Eukaryotic Microbial Diseases PDF

Eukaryotic Microorganisms and Related Infectious Diseases  Objectives For the exam be able to: Review the “Questions to think about” Match the species with the disease it causes Answer multiple choice questions relating to the diseases Study the information shown i...

Eukaryotic Microorganisms and Related Infectious Diseases  Objectives For the exam be able to: Review the “Questions to think about” Match the species with the disease it causes Answer multiple choice questions relating to the diseases Study the information shown in bold  Type of General Example microorgan Cell wall characteristics microorganisms ism Prokaryote If present, Escherichia coli, Unicellular consists of Staphylococcus Bacteria Live nearly peptidoglyca aureus, everywhere n Salmonella Prokaryote Consists of Methanogens, Unicellular pseudomurei extreme Archaea Live in extreme n thermophiles, environments extreme halophiles Eukaryotes Consists of Yeasts, molds Fungi Unicellular and chitin multicellular species Eukaryotes Absent Amoeba, Unicellular flagellates, Protozoa ciliates Eukaryotes Absent Flatworms, Multicellula Multicellular roundworms, r animal flukes, mites parasites Eukaryotes Consists of Red algae, green Unicellular and cellulose algae Algae multicellular species Not cellular Not cellular, Ebola virus, Only replicate in therefore influenza virus, Viruses a host cell absent measles virus,  Eukaryotic Microorganisms Mycology  Introduction to Mycology Mycology is the branch of microbiology that focuses on the study of fungi Most fungi are free-living and abundant in nature; only a few are members of the human microbiome Fungi are eukaryotic microorganisms Fungi can be either unicellular or multicellular  Introduction to Mycology Fungi have tough cell walls made of chitin The biosynthesis of chitin provides a target for antifungal agents Polyoxins and nikkomycins inhibit chitin synthesis Fungal plasma membranes contain ergosterol, which is a cholesterol analog not found in plant or animal cells Ergosterol provides a target for antifungal agents Imidazoles, triazoles, and Lamisil all inhibit ergosterol synthesis Questions to think about Which microorganisms are eukaryotes? What is mycology? What are the cell walls of fungi made of? What is unique about fungal plasma membranes? Why are these each good targets for antifungal agents?  Filamentous Fungi Filamentous fungi form branching tufts called mycelium As fungal hyphae expand, Fungal hyphae extend and its rigid chitinous cell wall form branches, generating a mycelium enables it to penetrate softer material, such as plant or animal tissue The mycelium may grow A Penicillium mycelium on large enough to be seen as agar a fuzzy colony  Filamentous Fungi Filamentous fungi can expand at great length, but eventually they run out of nutrients Begin to produce spores that are easily airborne and disseminate into the environment Fungal spores can also Conidiophores spread disease and cause (branched hyphae) producing conidia allergies (spores) Most fungi do not need to Life Cycle of Filamentous Fungi The expanding hyphae produce spores. Under certain environmental conditions, the spores can germinate, develop, and ultimately become hyphal cells. Hyphae will continue to grow, elongate, and branch and the cycle will repeat. Questions to think about Describe the structure of filamentous fungi. How do filamentous fungi disseminate into the environment? What component of filamentous fungi is responsible for infecting humans?  Single-Celled Fungi Unicellular fungi are called yeasts Yeasts grow rapidly and disperse easily in aqueous environments Most yeasts reproduce by mitosis, specifically through the asymmetric division process known as budding  Dimorphic Fungi Some species of fungi are dimorphic. They can exist in a mycelial or yeast form depending on the growth environment Soil, decaying vegetation, or in host tissues Cellular morphologies of dimorphic human fungal pathogens. In general, these fungi grow in a multicellular hyphal form at 25°C and switch to producing unicellular yeast forms at 37°C.  Pathogenic Fungi Nearly all fungal infections originate from an exogenous source either by inhalation or traumatic implantation of fungal spores The exception is infection caused by opportunistic fungal microbiota Questions to think about What are unicellular fungi called? What does it mean if a species of fungus is dimorphic? Which form of the fungus grows at room temperature? Which form of the fungus grows at body temperature?  