prof . dr. ihsan edan alsaimary department of microbiology - college of medicine - university of basrah - basrah -IRAQ ihsanalsaimary@gmail.com 00964 7801410838

1. Vibrio,and related organisms
(Aeromonas & Plesiomonas)
lect. 8
Prof.Dr.Ihsan Edan Alsaimary

2.  Similarities to Enterobacteriaceae
 Gram-negative
 Facultative anaerobes
 Fermentative bacilli
 Differences from Enterobacteriaceae
 Polar flagella
 Oxidase positive
 Formerly classified together as Vibrionaceae
 Primarily found in water sources
 Cause gastrointestinal disease
 Shown not closely related by molecular methods
General Characteristics of Vibrio,
Aeromonas and Plesiomonas

3.  Comma-shaped (vibrioid) bacilli
 V. cholerae, V. parahaemolyticus, V. vulnificus are most
significant human pathogens
 Broad temperature & pH range for growth on media
 18-37C
 pH 7.0 - 9.0 (useful for enrichment)
 Alkaline peptone water APW (pH8.6) - rapid isolation
from faeces (enrichment medium for V. cholerae)
*Grow on variety of simple media including:MacConkey’s agar
 Selective medium:TCBS (Thiosulfate Citrate Bile salts Sucrose) agar
 V. cholerae grow without salt
 Most other vibrios are halophilic
Morphology & Physiology of Vibrio

4. Taxonomy of Vibrio cholerae
ANTIGENIC STRUCTURE
O antigen : specific H antigen : less specific
>200 serogroups based on somatic O-antigen
 1- O1 serogroup subdivided into
 Two biotypes: El Tor and classical (or cholerae)
 Three serotypes: ogawa, inaba, hikojima
 Some O1 strains do not produce cholera enterotoxin
(atypical or nontoxigenic O1 V. cholerae)
 2- non-O1 V.cholerae: Other strains are identical
to O1 strains but do not agglutinate in O1 antiserum
(non-cholera (NCV) or non-agglutinating(NAG) vibrios)
(O139 serogroups)
 O1 and O139 serogroups are responsible for classic epidemic cholera

6. • 1-Toxins and enzymes
- heat stable endotoxin(LPS)
- enterotoxin (exotoxin [cholera toxin CT])
- CT is antigenically and pharmacologically
identical in all sero and bio types
2- Vascular permeability factor (VPF)
CT increases capillary permeability factor
3- Mucinase
Extreme cellular desquamation
4-Resistance
Susceptible to heat, drying, autoclaving temp, high pH, salty
can survive in linen for 1-3 days.
ElTor survive longer periods than the classical type
Virulence factors

7. Laboratory diagnosis
Specimens - From patients
- watery stools and mucous flakes From contacts and carriers
- rectal swabs
- Direct microscopy
• Not a reliable method Wet preparation in saline/dark field :Darting movement
• Movements stop on adding antisera
• Transport media
- Cary-Blair medium(semisolid medium) (recommended)
-Venkataraman-Ramakrishnan (VR)
Vibrios do not multiply
- Bile peptone
- and pepton water medium (sea salt medium)
• Enrichment medium - alkaline peptone broth
 Vibrios survive and replicate at high pH
 Other organisms are killed or do not multiply
• Selective/differential culture medium –
• TCBS agar V. cholerae grow as yellow colonies
• Biochemical and serological tests

8. Biochemical tests
• - Ferment glucose, maltose, mannitol and sucrose
but not lactose, salicin and arabinose, with
production of acid but not gas.
• Reduces nitrate.
• oxidase-positive .
• indole-positive.
Main tests to be performed to defferentiate between
classical and El Tor biotypes
VP _ +
Haemolysis _ +
Polymyxin B + _
Phage typing + _
(Mukherjee phage IV)

9. - Identification:
1. Presumptive identification:
V. Cholerae reactionsTest
Small, Gram -ve curved rods.Gram stain
Small, curved rods with darting motility.Wet mount
Positive.Oxidase test
Positive.String test
Acid yellow slant/acid yellow butt, no gas
produced.
Triple sugar iron
agar

10. String test is useful for ruling
out bacteria that share similarities
to vibrio species, particularly
Aeromonas species.
- The test is done by emulsifying a large
colony in a small drop of 0.5% sodium
desoxycholate in sterile distilled H2O.
Within 60 seconds, the cells lyse (loss of
turbidity) & DNA strings when a
loopful is lifted (up to 2-3 cm) from the
slide.
- All V. cholerae strains, as well as most
other vibrios, are positive, whereas
Aeromonas strains are negative.

