Lecture 2.3 - Eukaryotic Microbes PDF

Lecture 3 Eukaryotic Micro-organism (Mycology and Protozoa) Lecture 3 1 Mycology 2  Characteristics of fungi Aspergillus fumigatus Causes aspergillosis (farmer’s...

Lecture 3 Eukaryotic Micro-organism (Mycology and Protozoa) Lecture 3 1 Mycology 2  Characteristics of fungi Aspergillus fumigatus Causes aspergillosis (farmer’s lung) Can be microscopic organisms Eukaryotes Possess a nucleus Have several chromosomes Trichophyton rubrum Members of this genus cause athlete’s Diverse morphology foot Saccharomyces cerevisiae Lecture 3 3  Characteristics of fungi Fungi come in many shapes and structures Probably the fungi which are most important medically are either yeasts or filamentous fungi Some are harmful – e.g., produce contaminants Others can be beneficial – e.g., source of antibiotics Lecture 3 4  Characteristics of fungi Fungi possess a cell wall Wall is made of polysaccharides Mainly β-glucan with mannan and β-glucan chitin Chitin Lecture 3 5  Fungal growth Most medically important fungi have optimal growth temperatures of around 20ºC to 25ºC Therefore, they tend to exist outside the body However, some other mammalian species have fungi in their digestive tract (e.g., cattle, sheep, horses) Lecture 3 6  Fungal growth Filamentous fungi use complex reproductive strategies Often involves spore formation Often involves both sexual and asexual reproduction Lecture 3 7  Yeast Unicellular spherical fungi Typical diameter around 10 µm Facultative anaerobes Sexual and asexual examples Lecture 3 8  Yeast Asexual examples Some undergo binary fission Some use budding Lecture 3 9  Yeast Saccharomyces cerevisiae Candida albicans Used in bread making and Found in the intestinal tract, mouth brewing and vagina Lecture 3 10  Filamentous Fungi Typically have a “hairy” appearance Due to the hyphal growth of filamentous structures Lecture 3 11  Filamentous Fungi Hyphae can grow to several cm in length This results in an elaborative and extensive branched formation Produces a complex mass – the mycelium Lecture 3 12  Fungal infections Generic term is mycosis but can be split into 3 groups Superficial (cutaneous) Subcutaneous Systemic Lecture 3 13  Fungal infections Superficial (cutaneous) infections Affect the surface layer of the skin, nails, or hair e.g., candidiasis e.g., tinea (ringworm) Lecture 3 14  Fungal infections Subcutaneous infections Beneath or within structures Skin Nails Hair Lecture 3 15  Fungal infections Systemic infections Causes infections within the body Aspergillosis (farmer’s lung) Lecture 3 16  Antifungal Agents Generally fungal infections are unlikely to be fatal They can be highly unpleasant Possibly fatal in people who are immunocompromised Therefore, we need treatments for them Lecture 3 17  Antifungal Agents Fungi are eukaryotes Compounds which are specifically antibacterial are unlikely to be effective against fungi However generic anti-eukaryotic compounds may affect the patient Lecture 3 18  Antifungal Agents Although fungi and mammals are both eukaryotes there are differences Consider the fungal cell wall The membrane composition is different from that of mammals Lecture 3 19  Antifungal Agents Cholesterol is found in mammalian cells Cholesterol Ergosterol is a derivative of cholesterol and is found in fungi (and many protozoa) Fungi need it to survive and have it at high concentrations Ergosterol Thus, an agent attacking ergosterol will affect fungi but not mammalians Lecture 3 20  Antifungal Agents Shared reactions so not good points to target for blocking Ergosterol- specific reactions so good points to target for blocking Lecture 3 21  Antifungal Agents Fungal cells have two different cellular features which could be used to identify antifungals Cell wall Cell membrane Lecture 3 22 Protozoa 23  Protozoa Unicellular organisms Found in aquatic environments NB this does not have to be water