Dermatophytes Dermatophytes are a closely- related group of fungi (about 40 species) which use keratin as a nutrient source through the production of an enzyme, keratinase Dermatophytes cause cutaneous fungal infections collectively called “ringworm”  Dermatophytes The fungi that cause ringworm can live on skin and in the environment Ringworm is spread: Through contact with a person or animal who has a dermatophyte infection From the environment. The fungi can live on surfaces, particularly in damp areas like locker rooms and public showers. Treatment of dermatophyte infections generally involves topical antifungal agents  Dermatophytes Ringworm can occur on the scalp (tinea capitis), feet (tinea pedis, athlete’s foot), hands (tinea manus), nails (tinea unguium), groin (tinea cruris, jock itch) and body (tinea corporis) Histoplasma capsulatum Dimorphic fungus Causes histoplasmosis Also known as Darling’s disease, cave disease, and spelunker’s disease Histoplasmosis is acquired from inhaling fungal spores  Histoplasma capsulatum H. capsulatum grows in soil with high nitrogen content, especially in areas containing bird and bat excretions The fungi can be found in various bird or bat habitats (e.g., chicken coops, attics, barns, caves, roosting areas such as city parks and schoolyards)  Histoplasma capsulatum Once inhaled, the fungal spores convert into the yeast form, which can replicate within An the lungs estimated 500,000 people in the U.S. are exposed each year Most cases are asymptomatic, but in few cases (5%) acute pneumonia develops and less often is followed by progressive disseminated disease This level of disease occurs in debilitated and/or immunosuppressed individuals Histoplasma capsulatum Cryptococcus neoformans Monomorphic encapsulated yeast Causes cryptococcosis Cryptococcosis is acquired from inhaling the fungus  Cryptococcus neoformans The fungus is generally found in soil, on decaying wood, and in bird (pigeon) droppings Once inhaled, C. neoformans may infect the lungs causing a pneumonia-like illness Cough, shortness of breath, chest pain, and fever The organism has a high tendency for systemic spread to the brain and meninges Leading cause of fungal meningitis Headache, fever, neck pain, nausea and vomiting  Cryptococcus neoformans This disease is seen worldwide, but infections are extremely rare among people who have healthy immune systems; however, C. neoformans is a major cause of illness in people living with HIV/AIDS, with an estimated 1 million cases of cryptococcal meningitis occurring worldwide each year.  Candida species Yeast Many species are members of the human microbiome Found in the human oral cavity, vagina, Cangastrointestinal tract, lead and rectum to an opportunistic infections called candidiasis  Candida species Within the human, Candida species’ growth is limited by competition with other microbiota and the immune system. Disease results when the fungus overgrows and HIV/AIDS stressoffsets the balance. Risk factors diabetes cancer treatments include: nutrient steroids deficiency antibiotic usage wearing wet (eliminates bacterial clothing for microbiota) extended periods  Candida species Candidiasis that develops in the mouth or throat is called "thrush" or oropharyngeal candidiasis Characterized by white patches or plaques on the tongue and other oral mucous membranes, redness, and difficulty swallowing Thrush is uncommon in adults who are healthy and occurs most frequently in babies less than one month old, the elderly, and groups of people with weakened immune systems  Candida species Candidiasis that occurs on the genitals is sometimes called a “yeast infection”, and it happens when there is overgrowth of the normal fungal microbiota In women it is referred to as vulvovaginal candidiasis Nearly 75% of all adult women have had at least one yeast infection in their lifetime Symptoms include genital itching, burning, and vaginal discharge Men with genital candidiasis may experience an itchy external rash  Candida species If Candida species get into the bloodstream (candidemia), it can affect the blood, heart, brain, eyes, bones, or other parts of the body In the United States, candidemia is one of the most common causes of bloodstream infections in hospitalized patients People who develop invasive candidiasis are often already sick from other medical conditions, so it can be difficult to know which symptoms are related to a Candida infection. The most common symptoms are fever and chills that don’t improve after antibiotic treatment for suspected bacterial infections Parasitology  Introduction to Parasitology Parasitology is the branch of microbiology that focuses on the study of protozoa and parasitic worms Protozoa and parasitic worms have complex life cycles Protozoa are unicellular eukaryotic microorganisms Parasitic worms can be unicellular or multicellular (depending on the stage of development), and are not always microscopic  Introduction to Parasitology Infections originate from an exogenous source through either: Ingestion Giardia lamblia, Taenia species An arthropod bite Trypanosoma brucei, Trypansosoma cruzi, Plasmodium falciparum Transplacental transmission Toxoplasma gondii Direct penetration by the organism Acanthamoeba  Protozoa Trophozoite stage Form of the protozoa that actively feeds and multiplies Cyst stage Form of the protozoa that contains a protective membrane or thickened wall Allows the organism to survive outside of the host Questions to think about What is parasitology? What are protozoa? What are the two general stages of protozoan development? Describe each stage.  