COMPARISON OF METHODS FOR PROCESSING LITTER AND AIR FILTER MATRICES FROM POULTRY HOUSES TO OPTIMIZE POLYMERASE CHAIN REACTION DETECTION OF SALMONELLA TYPHIMURIUM

Polymerase chain reaction detection of foodborne Salmonella spp. in animal feeds

Foodborne salmonellosis continues to be a public health issue of considerable concern. Animal feed has been a major link in pre-harvest food animal production. Although monitoring systems and control measures are available to limit Salmonella spp. contamination on animal feeds detection methodology is relatively time consuming in the context of time inputs for feed processing and mixing. Current cultural methods of Salmonella spp. detection in feeds require several days for confirmation. This amount of time represents significant problems if control measures are to be effectively implemented in a fashion that keeps feed processing costs low. Molecular methods offer improved sensitivity and potential reduction in assay time. In particular, several commercial polymerase chain reaction (PCR) assays, and combined PCR-hybridization assays have been suggested as possible means to implement more rapid detection of Salmonella spp. extracted from animal feeds. It has now become possible to rapidly detect and confirm the presence of foodborne Salmonella spp. in feed matrices by commercial amplification detection systems. The primary challenges remaining are to develop more reliable recovery and extraction procedures for routine processing of samples from a wide variety of feed matrices and apply molecular techniques for assessing physiological status of Salmonella spp. contaminants in animal feeds.

Presence of Campylobacter inthe respiratory tract of broiler carcasses before and after commercial scalding

Campylobacter could be detected in the thoraco-abdominal cavity of broiler carcasses even if they were carefully eviscerated by hand with no evidence of intestinal rupture or leakage. If Campylobacter is present in the air sacs, which are unavoidably torn during evisceration, it could contaminate the thoraco-abdominal cavity of the eviscerated carcass. This study was done to determine if Campylobacter contamination is present in the respiratory tract of broilers prior to evisceration. Whole carcass rinses and respiratory tract washes were done on broiler carcasses collected at a commercial processing plant just before and just after scalding. Samples were cultured for presence and numbers of Campylobacter, Escherichia coli, coliforms, and total aerobic bacteria. Campylobacter isolates were subtyped by sequencing the short variable region of the flaA gene. The same subtypes of Campylobacter were detected in whole carcass rinse samples as in respiratory tract wash samples from individual broilers. Furthermore, the same numbers and subtypes of Campylobacter were recovered from respiratory tracts of carcasses collected before scalding and those collected after scalding. However, respiratory tracts of carcasses after scalding had higher numbers of E. coli, coliforms, and total aerobic bacteria than those tested before scalding. Although some bacterial counts were higher in the respiratory tracts of carcasses after scalding, Campylobacter counts were not. It appears that Campylobacter is present in the respiratory tracts of broilers as they enter processing, and contamination may be due to airborne bacteria during production or transport.

Efficacy of a commercial polymerase chain reaction-based assay for detection of Salmonella spp. in animal feeds

Salmonellosis is a cyclic problem in the food industry, to which animal feed has been contributory. Current conventional methods of Salmonella spp. detection require 96 h for detection and confirmation. With modern and just-in-time production schedules, a 96-h hold represents a significant expense in storage and decontamination. The commercially available assay, 'BAX for Screening/Salmonella' (BAX), is based on the principle of the polymerase chain reaction and may represent a significant decrease in assay time. Seven fresh feed formulations, two fresh feed ingredients, seven stored feeds and two stored feed ingredients were artificially contaminated with a primary poultry isolate of Salmonella typhimurium and analysed by conventional and BAX methodology. The results of BAX agreed with conventional plating results for 16 of 18 samples spiked with 1200 cfu 10 g(-1) of feed and 13 of 18 samples spiked with 40 cfu 10 g(-1) of feed. Indigenous Salmonella spp. were detected in five of eight samples of poultry diets by conventional methods. With BAX, Salmonella spp. could not be detected in any of the samples after only 7 h of enrichment but could be detected in two dietary samples after 13 h of enrichment and four dietary samples after 24 h of enrichment. Specific sequences of salmonella DNA that were extracted from poultry diets could be detected with BAX.

Recovery of a marker strain of Salmonella typhimurium in litter and aerosols from isolation rooms containing infected chickens

Screening of poultry flocks for foodborne pathogen Salmonella contamination is critical for Salmonella control in preharvest stages of poultry production. In this study, two sampling methods (litter and air filter) were compared for detection of S. typhimurium from experimentally infected chicks some of which had received either a probiotic competitive exclusion culture or transfer of cecal contents from salmonellae-free adult birds. At 4, 9, and 11 days after inoculation, S. typhimurium samples were enumerated by selective plating. For both types of sampling, the control birds yielded the greatest levels of environmental contamination followed by the samples from the probiotic inoculated birds with the birds receiving the cecal transfer culture having the lowest levels of contamination. Although the two sampling methods responded in a similar fashion, detection sensitivity needs to be increased for air filter sampling.