Variation in numbers of bacteria on paired chicken carcass halves

Bacterial counts from paired broiler carcass halves were examined for relationships between numbers and kinds of bacteria that might indicate fecal contamination. Broiler carcasses removed from a commercial processing plant just before chilling were split aseptically along the midline, and each side was rinsed in 400 mL of phosphate buffered saline for 1 min with either mechanical or hand shaking. Both halves of six carcasses were rinsed on four different days for a total of 24 carcasses sampled with each shaking method. Aerobic bacteria, coliforms, Escherichia coli, and Campylobacter jejuni were enumerated and summed to obtain whole carcass counts. There were no significant (P < 0.05) differences in numbers of bacteria recovered by the two rinse methods. In left-right comparisons, only E. coli was significantly different (P = 0.04), with the right side having higher counts (least-square means of 1.09 vs. 0.97). For aerobic plate count (APC), coliforms, E. coli, and Campylobacter, correlations between paired left and right side counts were between 0.78 and 0.86. The correlation between whole carcass counts and absolute left-right differences was significant for APC (0.43), but was not significant for coliforms, E. coli, and Campylobacter, so higher whole carcass counts were not associated with higher counts on one side of the carcass. Correlations between different bacteria on whole carcasses were significant for E. coli-APC (0.39), E. coli-coliforms (0.67), and APC-coliforms (0.71), but other combinations had non-significant correlations. The correlation was not significant between E. coli and Campylobacter, a relatively fragile organism whose presence can be interpreted to indicate fairly recent fecal contamination. There were no indications that high E. coli counts on inspection-passed, prechill carcasses indicated recent fecal contamination.