Vibrios, Pseudomonas, Campylobacter, Helicobacter

Other gram-negative bacilli

VIBRIOS

• Among the most common bacteria in surface waters worldwide

• Curved, aerobic rods; motile with polar flagella

• oxidase (+)

• grow best on alkaline media

• Often found in brackish water

Vibrio cholerae

• Classified based on somatic O antigen:1. V. cholerae O1 – most common cause of

epidemic & pandemic cholera2. V. cholerae O139 (Bengal strain) –

epidemic3. Non-O1 group

• Two biotypes (based on differences in biochemical reactions):1. El Tor – most common cause of

epidemics and cause of 7th pandemic2. Cholerae or classical

• Three serotypes (based on antigenic differences):Ogawa, Inaba, Hikojima

Vibrio cholerae

• MOT: fecal-oral

• Sources of infection: humans, marine shellfish (shrimp and oysters)

• Sensitive to gastric acid high infective dose

• Virulence factors:1. Mucinase – cause adherence to

cells of the brush border of the gut2. Choleragen – stimulate adenylyl

cyclase

Vibrio cholerae

Vibrio choleraeCholera

ToxinB subunit A subunit

Binds GM1 ganglioside (surface of

epithelial cells)

Carried to ER (retrograde transport)

Endocytosis

Reduced by protein disulfide isomerase

in ER

Cytosol

Unfolding

Refolding

Interact with cytosolic ADP

ribosylation factors

Activate G protein

Stimulate adenylate

cyclase

Inc. cAMP

Open CFTR

Cl released in lumen; secretion of HCO3 , Na+ &

water

Vibrio cholerae

• Clinical findings:

Voluminous watery diarrhea – hallmark; “rice water” stool

Loss of fluid and electrolytes – marked dehydration “washerwoman” hands Cardiac and renal failure Hypovolemic shock

Vibrio cholerae

• Diagnosis: Culture on MacConkey’s agar (slow

lactose fermenter) or TCBS (Thiosulfate citrate bile salt sucrose) agar plate for selective isolation

Oxidase (+) – distinguished from the family Enterobacteriaceae

Serology

• Treatment: Prompt and rapid fluid and

electrolyte replacement Tetracycline – shorten duration

Growth on TCBS agar plate

Vibrio parahaemolyticus

• Halophilic – grows on 8% NaCl solution

• MOT: ingestion of raw or undercooked seafood, especially shellfish such as oysters

• Mild to severe watery diarrhea, nausea and vomiting, abdominal cramps, fever self-limited

• No specific treatment indicated

Vibrio vulnificus

• Found in warm salt waters

• Causes severe skin and soft tissue infections (cellulitis), especially in shellfish handlers

• Rapid, fatal septicemia in immunocom- promised people who have eaten raw shellfish

• Treatment: doxycycline

Pseudomonas aeruginosa

• Gram-negative rods that resemble the Enterobacteriaceae but are strict aerobes

• Derive energy by oxidation of sugars rather than fermentation

• Oxidase (+)

• Able to grow in water containing only traces of nutrients

Pseudomonas aeruginosa

• Produce two pigments: Pyocyanin (blue) Pyoverdin (fluorescein) – yellow

green pigments that fluoresce under UVL

• Found chiefly in soil and water

• Found on the skin in moist areas

• Primarily opportunistic

Pseudomonas aeruginosa

• Virulence factors:

1. Endotoxins – cause sepsis and shock

2. Exotoxin A – cause tissue necrosis; inhibits eukaryotic protein synthesis similar to diphtheria exotoxin

3. Enzymes Elastases and proteases

4. Pyocyanin – damages the cilia and mucosal cells of respiratory tract

Pseudomonas aeruginosa

• Clinical:

1. Urinary tract infections2. Pneumonia in cystic fibrosis patients3. Burn wound infection4. Sepsis5. Ecthyma gangrenosum – black

necrotic lesions on skin6. Malignant external otitis7. Folliculitis 8. Osteochondritis of the foot due to

punctured wounds through the soles of gym shoes - most common cause

Ecthyma gangrenosum

Osteochondritis of foot

Pseudomonas aeruginosa

• Diagnosis:

1. Culture – non-lactose fermenting2. Oxidase production3. Biochemical reactions – confirmatory

• Treatment: Resistant to many antibiotics Ticarcillin or piperacillin +

aminoglycoside (gentamicin or amikacin)

Production of pyocyanin, water-soluble green pigment of Pseudomonas

aeruginosa. (left tube)

Campylobacter jejuni

• Comma- or S-shaped rods

• Microaerophilic (5% oxygen)

• Grows well at 420C

• Sources of infection: domestic animals

• MOT: fecal-oral (poultry, meat, unpasteurized milk common sources)

Campylobacter jejuni

• Clinical:

Enterocolitis – begins as watery, foul-smelling diarrhea bloody stools

Associated with 1. Guillain-Barre syndrome

Most common cause of acute neuro-muscular paralysis

Autoimmune disease2. Reactive arthritis3. Reiter’s syndrome

Campylobacter jejuni

• Diagnosis:

Culture Oxidase (+); sensitive to

nalidixic acid

• Treatment: erythromycin or ciprofloxacin

Helicobacter pylori

• Curved; gram-negative; similar in appearance to Campylobacter

• Strongly urease positive convert urea to ammonia neutralize gastric acid

• Rapidly motile – allow organism to penetrate protective mucus layer

Helicobacter pylori

• Most common cause of chronic gastritis

• Most common cause of duodenal ulcers

• Second most common cause of gastric ulcer

• Associated with development of gastric CA and gastric lymphoma

Helicobacter pylori

• Diagnosis:

Culture Urease production urea

breath test

Helicobacter pylori

Treatment:

Proton pump inhibitors (Omeprazole)

Antibiotics – amoxicillin, metronidazole, tetracycline

Bismuth salts