e.g., some protozoa are found in digestive tract of herbivores Four classes Amoebae Ciliates Entamoeba Balantidium coli Trichomonas Plasmodium vaginalis falciparum histolytica Flagellates Ciliate found in Flagellate which Sporozoan which Amoeba which contaminated causes causes malaria causes dysentry water trichomoniasis Sporozoa Lecture 3 24  Protozoa Replication by protozoa can be complicated Sexual and asexual replication used Cell division can be by different methods Fission, budding, schizogony Schizogony can be thought of as multiple fission – nucleus undergoes many divisions, and each is used to produce a new cell Lecture 3 25  Protozoa Most protozoa are non-virulent In some species they may be beneficial Many herbivores have ciliated protozoa in their digestive tracts These are not present in humans but have been described in some gorillas Lecture 3 26  Protozoa For species which are harmful there can be variation in the level of severity Route of infection / entry can affect severity Dose of initial infection can affect severity T. Vaginalis – sexual transmission T. brucei gambiense – animal vector (Tsetse fly) G. Intestinalis – oral (water, but can be faecal-oral) L. Panamensis – animal vector (Sand fly) Lecture 3 27  Protozoa Generally, the skin provides an effective barrier to many infections Oral ingestion and sexual transmission provide entry routes for organisms Cuts in the skin provide an entry route Insect bites are another way to penetrate the skin barrier Lecture 3 28  Protozoa Therefore, physical attachment to human tissue is necessary for infection – directly or indirectly Conditions arising are often chronic Can last several months, sometimes life-long Pose problems with complications from reinfections Lecture 3 29  Protozoal Infections Trichomoniasis In the UK protozoal infections are relatively rare One of more common is Trichomonas vaginalis Sexually transmitted infection Annually around 5,000 to 10,000 cases in UK Globally WHO estimate 160 million cases Trichomonas vaginalis annually Lecture 3 30  Protozoal Infections Trichomoniasis In females, infection is generally in the cervical area of the vagina or the urethra Symptoms vary but examples include: Vaginal spotting / bleeding Trichomonas Genital itching and/or sensation of burning vaginalis Increased frequency of urinating Pain while urinating / during sexual activity Vaginal discharge (white, grey, yellow, or green) which is often frothy Unpleasant “fishy” smell Lecture 3 31  Protozoal Infections Trichomoniasis Not all females actually show any symptoms Many males show no symptoms Trichomonas vaginalis (asymptomatic) Treatment often involves using metronidazole – a general inhibitor of DNA replication Metronidazole Lecture 3 32  Gastrointestinal (GI) Infections Cryptosporidiosis Another example of a protozoan causing infections in the UK is Cryptosporidium parvum Gastrointestinal infection Cryptosporidium Up to 5,000 cases annually in parvum UK Lecture 3 33  Gastrointestinal (GI) Infections Cryptosporidiosis Oral or faecal-oral infections Lecture 3 34  Gastrointestinal (GI) Infections Cryptosporidiosis Cryptosporidium parvum outbreak relatively recently http://www.bbc.co.uk/news/ uk-england-lancashire-338 16989 Lecture 3 35  Gastrointestinal (GI) Infections Cryptosporidiosis Cryptosporidium parvum can result in fairly severe diarrhoea for 2-7 days People also suffer from dehydration, nausea and vomiting as part of the symptoms Although it is unpleasant most people recover with little more needed than rehydration Lecture 3 36  Parasitology Giardiasis Giardia lamblia is another example of an intestinal protozoan Transmitted via contaminated food Giardia lamblia and water Attaches to the duodenal wall Watery diarrhoea and abdominal cramps Lecture 3 37  Parasitology Amebiasis Entamoeba histolytica is less common in this country Causes amoebic dysentery Entamoeba