THE CHANGING PATTERN OF COAGULASE-NEGATIVE STAPHYLOCOCCI AS INFECTIOUS PATHOGENS

Coagulase-negative staphylococci are commonly found among the normal f lora of human skin and mucous membranes, and can be divided into two g roups depending on whether they are resistant or susceptible to novobi ocin. Staphylococcus saprophyticus is the most commonly isolated bacte rium in the novobiocin-resistant group. It is a common pathogen of the urogenital tract and generally infects immunocompetent patients, part icularly young, sexually active men and women. The most frequently iso lated species of the novobiocin-susceptible group is Staphylococcus ep idermidis, which usually infects immunocompromised patients, such as p remature newborns and patients with leukaemia or other malignant disea ses who have been treated with cytostatic agents and thus acquired neu tropenia. Staphylococcus epidermidis is also common in intravenous dru g abusers, who are particularly susceptible to right-sided endocarditi s, and in patients with indwelling polymer bodies, such as prosthetic devices or intravenous catheters. In these patients, endogenous protei ns may coat the foreign body following implantation, creating a surfac e on which staphylococci can adhere and multiply. Since antibiotic the rapy often fails unless the foreign body is removed, strict aseptic te chniques and optimal surgery should be applied when inserting a cathet er or implanting a device. About 60% of nosocomial coagulase-negative staphylococcal isolates are methicillin-resistant and a high number of Staphylococcus epidermidis isolates are also resistant to erythromyci n, clindamycin and gentamicin. The glycopeptides, particularly vancomy cin, are the drugs of choice for nosocomial Staphylococcus epidermidis infections, at least at the beginning of therapy, before the degree o f antibiotic sensitivity has been ascertained. Community-acquired and Staphylococcus saprophyticus infections may show a broader spectrum of antibiotic susceptibility.