MedMic Unit 2 Pathogenic Fungi & Parasite PDF

Medical Microbiology (Course code: CCST4025) Unit 2 Pathogenic Fungi and Parasites 1 Pathogenic fungi and parasites Part I : How do fungi cause disease? Pathogenic properties of fungi Major fungal infections of human Part II: How do paras...

Medical Microbiology (Course code: CCST4025) Unit 2 Pathogenic Fungi and Parasites 1 Pathogenic fungi and parasites Part I : How do fungi cause disease? Pathogenic properties of fungi Major fungal infections of human Part II: How do parasitic protozoa cause disease? Pathogenic properties of parasitic protozoa Major protozoal infections of human 2 Part I: How do fungi cause diseases? 3  Fungi - Introduction Mycology: study of fungi The ‘root-like’ system (normally found in soil) is the mycelium Mycosis (plural: Mycoses = fungal which is made up of hyphae infections): mycotic infections – The fruiting bodies are often diseases caused by fungi exposed to facilitate reproduction and for the fungus to spread Fungi are eukaryotes (airborne spores) With a nucleus and a rigid cell wall made of chitin 4 A hypha http://4.bp.blogspot.com/-TlHLnKQ1t98/UWxpRc51Z0I/AAAAAAAAAFA/OdlGX_KlxsU/s1600/hypha.gif http://images.tutorvista.com/content/reproduction/spore-formation-in-mycellium-of-mucor.gif Different forms of fungi Unicellular forms  Yeast (aerobic, facultative anaerobic) http://bugs.bio.usyd.edu.au/learning/resources/Mycology/images/Topics/StructureFunction/buddingYea Multicellular forms: molds (aerobic) stCells.jpg  Filamentous molds (e.g. bread/ fruit molds)  Fleshy (complex) fungi (e.g. mushroom) http://www.scivit.de/blog/wp-content/uploads/2011/01/Anabaena2.jpg http://00.edu-cdn.com/files/static/wiley/9780470408810/EXAMINING_A_FUNGUS_01.GIF Dimorphism  Dimorphic fungi: able to grow as a yeast or a mold  depends on growth conditions (temperature) Opportunistic 5 http://medicscientist.com/wp-content/uploads/2011/01/350f8aa91b86700d0378b7ba2cb4231d.jpg  Some characteristics of fungi and how they live  Fungi DO NOT have Most fungi are saprophytes, they absorb nutrients from dead chlorophyll and cannot organisms. therefore carry out photosynthesis  Fungi can grow in soil, on living and dead plants, as well as on animals and humans. Some are parasites by absorbing nutrients from living organisms. (e.g. Cordyceps sinensis parasitizing on the ghost moth larvae) http://champignonscomestibles.com/wp-content/uploads/2011/10/culture-sur-bois.jpg http://www.aber.ac.uk/fungi/graffeg/decomp/digestion-by-hypha.jpg 6 http://3.bp.blogspot.com/-vQJHv24zt7g/T2meg-ni9qI/AAAAAAAAAAg/x- Gn0zCHHd8/s1600/333333Cordyceps_Sinensis.jpg http://www.alohamedicinals.com/img/wildcordyceps.jpg  Good fungi and Symbiosis Symbiosis: absorbing nutrients from still-living organisms, but providing something in return, such as protection or nutrients e.g. Mycorrhizae colonizes the host http://en.wikipedia.org/wiki/Mycorrhiza plant's roots. Creating a network of hyphae around the roots of the host plant that increases the plant's capacity to absorb more water and nutrients such as phosphorus, copper and zinc enhancing plant growth 7 right with Left plant without and http://giantveggiegardener.files.wordpress.com/2013/06/myco_tomato2plantsedit.jpg mycorrhiza, respectively. Reproduction – life cycle of Rhizopus nigricans (bread mold) Mitosis Hyphae Mitosis Spores Sporangium Meiosis Zygosporangium Fermentation  Spores are the reproductive bodies (a single cell)  A hypha begins to grow out of the spore, extend into the soil or food source to form the mycelium  When growing conditions are favorable, the fungus sends up fruiting bodies (more spores are 8 released) E.g. bread mold all spore are hiploid and can migrate to far distance https://bio.rutgers.edu/~gb101/lab6_protists/rhizolife.jpg http://www.mhhe.com/biosci/genbio/enger/student/olc/art_quizzes/genbiomedia/0446.jpg But some fungi cause diseases (pathogenic)  Pathogenic species invade tissues and digest material externally by releasing enzymes; they