Micro: Diarrheal Dzs in AIDS

Question 1

What is the initial evaluation of diarrhea?

Answer 1

routine stool studies: salmonella, shigella, campy
toxin assay/PCR: c. dificile
ova and parasite exam: giardia

Question 2

What are the basics of cryptosporidium parvum?

Answer 2

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

Question 3

What are the four clinical categories of AIDS related cryptosporidiosis?

Answer 3

cholera like illness requiring IV rehydration
chronic diarrheal illness
intermittent diarrheal illness
transient diarrheal illness

Question 4

What are important epidemiological features of cryptosporidium?

Answer 4

*water-borne, fecal-oral transmission

reservoir is humans, cattle, domestic animals

Question 5

What are the key clinical features of cryptosporidium?

Answer 5

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

Question 6

What is the pathogenesis of cryptosporidium?

Answer 6

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

Question 7

How is cryptosporidiosis diagnosed?

Answer 7

acid fast stain reveals *cryptosporidia oocysts

DFA, PCR, immunoassay can also be used

Question 8

What is the general treatment for cryptosporidiosis?

Answer 8

fluid and electrolyte replacement
immunocompetent is self-limited
HAART

Question 9

What is the microbiology of cyclospora?

Answer 9

single cell protozoan = “large cryptosporidium”, intracellular
*acid fast positive

Question 10

What features of cyclospora diarrhea can increase suspicion for this agent?

Answer 10

hx of travel, hx of berry consumption, community outbreak

Question 11

What is the epidemiology of cyclospora?

Answer 11

fecal-oral transmission
infected shed unsporulated cyst - not infectious until sporulated after days-wks in warm temps
person to person spread unlikely

Question 12

What is the basic pathogenesis of cyclospora?

Answer 12

invade jejunal epithelium and produce enteritis
require maturation outside of host
no evidence of long term immunity

Question 13

What is cyclosporiosis diagnosed?

Answer 13

wrinkled spheres on wet mount of stool sample, variable acid fast staining
under UV light, oocysts green/blue against black background
PCR

Question 14

What is the general treatment for cyclosporiosis?

Answer 14

TMP-SMX

Question 15

What is the microbiology of Isospora?

Answer 15

large, *ellipsoid oocysts
at excretion, *one immature sporoblast
maturation after excretion - *one sporoblast divides into 2, produce cyst wall, eventually contain 4 sporozoites

Question 16

What is the pathogenesis of Isospora?

Answer 16

fecal-oral transmission of oocysts
inf of epithelium of SI –> villous atrophy, crypt hypertrophy, inflammation, malabsorption
crampy non-bloody diarrhea and EOSINOPHILIA

Question 17

How is Isosporiasis diagnosed?

Answer 17

wet mount or acid fast visualization of characteristic large elliptical oocysts

Question 18

What is the general treatment for Isosporiasis?

Answer 18

TMP-SMX

Question 19

What is the microbiology of microsporidia?

Answer 19

produce resistant spores
possess polar filament
obligate intracellular protozoan parasites, measure 1-4 micrometers

Question 20

What are the clinical features of microsporidiosis?

Answer 20

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

Question 21

How is microsporidiosis diagnosed?

Answer 21

LM of fecal samples for genus, PCR to diagnose species

fluorescence stains spore bright pink/red

Question 22

What is the general treatment for microsporidiosis?

Answer 22

albendazole

HAART: CD4 greater than 100 associated w cessation of symptoms

Question 23

What are the features of MAC inf associated w AIDS?

Answer 23

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

Question 24

What are the features of viruses as causes of diarrhea in AIDS?

Answer 24

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

Question 25

What are the features of non-infectious causes of diarrhea in AIDS pts?

Answer 25

HIV enteropathy from HIV itself

adverse effect of HAART