[Predominance of multidrug resistant strains with reduced susceptibility to fusidic acid among methicillin-resistant Staphylococcus aureus strains (MRSA) isolated in the Gdánsk region].

The aim of the present study was to follow the changes in the drug resistance among the methicillin-resistant Staphylococcus aureus strains (MRSA) isolated from clinical samples in various hospitals during 8 years, with particular consideration of Gdansk area. The study was carried out on 225 strains of MRSA from which 95 were isolated in the years 1990-1995 and 130 in the years 1997-1998. The drug susceptibility was determined by the disc-diffusion method. The sensitivity to fusidic acid was determined by both disc-diffusion method and minimal inhibitory concentration (MIC) using agar dilutions. The results obtained show that in 1997-1998 in the hospitals of Gdansk area have been appeared MRSA strains which have not occurred before. These strains were intermediately sensitive or resistant to fusidic acid and simultaneously resistant to doxycycline, gentamicin, erythromycin, clindamycin, ciprofloxacin and rifampin. They represented 66.2% of all MRSA strains isolated in 1997-1998 and were present in majority of the hospitals monitored. Only in this group of staphylococci the strains additionally resistant to mupirocin (6.2%) occurred. Among the MRSA strains with reduced susceptibility to fusidic acid 64.4% were intermediately sensitive (MIC 8-16 mg/L) and 15.4% were resistant to this drug (MIC > 16). In 1997-1998 the percentages of MRSA strains resistant to rifampin, clindamycin and ciprofloxacin increased significantly from 12.6% to 90.8%, from 42.1% to 92.3% and from 18.9% to 92.3% respectively. The percentage of the chloramphenicol resistant strains decreased from 14.7% to 0.8%. Like in 1990-1995, the MRSA strains resistant to vancomycin and teicoplanin were not found out in the same period of time.