also take up nutrients directly from host tissues  Spores in the air can be inhaled causing a fungal infection in the Fungal infection in plants lungs Not uncommon http://ashleyaberneithy.files.wordpress.com/2011/08/xraywithdetection.jpg Humans do also suffer  or skin a lot from fungal infections 9 http://www.waaesd.org/wp-content/uploads/2013/11/W2122_maize-cob-colonized-by-aspergillus_IITA- image-gallery-photo_small.jpg http://medicalterms.info/img/uploads/diseasies/1274205754243/fungal-infection.jpg http://underarmrash.net/wp-content/uploads/2014/01/Ringworm.jpg  Fungal diseases (Mycoses) Fungal infections are caused by 3 types of fungi: 1. Yeasts Pathogenic dimorphic fungi are yeast 2. Molds like at 37°C and moldlike at 25°C. 3. Dimorphic fungi (fungi may grow as yeasts or molds)  Fungal pathogens invade tissues and destroy them or obstruct flow of bodily fluids (using the dead cells as food)  Fungal pathogens classified into 2 categories: http://classes.midlandstech.edu/carterp/Courses/bio225/chap12/lecture1.htm  Primary (true) pathogens : have virulence factors that allow them to invade and grow in a healthy host  Opportunistic pathogens : weak virulence; causes disease in hosts when immune 10 system becomes weak Fungal diseases – three main ways of infection 1) Fungal infections: growth of fungus on or in the body  Superficial  Subcutaneous  Systemic  Opportunistic 2) Intoxication (consumed) : mycotoxin  E.g. Aspergillus flavus (Aflatoxin) 3) Hypersensitivity: allergic reactions to molds & spores 11 Clinical classification of mycoses Fungal infections - Growth in/ on tissue: tissue destruction Fungal infections classified on the degree of tissue involvement and mode of entry into the host: 1. Superficial (or cutaneous) - infection to epidermis (skin, hair and nails) 2. Subcutaneous - infection beneath skin (dermis and underlying tissues) 3. Systemic - deep infections of the internal organs 4. Opportunistic - infections due to fungi with low inherent virulence Let’s take a look at each type of infection 12 Superficial mycose 1) Superficial mycose (Dermatomycosis) [Derma = skin] Dermatophytes: fungus that causes skin infection Infect only surface layers: skin, hair, nails (dermatophytes secrete enzymes that digest protein keratin as a nitrogen and energy source) Signs and symptoms: itching, scaling, broken hairs, ring-like patches of the skin, and thickened, discolored nails. Transmitted by direct & indirect contact (use same towels) Heat and moisture help fungi grow  common in areas of frequent sweating and skin folds (e.g. between the toes) 14 (Reproduced with permission from Richardson MD, Warnock DW, Campbell CK 1995 Slide Atlas of Fungal Infection: Superficial Fungal Infections. Blackwell Science, Oxford.)  Common superficial fungal infection (tinea)  The infections are generally  Infections caused by identified by its location on the dermatophytes are also sometimes body: known as "ringworm" or "tinea."  scalp (tinea capitis)  Note: "ringworm" is not caused  foot (tinea pedis: "athlete's by a worm, but by a type of foot") fungus.  skin/ body surface (tinea  Examples of dermatophytes corporis) involved in tinea:  nails (tinea unguium)  Epidermophyton: affect skin  Susceptibility to tinea infection is and nails increased by poor hygiene,  Trichophyton: infect hair, skin prolonged moist skin, and minor or nails skin or scalp injuries  Microsporum: infect hair or skin 15 Round spots of classic ringworm http://www.medicinenet.com/ringworm_pictures_slideshow/article.htm For reference only  Scalp (tinea capitis)  appears as scaly spots and Treatment: patches of broken hair on the  Anti-fungal powder and creams head are not effective  often in children  Take oral antifungal medicines  Infection by direct contact with to reach follicles (6-8 weeks of infected people or with treatment) contaminated objects (such as  Use medicated shampoo to combs, pillows, and sofas) reduce the risk of spreading  Fungus invades deep into hair follicles In a