[Correlation between coagulase typing and antibiotic susceptibility in methicillin resistant Staphylococcus aureus]

One hundred and fifty-two strains of Staphylococcus aureus isolated from clinical specimens from 1983 to 1987 were examined in their susceptibility against various antibiotics and in their coagulase typing. The isolation frequency of methicillin resistant strains (MRSA) was 61.6%, and highly methicillin resistant (MIC greater than 100 micrograms/ml) group occupied 81.3% of MRSA in 1987. From the study of coagulase type, it was found that current epidemic strains in our ward was type II. In MRSA, type IV strains were predominantly isolated until 1984, but after 1986 most of all MRSA strains belonged to type II. According to the coagulase type-classification of MRSA, the isolation frequency of type II was 97.5% of highly methicillin resistant group. Type II strains were more sensitive to MINO and OFLX than type IV, although in the susceptibility to DMPPC type II was less sensitive than type IV. In type IV, the percentage of beta-lactamase-producing strains was 79.3%, and type II, 33.3% with the high significance of statistical difference (p less than 0.01). In conclusion, a close correlation was suggested between beta-lactamase producing activity and the mechanism of resistance to non-beta-lactam antibiotics as to MINO, OFLX in type IV strains. On the other hand, in type II strains the mechanism of resistance seemed to be simply explained by changes of penicillin-binding-protein (PBP), and there was little concern with beta-lactamase, and other antibiotic-modifying enzymes.