Bacterial Skin Infections Midterm Notes PDF

**INTEGUMENTARY -- *Bacterial Skin Infections*** **1. Folliculitis** - **Cause**: - Caused by infection of the **hair follicle**. - The most common bacterial cause is **Staphylococcus aureus**. - **Pathophysiology**: - **Bacteria invade the hair follicle**, proliferating...

**INTEGUMENTARY -- *Bacterial Skin Infections*** **1. Folliculitis** - **Cause**: - Caused by infection of the **hair follicle**. - The most common bacterial cause is **Staphylococcus aureus**. - **Pathophysiology**: - **Bacteria invade the hair follicle**, proliferating around the follicle opening and inside the follicle. - This triggers the release of **chemotactic factors and enzymes** from the bacteria, leading to inflammation. - The infection manifests as **papules and pustules** surrounded by an area of erythema (redness). - **Transmission**: - **Direct contact** with contaminated surfaces or sharing personal hygiene items like razors, towels, or clothing. - Folliculitis can also result from contact with contaminated water (e.g., hot tubs or swimming pools). - **Risk Factors**: - **Prolonged moisture** on the skin, **occlusive clothing**, use of topical agents, **poor hygiene**, and **skin trauma** (like shaving) increase the risk. - **Immunosuppressed individuals** and those with predisposing skin conditions are more vulnerable. **2. Cellulitis** - **Cause**: - Infection of the **dermis and subcutaneous tissue**. - Caused by **Staphylococcus aureus**, **Streptococcus pyogenes**, and other **Streptococcal species**. - **Pathophysiology**: - **Bacteria penetrate through breaks in the skin** (cuts, abrasions, insect bites, etc.). - The infection spreads through the **dermis and subcutaneous tissue**, leading to **localized inflammation, swelling, and redness**. - The immune response increases **vasodilation**, making the affected area **warm, painful, and swollen** without a distinct border. - **Transmission**: - **Not directly transmissible**, but occurs through **breaks in the skin** that allow entry of bacteria from contaminated surfaces or other infections. - **Risk Factors**: - **Diabetes**, **peripheral vascular disease (PVD)**, **lymphedema**, **tinea pedis (athlete\'s foot)**, **insect bites**, and **immune suppression**. - **Breaks in the skin** (e.g., ulcers, cuts, or wounds) increase susceptibility to cellulitis. **3. Impetigo** - **Cause**: - Superficial skin infection, primarily caused by **Staphylococcus aureus** and/or **Streptococcus pyogenes**. - **Pathophysiology**: - **Bacterial toxins** disrupt the skin barrier, leading to the formation of vesicles (blisters) that eventually rupture. - The fluid in the vesicles dries, leaving behind **honey-colored crusts**. - Two forms exist: - **Non-bullous impetigo**: More common, lesions rupture, creating **flat, honey-colored crusts**. - **Bullous impetigo**: Caused by **Staphylococcus aureus**, leads to large fluid-filled blisters (bullae) that rupture and crust. - **Transmission**: - **Highly contagious**, transmitted via **direct contact** with infected individuals or **contact with contaminated surfaces** (e.g., towels, clothing, or shared items). - Children are particularly susceptible. - **Risk Factors**: - Most common in **children aged 2-5 years**, particularly in **hot, humid climates**. - **Poor hygiene**, **crowded living conditions**, and contact sports increase risk. **Summary Table of Bacterial Skin Infections** **Infection** **Cause** **Pathophysiology** **Transmission** **Risk Factors** ------------------ ---------------------------------------------- ------------------------------------------------------------------------------------------------------------------- ------------------------------------------------- -------------------------------------------------------------------------------- **Folliculitis** **Staphylococcus aureus** Infection of the **hair follicle**. Bacteria release enzymes and toxins, causing **papules and pustules** **Direct contact**, contaminated surfaces **Prolonged moisture**, occlusive clothing, shaving, trauma, poor hygiene **Cellulitis** **Staphylococcus aureus**, **Streptococcus** Infection of the **dermis and subcutaneous tissue**, causing localized **inflammation, swelling, redness** Entry via **breaks in skin** (cuts, ulcers) **Diabetes**, **PVD**, **lymphedema**, insect bites, immune suppression **Impetigo** **Staphylococcus aureus**, **Streptococcus** **Superficial skin infection**. Toxins disrupt the skin barrier, leading to **blisters and honey-colored crusts** **Direct contact**, contaminated items (towels) **Children (2-5 years)**, hot/humid climates, poor hygiene, crowded conditions