child with hair loss and scale on the scalp, fungal infection may be the cause. http://www.skinsight.com/child/tineaCapitisRingwormofScalp.htm Athlete's foot (tinea pedis)  Athlete's foot (tinea pedis), also known as ringworm of the foot (surface fungal infection of the skin of the foot)  Infection by direct contact with infected people, infected animals, contaminated objects (e.g. towels or locker room floors)  Over-the-counter antifungal or drying powders and creams are effective for athlete’s foot  Prevention:  Keep feet dry (discouraging further growth of the fungus) Scaling and erosion of the skin between the toes in a severe case of  Wear open-toed sandals (aeration) tinea pedis (athlete's foot). http://www.skinsight.com/adult/tineaPedisAthletesFoot.htm Skin (tinea corporis)  Tinea corporis, also known as ‘ringworm’ of the body (surface fungal infection of the skin)  Infections by direct contact with infected people, infected animals, contaminated objects (e.g. towels or locker room floors) Treatment:  Treated with topical creams and lotions Lesions of tinea corporis  Severe infections treated for 3–4 weeks with oral antifungal pills http://www.skinsight.com/adult/tineaCorporisRingwormofBody.htm Nails (tinea unguium)  Tinea unguium (fungal infection of the nails) also known as Onychomycosis  Uncommon during childhood  Found in fingernails or toenails  Onychomycosis  difficult to treat as nail plate prevents anti-fungal creams to penetrate  Nail infections best treated with oral and/or topical antifungal Tinea of the nails medications http://www.mycology.adelaide.edu.au/Mycoses/Cutaneous/Dermatophytosis/ Common superficial fungal infection (tinea) How to prevent Ringworm?  Shower and shampoo well after any  Good hygiene (e.g. regular sport that includes skin-to-skin handwashing) contact.  Avoid sharing hairbrushes, hats  Wear loose-fitting cotton clothing. and contaminated items (Beauty salons and barbershops should  Change socks and underwear at least disinfect instruments with once a day. approved disinfectants after each use)  Keep skin clean and dry.  Avoid pets with signs of skin disease  Wear slippers in locker rooms, public pools and bathing areas http://www.medicinenet.com/ringworm_pictures_slideshow/article.htm Subcutaneous mycosis (infection at lower layers of the skin) Involve tissues underlying skin Sporotrichosis (lymphatics) (“Rose gardener’s disease”) Sub-acute or chronic  Introduced into cuts and wounds Localized under the skin  Source: saprophytic fungi (e.g. Rarely enters the body Sporothrix schenckii – a system dimorphic fungus - living in soil and on decaying vegetation, can attack farmers and gardeners causing sporotrichosis) Treatment:  Take oral antifungal medicines 22 http://diggingri.files.wordpress.com/2010/01/sporotrichosis_1_040319.png http://www.mylifetechnologies.nl/Pictures/Skin-diseases1.jpg http://www.liguabc.lt/pav/galery/sistemine-raudonoji-vilklige.jpg Systemic mycosis (fungus enters the lymph or circulatory system) Involves internal organs Fungus takes advantage of its (sometimes affecting two or more dimorphic ability: organ systems simultaneously) Acquired by inhalation: lung Spores of dimorphic fungi (Inhale spores) → other internal inhaled into lungs (mold form when outside body) organs Inside body the fungus starts to Results from direct fungal grow as a yeast-like form from the infection spores Yeast form colonizes the lungs or enters the bloodstream to reach other parts of the body E.g. Blastomycosis (Blastomyces dermatitidis – found in soil) 23 http://www.cdc.gov/fungal/diseases/blastomycosis/causes.html Opportunistic mycosis (Low virulent type of fungus becoming very active) When does this ‘opportunity’ occur?  When an individual’s immune Example: system is weak Candida sp. - commonly found  The fungus takes this opportunity normal flora in mouth and to attack the system other orifices of the body are  Localized or systemic infections rather harmless. When immune system goes When and where can immune- down, the fungus grows fast compromised situation occur? and causes discomfort  AIDS patients (Candidiasis)  Person taking antibiotics “Oral thrush” (caused by C.  