skin, hair, and nails e.g. dermatophye and candida infections » Subcutaneous- affect the skin, muscle and connective tissue immediately below the skin e.g. mycetoma » Systemic- involve the blood and internal organs 33 e.g. blastomycosis (Blastomyces fungi).  CUTANEOUS FUNGAL INFECTIONS » Dermatophyte infections are common infections of the skin, hair, and nails. » Because of the circular skin patches found in dermatophytosis, they are often referred to as ringworm, or tinea infections. » The infectious fungi are typically caused by one of three Geni of fungus: Trichophyton Epidermophyton Microsporum » The fungi originate from infected humans, animals, or soils. » Transmission is usually from person to person or from animal to person. 34 35  DERMATOPHYTE INFECTION »Dermatophyte infections are restricted to dead keratin structures e.g. the skin and appendages (e.g. nails or hair). »Predisposing factors: Minor trauma, Repeated contact with moisture or perspiration Poor skin hygiene Specific skin chemistry 36 TINEA PEDIS (T/P podiatry abbreviation) 37 ONYCHOMYCOSIS (O/M podiatry abbreviation) 38  CANDIDA INFECTION » These yeasts are normal inhabitants of the mucous membranes of the nose, mouth, vagina, and anus. » Candida albicans can cause symptoms if local conditions or a weakened immune system allow it to overgrow. » Susceptibility to Candida infections is increased when the skin is weakened by injury, or prolonged exposure to wet environments e.g. around skin folds such as axillae, groin, interdigitally » Rarely Candida invades deeper tissues as well as the blood, causing life-threatening systemic candidiasis - 39 Candida infection of web of skin between the fingers - Candida is an uncommon cause of interdigital infection in the feet, dermatophytes are usually responsible. 40  MOULD INFECTION » Moulds such as Aspegillus fumigatus can cause lung infections in immunocompromised individuals especially » Can cause Aspergillosis via fungal spores inhaled from decomposing organic matter (A) - Typical sporing heads of the fungus in laboratory culture. (B) - Microscopic section of lung tissue, stained to show hyphae of Aspergillus in an air sac. Such a ball of hyphae growing 41  DIAGNOSIS AND TREATMENT » Key aspect for many conditions – symptoms, diagnosis and treatment » Clinical and visual examination with medical hx taking may diagnose infection or further investigation may be required » Microscopy and cultures including; Fungal skin scraping (T/P) or nail samples (O/M) Results would be positive if: For dermatophytes, either microscopy or culture is positive. For Candida species, both microscopy and culture are positive. For non-dermatophytes, both microscopy and culture are positive on at least two samples taken at different times. 42  DIAGNOSIS AND TREATMENT Interpret results with caution as false-negative rates for fungal culture may be as high as 30%. A negative test result cannot definitively exclude O/M  Arrange for repeat samples to be taken if the result is negative and there is a high clinical suspicion of O/M 43  TAKING A NAIL SAMPLE Clean affected nail/skin with alcohol spray (chlorhex.) to remove any residual cream etc If superficial white OM is suspected, use a scalpel blade to obtain scrapings of the surface of the nail. If deeper infection of the nail is suspected: - use sterile nippers to include the full nail thickness and take sample as far proximally as possible - Viable fungi are most likely to be found in the most proximal part of diseased nail - Distal nail samples should be avoided as contamination is common - Include scrapings of subungual debris Place nail samples into folded dark cardboard, seal and place in a plastic sample bag. Label the sample clearly before taking to lab. Keep the samples at room temperature (dermatophytes are inhibited at low temperatures, and humidity facilitates the growth of contaminants). 44  TREATMENT OPTIONS » Dependant upon the fungi present and the type of infection but may follow the below: » Topical antifungals – including creams, powders, lacquers or sprays for mild cases (e.g. terbinafine, miconazole, amorolfine, clotrimazole) » Oral antifungals – usually for more severe or persistent infections (e.g. fluconazole, terbinafine) » Laser therapy – an emerging therapy for onychomycosis, does it work? » Nail care – nail care may include nail trimming, debridement, filing, use of nail drill with the aim to help topical treatments penetrate the fungal debris and infected site » Preventative care – may include advice around foot care and hygiene, wearing breathable fibres e.g. socks and shoes, surgical spirit 45  IMPACT OF FUNGAL INFECTIONS ON PODIATRY PATIENTS » Consider prevalence  fungal infections are very common, with millions of cases globally. » They are especially prevalent in immunocompromised populations i.e. DM, HIV, cancer, autoimmune arthropathies » Some fungal infections such as T/P and O/M may become chronic and difficult to treat if left unchecked or may develop