Predominant staphylococci in the intensive care unit of a paediatric hospital

Abstract

Coagulase-negative staphylococci cause a significant number of infections, especially in immunocompromised patients, including premature neonates. Nosocomial strains present in the environment create a special risk.We studied staphylococci isolated from the intensive care unit of a paediatric teaching hospital over the period of six months in 1997. Biotyping and species identification were performed; resistance to methicillin and other β-lactam antibiotics and patterns of resistance to antimicrobial agents were determined.Staphylococcus cohnii was the predominant species of 147 isolates of staphylococci recovered from the ward environment. Strains were resistant to several antibiotics and 97% were resistant to methicillin. In isolates from infants (72) methicillin-resistant strains of Staphylococcus epidermidis were predominant. Susceptibility to β-lactams (penicillin, amoxycillin, amoxycillin-clavulanic acid and cephalosporins: cephalothin, cefuroxime and cefotaxime) showed differences between the two species. Some S. cohnii were susceptible to penicillin and amoxycillin despite methicillin-resistance. S. epidermidis were relatively susceptible to amoxycillin-clavulanic acid and cephalosporins. All strains investigated were susceptible to vancomycin, but nearly 30% demonstrated high-level resistance to mupirocin. The search for strains of the same origin showed clones belonging to S. epidermidis, S. hominis and S. saprophyticus but not S. cohnii.A large number of multiresistant, phenotypically different S. cohnii strains surviving in the ward environment may provide a reservoir of antimicrobial resistance genes.