[Hospital and district differences in susceptibilities to antibiotics of main clinical isolates].

A nationwide survey of susceptibilities of Staphylococcus aureus, Escherichia coli, Klebsiella sp. and Proteus mirabilis initiated in 1980 was continued in 1986. This report documents differences in susceptibilities of clinical isolates of the above microorganisms to ampicillin (ABPC), cefazolin (CEZ), cefmetazole (CMZ) and gentamicin (GM) among general hospitals throughout Japan. Clinical isolates of each species of microorganisms which were collected in 24 hospitals made up each study group and were collected at the Kosei General Hospital, Tokyo, from April 1980 to March 1986. We compared the variability in the resistant rates (MIC greater than or equal to 25 micrograms/ml) and MICs of each antibiotic for 50% and 80% of the isolates among the hospitals. MICs were determined by the serial 2 fold agar plate dilution method, standardized by the Japan Society of Chemotherapy, with an inoculum of approximately 10(6) CFU/ml or 10(8) CFU/ml. Susceptibility patterns of S. aureus to ABPC, CEZ and GM, of E. coli to ABPC, of Klebsiella sp. to CEZ and GM and of P. mirabilis to ABPC, CEZ and GM varied from hospital to hospital. On the other hand, the differences in the susceptibility patterns among the 6 districts of Japan were not obvious, because the differences were affected by different susceptibility patterns of each hospital located in each district.