Acanthamoeba species Acanthamoeba species are amoebas (a type of protozoa) Generally found in fresh water, tap water, hot tubs and soil  Acanthamoeba species Can cause keratitis Inflammation of the cornea Infection is usually associated with contaminated contact lenses Infection begins with mild inflammation but soon progresses to severe pain Extensive damage caused by the amoebas may require a corneal transplant or  Trypanosoma brucei Trypanosoma species are flagellated protozoa T. brucei causes African trypanosomiasis also known as “African sleeping sickness”  Trypanosoma brucei Transmitted to humans by the Tsetsefly tsetse flies inhabit stream vegetation, which is also commonly populated by humans T. brucei infects and deteriorates Leads the CNS to changes of behavior, confusion, sensory disturbances, poor coordination and sleep disturbances Without treatment, sleeping sickness is fatal  Trypanosoma cruzi T. cruzi causes American trypanosomiasis also known as Chagas disease Disease occurs in Central and South America 18 million are infected; 50,000 people die each year Population migration has introduced the Because disease intoofthe U.S. this, blood banks now screen for T. cruzi  Trypanosoma cruzi T. cruzi is spread by the reduviid bug or “kissing bug” Bites people near the lips. While the bug feeds, it defecates (contains the protozoa). Scratching Lives in thethe bite introduces thatched roofs of huts (near the protozoa into the wound humans) Initial symptoms: fever and swollen glands 20-30% of people develop chronic form of the disease (can last up to 20  Toxoplasma gondii Protozoa Causes toxoplasmosis Cats are a significant carrier Infection in healthy people is mild The primary danger is congenital infection Mothers infected for the first time while pregnant may result in stillbirth or a child born with brain damage/visual problems  Toxoplasma gondii Transmission generally occurs when food or water is contaminated with feces containing the protozoa Cleaning a cat litter box can also lead to exposure  Plasmodium falciparum Causes malaria Spread by the Anopheles mosquito Malaria affects over 200 million people worldwide and causes 600,000 deaths each year Endemic  Plasmodium falciparum Mosquito bite introduces the protozoa into the host’s blood stream, which infects and lyses host red blood cells Symptoms Causes anemia are chills, fever, vomiting, Lysed RBCs block headache Symptoms blood vessels, leading appear in intervals of 2-3 days, to tissue death alternating with asymptomatic periods  Giardia lamblia Causes giardiasis A prolonged diarrheal disease associated with nausea, weakness, and weight loss Can persist for weeks Outbreaks occur most often during camping and swimming seasons Infection occurs from drinking untreated contaminated water Water supplies are often tested for Giardia. If found, the water must be  Giardia lamblia Once in the animal host, the cyst converts to the flagellated trophozoite and firmly attaches to the intestinal wall  Parasitic Worms (Helminths) Helminths are multicellular animals that possess fully differentiated organs Helminths include 3 categories: Nematodes (roundworms) – cylindrical Trematodes (flukes) – oval-shaped Cestodes (tapeworms) – flatworms trematode nematode cestode Parasitic Worms (Helminths) Helminths have three main life-cycle stages: eggs, larvae, and adults Eggs are released into the environment Larval stages may be free-living or parasitize a host Adult worms infect a final host Questions to think about What are the 3 categories of parasitic worms (helminths)? What are the 3 life-cycle stages of helminths?  Taenia species Taenia species are also called Tapeworms “tapeworms” are composed of a head and successive segments The head has a special sucking device called a “scolex” Each segment contains both male and female reproductive organs and are full of eggs (that look like sesame seeds) that pass  Taenia species Human transmission generally occurs when uncooked meat containing the larvae is ingested From pork, beef, or fish A tapeworm may grow for many years inside the digestive tract of its host without notice May grow to be 2-15 meters long Some of the offspring may migrate to the muscle, brain, or liver and form cysts Taenia species