exam V pathogens Flashcards
malassezia species: natural reservoir, transmission
commensal yeast on normal patients
transmitted endogenously or via contact w/ infected individual
malassezia species: ID
ID by KOH prep and stain: can see spaghetti and meatballs pattern
malassezia species: treatment
topical selenium sulfide, zinc pyrithioine, azoles
tinea versicolor: caused by, symptoms
caused by malassezia species
superficial skin only
asymptomatic, w/ hypo or hyperpigmented lesions
epidermophyton, microsporum, trichophyton: natural reservoir, transmission
on skin, transmitted by direct contact w/ human or desquamated skin, can also be endogenous
epidermophyton, microsporum, tricophyton: ID
KOH mount
shines yellow-green under wood’s light
tinea pedis: cause, symptoms, treatment
- caused by epidermophyton, microsporum, tricophyton
- more common in boys, mostly adolescents and adults
- wet environments are risk
- interdigital macerations
- treated w/ topical azole
tinea cruris, corporis, capitis: cause, symptoms, treatment
- caused by epidermophyton, microsporum, or trichophyton
- annular itchy, scaly patch w/ clear center
- treated w/ topical azole
onychomycosis: cause, symptoms, treatment
- caused by epidermophyton, microsporum, or tricophyton
- more common in men
- usually yellow-green discoloration w/ subungual debris
- need oral azole or terbinafine
madurella mycetomatis: reservoir, transmission, risks
- in soil, plants, considered tropical
- transmitted by trauma (splinter, thorn) into subcut
- risks to farmers, forest workers
madurella mycetomatis, chromoblastomycosis: pathogenesis
slow, chronic course: years w/ painless swelling, intermittent pus, granular exudate
lesions form nodules, macrophages form granulomas
madurella mycetomatis: ID
clinical presentation: ulcerated nodule, brawny edema, black grains
biopsy: KOH prep
madurella mycetomatis: treatment
itraconazole
chromoblastomycosis: reservoir, transmission
woody plants, rotten wood, soil
inoculation by trauma
chromoblastomycosis: ID, treatment
- ID by biopsy w/ cayenne pepper appearance
- treated w/ itraconazole
sporotrichosis: reservoir, transmission, risks
in soil, plant matter
enters through cuts, scrapes
risk/classic presentation is gardening
sporotrichosis: pathogenesis
nodule –> infection spreads along lymphatic tract
sporotrichosis: ID
- observation of dimorphic fungal forms at different temperatures (hyphae below 37, yeast above 37)
- cigar-shaped budding
sporotrichosis: treatment
itraconazole
histoplasmosis: natural reservoir, transmission, risks
- in bird, bat droppings, endemic to midwest
- inhaled
- risk to someone cleaning barn, spelunking
histoplasmosis: ID, treatment
ID: silver stain shows dimorphic forms, narrow-based budding yeast
treatment: amphotericin B or itraconazole
histoplasmosis: disease
Tb-like presentation, atypical pneumonia
coccidioides: reservoir, transmission, risks
- in soil in southwest US
- inhalation of arthroconidia
- risk to those who travel to southwest US
coccidioides: ID, treatment
- ID by Hx travel, serology
- itraconazole
coccidioides: disease
valley fever: acute self-limiting pneumonia
candida albicans: characteristics, reservoir, transmission, risks
- non-dimorphic, opportunistic pathogen
- normal flora, transmitted by breach of mucocutaneous barrier
- bloodstream infection after IV, implanted devices, HIV pts at risk
candida albicans: ID, treatment
- ID by KOH stain, culture
- treated w/ nystatin
oropharyngeal candidiasis: symptoms
- pseudomembrane: white plaque on buccal mucosa, palate, tongue
- atrophic form: erythema, no plaque
- cotton mouth
candida albicans infections in HIV patients
- esophageal candidiasis (painful swallowing, substernal chest pain) is HIV-defining
- candidemia (HIV and ICU patients)
pneumocystitis jirovecii: characteristics, reservoir, transmission, risks
- opportunistic, has dual life cycle between haploid and diploid
- reservoir is humans, transmitted by infected humans
- risk to HIV patients (life-threatening)
pneumocystis jirovecii: pathogenesis, treatment
- cell membrane does not have ergosterol –> resistant to standard fungal treatments