Cancer patient - chemo therapy albicans)  Organ transplant patients where the immune system is suppressed Common cause of vaginitis by drugs deliberately to avoid (causing severe itching) rejection of transplant 24 http://en.wikipedia.org/wiki/Oral_candidiasis Another opportunistic fungus causing brain injury Cryptococcosis is initiated by the Aspergillus flavus also a systemic inhalation of Cryptococcus neoformans pathogen to cause Aspergillosis (encapsulated yeast).  Inhalation of spores causes fungal balls in lungs and can  Starts as a lung (pulmonary) infections, invade the eyes, heart and brain but spread via the bloodstream to the  A serious threat to AIDS, brain to cause meningitis (inflammation of the brain) leukemia, and organ transplant patients  Route of infection is by inhalation – lung → blood → CNS where it causes meningitis  Cerebrospinal fluid sent for culture AIDS patients are very vulnerable to this diseases (due to this systemic pathogen) 25 http://pathmicro.med.sc.edu/mycology/mycology-3.htm http://www.jaypeejournals.com/eJournals/_eJournals%5C57%5C2010%5CMay-August%5Cimages/12-1.jpg For reference only Cryptococcus neoformans stained by india ink stain Candida auris Culture of Candida  Sabouraud's dextrose agar  Chloramphenicol is added as selective agent Summary of fungal infections of humans Disease Fungal pathogen Category Incidence Ringworm (or tinea) Dermatophytes Molds Common Sporotrichosis (skin Sporothrix Dimorphic Rare disease) schenckii fungi Blastomycosis (a disease Blastomyces Dimorphic Rare of lungs and skin) dermatitidis fungi Candidiasis (Thrush) Candida albicans Yeast Common Candidiasis (Yeast Vaginitis) Cryptococcosis (lung Cryptococcus Yeast Common infection) neoformans Aspergillosis (lung Aspergillus spp. Molds Common infection) 29 Microbial intoxication (Case: Fungi produce a harmful product – human consumes it without realizing) Peanuts when harvested in large quantities and improperly stored (humid condition) may become infested with fungi (mold) The fungi produce harmful chemicals (e.g. aflatoxins) that can cause liver cancer when consumed. Peanut oil and other vegetable oils are tested for aflatoxins before the oil is packaged and sold. 30 http://www.omafra.gov.on.ca/CropOp/images/general_agronomics/pest-management/general- http://content.answcdn.com/main/content/img/oxford/oxfordBiochemistry/0198529171.aflatoxin.1.jpg pests/diseases/peanut_black_hull_zoom.jpg  Hypersensitivity (allergy) Allergic reactions to molds & spores Mold often found is damp (moist) areas of  Toxic black mold the house. Especially in bathrooms and (Stachybotrys chartarum) cellars. and household molds can grow on cellulose and release toxins into the air, e.g. moldy wall paper  The spores from toxic black mold are both toxic and allergenic  Cause serious symptoms and health problems in human E.g. sneezing, sore eyes or a runny nose 31 http://blackmold.awardspace.com/pictures/mold-leak.jpg For reference only Antifungal drugs Part II: How do parasitic protozoa cause disease? 33 Parasitic protozoa - Introduction  Parasitology: study of parasites  Many parasitic protozoa are pathogens  Parasites: organisms living in another living  Protozoa are classified organisms (hosts) and usually depriving taxonomically by their mode of the host of nutrients. locomotion: Two major groups: 1. Amoebas move by (1) Protozoa pseudopodia microscopic, unicellular eukaryotes 2. Flagellates move by flagella (2) Helminths 3. Ciliates move by cilia macroscopic, multicellular worms (not 4. Sporozoans are nonmotile included in this course) 34 For reference only Helminths Parasitic protozoa Amoebas Flagellates  move by extending cytoplasmic  move by twolocomotion or more whip-like projections (pseudopodia) projections(flagella) that rotate outward from the main cell body and propel