ANTIMICROBIAL RESISTANCE AND EPIDEMIOLOGY OF ESCHERICHIA-COLI IN BROILER BREEDER CHICKENS

Escherichia coli isolates were obtained from two flocks of broiler bre eder chickens beginning at 1 day old. Antimicrobial sensitivities were determined and isolates were grouped on the basis of their antibiogra m patterns. In both flocks there was an initial dramatic shift in the antimicrobial resistance patterns of the E. coli isolates which change d from sensitive to multiresistant. Both flocks were given spectinomyc in in drinking water during the first 3 days on the rearer farm. Stati stical analysis of the E. coli isolates in Flock 2 revealed that there was a significant difference between E. coli obtained from 1-day-old birds and those obtained from 1-week-old birds in terms of the proport ion of isolates that were resistant to spectinomycin. It is possible t hat the use of spectinomycin selected for resistant E. coli isolates w hich became dominant in the flocks soon after treatment. There was a s trong association between resistance to spectinomycin and resistance t o other antimicrobial agents, in particular, sulphafurazole and chlora mphenicol.