- treat w/ TMP-SMX
pneumocystis jirovecii: ID
- staining, visualization of cup shaped cyst
- ground glass opacity on CT scan
cryptococcus neoformans: treatment, ID
- treated w/ fluconazole and amphotericin B
- ID by antigen test
aspergillus: reservoir, transmission
- common mold
- transmitted by inhalation
aspergillus: pathogenesis
- invasive infection: not enough immune response causes aspergillosis (pneumonia, sinusitis by hyphae invading tissue)
- colonization: too much immune response leads to mast cell degranulation, eosinophilia
aspergillus: treatment
- ABPA needs glucocorticoid for allergy, itraconazole for fungus
- aspergillosus is treated w/ voriconazole, sometimes amphotericin B
aspergillus: ID
- CT scan of lungs, sinuses: ground glass infiltrates, fungus ball in lungs
- biopsy, culture, histology: hyphae w/ acute branching angle
mucormycosis: reservoir, transmission, risks
- ubiquitous
- transmitted by inhalation or trauma
- more of a risk to immunosuppressed, diabetics (like acidic environment/high glucose for growth)
mucormycosis: ID, treatment
- right angle branches and ribbon-like hyphae
- treated w/ surgical debridement
rhino-orbito-cerebral mucormycosis
- diabetics more at risk
- inoculation of sinuses
- progresses to surrounding areas, leads to black eschar in affected regions
cutaneous mucormycosis
- central dermal necrosis
- red/purple edematous cellulitis
- mold may be visible
pulmonary mucormycosis
- pneumonia w/ infarction, can disseminate to heart (chest pain, hemoptysis)
- less common in diabetics
entamoeba histolytica: reservoir, transmission, risks
- humans are only reservoir that excrete amoebic cysts
- fecal-oral transmission
- more likely in mexico, central america, areas w/ poor sanitation/sewage systems
entamoeba histolytica: pathogenesis
- cyst is ingested
- trophozoites are released in intestines in response to gastric acid
- invade colon, replicate
- encyst again
entamoeba histolytica: ID, treatment
- ID in stool sample: can see ingested RBCs within trophozoites
- treated w/ metronidazole
amebiasis
- caused by entamoeba histolytica
- can be asymptomatic or cause watery diarrhea
- gradual onset
- rare: toxic megacolon, liver abscess w/o jaundice
giardia lamblia: reservoir, transmission, risks
- found in many mammals, beavers
- transmitted by ingestion of cysts in contaminated water, fecal-oral
- risk to backpackers, kayakers, developing nations. most common 3rd world water infection
giardia lamblia: pathogenesis
- exists in environment as quadrinucleate cyst
- trophozoites are active
- trophozoites passed in stool, encyst
giardia lamblia: ID, treatment
- stool exam to visualize falling leaf motility of trophozoites, iodine prep for cysts
- stool antigen test
- treated w/ metronidazole
acute vs chronic giardiasis
- symptoms are the same: greasy floating stool, flatulence, malabsorption, lactose intolerance
- chronic lasts more than a month, acute lasts less than a month
cytosporum parvum: reservoir, transmissiion, risks
- in most mammals, especially cows
- transmitted by ingestion of oocysts
- risk in poorly treated water, childcare, camps, most common parasite in poorly treated water
cytosporum parvum: ID, treatment
- acid-fast stain: light pink round cysts in stool
- can use ELISA and IF for antigen detection
- treat w/ fluid and salt replacement
trichomoniasis vaginalis: reservoir, transmission
- infected humans
- spread sexually
trichomoniasis vaginalis: ID, treatment
- genital exam, wet mount of motile organism. can do antigen test
- treat w/ metronidazole
trichomoniasis: symptoms
- mild to severe vaginitis
- yellow-green discharge w/ bubbles
- shift in flora towards anaerobes
- strawberry cervix
malaria: reservoir, transmission
- in infected humans
- transmitted by mosquito vector
malaria: pathogenesis
infected RBCs release substances that stimulate TNFa and IL-1 release
malaria: ID, treatment, prevention
- blood smear
- thick smear lyses cells, so extracellular parasite is visible; thin smear maintains cells, can see intracellular parasite