the cells through their liquid environment  feed by engulfing food particles with their pseudopodia  ingest food particles through an tife span of amoeba is 2 days oral groove called a cytostome it has 2 stages (mouthlike opening) Flagellate http://water.me.vccs.edu/courses/ENV108/Lesson2_print.htm http://classes.midlandstech.edu/carterp/Courses/bio225/chap12/lecture4.htm  Parasitic protozoa Ciliates Sporozoans  move by many hairlike  They are obligate, intracellular projections (cilia) arranged in parasites rows cover the cell surface  have nonmotile adult forms  Most ciliates have cytostomes  E.g. Plasmodium sp. causes that pass food particles through a malaria cytopharynx and finally into vacuoles where digestion takes  Sporozoans can have complex place. life cycles with more than one host:  There are some 7,000 species of ciliates, only Balantidium coli is  definitive host: harbors the pathogenic for humans, and the sexually reproducing stage disease, balantidiasis, is rare.  intermediate host: provides the environment in which Cilia asexual reproduction occurs may fuse tgt near cytoplasm http://classconnection.s3.amazonaws.com/627/flashcards/379627/jpg/protozoa1306682022093.jpg Parasitic protozoal infection  A typical protozoal life cycle has pouch 2 stages: 1. Trophozoite: motile, feeding, reproducing stage 2. Cyst: non-motile, dormant stage ameoba  Cyst provides protection during Common examples of protozoal adverse environmental infections: conditions – Blood and tissue: Malaria  Protozoal infections are most – Intestinal: Giardiasis & often acquired by ingestion or Amebiasis inhalation of dormant stages. Protozoa Example Protozoal infection Amoeba Entamoeba histolytica Amebiasis Flagellate Giardia lamblia Giardiasis 38 Sporozoan Plasmodium falciparum Malaria http://cal.vet.upenn.edu/projects/dxendopar/images/parasiteimages/protozoa/e_hist1.gif Entamoeba histolytica Classification: Protozoa. Amoeba. Major human disease caused by parasitic protozoa – (1) Amebiasis  Disease: Amebiasis  Geographic Distribution: Worldwide  Location in host: intestine or extraintestinal locations such as liver, lungs, brain, and other tissues.  Diagnosis: By demonstration of trophozoites and cysts in faeces. Morphology:  Trophozoites: spherical to elongate in shape, measuring 12- 30 um  Cysts: spherical shape and measure 10-20um. Mature cysts have four nuclei. Major human disease caused by parasitic protozoa – (1) Amebiasis  Amebiasis (or Amebic dysentery) is caused by Entamoeba histolytica (ameba) Common occurrence  Protozoal GI infection  50 million people are infected  Infection of intestines that can spread worldwide (mostly in tropical to the liver via circulatory system countries in areas of poor sanitation)  occurs usually in the large intestine and causes internal inflammation  In industrialized countries most of the infected patients  Symptoms: bloody diarrhea, dysentery, are immigrants, chills, fever and colitis institutionalized people and  Transmission: those who have recently visited developing countries.  By ingestion of cysts in fecally contaminated water or foods  By flies transporting cysts from feces to food  Via the fecally soiled hands of infected food handlers 41 Entamoeba histolytica Trophozoites Entamoeba histolytica Cysts  Amebiasis  Inside humans E. histolytica lives and  Trophozoites can further spread to the liver multiplies as a trophozoite.  In colon, trophozoites form cysts that pass  The life cycle of E. histolytica does not in the feces. require any intermediate host.  Only cysts can survive longer periods (up  Mature cysts (spherical) are passed in the to many weeks outside the host) and infect feces of an infected human. other humans.  If the cysts survive the acidic stomach, they  If trophozoites are ingested, they are killed transform back into trophozoites in the small by the gastric acid of the stomach. intestine.  