Epidemiological 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-resistant Staphylococcus aureus (MRSA), that were also resistant to lincosamides and streptogramin A (LS(A)-MRSA), was observed in a French university hospital, Twenty-seven isolates from the outbreak were characterised, including 17 isolates from a plastic surgery ward and six control strains of MRSA, The strains were examined by antibiotyping and biotyping, and by three molecular methods: plasmid analysis, ribotyping and insertion sequence (IS) typing with IS256 sequence as a probe, Antibiotyping (five antibiotypes) was discriminatory because of the uncommon resistance phenotype of the epidemic strain, Biotyping (three biotypes), DNA plasmid analysis (four profiles) and ribotyping (two profiles) 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 considered as highly related to the epidemic strain, while those with a coefficient 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 spread of the epidemic strain throughout the hospital.