[The enzymatic mechanisms of resistance to aminoglycoside antibiotics in methicillin-cephem-resistant Staphylococcus aureus].

We investigated enzymatic mechanisms of resistance to aminoglycoside antibiotics in methicillin-cephem-resistant Staphylococcus aureus (MRSA) by elucidation of the structures of the enzymatic reaction products. According to the MIC data, MRSA, (46 strains) can be classified into 3 groups as follows. 1. Group I (35 strains) was highly resistant to gentamicin (GM) and tobramycin (TOB), and produced 2"-aminoglycosides phosphotransferase (APH (2"]. 2. Group II (8 strains) was sensitive to GM, but was highly resistant to TOB, and produced 4'-aminoglycosides adenylyl-transferase (AAD (4']. 3. Group III (3 strains) was sensitive to GM and TOB, but was highly resistant to kanamycin, and produced 3'-aminoglycosides phosphotransferase (APH (3']-III. Arbekacin (HBK) was the most stable antibiotic to all of the inactivating-enzymes produced by MRSA, and all MRSA were sensitive to HBK.