Trophozoites migrate to the large intestine 44 where they live and multiply by binary fission. Giardia lamblia Classification: Protozoa. Flagellate. Major human disease caused by parasitic protozoa – (2) Giardiasis  Disease: Giardiasis  Geographic Distribution: Worldwide  Location in host: Small intestine  Diagnosis: By demonstration of trophozoites and cysts in faeces. Morphology:  Trophozoites: pear-shaped, measuring 10-20um, eight flagella, falling leaf motility  Cysts: oval to ellipsoid in shape and measure 8-19um. Mature cysts have four nuclei. Major human disease caused by parasitic protozoa – (2) Giardiasis  Some trophozoites encyst into  Giardiasis is caused by cysts which are released in a flagellate Giardia lamblia bowel movement.  Flagellated protozoan infection  Cysts are found in firm stool of duodenum (small intestine) whereas both trophozoites and  Each cyst releases two cysts are present in loose stool. trophozoites in the small  The feces might contaminate soil, intestine. water, food or surfaces such as bathroom sinks. Life cycle:  Symptoms: diarrhea, steatorrhea (loose, pale, fatty stools),  It attaches to the mucosa and abdominal cramps absorbs nutrients that it gets from the intestinal wall.  Transmission: – Via fecal-oral route  After eating enough, they go through another transformation – By ingestion of cysts in fecally and multiply by binary fission. contaminated water or foods – From person 47to person by soiled hands to mouth (poor hygiene) http://microbiology.mtsinai.on.ca/pig/protozoa4.shtml Giardia lamblia Trophozoites Giardia lamblia Cysts Plasmodium falciparum Classification: Protozoa. Sporozoan. Major human disease caused by parasitic protozoa – (3) Malaria  Disease: Malaria  Geographic Distribution: Worldwide, but widely distributed in, the tropics and subtropics, particularly Africa and Asia.  Location in host: Red blood cells, Hepatic cells  Diagnosis: By demonstration of parasite stages in red blood cells. Examples of human disease caused by parasitic protozoa – (3) Malaria  Malaria is caused by sporozoa  Two types of hosts: Plasmodium species humans  There are four major species that cause malaria. The most widespread female Anopheles mosquitoes species is Plasmodium vivax and the  Sporozoa most serious is Plasmodium falciparum Reproduce asexually in human  Systemic sporozoan infection of blood (intermediate host) Reproduce sexually in the  Symptoms: Chills, fever, anaemia and liver enlargement mosquito (definitive host)  Transmission:  Mosquito carries the disease from one human to another (act as a "vector").  by the bite of a female Anopheles mosquito while taking a blood  P. falciparum cannot complete its life meal from human (injection of cycle at temperatures below 20 °C. sporozoites into the bloodstream)  by blood transfusion or blood- contaminated needles and syringes 53 Anopheles mosquito http://www.petsfoto.com/top-10-deadliest-insects/ Plasmodium species  Diagnosis of malaria depends on the examination of blood films.  Species identification is possible on the morphological characteristics of the plasmodia in the blood firm.  The percentage of erythrocytes which are parasitized is an index of the severity of the clinical disease.  Malaria Ring form of Plasmodium falciparum in red blood cell  Infected mosquito injects sporozoites to human  Gametocytes are picked up by a female Anopheles mosquito during a blood meal  Sporozoites migrate to liver  Sexual reproduction occurs in the mosquito  Sporozoans reproduce asexually in human cells (new sporozoites are formed). by schizogony producing merozoites  When the Anopheles mosquito takes a blood  Merozoites are released and invade RBC meal on another human, the sporozoites are  Merozoites become trophozoites in RBC injected with the mosquito's saliva and start another human infection if they parasitize the  Some merozoites become gametocytes liver cells. Copyright@2013 Wolters Kluwer Health| Lippincott Williams & Wilkins 55 For reference only If something is important enough, even if the odds are against you, you should still do it. Elon Musk Exercise 2