Lincomycin resistance in methicillin-resistant Staphylococcus aureus strains of hospital origin

A total of 170 Staphylococcus aureus strains isolated during a one-year period at the University Hospital of Patras Medical School were examined for resistance to a battery of antimicrobial agents by disk diffusion and minimum inhibitory concentration (MIC) determination. Fifty-five isolates were lincomycin- and methicillin-resistant (LMRSA). In the group of 55 LMRSA isolates 13 were also resistant to vancomycin. All the LMRSA isolates were not typed by the international set and the experimental phages 88A and 25 at routine typing dilution (RTD), while 18 isolates were lysed by phages at 100XRTD and 1000XRTD. Reverse phage-typing and heat shock treatment of the LMRSA isolates had no effect on their typability. Plasmid profiles coupled with restriction endonuclease analysis of plasmid DNA established that the LMRSA isolates represent different strains. Membrane-protein profiles by polyacrylamide gel electrophoresis (PAGE) showed that LMRSA strains could belong to one group. This method proved useful and sensitive for characterization of LMRSA.