Staphlococci

Staphlococci are gram positive cocci. There are two main types Staphlococcus albus and Staphlococcus aureus.

Staph. Albus (white) is also called Staph. epidermidus and is a normal skin commensal. It is normally not pathogenic. However if it is innoculated into prosthetic materials such as joint or valve replacements it may become virulent. It has the ability to avoid the host immune defence by forming biofilms. Most Staph. epidemidis is sensitive to penicillin.

Staph. aureus (gold) is a normal skin commensal in 15% of people. It may reside in the skin flexures, and the nose. It is a virulent pathogen and causes skin infections such as folliculitis, styes, furuncules and carbuncles. It readily colonises percutanous venous catheters. It is one of the main causes of septic arthritis, and ostomyelitis. It may cause bacterial endocarditis, particularly in intra venous drug abusers. Most Staph. aureus is resistant to penicillin due to the production of $\beta$-lacatamase enzymes which cleave the $\beta$-lactam ring of the antibiotic rendering it inactive. Flucloxacillin, however is not affected and is the drug of first choice for infections caused by Staph. aureus.

Worringly, strains of Staph. aureus have become resistant to many drugs and the methicillin resistant strains MRSA are prevalent. As usual, all medical personel are advised to wash their hands between patient contacts and comply with the recomendations of the infection control team.