MIcrobiology Exam 2 - Parasitology and Mycology Flashcards
Parasite definition
an organism living in or on another and benefiting at the expense of the other (technically includes all flora found in and on us
- generally reserved for eukaryotic organisms
- includes broad range of animals
parasites examples
malaria giardiasis ascariasis toxocariasis head lice acanthamoeba
malaria - what it means, bug involved and what carries (transmits) it
“bad air”
blood parasites of the protozoan genus Plasmodium
Anopheles mosquito
what species infect humans with malaria?
4 of them: P. falciparum P. vivax P. ovale P. malariae *don't have to list these from memory, but should be able to recognize for exam
which malaria-infecting species is predominant in endemic regions?
P. falciparum
malaria epidemiology and transmission
epidemiology:
350-500 mill infections/yr w/ high rate of mortality (about 1 mill deaths annually, mostly young children)
transmitted by the Anopheles mosquito (vector)
geographic distribution correlates to vector (mostly tropical areas)
1st stage of malaria
human liver stage (exo-erythrocytic cycle, is OUTSIDE the blood)
sporozoites from mosquito infect liver cell -> mature into schizonts (many more progeny are made) ->schizont ruptures and releases merozoites -> they enter the next stage
2nd stage of malaria
human blood stage (erythrocytic cycle)
undergo asexual replication in erythrocytes and infect RBC’s -> immature trophozoite (ring stage) -> either goes back into schizont stage w/ rupture OR matures and -> becomes gametocytes
3rd stage of malaria
mosquito stages
gametocytes (male=micro, female=macro) ingested by Anopheles mosquito during a blood meal -> sporogonic cycle (parasites multiply) -> micros penetrate macros, generate a zygote -> zygotes become motile and elongated -> invade the midgut wall of mosquito and develop into oocysts -> oocysts grow, rupture, release sporozoites -> they go to mosquito’s salivary glands -> mosquito bites human
how many hosts does the parasite life cycle involve?
2 (human and mosquito)
malaria clinical findings
uncomplicated:
-fever, chills, sweats, headache, nausea, vomiting, myalgia, weakness
-can get involvement of spleen, kidneys, lungs, NS
severe (particularly P. falciparum):
-cerbral malaria, severe anemia, hemoglobinuria, pulmonary edema or ARDS, reduced platelets, cardio collapse and shock
-relapses seen w/ P. vivax or P. ovale (will get dormant pop.’s called “hypnozoites, which can then lead to a relapse)
dx and tx for malaria
dx: microscopy (look for schizonts in culture)
tx: variety of compounds
-> chloroquine and quinine (blocks heme detoxification)
• Resistance levels are high
– Vaccine development currently unsuccessful
giardiasis - what is it and where found
Protozoan flagellate Giardia intestinalis (the one that infects humans)
• Worldwide distribution, common in United States
giardiasis transmission
contaminated water, food or hands/fomites with infective cysts (trophozoites are also passed in stool but do not survive the environment)
giardiasis clinical findings
– Incubation 1 to 14 days
– Self limiting infection typically 1 to 3 weeks
– Diarrhea, abdominal pain, bloating, nausea, vomiting
• Can become chronic
dx and tx for giardiasis
Diagnosed by microscopy
• Cysts or trophozoites in feces
– Treated with metronidazole and tinidazole
toxocara - what is it and where found
Nematode Toxocara canis or T. cati
– Dog or cat roundworm
• Worldwide distribution
toxocara transmission
we get exposed to infected animal’s feces in environment, gets into us, but parasite gets “lost” in our body b/c not in its home
toxocara clinical findings
Many asymptomatic infections with +ve serology
– Visceral larval migrans (VLM)
• Mostly preschool children
• Larva invade liver, heart, lungs, brain, muscle
• Fever, anorexia, weight loss, cough, wheezing, rashes, hepatosplenomegaly, hypereosinophilia
• Death (rare) due to heart/lung/neurological involvement
– Ocular larval migrans
• Opthalmological lesions and damage to eye
• Risk of misdiagnosis as retinoblastoma
toxocara dx and tx
Diagnoses by history, symptoms and antibodies
– Treatment with albendazole (targets microtubules) and anti-inflammatories
ascariasis - what and where found
Nematode Ascarislumbricoides
• Worldwide distribution
– Most common helminthic infection
– Rural areas of southeastern United States
ascariasis transmission
feces, hand to mouth, poor personal hygiene
-can migrate viscerally to the lungs; you cough them up and then swallow them -> back down the intestinal tract (yuck).
ascariasis clinical findings
Usually no acute symptoms
– High body burden can cause abdominal pain due to obstruction
– Migrating adults can block biliary track or be expelled orally
– Can develop pulmonary symptoms during larval migration (Loeffler’s syndrome)
ascariasis dx and tx
– Diagnoses by microscopy of stool
– Effective drug treatment (ex. albendazole)
head lice - what and where
• Pediculosis
• Pediculus humanus capitis – a human ectoparasite
found everywhere?