more rapidly in these patients 46  IMPACT OF FUNGAL INFECTIONS ON PODIATRY PATIENTS » Diabetic patient example: » Increased risk: high blood sugar levels can impair immune function making it harder for the body to fight infections and creating havens for pathogens to thrive » Neuropathy: reduced sensation to feet may prevent patients from noticing an infection until it becomes more severe, or they may not notice at all » Risk factors: other factors such as poor vision, poor mobility, living alone will also increase the risk of something going un-noticed. Drug use, other body system problems e.g. kidney issues will also dampen immune response » Poor circulation: without adequate vascular supply the body is unable to supply necessary oxygenation and nutrient to areas, so an infection may not heal or could easily worsen and cause more severe consequences 47 PROTOZOA 48  PROTOZOANS » Microscopic single celled organisms » Eukaryotic, non-filamentous » Vary in size and shape » Live in moist habitats including fresh water, the ocean and soil » Some are regarded as parasitic and pathogenic e.g., Plasmodium cause Malaria » Protozoans are motile; nearly all possess flagella, cilia, or pseudopodia that allow them to navigate their aqueous habitats. 49  PROTOZOANS » Protozoa that are infectious to humans can be classified into four groups based on their mode of movement: » Sarcodina – the ameba, e.g., Entamoeba » Mastigophora – the flagellates, e.g., Giardia, Leishmania » Ciliophora – the ciliates, e.g., Balantidium » Sporozoa – organisms whose adult stage is not motile e.g., Plasmodium, Cryptosporidium 50  MALARIA » Some species of protozoa establish a dormant hepatic phase  relapsing malarial illness months-years after infection » Hepatocytes rupture & liberate plasmodia to attach to/enter RBCs for further replication » Rupturing RBCs  chills, fever, rigor » Sometimes death if untreated - brain, kidney and liver damage from pigment, cellular debris & capillary blockage by masses of adherent RBCs 51  MALARIAL CYCLE » Four kinds of malaria parasites from mosquitos infect humans: Plasmodium falciparum, P. vivax, P. ovale, and P. malariae. » World Health Organisation reported in 2023, there were an estimated 263 million malaria cases and 597 000 malaria deaths in 83 countries. The WHO African region accounted for 94% of these cases and 95% of the global malaria related deaths. » P.vivax invades immature erythrocytes Parasites of blood cells and require 2 HOSTS 1. Mosquito for sexual reproduction 2. Humans/animals for asexual reproduction » Human infection usually follows a bite of an Anopheles mosquito via saliva Less commonly due to vertical transmission(mother to baby), or infected blood contamination from shared needles or transfusion » Infection carried to liver for asexual reproduction for 8-25 days » Incubation 10-17 days then flu-like symptoms - Chills, rigors, high temps » Chronic infection may lead to brain, kidney, liver damage 52  OTHER PARASITIC INFECTIONS » Toxoplasma gondii caused by an intracellular parasite from a feline host  toxoplasmosis (pregnancy and AIDS) » Leishmania caused by a flagellated protozoa by insect transmission  leishmaniasis (similar symptoms to malaria) » Gasterophilus and hypoderma caused by infestation of dipterous larvae by insect transmission  myiasis (fly strike) » Acanthamoeba or Entamoeba histolytica caused by a pathogenic ameba from indirect transmission  cutaneous amebiasis (swelling, ulceration and necrosis)  dysentery » Sarcoptes scabiei caused by cutaneous ectoparasitic infestation from direct and indirect transmission  mange and/or scabies 53 54  CASE STUDIES 1. A 45-year-old diabetic patient presents with thickened, discoloured toenails. - Discuss the potential diagnosis and clinical features that would confirm your suspicions. - What would be your plan of action and treatment for this patient? 55  CASE STUDIES 2. A 25-year-old athlete presents complaining of itching between their toes. There is some whiteness between the toes and scaling and redness. - Discuss the potential diagnosis and potential pathogens that may be responsible. - What would be your plan of action and treatment for this patient? 56  POST LECTURE CONSOLIDATION » Post-lecture consolidation: » 1. Review the lecture notes and supporting YouTube video on fungi » 2. Attempt the MCQ quiz at the end of this learning unit and test your knowledge! » Websites/Reading: https://www.youtube.com/watch?v=rB1JUT3nzmM – (What are Fungi?) https://www.youtube.com/watch?v=QcuPKy_Slng – (Overview of Fungal Structure) Drexler M. What You Need to Know About Infectious Disease.(2010). In: NIH (Internet). National Academies Press. Available from: https://www.ncbi.nlm.nih.gov/books/NBK209710/ Dekaboruah, E., Suryavanshi, M.V., Chettri, D., Verma, A.K. (2020) Human microbiome: an academic update on human body site specific surveillance and its possible role.. 202(8), 2147–2167. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC7284171/ 57