The survey, whose results were released this month, was carried out from July 2007 to June 2008 on 6,550 rinsate samples from broiler carcasses that were collected at 182 poultry processing plants that slaughtered young chickens and produced whole carcasses under Federal Inspection.

Samples were taken at two different location points (Re-Hang and Post-Chill) in the production process and were collected from two separate shifts.

These samples were analysed to estimate the percent positive rate and levels of Salmonella, Campylobacter, generic Escherichia coli, Aerobic Plate Count (APC), Enterobacteriaceae and total coliforms.

The presence and concentration of specific microbiological targets were compared to determine if significant differences existed between samples taken at Re-Hang and Post-Chill and during the separate shifts.

The survey aimed to discover if there were any differences in the prevalence between the different stages in production – Re-Hang and Post Chill – and also between the different shifts after wash-down and cleaning.

The report says: "The per cent positive rate for the organisms from samples taken at Post-Chill was 8.15 per cent (qualitative) for Salmonella, 97.07 per cent for the Aerobic Plate Count, 57.40 per cent for Enterobacteriaceae, 47.82 per cent for Total Coliforms, and 38.66 per cent for Generic Escherichia coli. The percent positive rate, compositing qualitative and quantitative test results, for Campylobacter was 46.60 per cent.

"When quantitative results from Re-Hang and Post-Chill were compared, a reduction in the percentage positive rate was observed for both Campylobacter (Re-Hang, 71.36 per cent; Post-Chill. 10.66 per cent; P<0.05; p=0.00) and Salmonella (Re-Hang, 40.70 per cent; Post-Chill, 5.19 per cent; P<0.05; p=0.00).

"In comparing the levels of Campylobacter, Salmonella and generic E. coli between Shift One and Shift Two (in plants that have two production shifts), there were no statistically significant differences (P>0.05) between the shifts when comparing the levels of each bacteria.

"The Salmonella serotypes isolated most often from the young chicken samples during this survey were Kentucky, Heidelberg, Typhimurium and Typhimurium (Copenhagen), and these findings were consistent regardless of shift or whether the sample was obtained at Re-Hang or Post-Chill."

The report says that the first shift was defined as the first shift after plant clean-up in which chickens would be slaughtered. The researchers expected that bacterial levels on chicken carcasses would be lower during first shift but, as chicken slaughter continued during the day, the levels would increase the longer the samples were collected from clean-up.

However, the analysis indicated that there was no statistically significant difference in the levels of the bacteria analysed between first and second shift, suggesting that at least in the plants taking part in the study, the length of time from clean-up to sample collection does not influence pathogen levels on broiler carcasses.

The survey also took the chance to use a new method of analysing Campylobacter – a direct plating method – that gives a direct enumeration of Campylobacter from chicken rinsates and giving an actual level of contamination.

The researchers said that it allowed them to detect more carcasses that were actually positive.

Further Reading

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You can view the full report by clicking here.