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We compared the prevalence of antibiotic-resistant Escherichia coli isolates from household-level producers of broiler
(commercial source breeds) and local chickens in the Arusha District of Tanzania. Households were composed of a single
dwelling or residence with independent, penned broiler flocks. Free-range, scavenging chickens were mixed breed and loosely
associated with individual households. A total of 1,800 E. coli isolates (1,200 from broiler and 600 from scavenging local
chickens) from 75 chickens were tested for their susceptibility against 11 antibiotics by using breakpoint assays. Isolates from
broiler chickens harbored a higher prevalence of antibiotic-resistant E. coli relative to scavenging local chickens, including
sulfamethoxazole (80.3 versus 34%), followed by trimethoprim (69.3 versus 27.7%), tetracycline (56.8 versus 20%),
streptomycin (52.7 versus 24.7%), amoxicillin (49.6 versus 17%), ampicillin (49.1 versus 16.8%), ciprofloxacin (21.9 versus
1.7%), and chloramphenicol (1.5 versus 1.2%). Except for resistance to chloramphenicol, scavenging local chickens harbored
fewer resistant E. coli isolates (P , 0.05). Broiler chickens harbored more isolates that were resistant to 7 antibiotics (P ,
0.05). The higher prevalence of antibiotic-resistant E. coli from broiler chickens correlated with the reported therapeutic and
prophylactic use of antibiotics in this poultry population. We suggest that improved biosecurity measures and increased
vaccination efforts would reduce reliance on antibiotics by these households. |
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