Drug Resistance and R Plasmids in <i>Escherichia coli isolated</i> from one Flock of Growing Broiler at the Age of one Day and 28 Days Old

Abstract

Eight hundred and fifteen, and 692 strains of Escherichia coli were isolated from one flock of growing broiler when they were one day old (designated as A group) and 28 days old (B group), respectively.These strains were examined for sensitivity to tetracycline (TC), chloramphenicol (CP), streptomycin (SM), sulfonamides (SA), kanamycin (KM), aminobenzylpenicilline (AB-PC) and nalidixic acid (NA).Of 815 strains (A group) and 692 strains (B group) examined, 789 (96.8%) and 678 (98.0%) were resistant to one or more of the drugs tested, respectively.The strains showing double and triple resistance patterns were isolated mainly from A group, however, high incidence of triple or furthermore resistance patterns were recognized among the strains isolated from B group.In the both groups, about 10% of the strains examined were resistant to only one drugs tested, but the remaining 90% them were multiply resistant to two or more of the drugs.The drug resistance patterns recognized commonly among strains isolated from either groups of A or B, were single (SA or TC), double (TC-SA) and triple (TC-SM-SA) resistance patterns.Of 789 (A group) and 678 (B group) resistant strains, 134 and 223 strains were selected for R plasmids transfer tests. R plasmids were detected among the resistant strains of each group, at the almost identical rate of 40.0% (A group) and 38.6% (B group), respectively.It was suggested that kind of drugs used, doses and frequency of medications were related to developing of resistant strains.It was recognized that the drug resistant trains of E. coli were isolated even from day-old chicks (prefeeding) at a high frequency, and a tendency to increasing of isolation of strains having more wide multiple resistant patterns were observed in aged chickens.