Micro Enteric Bacteria 3

Question 1

vibrio cholerae bacteriology

Answer 1

curved, comma-shaped, gram - rod with polar flagellum;
aerobic, facultatively anaerobic;
dual lifecycles (planktonic in indian ocean and pathogenic in drinking water supply)

Question 2

what indicates v. cholerae pathogenicity?

Answer 2

o cell wall antigen

Question 3

what o cell wall antigens cause epidemic disease in v cholerae?

Answer 3

O1 and O139

Question 4

why are O1 and O139 pathogenic?

Answer 4

lysogenic bacteriophage - carries gene for primary choleragen enterotoxin (which is GI exotoxin)

Question 5

how is v cholerae transmitted?

Answer 5

fecal-oral shed by asymptomatic carriers in incubation;

travel to untreated water or undercooked shellfish

Question 6

who is most susceptible to v cholerae? why?

Answer 6

people on antacids or with gastrectomy because high infectious dose - usually killed by stomach acid

Question 7

how does v cholerae cause disease?

Answer 7

if survives past stomach acid - reach small intestine where it secretes MUCINASE to clear path to brush border and attaches using toxin coregulated pilus (TCP) and colonize - then secretes cholera toxin

Question 8

describe cholera toxin

Answer 8

choleragen: A-B subunit structure - “A” causes persistent activation of adenylate cyclase leading to loss of water adn ions from attached cell

Question 9

what disease is caused by v cholerae?

Answer 9

massive watery diarrhea - more than any other infectious gastroenteritis - death from dehydration and electrolyte imbalance

Question 10

what is seen on exam for v cholerae?

Answer 10

“rice water stool” - large volumes of watery diarrhea - no pain, blood or neutrophils in stool but acidosis and hypokalemia from loss of bicarb and K;
dehydration leads to cardiac and renal failure (skin dehydration test)

Question 11

v cholerae labs

Answer 11

isolated on media - salt-tolerant (because it’s from the ocean!), oxidase positive, ferments sucrose; darkfield microscopy of stool sample reveals motile vibrios

Question 12

v cholerae treatment

Answer 12

rehydrate and rebalance electrolytes - tetracycline if needed

Question 13

v parahaemolyticus bacteriology

Answer 13

gram - curved motile rod, oxidase +, saltwater-borne (warm ocean water), halophile

Question 14

v parahaemolyticus pathogenesis

Answer 14

enters humans through undercooked seafood –> secretes enterotoxin similar to choleragen –> causes diarrhea

Question 15

v parahaemolyticus on exam

Answer 15

nausea, vomiting, abdominal cramps, diarrhea, fever;

self limited

Question 16

what disease is commonly caused by v parahaemolyticus? v vulnificus?

Answer 16

para: gasteroenteritis; vulnificus: cellulitis

Question 17

v parahaemolyticus treatment

Answer 17

previously healthy: oral rehydration: self-limited

iron overload, pre-exsiting liver disease, immunosuppressed, high fever = doxycycline and IV rehydration

Question 18

v vulnificus bacteirology

Answer 18

gram - curved motile rod, oxidase positive, some encapsulated, salt water born = halophile

Question 19

v vulnificus pathogenesis

Answer 19

infects shellfish contaminated wounds –> causes cellulitis and rapidly-fatal septicemia when in immunocompromised

Question 20

what is produced by v vulnificus? (virulence factors)?

Answer 20

hemolysin, protease exotoxin, siderophores

Question 21

which bug has the highest fatality rate for foodborne disease?

Answer 21

v vulnificus (esp in those with history of chronic liver disease)

Question 22

v vulnificus treatment

Answer 22

1. surgical care: debride early and often
2. ceftazidime + doxycycline or antipsudomonal penicillin
3. admit/observe for sepsis, DIC, ARDS, renal failure

Question 23

campylobacter bacteriology

Answer 23

comma or s shaped gram - rod, oxidase and catalase positive, microaerophilic, grows well at 42C, reservoir in guts of domestic animals

Question 24

campylobacter pathogenesis

Answer 24

transmitted fecal-oral, sexual contact, sick pets with low infectious dose - colonizes both intestines (NOT just M cells!! - just epithelium) causing blood and pus in diarrhea (some have cholera like enterotoxin causing a watery diarrhea)

Question 25

what does c. jejuni strongly predispose patients to?

Answer 25

guillain-barre syndrome, reactive arthritis, HUS

Question 26

campylobacter exam

Answer 26

common in children and MSM, incubation in days-week, initially watery foul-smelling diarrhea that progresses to bloody stools with fever and abdominal pain - need to rule out bacteremia

Question 27

what does campylobacter bactermia lead to?

Answer 27

meningitis, vascular infection, abscess

Question 28

campylobacter lab

Answer 28

stool sample culture - blood agar with antibiotics to inhibit normal flora - dual temperatures (only grows on 42C), oxidase positive, gram -

Question 29

campylobacter treatment

Answer 29

rehydrate for simple gastroenteritis - treat if patient is pediactric, high fever, bloody, 8+ stools/day, worsening, more than a week, pregnant, HIV with azithromycin, or erythromycin in peds
DO NOT TREAT THE DIARRHEA!

Question 30

h pylori bacteriology

Answer 30

curved gram -, similar to campylobacter but strongly UREASE +

Question 31

what organism is also urease positive besides h pylori?

Answer 31

proteus causing UTIs (makes stones)

Question 32

what does h pylori cause?

Answer 32

gastritis, peptic ulcer, MALT lymphoma

Question 33

h pylori pathogenesis

Answer 33

transmission unknown - attach to mucus secreting cells of stomach - secrete urease virulence factor breaking down urea into ammonia which nenutralizes stomach pH allowing bacterial growth and irritating stomach lining - WBC infiltrates also and upregulates caspases (causing apoptosis in nearby cells)

Question 34

h pylori lab

Answer 34

“urea breath” test - patient ingests radiolabeled urea, if infected will exhale radiolabeled carbon dioxide; biopsy has bacteria visible on gram stain, antigen present in stool, IgG in serum

Question 35

h pylori treatment

Answer 35

normalize gastric pH with bismuth salts (pepto bismol), proton pump inhibitors to reduce pain and speed healing, kill bacteria with TRIPLE DRUG THERAPY