Chapter 25 : Vibrio, Aeromonas

Question 1

Describe the general features of vibrio and Aeromonas (common feature)

Answer 1

Oxidase positive
MacConkey positive
Glucose fermenting

Question 2

What is the microscopic appearance and general characteristics of Vibrionaceae and Aeromonas ?

Answer 2

Vibrionaceae: They appear to have curved rods (comma shaped gram-negative rods) with polar flagella, Motile, Halophilic, facultative anerobic and alkalinophilic

Aeromonas: Straight gram negative rods with rounded ends to coccobacillary facultative anerobes that occur singly or in pairs, Catalase positive

Question 3

What is the natural habitat and mode of transmission of theses species?

Answer 3

Vibrio: they are normally found in salt water and brackish and they are associated with pandemic outbreaks
Mode of transmission: they are usually transmitted by ingestion of contaminated water or seafood

Aeromonas: They are usually found in aquatic environments all over the world
Mode of transmission: Ingestion of contaminated water and sea food

Question 4

What are the serotypes of Vibrio cholerae? and also describe the disease associated with this species

Answer 4

Two serotypes of Vibrio cholera are:

• V.cholerae 01: this strain is the one responsible for the majority of outbreaks
• V.cholerae 0139: Strain is only found in Bangladesh

Vibrio Cholerae has the ability to survive in fresh water( it is a facultative halophile meaning it has the ability to survive in both fresh and salty water and mostly infects humans it causes a disease called CHOLERA with is a server gastroenteritis, cholera my be symptomatic or asymptomatic

Question 5

What are the Virulence factors of Vibrio cholerae?

Answer 5

• -Cholera toxin which causes mucosal cell hypersecretion of water
• -Motility and mucinase which allow them to facilitate entry in cells
• -

Question 6

Describe the pathogenicity of the cholera toxin

Question 7

What is the colonial appearance of Aeromonas?

Answer 7

Blood agar: Large, round, raised, opaque colonies and it is beta-hemolytic
MacConkey Agar: Both NLF and LF

Question 8

What is the colonial appearance of Vibrio Species?

Answer 8

Blood agar: Medium to large, smooth, opaque, iridescent with a greenish hue

Question 9

How is a culture performed for vibrio species?

Answer 9

ALL stool samples that are suspected to have vibrio species must be transported in a Cary-Blair transport medium so as to keep species viable
The stool after that will be platted to a TCBS( thiosulfate citrate bile salts sucrose) agar and this will detect whether they are sucrose fermenters or not
—Sucrose fermenter will have yellow colonies ( V.cholerae)
—Non sucrose fermenter will have green colonies (.parahaemolyticus and V.

NOTE that chromogenic agar support the growth of V.parahaemolyticus and other species colonies will be pale blue or violet

Question 10

What are the laboratory tests used for the diagnosis of Vibrio?

Answer 10

Macroscopic appearance of stool: Rice water appearance
Microscopic appearance: Comma-shaped gram negative bacteria with polar flagella which enables it to be motile
Selective media: Thiosulfate-Citrate Bile salts sucrose agar which will show yellow colonies
Oxidase Positive
String test positive
Have the ability to grow on Nutrient broth with and without NaCl supplementation( V.Parahemolytics and V.vulnificus cannot grow without NaCl) String test positive( test is used to differentiation of oxidase positive genera like the Vibrio and Aeromonas )
Serological testing to identify the strain

Question 11

What is the spectrum of Vibrio cholera and Aeromonas spp?

Answer 11

V.Cholera results in profuse watery diarrhea leading to diarrhea and death within 48 hours if left untreated

Aeromonas causes gastroenteritis, wound infections, bacteremia, endocarditis, pneumonia