[Drug-resistance and its transferability of Shigella strains isolated in 1986 in Japan].

Two hundred and fifty Shigella strains isolated in Japan were examined for their drug-resistances and their conjugal transferability. Drugs used and the isolation frequency of resistant strains were: sulfanilamide (SA) 96%, streptomycin (SM) 85%, tetracycline (TC) 82%, fosfomycin (FOM) 76%, chloramphenicol (CP) 51%, trimethoprim (TMP) 46%, ampicillin (ABPC) 45%, nalidixic acid (NA) 6%, kanamycin (KM) 5%, cephaloridine (CER) 4%, gentamicin (GM) 0%, amikacin (AMK) 0%, colistin (CL) 0%, norfloxacin (NFLX) 0%. All of the KM-resistances and none of the FOM-resistances were transferable. Each 20 to 30% of CP, TC, SM, SA or ABPC-resistant isolates transferred each drug-resistance. Two thirds of the isolates were brought to Japan by travellers mostly from South-East Asia. The isolation frequency of resistant strains was not different between domestic and foreign strains except that NA-resistance was not found in foreign strains. The frequency of isolates carrying transferable R plasmids were higher in domestic strains than foreign strains. Most of the isolated had multiple drug-resistance. Major resistance types were: (CP, TC, SM, SA, ABPC) 22%; (TC, SM, SA, TMP) 20%; (CP, TC, SM, SA, ABPC, TMP) 16%; (TC, SM, SA) 8%. Strains showing different resistance types were different among each other in their serum type, conjugal transferability, and derived country. Stepwise evolution of multiple resistance in one country was not demonstrated. The resistance types of Shigella isolates in Japan have been influenced by yearly change of imported strains.