- hematological changes: anemia, thrombocytopenia
- treat w/ chloroquine
- prevention w/ prophylaxis for travelers
malaria tertian
- symptoms every other day
- chills, fever, sweating, jaundice, headache, bone ache
toxoplasma gondii: reservoir, transmission, risks
- many animals. cats are definitive host
- transmitted orally, transplacentally
- immunocompromised and fetuses at greater risk
toxoplasma gondii: ID, treatment
- serology
- pyrimethamine w/ sulfadiazine or clindamycin
toxoplasmosis
prenatal: 70% seem fine initially, but later have late visual and mental issues (chorioretinitis)
adults: flu-like
immunocompromised: disseminated, cysts in visceral organs, eyes, CNS
leishmania: reservoir, transmission, risks
- in several mammals
- sand fly vector
- more common in south america, middle east
leishmania: pathogenesis
promastigote form replicates in sand fly gut
amastigote form is non-motile, replicates in macrophages
leishmania: ID, treatment
- stained biopsy sample from human host shows amastigotes. can use PCR, serology
- local treatment: pentavalent treatments intralesionally
- systemic treatment: miltefosine for new world species. pentavalent treatment or amphotericin
cutaneous leishmaniasis
- centrifugally growing
- papular, central crusting
- heal spontaneously, leaving scar
mucocutaneous leishmaniasis
- presents the same as cutaneous, but does not heal
- causes severe disfiguration
ascaris lumbricoides roundworm: reservoir, transmission
- in small intestine of host (children)
- transmission is fecal-oral
ascaris lumbricoides roundworm: ID, treatment
- ID by kato-katz smear egg detection
- treated w/ oral albendazole
ascariasis: phases
- chronic intestinal: usually asymptomatic, or has mild abdominal distension and pain
- migratory: IgE production, eosinophilia, nausea, vomiting, obstruction
necator americanus, ancylostoma duodenale hookworms: reservoir, transmission
- eggs in human stool survive in contaminated water, soil
- necator is found in americas, africa, southeast asia
- ancylostoma is found in africa, india, china
necator americanus, ancylostoma: ID, treatment
- ID by eggs in fresh stool, larvae in old stool
- treat w/ oral albendazole
enterobius vermicularis pinworm: reservoir, transmission, risks
- found in infected humans
- transmission is fecal-oral
- most common helminth infection in US
enterobius vermicularis: ID, treatment
- microscopy of sample obtained early in morning before defecation, by tape on perianal region
- treated w/ albendazole
strongyloides stercoralis: reservoir, transmission, risks
- in infected humans
- larvae from feces enter soil, develop into filariform larvae, which enter skin and replicate (autoinfection)
- tropical disease
strongyloides stercoralis: ID, treatment
- usually symptoms w/ eosinophilia, tropical exposure, larvae in stool
- treat w/ oral ivermectin
strongyloides stercoralis: symptoms
- abdominal pain like that of peptic ulcer, diarrhea, vomiting
- itching, red blotches on skin
- vermicious pneumonia when lungs are infiltrated
trichuris trichiura: reservoir, transmission, risks
- infected humans
- transmission is fecal-oral
- more likely in children in poverty
trichuris trichiura: ID, treatment
- microscopy to visualize tapered ends, terminal plugs of ova
- albendazole
trichuris trichiura: symptoms
- heavy infections cause abdominal pain, diarrhea
- can lead to IBD, colitis
trichinella spiralis: reservoir, transmission
- in striated muscle of carnivores, omnivores
- transmitted by eating undercooked meat
trichinella spiralis: pathogenesis
- 3rd stage larvae develop into adult worms in intestines
- female worms lay stage 1 larvae: initiates systemic infection by penetrating gut wall
- travels through lymph, blood
- enter striated muscle and encyst
trichinella spiralis: ID, treatment
- triad of periorbital edema, myalgia, eosinophilia
- elevated muscle enzymes
- definitive = cysts in striated muscle
- treat w/ albendazole and steroids
trichinella spiralis: infection phases
- enteral: watery diarrhea that can last for weeks
- systemic: weakness, myalgia, facial/periorbital edema, urticarial rash
