Possible usefulness of cephem antibiotics with anti-staphylococcal activity for preventing the spread of methicillin-resistant Staphylococcus aureus.

The validity of clinical use of cephem antibiotics for preventing the spread of methicillin-resistant Staphylococcus aureus (MRSA) was investigated using a methicillin-susceptible S. aureus (MSSA) carrying mecA gene. It became evident that drug with anti-staphylococcal activity, such as cefuzonam (CZON) or cefazolin (CEZ), has comparatively low selectivity of high-level methicillin resistant clones (methicillin MIC range from 25 to 800 micrograms/ml) from MSSA carrying mecA gene among cephem antibiotics tested. At concentrations over 1.56 micrograms/ml of both CZON and CEZ, about a 2-3 log10 decrease in viable count was observed. Therefore, it seems that much satisfactory disappearance of bacterial cells can be obtained in cooperation with host defence mechanisms.