Analysis of pristinamycin-resistant Staphylococcus epidermidis isolates responsible for an outbreak in a Parisian hospital

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Abstract
In 1990, over a 6-month period, an increase from 1 to 10% in the incidence of pristinamycin resistance among coagulase-negative staphylococci was observed in four intensive care units of a Parisian hospital. Twenty-three such isolates, as well as 25 pristinamycin-susceptible Staphylococcus epidermidis isolates, were collected and typed by analyzing various bacterial constituents. Two structurally related plasmids of 7.3 and 14.3 kb, carrying the gene vga encoding resistance to pristinamycin, were detected in the 23 pristinamycin-resistant coagulase-negative staphylococci which were identified as S. epidermidis. Although related by numerous common characteristics, 20 of these 23 isolates could be divided into two types, A (17 isolates) and B (three isolates). These types were characterized on the basis of their plasmid contents and hybridization patterns obtained when the EcoRI-digested DNA was probed with plasmid pIP1551 containing an internal fragment of the insertion sequence IS256. These findings suggest that the dissemination of type A epidemic strains was, in large part, responsible for the outbreak.