Common Skin Infections

BACTERIAL INFECTIONS

Thanks to the introduction of antibiotics and improvements to sanitation and living conditions, bacterial infections are much less of a problem in many parts of the world than, say, 30 years ago. Nonetheless, increasing antibiotic resistance and emergence of virulent strains such as Panton- Valentin Leucocidin Staphylococci mean that these are shifting sands, and recognition and swift treatment of cutaneous bacterial infections remains as important now as then.

There are 3 key features to the development of bacterial infection:

• The integrity of the epidermis - provides a barrier to entry by bacteria. This is one reason why patients with altered barrier function in atopic eczema (and with filaggrin mutations) have such problems with staphylococcal super-colonisation and infection.
• The skin's normal bacterial (and fungal) flora prevent colonisation by pathogenic organisms. 
• Host immunity.

Infection normally requires a small break in epidermal integrity to gain access such as trauma, leg ulcers, surgical wounds, IV drug user injection sites, fungal infections (e.g. athlete's foot). Also, abnormal scaling of the skin (e.g. in eczema) encourages bacterial adherence. Immunosuppression (Diabetes Mellitus, AIDS, drugs) is associated with an increased incidence of infection.

In the UK, Impetigo/cellulitis/boils (usually staphylococcal driven) are the most common infections we see, whereas in developing countries TB, Leprosy and impetigo account for most cutaneous infections. 

STREPTOCOCCAL AND STAPHYLOCOCCAL INFECTIONS

Streptococcus sp                                            Staphylococcus aureus