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 (Medicine, Year 3). The free AceMed note covers it in 9 sections, about 148 words (3 min of reading), with 16 flashcards.

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. Entry:

Trauma, surgery, bites, or hematogenous seeding

2. Adherence & Toxin Production:

S. aureus: coagulase, protein A, hemolysins
Clostridium: alpha-toxin → tissue necrosis, gas production

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)