03 - Microbes 9 through 13 (gram-negative bacilli)

Question 1

What are the antigens of Gram-negative bacilli?

Answer 1

Cell Wall Antigen O

Flagella Antigen H

Capsule Antigen K

Lipid A = Endotoxin

Question 2

What are the three Gram-negative bacilli that are curved?

Answer 2

Vibrio cholerae

Campylobacter jejuni

Helicobacter pylori

Question 3

Gram-negative bacilli that are curved with most pathogens in the antigenic groups O1 or O139?

Answer 3

Vibrio cholerae

Question 4

Vibrio cholerae is an etiologic agent of?

Answer 4

Cholera — enterocolitis syndrome (gastroenteritis)

Question 5

Transmission and epidemiology of Vibrio cholerae

Answer 5

Endemic to areas w/ poor sanitation e.g. tropical Asia (especially India), Africa, parts of S & C America — several hundred thousand cases annually

Usual transmission of epidemic cholera is through ingestion of contaminated water drinking, food preparation, bathing

Question 6

What is the pathogenesis of cholera?

Answer 6

organisms ingested in large numbers

Incubation period – few hours to five days

Non-invasive organisms localize in small intestine

Cholera toxin produced (enterotoxic exotoxin)

Question 7

What occurs when the Cholera toxin produced (enterotoxic exotoxin)?

Answer 7

stimulates hypersecretion of water and chloride

reverses ion transport in gut (alters intestinal permeability)

Causes massive diarrhea – “rice water stools” – up to 16 liters a day — severe dehyrdation

Question 8

What is the typical mortality of cholera?

Answer 8

up to 50% if untreated

Question 9

What is the treatment and control of cholera?

Answer 9

good hygiene / disinfect feces and vomitus contaminated items

oral replacement of fluid w/ electrolytes

IV of balanced multi-electrolytes

ABX - TETRACYCLINE and other broad spectrum (typically for severely compromised patients)

(No effective immunization)

Question 10

key takeaways for Tx of cholera?

Answer 10

ABX - TETRACYCLINE and other broad spectrum

No effective immunization

Question 11

Lab Dx of cholera?

Answer 11

special request for culture needed in US due to rarity and need for special media (alkaline and selective)

Question 12

If you have a microbe that requires a selective and alkaline media for culture which is it most likely?

Answer 12

cholera vibrio

Question 13

Which microbe is an etiologic agent of a gastroenteritis due to the ingestion of contaminated shellfish (especially oysters)— a common cause of GE in Asian coastal regions, lower freq in US

Answer 13

Vibrio parahemolyticus

Question 14

Which microbe is found in warm, coastal seawater and is an etiologic agent of infrequent, acute infection?

Answer 14

Vibrio vulnificus

Question 15

Acute gastroenteritis and septicemia due to ingestion of raw or undercooked seafood, particularly raw oysters (very high fatility rate about 50%)

Severe cellulitis due to seawater contaminating a break in the skin – causes severe skin / tissue infection with hemorrhagic bullae and necrotizing fasciitis (high fatality rate about 15%)

Answer 15

Vibrio vulnificus

Question 16

What are the normal etiologic agents of virbrio vulnificus?

Answer 16

Acute gastroenteritis and septicemia due to ingestion of raw or undercooked seafood, particularly raw oysters (very high fatility rate about 50%)

Severe cellulitis due to seawater contaminating a break in the skin – causes severe skin / tissue infection with hemorrhagic bullae and necrotizing fasciitis (high fatality rate about 15%)

Question 17

What is the only microbe that has “s” or gull wing shapes as a description of the gram stain?

Answer 17

Campylobacter jejuni

Question 18

Describe the gramstain of Campylobacter jejuni:

Answer 18

Gram-negative bacillus, thin curved rods, occassionally has “s” or gull wing shapes

Question 19

What is the typical transmission and epidemiology of Campylobacter jejuni? incubation period?

Answer 19

ingestion of fecal contaminated food, especially undercooked CHICKEN or contamination of other foods from uncooked chicken, raw milk (from cattle feces), and non-chlorinated water

Incubation period: 2-5 days, symptoms resolve in 3-6 days

Question 20

pathogenicity of Campylobacter jejuni makes it #1 or 2 in N. America (similar to salmonella)…. what are some signs and symptoms?

Answer 20

Ulceration of intestinal mucosal epithelium causing diarrhea (infrequently bloody stools), abdominal pain, nausea, vomiting, (infrequent fever)

Question 21

What are the virulence factors of Campylobacter jejuni?

Answer 21

Grows in human bile
Flagella promote chemotaxis to colonize the intestine
Adhesive molecules promote attachment
Production of Cytolethal Distending Toxin (CDT) - AB-type toxin that has DNase activity (directly damages DNA)

SOME ARE ABX RESISTANT

Question 22

Treatment and control of Campylobacter jejuni?

Answer 22

Generally no ABX, only rehydration and electrolyte replacement

Question 23

Lab Dx of Campylobacter jejuni:

Answer 23

Selective culture media w/ ABX

Microaerophile

Incubation of primary isolation media at 42 deg C permits differentiation from species who can grow only at 37 deg C

Question 24

What is the gram stain of Helicobacter pylori?

Answer 24

Curved gram-negative bacillus

Question 25

Helicobacter pylori is an etiologic agent of what?

Answer 25

peptic ulcers – causes chronic inflammatory lesions of the gastric mucus layer

Question 26

Diagnostic testing for Helicobacter pylori?

Answer 26

Breath test to detect UREASE production (only UREASE mentioned in list)

Endoscopy and biopsy – microaerophilic environment & special growth media; DNA probe

Question 27

What is the only microaerophilic microbe?

Answer 27

Campylobacter jejuni… BUT H. pylori ALSO requires amicroaerphilic environment for growth on special media

Question 28

UREASE breath test +

Answer 28

Helicobacter pylori