Mircrobiology Lecture -13 Cholerae

Taxonomy Family

Vibrionaceae

Genus

Vibrio

Species

V.cholerae O1 cholerae (classica) V.cholerae.O1 eltor V.cholerae O139 bengal V.cholerae non O1 V.parahaemolyticus V.vulnificus V.alginolyticus V.damsela V.mimicus V.fluvialis V.metschnikovii

Vibrio species Gram negative Short, curved, rod-shaped Rapidly motile as a result

of single polar flagellum Facultative anaerobes Growth of many Vibrio strains reguires or is stimulated by NaCl V.cholerae do not reguire salt for growth but can tolerate it. Culture on blood Mac Conkey agar.

Antigens Flagella (H) antigen – common for genus Vibrio. Somatic O antigen – useful for distinguishing

strains of vibrious. O antigen consist of 3 components ABC. Formula AB – serotype Ogawa. Formula AC – Inaba. Formula ABC – Hikojima.

The medically important vibrios Organism

Human Disease

V.cholerae serogroups O1 and O139 V.Cholerae serogroups nonO1\non-O139

Epidemic and pandemic cholera. Cholera-like diarrhea; mild diarrhea; rarely, extraintestinal infection. Gastroenteritis, perhaps extraintestinal infection.

V.parahaemolyticus Others V.mimicus, V.vulnificus, V.hollisae, V.fluvialis, V.damsela, V.anginolyticus, V.metschnikovi.

Ear, wound, soft tissue, and other extraintestinal infections, all uncommon.

Vibrio Species associated with human disease

Species

Source of infection

Clinical disease

V.cholerae

Water, food

Gastroenteritis

V.parahaemolyticus

Shellfish, seawater

Gastroenteritis, wound infection, bacteremia

V.vulnificus

Shellfish, seawater

Bacteremia, wound infection, cellulitis

V.alginolyticus

Seawater

Wound infection, external otitis

V.hollisae

Shellfish

Gastroenteritis, wound infection, bacteremia

V.fluvialis

Seafood

Gastroenteritis, wound infection, bacteremia

Species V.damsela V.metschnikovii V.mimicus

Source of infection Seawater Unknown Fresh water

V.furnissii Seawater V.cincinnatiensis Unknown V.carchariae

Seawater

Clinical disease Wound infection Bacteremia Gastroenteritis, wound infection, bacteremia Gastroenteritis Bacteremia,meni ngitis Wound (shark bite)

Virulence factors of Vibrio cholerae O1 and O139 Virulence factor

Biologic effect

Cholera toxin

Hypersecretion of electrolytes and water.

Coregulated pilus

Adherence to mucosal cells

Accessory colonization

Adhesin factor

Hemagglutination-protease (mucinase)

Induces intestinal inflammation and degradation of tight junctions

Siderophores

Iron sequestration

Neuraminidase

Increase toxin receptors

Virulence factors of other Vibrio species Organism

Virulence factors

V.parahaemolyticus

Thermostable direct hemolysin Serum resistance, antiphagocytic, polysaccharides, cytolysins, collagenase, protease, siderophore Collagenase Heat-stable and heat-labile enterotoxin, hemolysin Cytolysin

V.vulnificus

V.alginolyticus V.hollisae V.damsela

Mechanism of action of cholera toxin

Mechanism of action of cholera toxin

The cAMP causes the active secretion of sodium (Na+), chloride (Cl), potassium (K+), bicarbonate (HCO3), and water (H2O), out of the cell into the intestinal lumen.

Summary of Vibrio vulnificus infections Physiology and structure: • Curved gram-negative bacilli. • Facultative anaerobe • Fermenter • Simple nutritional requirements but requires salt for growth.

Virulence: • Resistant to complement- and antibody-mediated serum killing (thus, systematic infections). • Antiphagocytic capsule • Production of hydrolytic enzymes (cytolysins, collagenase, proteases).

Epidemiology: • Infection associated with exposure of a wound to contaminated salt water or ingestion of improperly prepared shellfish. Diseases: • Wound infections that can progress rapidly to formation of bullae and tissue necrosis. • Septicemia following ingestion of contaminated shellfish. • High mortality rate in immunocompromised patients.

Diagnosis: Culture wounds and blood. Treatment,prevention, and control. • Life-threatening illness that must be promptly treated with antibiotics. • Tetracyclines or aminoglycosides treatment of choise. • No vaccine is available.

Summary of Vibrio parahaemolyticus infections Physiology and structure: • Curved gram-negative bacilli. • Facultative anaerobe. • Fermenter. • Simple nutritional requirements but requires salt for growth.

Virulence: • Hemolysin. • Adhesin. Epidemiology: • Organism found in estuarine and marine environments worldwide. • Assotiated with consumption of contaminated shellfish. • Is a major pathogen in countries where raw fish is eaten.

Diseases: Diarrhea ranging from mild disease to a cholera-like illness. Typical presentation is an explosive, watery diarrhea. Less commonly associated with wound infections and bacteremia. Diagnosis: Culture should be perfomed as with V.cholerae. Treatment, prevention, and control: Self-limited disease, although antibiotics can shorten symptoms and fluid loss. Disease prevented by proper cooking of shellfish. No vaccines are available.

Campylobacter species Gram negative; Curved, spiral, or S-

shaped rods; Single, polar flagellum, resulting in characteristic darting motion; Microaerophilic; Do not ferment carbohydrates; Culture on selective medium (blood agar containing antibiotics to inhibit growth of other fecal flora).

Campylobacter jejuni. The photograph is of a modified fuchsin stain of organisms recovered from a stool culture obtained from a 1-year old Guatemalan girl suffering 3 days of diarrhea as a result of a Campylobacter infection. A smear of the cultured organism was stained with undiluted carbolfuschin ZiehlNeelsen solution (Merck) for 3 minutes at room temperature.

Helicobacter pylori Gram-negative; Curved or spiral rods; Multiple polar flagella,

which give organism rapid, corkscrew motility; Urease positive; Culture on selective medium, containing antibiotics to inhibit growth of other fecal flora.