Annual changes in isolation of MRSA in our department and chemotherapeutic effect of antibiotics including minocycline against postoperative infections of methicillin-resistant S. aureus

Assessment has been made, using MIC values and coagulase types, of 214 strains of Staphylococcus aureus isolated from the lesions of inpatients at the First Surgical Department, Hiroshima University, from 1983 to 1988. The obtained results are summarized below: 1. Frequency of MRSA among all the strains of S. aureus during a period from 1983 to 1987 was higher than 50%. 2. Highly methicillin-resistant strains (MIC of methicillin greater than 100 micrograms/ml) emerged in 1984 and thereafter, showed a trend of increase through 1987. 3. The highly methicillin-resistant strains are of coagulase II type strain and they are considered to be inhospital epidemic strains. 4. Both ofloxacin and minocycline (MINO) showed good activities against highly methicillin-resistant strains, but many resistant strains were resistant to beta-lactam and aminoglycoside agents. Based on the above basic assessment, chemotherapies mainly using MINO were performed on cases of MRSA infections experienced at the First Surgical Department, Hiroshima University in a period from July, 1987, to November, 1988, and the following results were obtained. 1. Drugs used were: single MINO in 2 cases; MINO+imipenem/cilastatin (IPM/CS) in 4 cases; MINO+IPM/CS+tobramycin in 1 case; MINO+cefmetazole (CMZ) in 1 cases; and MINO+fosfomycin+CMZ (changed to MINO+Amikacin) in 1 case, a total of 9 cases. Clinical result showed remarkable effectiveness of these therapies in 3 cases with some degrees of effectiveness in 6 cases, thus the therapies were all effective or better. 2. No particular abnormality was observed in subjective or objective symptoms or clinical laboratory tests, judged from values obtained before and after administration of MINO. The above results agreed with well those of the basic assessment, suggesting the possibility that the chemotherapies mainly using MINO would exhibit effectiveness on MRSA infections.