Apart from Acinetobacter spp. and Micrococcus spp., few bacteria other than coryneforms and staphylococci are found resident on skin. In this chapter are described the Gram-negative and Gram-positive bacteria regularly found on skin, together with those that contribute to well-recognized skin infection.

Gram-negative bacteria

Gram-negative bacilli are comparatively rare on normal skin, except for acinetobacter, which forms part of the normal flora in about a quarter of the population. Proteus is found on the nasal mucosa of about 5 per cent of individuals and both proteus and pseudomonas are found on the toe webs. The hands may also be temporarily colonized by a variety of bacilli. Apart from these sites the general skin surface of normal persons is sparsely colonized (Table 9.1) and the majority of organisms are probably transients or contaminants.

Acinetobacter spp.

Acinetobacter is the only genus of Gram-negative bacilli regularly found as a member of the skin flora in a significant number of individuals. About 25 per cent of normal adults carry acinetobacter in the axillae, groin, toe webs and antecubital fossa. In patients with eczema the carrier rate may be higher, especially on lesions, whilst in hospitalized patients with renal disease the carrier rate may exceed 50 per cent. Carriage of acinetobacter is more common in the summer months, probably due to increased sweating, and this is reflected in a pronounced summer maximum of endemic surgical wound infection, especially in young adults.