닭 대장균의 특성에 관한 연구 I. 혈청형 및 항균성 약제 내성

Studies on characterization of avian escherichia coli I. Serotypes and antimicrobial drug resistance

Five hundred and one Escherichia coli isolates were obtained from chicken with colibacillosis in domestic area over a 7-year period(1979 to 1985). By using the E. coli antisera of 20 different O groups, 36(22.4%) of the 161 isolates tested were classified into 12 O groups, but the remain 125(77.6%) could not be typable. The predominant O groups were O119(3.7%), O25(3.1%), and O78(2.5%) and followed by O45, O1a1b, O15, O18ac18ac(each 1.9%) O2a2b, O8, O13, O86(each 1.2%), and O111ab111ac(0.6%) in decreased order. By the use of disc diffusion method, 501 E. coli isolates were screened for resistance to 13 antimicrobial drugs in common use. The majorities of the isolates were risistant to tetracycline(86.4%), streptomycin(85.0%), sulfonamides(80.6%) and nitrofurantoin(64.5%), while the percentages of them resistant to cephalothin, trimethoprim+sulfamethoxazole and gentamicin were 18.4%, 8.6% and 0.2%, respectively. About 36 to 25% of the isolates were resistant to carbenicillm, ampicillin, chloramphenicol, neomycin, and kanamycin. All of the isolates were susceptible to colistin. Multiple resistances to two or more drugs were observed in 95.2% of the isolates but the frequency of the isolates multiply resistant to 6 or more drugs decreased gradually from 53.8% in 1980 to 23.8% in 1985.