Enteric Bacteria 3

Question 1

v. cholerae bacteriology

Answer 1

curved, comma shaped gram negative oxidase positive. aerobic and facultatively anaerobic. 2 reservoirs: humans and plankton ecosystem of indian ocean. O cell wall antigen indicates pathogenicity: O1 and O139 are epidemic. Non-O1 cause sporadic or no disease, occasionally cause shellfish food poisoning

Question 2

v. cholerae pathogenesis

Answer 2

fecal-oral. shed by asymptomatic carriers in incubation or convalescence. travels to untreated water or undercooked shellfish. usually killed by stomach acid. survivors reach small intestine and sccrete mucinase to get into brush border, attach by toxin coregulated pilus, growing bacteria secrete cholera toxin

Question 3

where does the B subunit of cholerae bind?

Answer 3

B binds the ganglioside receptor GM1 on intestinal lining

Question 4

what does the A subunit of cholerae cause?

Answer 4

persistent activation of adenylate cyclase, leading to loss of water and ions. Massive watery diarrhea

Question 5

v. cholerae exam

Answer 5

mild cases don’t present. 5% proced to rice water stool. no pain, blood, or neutrophils in stool. some vomiting, no fever. acidosis and hypokalemia. dehydration.

Question 6

pediatric symptoms of cholerae

Answer 6

drowsy, coma. fever. hypoglycemic convulsions

Question 7

cholerae lab

Answer 7

isolate on buffered media. find oxidase positive, only slightly lactose fermenting. ferments sucrose. gives acid reaction on triple sugar iron agar. specific antisera will halt motility. darkfield microscopy of stool sample reveals motile vibrios

Question 8

cholerae treatment

Answer 8

rehydrate and rebalance electrolytes. can treat with short course of tetra, doxy cycline or furazolidone or ciprofloxacin after IV rehydration

Question 9

v. parahaemolyticus bacteriology

Answer 9

oxidase pos, gram neg curved rod. saltwater borne. halophile.

Question 10

v. parahaemolyticus pathogenesis

Answer 10

leading cause of gastroenteritis in those who eat undercooked seafood, mainly shellfish. secretes a hemolysin and an enterotoxin similar to choleragen.

Question 11

v. parahaemoltyticus exam

Answer 11

N/V, cramps, fever. usually self limited. predisposing factors: immunodeficiency, liver disease, iron overload, kidney disease

Question 12

v. parahaemolyticus lab

Answer 12

bloodwork for DIC, HBV, HCV, iron. culture in 8% NaCl. ideally culture from stool on thiosulfate-citrate-bile salts-sucrose media.

Question 13

v. parahaemolyticus treatment

Answer 13

in a previously healthy patient, will be self limited. oral rehydration needed. if complicating factors or high fever, doxycycline or quinolone, IV rehydration

Question 14

v. vulnificus bacteriology

Answer 14

oxidase + gram - curved motile rod. some encapsulated. saltwater borne. halophile.

Question 15

v. vulnificus pathogenesis

Answer 15

infects shellfish contaminated wounds. cellulitis progressing to necrotizing fasciitis in shellfish market workers. can also infect wounds exposed to seawater. causes septicemia in immunocompromised people. pre-existing liver disease predisposes to poor outcome

Question 16

what toxins does v. vulnificus make?

Answer 16

hemolysin and protease exotoxons. also makes siderophores, infection exacerbated by iron overload

Question 17

v. vulnificus exam

Answer 17

cellulitis with history of handling raw shellfish. foot injuries from stepping on seashells. severe pain -> numbness. things predisposing to complication: immunodeficiency, liver disease, iron overload, kidney disease

Question 18

v. vulnificus lab

Answer 18

bloodwork for DIC, HBV, HCV, iron. gram stain and culture from aspirate of wound site and adjacent blood. biopsy demonstrates gram negative bacilli, acute inflammation, tissue necrosis and fat infarction

Question 19

v. vulnificus treatment

Answer 19

surgical care at the wound site. ceftazidime + doxycycline or antipseudomonal penicillin. alts: cefotaxime or fluoroquinolones

Question 20

campylobacter bacteriology

Answer 20

comma or S shaped gram neg rods. motile. oxidase and catalase pos. microaerophilic. grows well at 42C. reservoir in guts of domestic animals. transmitted fecal-oral, sexual contact, sick pets.

Question 21

campylobacter pathogenesis

Answer 21

low infectious dose. both intestines are colonized and invaded. bloody diarrhea with pus, crypt abscesses and ulceration. some strains produce a choleralike enterotoxin -> watery diarrhea.

Question 22

c. jejuni pathogenesis

Answer 22

infection strongly predisposing for Guillain Barre syndrome. can alternatively rtrigger reactive arthritis. rarely causes hemolytic uremic syndrome

Question 23

campylobacter exam

Answer 23

common in kids. initially watery, foul smelling diarrhea. progresses to bloody stools with fever and ab pain. Sigmoidoscopy: focal mucosal edema, hyperemia, patchy petechiae, ulceration.

Question 24

campylobacter lab

Answer 24

stool sample culture: blood agar plates with antibiotics. 42C +25C (fails at low temp). 5% oxygen, 10% CO2. grows slow in culture, may have seagull appearance. microscopic exam of fecal smear for darting motility, leukocytes, erythrocytes. gram stain of fecal smear.

Question 25

campylobacter treatment

Answer 25

simple gastrotenteritis: self limited, rehydrate. antibiotics may be used if patient is a kid or has bad symptoms or for a long time. azithromycin in adults, erythromycin in kids and prego. do NOT use antimotility agents to treat the diarrhea

Question 26

h. pylori bacteriology

Answer 26

curved gram neg rods. strongly urease positive.

Question 27

h. pylori pathogenesis

Answer 27

transmission mode unknown. probably person-person within households. bacteria attach to mucus secreting cells of stomach with flagella virulence factor. break down urea -> ammonia with urease. ammonia neutralizes stomach pH, allowing bacterial growth. appears to upregulate caspases, leading to apoptosis in nearby cells

Question 28

h. pylori exam

Answer 28

obtain family history of gastric cancer. gastritis, peptic ulcer. recurrent pain, bleeding into GI. imaging studies can diagnose ulcers, cancer. EGD with biopsy visualizes damage to stomach lining and diagnoses cancer

Question 29

h. pylori treatment

Answer 29

reduce irritation with bismuth salts. Proton pump inhibitors may be used to relieve pain and help ulcers heal. kill bacteria with triple therapies.