EPIDEMIOLOGIC-STUDY OF AN OUTBREAK OF INFECTION WITH STAPHYLOCOCCUS-AUREUS RESISTANT TO LINCOSAMIDES AND STREPTOGRAMIN-A IN A FRENCH HOSPITAL

A significant increase in the incidence of isolates of methicillin-res istant Staphylococcus aureus (MRSA), that were also resistant to linco samides and streptogramin A (LS(A)-MRSA), was observed in a French uni versity hospital, Twenty-seven isolates from the outbreak were charact erised, including 17 isolates from a plastic surgery ward and six cont rol strains of MRSA, The strains were examined by antibiotyping and bi otyping, and by three molecular methods: plasmid analysis, ribotyping and insertion sequence (IS) typing with IS256 sequence as a probe, Ant ibiotyping (five antibiotypes) was discriminatory because of the uncom mon resistance phenotype of the epidemic strain, Biotyping (three biot ypes), DNA plasmid analysis (four profiles) and ribotyping (two profil es) were poorly sensitive, in contrast to IS-typing (12 profiles), By the latter method, a coefficient of similarity (percentage similarity) compared to the predominant IS profile was calculated, Strains with a coefficient of similarity greater than or equal to 82% were considere d as highly related to the epidemic strain, while those with a coeffic ient of similarity less than or equal to 40% were regarded as distant, Results obtained with the five markers confirmed that an outbreak of hospital infection had occurred in the plastic surgery ward, with spre ad of the epidemic strain throughout the hospital.