The changing pattern of coagulase-negative staphylococci as infectious pathogens

Abstract

Coagulase-negative staphylococci are commonly found among the normal flora of human skin and mucous membranes, and can be divided into two groups depending on whether they are resistant or susceptible to novobiocin. Staphylococcus saprophyticus is the most commonly isolated bacterium in the novobiocin-resistant group. It is a common pathogen of the urogenital tract and generally infects immunocompetent patients, particularly young, sexually active men and women. The most frequently isolated species of the novobiocin-susceptible group is Staphylococcus epidermidis, which usually infects immunocompromised patients, such as premature newborns and patients with leukaemia or other malignant diseases who have been treated with cytostatic agents and thus acquired neutropenia. Staphylococcus epidermidis is also common in intravenous drug abusers, who are particularly susceptible to right-sided endocarditis, and in patients with indwelling polymer bodies, such as prosthetic devices or intravenous catheters. In these patients, endogenous proteins may coat the foreign body following implantation, creating a surface on which staphylococci can adhere and multiply. Since antibiotic therapy often fails unless the foreign body is removed, strict aseptic techniques and optimal surgery should be applied when inserting a catheter 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 erythromycin, clindamycin and gentamicin. The glycopeptides, particularly vancomycin, are the drugs of choice for nosocomial Staphylococcus epidermidis infections, at least at the beginning of therapy, before the degree of antibiotic sensitivity has been ascertained. Community-acquired and Staphylococcus saprophyticus infections may show a broader spectrum of antibiotic susceptibility.