histolytica Most cases in the UK are in people who caught it whilst abroad Lecture 3 38  Parasitology Amebiasis Entamoeba histolytica can infect other primates Around 50 million people worldwide have been infected Entamoeba histolytica histolytica literally means “tissue destroyer” Lecture 3 39  Parasitology Amebiasis Entamoeba histolytica infects the lumen of the GI tract – generally the bowel Leads to ulceration of the mucosal tissue of the Entamoeba histolytica epithelial parts of the tract Severe cramps, colitis and bloody diarrhoea Lecture 3 40  Parasitology Amebiasis Entamoeba histolytica As with Trichomonas vaginalis, both amoebic dysentery Giardia lamblia (Entamoeba histolytica) and giardiasis (Giardia lamblia) can be treated with Metronidazole Trichomonas vaginalis Metronidazole Lecture 3 41  Blood and Tissue Infections Toxoplasmosis Toxoplasma gondii is the source of toxoplasmosis About 400 cases in the UK annually Can infect almost all warm-blooded animals Toxoplasma gondii Only cats are known to be sites for sexual reproduction of Toxoplasma gondii Lecture 3 42  Blood and Tissue Infections Toxoplasmosis Toxoplasma gondii is widespread across the globe with around 30- 50% of the population having been thought to be exposed at some time In addition to undercooked meat, direct handling of cat faecal material is a major source of infection Lecture 3 43  Blood and Tissue Infections Toxoplasmosis Most cases of exposure are benign Rare cases of parasitic invasion Invades tissues of lung, heart, CNS, eyes, etc. Causes cell destruction Can cause behavioural changes e.g., increased risk-taking Schizophrenia, suicide attempts, “road rage” linked to toxoplasmosis Lecture 3 44  Blood and Tissue Infections Toxoplasmosis Acute symptoms can include: Chills Fevers Lymphadenitis Fatigue Blindness Treatment includes drug therapy with: Pyrimethamine Sulfadiazine Folic acid Lecture 3 45  Parasitology Leishmaniasis Leishmania are a genus of intracellular parasites Leishmania sp. Transmitted by female sand flies which have been infected Sand fly Lecture 3 46  Parasitology Leishmaniasis Two forms of leishmaniasis exist Cutaneous Cutaneous example Visceral Form of the disease varies Geographical variation Strains / species of parasite Visceral example Lecture 3 47  Parasitology Leishmaniasis The visceral results in invasion of reticuloendothelial phagocytes This causes enlarging of the abdominal organs Treatment is normally with sodium stibogluconate – an antimonial compound Lecture 3 48  Parasitology Malaria Malaria is the condition which is the biggest protozoal problem Although not really a problem here Kills about 600,000 people per year Infects about 200 million per year Lecture 12 49  Parasitology Malaria Caused by the sporozoan Plasmodium This is a genus of protozoa with a number of species Causes malaria in a number of different vertebrate species Lecture 3 50  Parasitology Malaria This protozoal lifecycle is complex Uses an insect intermediate Anopheles This is the stage involving mosquito sexual reproduction Human stage is asexual Lecture 3 51  Parasitology Malaria In humans the infection takes Anopheles mosquito place after being bitten by the mosquito Hepatocytes (liver) Erythrocytes (blood) Lecture 3 52  Parasitology Malaria Symptoms of malaria include: Periodic fevers – every 48-72 hours Rupturing to release mature erythrocytic schizonts Chills Headaches Abdominal pains Nausea Vomiting Lecture 3 53  Parasitology Malaria Prevention: Since 2021 vaccine Antimalarials taken prophylactically Control of Anopheles mosquito / bite prevention Treatments: Antimalarials Symptomatically Quinine Lecture 3 54  Parasitology Doxycycline Malaria Treatments involve: e ve nt a P r tive doxycycline Atovaquone atovaquone/proguanil mefloquine (prophylactic) Mefloquine artemisinin Curati ve Artemisinin Lecture 3 55  Lecture 4 Virology and Viral Infection Lecture 3 56