Micro: Diarrheal Dzs in AIDS Flashcards
What is the initial evaluation of diarrhea?
routine stool studies: salmonella, shigella, campy
toxin assay/PCR: c. dificile
ova and parasite exam: giardia
What are the basics of cryptosporidium parvum?
intracellular protozoan parasite
infective stage is thick walled *round oocyst
can complete life cycle w/i single host
*acid fast positive
outer shell allows survival outside body and resistance to chlorine disinfectant
What are the four clinical categories of AIDS related cryptosporidiosis?
cholera like illness requiring IV rehydration
chronic diarrheal illness
intermittent diarrheal illness
transient diarrheal illness
What are important epidemiological features of cryptosporidium?
*water-borne, fecal-oral transmission
reservoir is humans, cattle, domestic animals
What are the key clinical features of cryptosporidium?
profuse and watery diarrhea, cramping
lasts 1-2 wks in immunocompetent, more prolonged and variable course in AIDS
NO dissemination
need CD4 and IFN-gamma to control
What is the pathogenesis of cryptosporidium?
ocysts go to SI and rupture, releasing 4 sporozoites - carry out life cycle in microvilli of SI –> atrophy, blunting, or *loss of villi
as few as 10 oocysts can cause inf
How is cryptosporidiosis diagnosed?
acid fast stain reveals *cryptosporidia oocysts
DFA, PCR, immunoassay can also be used
What is the general treatment for cryptosporidiosis?
fluid and electrolyte replacement
immunocompetent is self-limited
HAART
What is the microbiology of cyclospora?
single cell protozoan = “large cryptosporidium”, intracellular
*acid fast positive
What features of cyclospora diarrhea can increase suspicion for this agent?
hx of travel, hx of berry consumption, community outbreak
What is the epidemiology of cyclospora?
fecal-oral transmission
infected shed unsporulated cyst - not infectious until sporulated after days-wks in warm temps
person to person spread unlikely
What is the basic pathogenesis of cyclospora?
invade jejunal epithelium and produce enteritis
require maturation outside of host
no evidence of long term immunity
What is cyclosporiosis diagnosed?
wrinkled spheres on wet mount of stool sample, variable acid fast staining
under UV light, oocysts green/blue against black background
PCR
What is the general treatment for cyclosporiosis?
TMP-SMX
What is the microbiology of Isospora?
large, *ellipsoid oocysts
at excretion, *one immature sporoblast
maturation after excretion - *one sporoblast divides into 2, produce cyst wall, eventually contain 4 sporozoites
What is the pathogenesis of Isospora?
fecal-oral transmission of oocysts
inf of epithelium of SI –> villous atrophy, crypt hypertrophy, inflammation, malabsorption
crampy non-bloody diarrhea and EOSINOPHILIA
How is Isosporiasis diagnosed?
wet mount or acid fast visualization of characteristic large elliptical oocysts
What is the general treatment for Isosporiasis?
TMP-SMX
What is the microbiology of microsporidia?
produce resistant spores
possess polar filament
obligate intracellular protozoan parasites, measure 1-4 micrometers
What are the clinical features of microsporidiosis?
multi system illness w diverse manifestations, watery diarrhea most common
enterocytozoon bieneusi: diarrhea, acalculous cholecystitis
encephalitozoon intestinalis: intestinal tract, occular, GU, respiratory
mainly in CD4 less than 50
How is microsporidiosis diagnosed?
LM of fecal samples for genus, PCR to diagnose species
fluorescence stains spore bright pink/red
What is the general treatment for microsporidiosis?
albendazole
HAART: CD4 greater than 100 associated w cessation of symptoms
What are the features of MAC inf associated w AIDS?
fever, weight loss, anorexia, night sweats
watery diarrhea common without leukocytes
small bowel biopsy shows macrophages filled w AF bacilli
tx: macrolide and ethambutol + HAART
What are the features of viruses as causes of diarrhea in AIDS?
CMV produces colitis = punctuate hemorrhages w ulcerations on colonoscopy
biopsy shows intranuclear inclusions
fever, small-volume occasionally bloody diarrhea WITH leukocytes
tx: ganciclovir or foscarnet
