Vibrio, Pseudomonas, and Legionella

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Vibrio, Pseudomonas, and Legionella

• Louise S. Thai, M.D.

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Learning Objectives

• V. cholerae
• V. parahaemolyticus
• V. vulnificus
• P. aeruginosa
• L. pneumophila

• Characteristics
• Virulence Factors
• Epidemiology
• Pathogenesis
• Treatment Prevention

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Vibrio cholerae

• Gram (-), comma-shaped
• Optimum pH 8.0 - 9.5
• Motile
• Oxidase positive

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Antigenic Structure

• 139 O-serotypes
• V. cholerae O1 and O139 ? Epidemic Cholera
• V. cholerae O1
• biotype El Tor
• classical biotype (cholerae)

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Major Virulence Factors

• Pili
• Enterotoxin (CT)
• A-B toxin
• ADP-ribosylating toxin ? Adenylate cyclase ? ?
  cAMP ? ? Diarrhea
• zot
• ace

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Epidemiology

• Halophilic
• Grows at 10? C - 30? C
• Transmission fecal-oral
• Shellfish
• Contaminated water
• Geographic distribution developing world
• Pandemics caused by V. cholerae O1
• 1992 Epidemic of O139 Bengal cholera

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Pathogenesis

• Bacteria adhere with the help of adhesion
  molecules
• CT, zot and ace produced
• Efflux of Na and Cl ions
• Water follows
• Profuse diarrhea

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Clinical Aspects

• Watery diarrhea (rice water stool)
• No abdominal pain
• Symptoms related to severe dehydration
• Cardiac failure
• Renal failure
• Acidosis
• Hypokalemia
• Mortality rate without treatment 50

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Lab Diagnosis

• Lactose (-)
• Oxidase positive
• TSI Acid/acid
• Agglutination in specific antisera

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Treatment and Prevention

• ORS
• Doxycycline or tetracycline
• Trimethoprim/Sulfamethoxazole for children
• Clean water and food supply
• No perfect vaccine

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Vibrio parahaemolyticus

• Marine organism
• Contaminated seafood
• Rare in the US
• Common in Japan
• Enterotoxin-mediated
• Nausea, vomiting
• Abdominal cramps
• Diarrhea
• Fever

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Vibrio vulnificus

• Fulminant necrotizing wound infections
• Septicemia following consumption of shellfish
• Mortality rate 50

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Pseudomonas aeruginosa

• Gram (-) rods
• Strict aerobe
• Non-fermenter
• Oxidase positive
• Can grow in water
• Pigment producing

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P. aeruginosa
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Major Virulence Factors

• Adhesins
• Alginate capsule
• Elastase
• Phospholipase
• Multidrug resistance

• Endotoxin
• Exotoxin A
• MOA DT-like
• Tissue damage
• Exoenzyme S
• MOA Exotoxin A- and DT-like

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Pathogenesis

• Normal flora
• Prefers moist areas of the body
• One of the leading causes of nosocomial
  infections
• Opportunistic pathogen, causes disease in
• Immunosuppressed
• Patients with burn injury
• CF patients

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Clinical Aspects

• UTI
• Wound Infections
• Pneumonia in CF patients
• Swimmers ear
• Malignant otitis externa in diabetics

• Folliculitis
• Osteochondritis
• Corneal ulceration
• Endocarditis
• Septicemia with the mortality rate of gt50
• Ecthyma gangrenosum

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Lab Diagnosis

• Lactose (-)
• Pigment pyocyanin
• Fluorescein
• Pleasant fruity odor
• Oxidase ()

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Treatment and Prevention

• Aminoglycosides Beta-lactams
• Infection Control

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Legionella pneumophila

• Common cause of community and hospital- acquired
  pneumonia
• Commonly present in A/C cooling tower, shower and
  other water systems
• No person-to-person transmission

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General Characteristics

• Slender
• Gram-negative
• Motile
• Nutritionally fastidious (L-cysteine required)
• Chlorine resistant

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Pathogenesis

• Lung tropism
• Coiled phagocytosis
• Prevention of phagolysosomal fusion
• Proliferation in the lung ? cell death ?
  necrotizing multifocal pneumonia

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Legionnaires Disease

• WHO? Immunocompromised, smokers, patients with
  chronic lung disease
• Myalgia, headache, fever and chills, dry cough ?
  productive cough
• Chest pain, vomiting, diarrhea, confusion, and
  delirium
• MOSF ? Shock ? Death
• Mortality rate 50

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Other Legionelloses

• Pontiac Fever
• Milder and less common than Legionnaires d.

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Lab Diagnosis

• Lung aspirate and bronchial washings
• Medium BCYE
• Ground-glass like colonies
• IFA
• Serology

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Treatment and Prevention

• Erythromycin
• Decontamination of water supplies