Methicillin-resistant
Staphylococcus aureus (MRSA) were isolated from samples collected from various patients during 1986, and antibacterial activities of 6 aminoglycosides (AGs)(netilmicin (NTL), gentamicin (GM), sisomicin (SISO), dibekacin (DKB), tobramycin (TOB) and amikacin (AMK)) and 4 β-lactam antibiotics (cefazolin (CEZ), cefmetazole (CMZ), cloxacillin (MCIPC) and methicillin (DMPPC)) against these MRSA were evaluated.
Among these 6 AGs, NTL was the most potent, and its MIC
50 and MIC
80 were 1.56 and 3.13μg/ml, respectively. Antibacterial activities of GM, SISO, DKB and TOB were weak, and MIC
50's of GM and DKB were both 100μg/ml, while those of SISO and TOB were 50 and>100 μg/ml, respectively. Frequency of highly resistant specimens to AMK was rather low and its MIC
50 and MIC
80 were 12.5 and 25μg/ml, respectively.
As for antibacterial activities of the above 4 β-lactam antibiotics, the MIC
50 and MIC
80 of CMZ were 6.25 and 12.5μg/ml, respectively, and therefore, its antibacterial activity to MRSA is relatively good. However, MIC
50´s of CEZ, MCIPC and DMPPC were all>100μg/ml, showing poor antibacterial activities.
Recently, MRSA became a problem in various fields of clinical practice, and a number of literatures reporting refractory infections caused by MRSA have been published 1-5). Since MRSA is featured as multiply resistant bacteria 6), it is known that MRSA is resistant to the majority of existing antibiotics (penicillins, cephems, macrolides, AGs,
etc.).
In 1985, we reported results of our study concerning the antibacterial activities of a number of CEPs and some of AGs against multiply resistant
S. aureus including MRSA6). Antibacterial activities mainly of AGs against MRSA freshly isolated from clinical samples have been evaluated in the present study.
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