[Changes of methicillin-resistant Staphylococcus aureus (MRSA) phagotypes in Gdansk in 1990-1998]

The aim of the study was the assessment of changes in the occurrence of various MRSA phagotypes in hospitals in the Gdańsk area in 1990-1998. The study was carried out on 175 MRSA strains: 45 strains isolated in 1990-1995 and 130 in 1997-1998. The studied staphylococci were obtained from various clinical materials from patients in 18 hospitals. Phagotyping was done with a set of 10 experimental phages from MRSA strains obtained from the Central Public Health Laboratory in London. Drug-resistance was determined by the disc-diffusion method and in case of strains with medium susceptibility to fusidic acid the minimal inhibitory concentration (MIC) was determined by serial dilutions on solid medium. The study showed among MRSA strains isolated in 1997-1998 a new, previously not known strains with phage pattern MR25/M5 predominated (57.7%). Its presence was found in various hospitals in that area. MRSA belonging to MR25/M5 phagotype were mostly resistant to doxycycline, gentamycin, erythromycin, clindamycin, ciprofloxacin, rifampicin and were resistant or only had medium susceptibility to fusidic acid. The MIC values for strains with medium susceptibility to fusidic acid (4-8 micrograms/ml) showed an evident decrease of the susceptibility to this antibiotic, formerly common in MRSA. At the same time, in 1997-1998 a considerable decrease was observed of the number of MRSA strains belonging to MR8/MR12/MR25/30/33/38/M5/622 phagotype (from 31.1% to 0.8%), and disappearance of strains with phagotypes MR25/56B/M3 and MR8/MR25/622, which in 1990-1995 accounted for 15.6% of the studied staphylococci.