Mupirocin resistance in coagulase-negative staphylococci, after topical prophylaxis for the reduction of colonization of central venous catheters.

Topical mupirocin was routinely applied to insertion sites of central venous catheters (CVC) of neonates in a neonatal intensive care unit. After five years, mupirocin resistance was recorded in 42% of clinical isolates of coagulase-negative staphylococci (CNS). This decreased to 21% during a mupirocin-free interval of five months. We performed a prospective study on the significance of mupirocin use on the staphylococcal skin flora of 15 newly admitted neonates. During treatment, mupirocin-susceptible strains were replaced by highly resistant ones. After treatment, all but one neonate harboured at least one resistant strain; 29% of all strains were moderately resistant (mupirocin minimum inhibitory concentrations (MICs) 16 mg/L) and 55% were highly resistant (MICs > 1024 mg/L). One CVC (7%) became colonized with a resistant strain. One year after stopping routine mupirocin application the incidence of resistance had dropped to 13%; CVC colonization was recorded in 2.4%.