lice transmission
Some transmission via fomites
lice clinical findings
Majority of infestation are asymptomatic
– Symptoms include “tickling feeling of something
moving in the hair”, itching (an allergic reaction to louse saliva), and irritability
• Secondary bacterial infection can be a complication
fungi types
Molds, yeast and fleshy fungi
• 150 species are pathogenic to humans
fungi structure
Similar to other eukaryotes
– Nuclei, mitochondria, 80S ribosome, etc.Thick cell walls comprised of glucans or chitin (know that)
– Unlike bacterial bacterial peptidoglycan
• Membranes contain ergosterol and zymosterol
– Unlike us (we have cholesterol)
fungi reproduction
Reproduce by asexual budding or sexual spores
• Play an important role in turnover of nutrients in the environment
yeast - what and reproduction
Unicellular fungi
– larger than most bacteria
• Reproduce primarily by budding
– fungi imperfecti
medically relevant species of fungi
– Exogenous - Cryptococcus neoformans,
Aspergillus
– Endogenous - Candida
candida - what
Normal flora of the oral cavity, gut, vagina
and occasionally the skin
– Candida albicans, C. glabrata, and others
• Yeast phase referred to as blastospores
– Single, oval buds - 5µm
• Can form elongated filaments
– pseudohyphae
candida control and defense
Generally, Candida exists as a normal
component of the oral flora BUT can become an opportunistic pathogen
• Kept in check by …
– Physical barriers, saliva, microbial competition
and phagocytosis
– sIgA can restrict surface adhesion
when candida goes bad, what can happen?
Vulvovaginal candidiasis (VVC)
– “yeast infection”
– Overgrowth in response to hormonal changes, pH change, change
in normal flora
– Itching/burning sensation
– Readily diagnosed with microscopy
• Invasive candidiasis
– Candidemia and disseminated infection
– *Neonates, surgical patients, immunosuppressed
– Fever and chills that are unresponsive to antibiotics
– *(systemic) involvement of kidney, liver, bone, muscle, joints, spleen or eyes
– *Death due to organ failure in 50% of untreated cases
– Diagnosed by microscopy
In the oral cavity you get a superficial
mycoses
• Oropharyngeal candidiasis (OPC)
– proliferation triggering inflammation
– ex. white pseudomembrane on buccal mucosa
• Pseudomembranous candidiasis
– Thrush
– No penetration of epithelium
– Easily wiped off revealing raw, inflamed tissue
underneath
factors predisposing to pseudomembranous candidiasis (thrush)
chronic local irritants ill-fitting appliances inadequate care of appliances disturbed oral ecology or marked changes in the oral microbial flora by antibiotics, corticosteroids, xerostomia dietary factors immunological and endocrine disorders (e.g. diabetes mellitus) malignant and chronic diseases (can be an indicator of a more severe systemic infection - want to find out the cause) severe blood dyscrasias radiation to the head and neck abnormal nutrition age (very young or very old) hospitalization oral epithelial dysplasia heavy smoking
agar used to culture candidiasis
Sabouraud agar
**this has been on boards
other types of candida and associated lesions
Oral mucosa – Erythematous candidiasis – Hyperplastic candidiasis (these 2 are a little different, he didn't know how) • Associated lesions – Denture stomatitis – Median rhomboid glossitis (one of many causes?) – Angular cheilitis
tx for candidiasis
• Polyenes – ex. Nystatin, Amphotericin B – Binds ergosterols in membrane causing leakage • Azoles – ex. Fluconazole, Miconazole – Inhibits ergosterol synthesis – **resistance high in C. glabrata** -> KNOW • Echinocandin B – Interferes with glucan synthesis (targets glucan of cell walls instead of sterols)
cryptococcosis - what, transmission, epidemiology
Cryptococcus neoformans
– Normal flora in birds (pigeons) -> NOT normal for us (is exogenous pathogen)
– Transmitted by inhalation
Epidemiology:
- High mortality (12% in US, 75-90% in Africa)
cryptococcosis symptoms
Symptoms similar to pneumonia
– Can lead to fungaemia, meningoencephalitis
cryptococcosis tx
Treated with fluconazole and amphotericin
aspergillosis - what
Aspergillusspp. (A. fumigatus, A. flavus, etc.)
– Found in soil, plants, decaying organic matter
aspergillosis types with symptoms
Allergic bronchopulmonary aspergillosis (ABPA)
– Wheezing/coughing
• Aspergilloma (fungus ball) in lung or other organs
• Invasive aspergillosis
– Fever, chest pain, cough, shortness of breath
– Dissemination throughout organs, including brain
– Treated with voriconazole (cytochrome target)
dermatophytes - what
Tinea or ringworm
• Caused by many species of fungi
– Trichophyton rubrum, T. tonsurans
– Microsporum canus
dermatophytes transmission
Spread by contact
dermatophytes types
Appears as infections on the skin, hair, or nails – Tinea barbae – beard – Tinea corporis – body – Tinea pedis – feet (athelete’s foot) – Tinea cruris – groin (jock itch) – Tinea capitis – scalp
dermatophytes clinical findings
Symptoms:
– Appear 4-14 days post-exposure
– Itchy, red, raised, scaly patches that may blister and ooze
– Sharply-defined edges, often redder than adjacent tissue, and may be “ring-like”
– Balding patches in hair
– Thick, discolored and perhaps crumbly nails
dx and tx
Diagnosed by KOH test, biopsy and culture
• Treated with topicals (miconazole, clotrimazole, etc.) or systemically (ketoconazole)
• Controlled with good hygiene
In what stage of malaria do you see clinical manifestations of the disease?
The blood stage
What are the 2 kinds of larva in toxocariasis?
Visceral larval migrans (affects liver, lungs, heart, brain, muscles) - death in rare cases
Ocular larval migrans (lesions/damage to eye, often misdiagnosed as retinoblastoma)
Most common helminthic infection
Ascariasis
What is albendazole effective at treating?
Infections due to “wormy” stuff; i.e. Toxocariasis and Ascariasis
Other oral types of candidiasis besides pseudomembranous
“Eh” (b/c Jardine didn’t know much about)
Erythmatous candidiasis
Hyperplastic candidiasis
In what yeast is resistance to azoles (drugs) high?
C. glabrata
