[The taxonomic distribution, characteristic and susceptibility against antimicrobial agents of methicillin-resistant staphylococci isolated from blood].

The species, mecA gene, beta-lactamase activity, the ability of slime formation and drug susceptibilities of 386 strains of staphylococci which were isolated from blood in our laboratory were studied. The coagulase typing of each strains identified as S. aureus was also determined. These 386 strains consisted of various species, e.g., S. aureus, S. epidermidis, S. capitis, S. caprae, S. hominis, S. simulans, S. haemolyticus, and S. lugdunensis. mecA (methicillin-resistant gene) was detected in 84 (67.7%) of 124 S. aureus and 195 (75.3%) of 259 CNS, but there was no statistical difference. However mecA positive rate was higher in S. epidermidis and S. caprae, lower in S. hominis compared with S. aureus, S. lugdunensis having mecA has not been reported, but one of two our S. lugdunensis strains had mecA. The positive rate (77.4%: 65/84) of beta-lactamase of methicillin-resistant Staphylococcus aureus (MRSA) was lower than that (95.5%: 187/195) of methicillin-resistant coagulase-negative staphylococci (MRCNS). Concerning the ability of slime formation, CNS had higher positive rate, especially in case of MRCNS (46.2%: 84/182) than S. aureus. On the other hand, MRCNS showed a tendency to be less resistant to some antimicrobials than MRSA. Especially against cephalothin (CET), the resistant rate of MRSA and MRCNS were 86.9% and 5.6%, respectively. Among the main species of MRCNS, S. capitis and S. caprae were more resistant than S. epidermidis and S. simulans to cefaclor (CCL), cefmetazole (CMZ), flomoxef (FMOX) and fosfomycin (FOM). Hereafter, one should be careful about infectious disease caused by CNS especially in immuno-compromised host, because many species of CNS have higher positive rate of beta-lactamase and slime formation than S. aureus beside mecA.