2. OBJECTIVES
Describe the gram stain morphology of Vibrio species.
Discuss the clinical significance of Vibrio cholerae.
List the selective media for the isolation of Vibrio species and
describe the different colony morphologies observed on the
media.
Discuss the mode of transmission of Vibrio cholerae.
Identify Vibrio cholerae based on biochemical reactions.
Explain the role of the vibrio toxin the pathogenesis of cholera
infections.
Differentiate the species of Vibrio species discussed in this
unit based on colony morphology on Thiosulfate Citrate Bile
Salts Sucrose (TCBS) and clinical symptoms of patient.
4. GENERAL CHARACTERISTICS
More than 30 recognized species
Approximately 12 species have been associated with human
disease
Persists in the environment:
Grows in saltwater, freshwater
Causes human disease because it can adapt to colonize intestinal tract
if ingested
7. GENERAL BIOCHEMICAL
CHARACTERISTICS
Most are:
Indole positive
Urea negative
Nitrate positive
Most are oxidase positive
Posses the vibriostatic compound O/129
8. MEDIA AND GROWTH
Media
Grow quite readily on various routine media
Use of Thiosulfate-Citrate-Bile Salts-sucrose agar (TCBS) has
enhanced recovery
Alkaline peptone water - enrichment broth
Conditions for growth
Facultative anaerobes
Cultures should be incubated at 35°C in air or CO 2
9. COLONY MORPHOLOGY
On TCBS agar:
Sucrose fermenters are yellow
V. cholera and V. alginolyticus
Non-sucrose fermenters are green
V. parahaemolyticus
On BAP and chocolate agar:
Most are iridescent with a greenish hue
11. EPIDEMIOLOGY
Mostly found in aquatic environments
Transmitted:
Fecal-oral route
Contact with contaminated water
Ingestion of contaminated shellfish or other seafood
12. VIRULENCE FACTORS
Production of Cholera toxin or choleragen
Provokes an accumulation of cyclic AMP in the cell
membrane which causes mucosal cells to
hypersecrete electrolytes and water into the lumen of
the GI tract which results in watery diarrhea and fluid
loss = rice -water stools
Such a rapid fluid and electrolyte loss leads to severe
dehydration, hypovolemic shock, metabolic acidosis
and death in just a matter of hours
13. CLINICAL SIGNIFICANCE
Etiologic agent of cholera
Cholera is mostly seen in Asia and South America
Causes both intestinal and extraintestinal infections
Infections are acquired by ingesting contaminated food or
water
Characteristic “rice-water” stools
14. EPIDEMIOLOGY
Contaminated water enters stomach
Bacterial cells adhere to gastric and intestinal
mucosal epithelial cells
Enterotoxin is produced
Increase in cyclic AMP - prevents the re-absorption of
Na+ ions and the excretion of sodium bicarbonate and
potassium
Causes water to leave the epithelial cells into
intestinal lumen causing "rice water" stools
It may lead to death in matter of hours
15. SPECIMEN MANAGEMENT
Stool specimens are preferred - must be transported in Cary -
Blair medium
Rectal swabs acceptable
16. MEDIA FOR ISOLATION
Will grow on BAP, Choc, and MAC (non -lactose fermenter on
MAC)
Alkaline peptone water broth for enrichment
Thiosulfate Citrate Bile Salts Sucrose (TCBS) - selective and
differential media (yellow or green colonies)
Yellow - ferment sucrose
Green - do not ferment sucrose
21. BIOCHEMICAL CHARACTERISTICS
String test
Principle:
Addition of 0.5% sodium deoxycholate causes most Vibrio spp. to lyse and
release DNA, which can be pulled up into a string with a inoculating loop
22. TREATMENT
Therapy - fluid and electrolyte replacement
Antimicrobial therapy will shorten the course of the disease
and may decrease bacterial excretion
Tetracycline is the drug of choice
30. CLINICAL SIGNIFICANCE
Acute gastroenteritis associated with the ingestion of raw
contaminated seafood, particularly oysters
Usually mild but can be fatal
Endemic in Japan; #1 cause of “summer diarrhea”
Usually self-limiting disease
Rare extraintestinal pathogen
35. CLINICAL SIGNIFICANCE
Second most pathogenic
Causes wound infections:
Wound infections – after exposure to marine animals or marine
environment
Wound infections may lead to septicemia
Primary septicemia – 24 hours after ingestion of raw oysters
40. OBJECTIVES
Discuss the clinical significance of Campylobacter and
Helicobacter pylori.
Summarize specimen collection and transport procedures for
Campylobacter and Helicobacter.
Select appropriate culture media and incubation conditions
for Campylobacter cultures.
Compare the methods for obtaining microaerobic conditions.
Describe the microscopic morphology of Campylobacter and
Helicobacter.
Differentiate species of Campylobacter based on biochemical
identification.
Explain the principle and procedure of the CLO test and breath
tests for the detection of Helicobacter.
44. SPECIMEN MANAGEMENT
Stool and rectal swabs - if specimen cannot be cultured within
4 hours of collection, place in Cary -Blair transport medium
Blood
45. GROWTH CONDITIONS
Optimal temperature for growth is 42 ̊C
Microaerophilic (5-10% oxygen)
Capnophilic (8-10% CO 2 )
Needs at least 48-72 hours for growth
46. MICROSCOPIC CHARACTERISTICS
Curved gram negative rods
Comma shapes, "S" shapes and gull wing
forms are seen
Organisms may occur in short or occasionally
long chains
Oxidase positive
Non-sporeforming
Cells have a single polar unsheathed flagellum
at one or both ends = “darting motility”
47. MEDIA FOR ISOLATION
Media
Campy BAP (most commonly used)
Butzler Medium
Skirrow medium
Campy-Thio for enrichment
Examine at 24, 48 and 72 hours
48. COLONY MORPHOLOGY
Colonies smooth
Convex
Translucent
May be flat and watery with irregular edges
They may be pinpoint to spreading over large areas of the
plate
51. BIOCHEMICAL CHARACTERISTICS
C. coli
Hippurate negative
Resistant to cephalothin
Susceptible to nalidixic acid
C. jejuni
Hippurate positive
Resistant to cephalothin
Susceptible to nalidxic acid
52. TREATMENT
Antimicrobic therapy is not recommended in most cases of
diarrhea
Supportive care and fluid replacement
When needed:
Erythromycin is the drug of choice
Systemic infections are treated with Gentamycin
54. CLINICAL SIGNIFICANCE
Found only on mucus-secreting epithelial cells of the stomach
Causative agent of active chronic gastritis (type B gastritis) =
Peptic ulcer disease
56. SPECIMENS
Stool cultures are not often done for detection of Helicobacter
pylori
Specimens/test of choice include:
Invasive (tissue biopsy)
CLO rapid urease test
Non-invasive
Urea breath test
Serological detection of IgG