Vibrio, Helicobacter, and Campylobacter Bacteria: Biological Features and Pathogenicity

Vibrio, Helicobacter, and Campylobacter Bacteria: Biological Features and Pathogenicity

1. Vibrio

• Biological Characteristics:

• Comma-shaped

• Motile due to a single flagellum at one end

• Facultative anaerobe

• Indole (+), Oxidase (+), Catalase (+)

• Glucose (+), Lactose (-) non-gas producer

• Urease (-)

• Nitrate -> Nitrite conversion

• Requires NaCl for growth

• Pathogenic Species:

• Vibrio cholerae (cholera bacterium)

• Vibrio parahaemolyticus

• Antigenic Structure:

• Possesses O antigens

• Some have H antigens

• Pathogenesis:

• Enters the body through the oral route.

• Adheres to the small intestinal mucosa (non-invasive)

• Secretes cholera toxin

• Effects of Cholera Toxin:

• Causes intestinal mucosal cells to decrease Na+ absorption, increase water and Cl- secretion -> acute diarrhea.

• Diagnosis:

• Staining, wet mount of stool and vomit samples

• Direct fluorescent antibody test

• Culture isolation on alkaline peptone medium, alkaline agar, TCBS

• Serological testing

2. Helicobacter

• Biological Characteristics:

• Gram-negative rod, mostly slightly curved and spiral-shaped.

• Motile due to flagella at the end.

• Non-spore-forming.

• Oxidase (+), Catalase (+)

• Microaerophilic.

• Difficult to culture.

• Species Pathogenic to Humans:

• H. pylori

• H. cinaedi

• H. fennelliae

• Pathogenic Features of Helicobacter pylori:

• Commonly found, can cause gastritis, peptic ulcers, and gastric cancer.

• Multiple virulence factors contribute to gastritis, peptic ulcer, and gastric cancer development:

• Urease: hydrolyzes urea -> alkalizes the environment -> protects the bacteria and is toxic to cells.

• Acid inhibitory protein (AIP): inhibits acid HCl secretion by cells.

• Flagella: helps bacteria penetrate the mucus layer of the intestinal mucosa.

• Adhesins: help bacteria adhere to epithelial cells.

• Mucinase: breaks down mucus on the surface of the intestinal mucosa.

• Catalase: breaks down H2O2, helping bacteria survive in phagosomes.

• Vaculoating: toxic to epithelial cells.

• CagA: stimulates cells to secrete interleukin-8 -> linked to the progression of peptic ulcer disease to gastric cancer.

• Diagnosis:

• Staining, Gram staining of gastric biopsy samples

• Culture isolation (difficult)

• Gastric biopsy -> histopathological diagnosis

• Urease, CLO test

• Serological methods

3. Campylobacter

• Biological Characteristics:

• Gram-negative bacillus, comma-shaped

• Motile like a corkscrew

• Non-spore-forming

• Single flagellum at one end

• Indole (-), Oxidase (+), Catalase (+)

• Urease (-)

• H2S (-)

• Antigenic Structure:

• 90 O antigens; 112 H antigens

• No K antigens

• Pathogenic Species:

• Campylobacter jejuni

• Campylobacter fetus

• Campylobacter coli

• Campylobacter intestinalis

• Pathogenic Features of Campylobacter jejuni:

• Causes diarrhea, bacteremia, meningitis.

• Virulence Factors of C. jejuni:

• Flagella

• Adherence factors

• Invasive factors

• C3b complement inhibitory factor: inhibits phagocytosis

• Pathogenic Features of C. fetus and C. coli:

• Rare

• Cause diarrhea, bacteremia, meningitis

• Pathogenic Features of Campylobacter intestinalis:

• Very rare

• Causes bacteremia

• Diagnosis:

• Staining of cerebrospinal fluid sediment (purulent meningitis)

• Culture

Note: This article is intended to provide general information and is not a substitute for professional medical advice. If you have any health concerns, please contact a doctor for timely advice and treatment.