Microbiology · MU Sofia

108. Microbiological Aspects of Skin, Wound, Muscle, Joint, and Bone

Covers bacterial infections of skin, wounds, muscle, joints and bone, starting with the tissues affected and the normal skin flora that can turn opportunistic. It then sets out causative organisms for each site in a table, followed by pathogenesis, clinical presentations, laboratory diagnosis, treatment approaches and prevention.

Inside: 9 sections · 1 labelled picture · 6 tables · 16 flashcards · 3 min

Topic 108 of 113 in the MU Sofia syllabus for Microbiology (Dental Medicine, Year 2). The free AceMed note covers it in 9 sections, about 148 words (3 min of reading), with 16 flashcards.

In this note

  1. Microbiological Aspects of Skin, Wound, Muscle, Joint, and Bone Infections
  2. I. Overview
  3. II. Normal Flora and Opportunism
  4. III. Causative Organisms by Infection Site
  5. IV. Pathogenesis
  6. V. Clinical Presentations
  7. VI. Laboratory Diagnosis
  8. VII. Treatment Considerations
  9. VIII. Prevention and Control

I. Overview

These infections are part of soft tissue and musculoskeletal infections, often caused by bacteria entering via trauma, surgical wounds, or hematogenous spread.

Affected tissues:

  • Skin: impetigo, erysipelas, cellulitis
  • Wounds: surgical, traumatic, diabetic ulcers
  • Muscles: myositis, gas gangrene
  • Joints: septic arthritis
  • Bones: osteomyelitis

II. Normal Flora and Opportunism

  • Skin is colonized by:
  • Staphylococcus epidermidis, Corynebacterium spp., Propionibacterium acnes
  • These can become opportunistic pathogens, especially with breached barriers.

IV. Pathogenesis

  1. 1. Entry:
  • Trauma, surgery, bites, or hematogenous seeding
  1. 2. Adherence & Toxin Production:
  • S. aureus: coagulase, protein A, hemolysins
  • Clostridium: alpha-toxin → tissue necrosis, gas production
  1. 3. Inflammation & Spread:
  • Localized (abscess, cellulitis) or systemic (sepsis)
  • Deep infections (e.g., joint/bone) can cause long-term disability

VI. Laboratory Diagnosis

A. Sample Collection

  • Pus, aspirates from joints, wound swabs (deep layers), bone biopsies
  • Avoid superficial swabs unless no alternative

B. Tests

VIII. Prevention and Control

  • Hand hygiene & wound care
  • Proper surgical asepsis
  • Control of diabetes and vascular insufficiency
  • Prompt drainage of abscesses
  • Vaccination (e.g., tetanus prophylaxis)

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