Topic Overview

Acinetobacter, Moraxella, and Pseudomonas aeruginosa

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Acinetobacter

 

 

 

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Definition and Key Features

• Gram-negative

• Non-motile bacteria

Major species:

• Acinetobacter baumannii

• A. lwoffii

• A. haemolyticus

• Part of normal skin flora

Common sites:

• Axillae

• Groin

• Toe webs

• Dry skin areas

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Epidemiology

• Present in ~20% of normal individuals

Higher risk:

• Young

• Elderly

Seasonal pattern:

• Peak in summer

• Associated with sweating

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Clinical Relevance

Opportunistic infections:

• Septicaemia

• Meningitis

• Osteomyelitis

• Wound infections

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Skin infections:

• Pustules

• Cellulitis

Common settings:

• Burns

• Battle wounds

• Indwelling IV catheters

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Moraxella

 

 

 

4

Definition and Key Features

• Gram-negative bacteria

Main species:

• Moraxella catarrhalis

• Primarily respiratory pathogen

• Rarely causes cutaneous infections

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Clinical Manifestations

Systemic infections:

• Gonococcaemia-like illness

• Skin lesions

• Bacteraemia:

  • Petechial rash

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Arthritis and Skin Lesions:

• Joint inflammation

• Associated skin findings

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Association

• Respiratory infections

• Otitis media

• Conjunctivitis

(More common than skin involvement)

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Pseudomonas aeruginosa

 

 

 

4

Definition and Characteristics

• Gram-negative

• Aerobic rod

Also known as:

• P. pyocyanea

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Pigments

• Pyocyanin → blue-green

• Pyoverdin → yellow

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Habitat

• Moist skin areas:

  • Anogenital region

  • Axillae

  • External ear

• Environment:

  • Soil

  • Water

  • Hospital settings

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Epidemiology

• Colonizes:

  • Burns

  • Ulcers

  • Moist lesions

• Important nosocomial pathogen

• Common in ICU settings

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Clinical Features

Localized infections:

• Periumbilical infection (infants)

• Tropical immersion foot:

  • Toe web maceration

  • Erosions

  • Green fluorescence (Wood’s lamp)

• Gram-negative folliculitis:

  • Hot tub / jacuzzi exposure

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Severe infections:

• Burn infections:

  • Edema

  • Discolored slough

• Ecthyma gangrenosum:

  • Necrotic ulcers

  • Central eschar

  • Seen in immunocompromised

• Septicaemia (severe cases)

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Pathogenesis

• Colonizes damaged tissue

• Prefers sites with disrupted normal flora

Virulence factors:

• Exotoxins

• Enzymes

• Pigments

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Management

Antibiotics:

• Combination therapy (resistant strains)

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Prevention:

• Infection control in hospitals

• Proper maintenance:

  • Whirlpool baths

  • Jacuzzis