GI pathogens

Question 1

most common causes of food-borne illness in US

Answer 1

Campylobacter spp. (bacterial)
Giardia lamblia (parasitic)
Noroviruses (viral)

Question 2

most frequent etiology of travelers diarrhea

Answer 2

E. coli

Question 3

inflammatory vs non inflammatory diarrhea

Answer 3

Inflammatory: mucous or blood in stool, PMNS and RBCs, local tissue destruction, fever, 2-4 day incubation period
Noninflammatory: watery stool, toxin mediated or caused by virus, no fever, 1-12 hour incubatin period

Question 4

Vibrio cholerae: what kind of bacteria? where? spread?unique features?

Answer 4

curved gram neg rod “comma shaped”, salt water (sea foods and contaminated water), causes epidemics and pandemics

Question 5

what type causes cholera epidemics?

Answer 5

serogroup O1, two biotypes (classic and El Tor). O139 is the most recent one in India

Question 6

pathogenesis of cholerae infection: load required, toxins/other things?

Answer 6

huge bacterial load required b/c most are killed by stomach acid. Uses pili (toxin co-regulated pili) to adhere to intestine. Toxin (CTX) is A-B and is encoded by a phage which is received by the TCP. A1 part of toxin ^ cAMP, activates CFTR channel, increasing Cl secretion and decreased Na uptake causing secretory diarrhea

Question 7

clinical disease of cholera

Answer 7

death by dehydration in 12 hours. mucus flecks in stool “rice water”. Usually no fever

Question 8

diagnosis and tx of cholera

Answer 8

culture on TCBS agar, oxidase positive. Give fluids and antibiotics (doxycyclin/ tetracyclin)

Question 9

ETEC: what is it? what does it cause? toxins?

Answer 9

gram neg bacilli. Enterotoxigenic E coli. Heat labile (LT: ^ cAMP leads to ^ CL secretion) and heat stable (ST: ^ cGMP leads to decreased resorption of NaCl) toxin

Question 10

staph aureus food poisoning: what causes sickness?

Answer 10

heat stable enterotoxin (ABCDE), picnic foods. Antibiotics are not useful (illness due to toxins)

Question 11

Rotavirus: significance? fever?

Answer 11

1 cause of fatal diarrhea in children (day-care, kindergarten, esp in winter). yes: exception to noninflammatory fever rule.

Question 12

Norovirus: what does it cause? how is it spread? where?

Answer 12

“stomach flu”. fecal oral from not washing hands. cruises and airplanes. Also an exception to noninflammatory fever rule.

Question 13

Giardia lambia

Answer 13

unicellar parasite. trophozoite and cyst (survives in environment) forms. fecal-oral. adheres to small intestine. gassy, fatty diarrhea

Question 14

cryptosporidium

Answer 14

unicellular parasite. fecal-oral (cysts in water). important in AIDS. acid-fast stool stain

Question 15

shigella spp.: what is it? spread?

Answer 15

fingers, food, flies, feces, fomites. Survives gastric acid. Transcytose M cells then live in enterocytes. Does not move to bloodstream. Hemolytic uremic syndrome

Question 16

campylobacter jejuni: shape, sickness, causes, complications

Answer 16

curved gram-neg rod “seagull”. Bloody diarrhea. Ingestion of contaminated poultry (more common than salmonella). Guillain-barre syndrome

Question 17

bloody diarrhea, no fever

Answer 17

enterohemorrhagic e coli (EHEC)

Question 18

tender abdomen with mass mimicing appendicitis

Answer 18

yersinia enterocolitica

Question 19

c. diff.: general?

Answer 19

gram+ rod, spore forming, antibiotic associate diarrhea. 2 toxins: a and b. Pseudomembranous colitis (PMC): toxic megacolon, perforation and death

Question 20

c diff treatment

Answer 20

oral metronidazole, oral vancomycin

Question 21

entamaoeba histolytica: disease? diagnosis

Answer 21

amebiasis: dysentery, liver abcess, flask-shaped ulcer in colon rupture. trophozoites or cysts.

Question 22

clostridium perfringens: toxin? mechanism?

Answer 22

alpha exotoxin. Phospholipase degrades phospholipid C of cell membranes. Leads to gas gangrene and hemolysis

Question 23

bacillus cereus

Answer 23

reheated rice syndrome.