11. Pathogenesis of V.cholerae
 Incubation period: 2-3 days
 As more fluid is lost, feces-streaked stool changes
to rice-water stools:
 Colorless, Odorless , No protein ,Speckled with mucus
Source of infection : contaminated water from feces of human
carriers or patients with cholera & marine shellfish
Transmitted by contaminated food & water
Predisposing factors Poor sanitation, Overcrowding, Malnutrition
Infective dose :Organism very sensitive to gastric acid
Patients using antacid drugs-the dose is reduced
High infectious dose: >108 CFU
103 -105 CFU with achlorhydria or hypochlorhydria
(lack of or reduced stomach acid)
Death may occur from:
1 - Hypovolaemic shock. 2- Metabolic acidosis. 3 - Uraemia resulting from acute
tubular necrosis.

12. control (precautionary )measures
- Carriers can be detected
- Water and sewage can be tested for Vibrios
- Increased sanitation
- purification of water
- Isolation of patients
-Vaccines
Immunity
Antibodies can be detected after an infection
However, there is only a limited protection,
repeat attacks are not common for 6-12 months
• Treatment
• 1- Fluid and electrolytes replacement.
• 2- Acid base balance adjustment.
• 3- Antibiotics such as tetracycline or ciprofloxacin.
-Sodium chloride (3.5 g/L)
- Potassium chloride (1.5 g/L)
-Rice flour (30-80g/L)
-Trisodium citrate (2.9 g/L)

13. Mechanism of Action of Cholera Toxin
Cholera toxin (or choleragen):
It contains 5 binding (B) subunits and an active (A) subunit.
The toxin binds, through its B subunits, to specific receptors on the intestinal
epithelial cells. Then it releases the enzymatically active (A) subunit that
enters the cells and activates the adenylate cyclase enzyme causing a rise in
cAMP production.
This causes massive secretion of electrolytes (Na+, K+, Cl-, and HCO3-) and
water into the lumen of the SI.

14. Other
Vibrio Infections

15. • Vibrio parahaemolyticus: It is a halophilic
(salt-loving) Vibrio associated with enteritis
and is acquired by ingestion of raw or
improperly cooked sea foods produced by
thermostable direct haemolysin.
• V. vulnificus: it is a halophilic vibrio, which
ferments lactose associated with wound
infections as well as fatal septicemias.
• Non-O1/0139 serogroups of V. cholerae:
cause diarrhea

16. Other Vibrionaceae genera
Vibrios-related organisms
Aeromonas
&
Plesiomonas

17. Characteristics and Epidemiology of
Aeromonas (Family Aeromonadaceae)
 Gram-negative facultatively anaerobic bacillus
resembling members of the Enterobacteriaceae
 Motile species have single polar flagellum
(nonmotile species apparently not associated with
human disease)
 16 phenospecies: Most significant human
pathogens A. hydrophila, A. caviae, A. veronii
biovar sobria
 Ubiquitous in fresh and brackish water
 Acquired by ingestion of or exposure to
contaminated water or food

18.  Associated with gastrointestinal disease
 Chronic diarrhea in adults
 Self-limited acute, severe disease in children
resembling shigellosis with blood and leukocytes
in the stool
 3% carriage rate
 Wound infections
 Opportunistic systemic disease in immunocompromised
 Putative virulence factors include:
 endotoxin; hemolysins; eneterotoxin;
proteases; siderophores; adhesins
Clinical Syndromes of Aeromonas

19. Characteristics of Plesiomonas
 Formerly Plesiomonadaceae
 Closely related to Proteus & now classified as
Enterobacteriaceae despite differences:
 Oxidase positive
 Multiple polar flagella (lophotrichous)
 Single species: Plesiomonas shigelloides
 Isolated from aquatic environment (fresh or
estuarine)
 Acquired by ingestion of or exposure to
contaminated water or seafood or by exposure
to amphibians or reptiles
 Self-limited gastroenteritis: secretory, colitis or
chronic forms
 Variety of uncommon extra-intestinal infections

20. Differentiating the Vibrio Group
Organism
Vibrio cholera
Other Vibrio
Aeromonas
Plesiomonas
TESTS
Growth
in 5%
NaCl
-
+
-
-
Sensitive
to O1291
Vibriostat
+
+
-
+
Growth in
NB with no
added NaCl
+
-
+
+
Growth
On TCBS2
+
+
-
-
1150ug Disk; 2Thiocitrate bilesalts sucrose agar