W. R. Hudson

Sources of salmonella on broiler carcasses during transportation and processing: modes of contamination and methods of control

Aims: The prevalence and types of salmonella in broiler chickens during transportation and during slaughter and dressing were studied. This was part of a comprehensive investigation of salmonellas in two UK poultry companies, which aimed to find the origins and mechanisms of salmonella contamination.

Effect of changes in processing to improve hygiene control on contamination of poultry carcasses with campylobacter.

Examination of neck skin and caecal samples taken at a commercial processing plant from 15 randomly chosen poultry flocks showed that all flocks were contaminated initially with thermophilic Campylobacter spp., even in the apparent absence of caecal carriage. During processing, numbers of campylobacter on skin samples were reduced by between 10 and 1000-fold. To improve hygiene control generally, chlorinated-water sprays were used to limit microbial contamination on equipment and working surfaces. In addition, chlorine concentrations in process water were increased and any unnecessary carcass contact surfaces in the processing plant were removed. When comparing flocks before and after the changes, it was found that numbers of campylobacter on packaged carcasses were significantly lower after the changes had been made (P 0.001). In practice, however, the reduction would be likely to have little impact on consumer exposure to campylobacter infection.

The ultra rapid chilling of pork

Pork carcasses and sides were ultra rapidly chilled in air at -30°C and 1 m/s for 4 h and compared with controls chilled in air at 0°C and 0·5 m/s for 24 h. All the required heat was removed during the 4-h process, there was a 1% saving in evaporative weight loss, the pork could be cut and packed immediately and there were no important differences in appearance and bacteriological quality. The loin from sides, but not carcasses, froze during chilling and showed a fourfold increase in drip loss. Loins from both sides and carcasses were tougher than the controls.

Use of a marker organism in poultry processing to identify sites of cross‐contamination and evaluate possible control measures

1. Nine different sites at a poultry processing plant were selected in the course of a hazard analysis to investigate the degree of microbial cross-contamination that could occur during processing and the effectiveness of possible control measures. 2. At each site, carcases, equipment or working surfaces were inoculated with a non-pathogenic strain of nalidixic acid-resistant Escherichia coli K12; transmission of the organism among carcases being processed was followed qualitatively and, where appropriate, quantitatively. 3. The degree of cross-contamination and the extent to which it could be controlled by the proposed measures varied from one site to another.

Microbiological survey of five poultry processing plants in the UK

1. Neck skin samples were taken from chickens and turkeys at all the main stages of processing to monitor changes in total viable count (TVC) and counts of coliforms and pseudomonads. 2. Processing reduced TVC by up to 100-fold. Geometric mean counts after packaging were log10 4.4 to 5.3 CFU/g whilst corresponding counts of coliforms were 2.7 to 3.8 CFU/g. 3. Increases in mean TVC or coliforms as a result of either defeathering or evisceration did not exceed 0.6 log. 4. Pseudomonads represented only a minor fraction of the initial microflora of the bird and were often reduced by scalding to a figure which could not be detected by direct plating of samples; however, subsequent contamination resulted in means between log10 2.9 and 4.0 CFU/g for packaged carcases. 5. Although Staphylococcus aureus was readily isolated from defeathering equipment, mean counts from defeathered carcases were always below log10 3.0 CFU/g.

Observations on the distribution and control of Salmonella species in two integrated broiler companies

The effectiveness of deaning and disinfecting broiler farms and the persistence of Salmonella species in two integrated broiler companies was investigated for two years. Both companies used a cleaning and disinfection regime which included the application of a spray of phenolic disinfectant followed by fogging with formaldehyde solution, and this was highly effective in preventing carry-over of infection in the broiler houses. The disinfection of service areas and areas outside the houses was less effective but it had no influence on the Salmonella status of later flocks. Both companies had persistent problems with the contamination of pellet cooling systems in their feedmills with Salmonella 4, 12:d:- in company A, and with Salmonella binza and Salmonella ohio in company B. The hatcher incubators of both companies were also persistently contaminated with Salmonella livingstone and Salmonella thomasville in company A and with Salmonella senftenberg in company B. At both companies sites Salmonella enteritidis and Salmonella typhimurium DT104 were also isolated occasionally from various locations.

Relevance of abattoir hygiene assessment to microbial contamination of British beef carcases

Eleven beef abattoirs were visited, each on five separate occasions. On each occasion, an audit was carried out according to the official Hygiene Assessment System (HAS) and 10 carcases were sampled at four different sites to assess total viable counts and counts of presumptive coliform bacteria. The HAS scores ranged from 11 to 84 (maximum 100), and the logarithmic mean total viable counts for all sampling sites on each batch of carcases varied between 1.98 and 4.14 colony forming units/cm2. The mean prevalence of coliform contamination ranged from 0 to 85 per cent. There was a significant negative correlation (P<0.001) between the mean HAS scores and the mean total viable count for each abattoir, but not between the HAS scores and the numbers of coliforms. Within the HAS, the mean scores for all five categories, before weighting, showed a significant correlation with the mean total viable count (P<0.001); however, the categories concerned with slaughter and dressing, and personnel and practices were of most value in determining trends in carcase contamination. A new advisory classification is proposed for levels of microbial contamination on beef carcases.

Assessing abattoir hygiene with a marker organism

A study was made to evaluate the use of a marker organism for assessing whether hygienic slaughter practices were being followed at red meat abattoirs. The organism, a nonpathogenic strain of Escherichia coli K12 that was resistant to nalidixic acid, was detected and counted on a highly specific isolation medium. With beef carcases, the practice of bagging the excised anus reduced, but did not prevent the spread of the organism from an inoculum applied in the anal region before the hide was removed. The carcases of sheep that were processed at a low-throughput abattoir, were contaminated with the marker after the fleece had been inoculated at a single site. The contamination was significantly reduced (P<0.001) when the operative responsible for flaying had cleaned his hands, arms and apron before and during the handling of each carcase, and used a knife which was freshly pasteurised on several occasions. However, the subsequent washing of carcases had little or no effect on the levels of the marker organism. It was concluded that the marker may be of value in assessing hygiene control, improving present practices, and training abattoir staff.

The bacteriological quality of British beef 2. Frozen minced beef.

Frozen minced beef was obtained from five commercial wholesale producers, and the aerobic plate count, and counts of coliforms, Escherichia coli type 1 and Staphylococcus aureus, determined. No E. coli O157:H7 or salmonellas were detected. The results were evaluated in relation to: (1) two earlier surveys involving fresh mince purchased from retail butchers and supermarkets in the UK (Roberts et al., 1980; Hudson et al., 1986); and (2) the standards set out in Annex II of the Minced Meat Directive 94/65/EC. In respect to the latter, none of the 99 samples of mince examined was unsatisfactory.

The bacteriological quality of British beef 3. Frozen primal joints.

The bacteriological status of 286 primal cuts stored frozen in intervention stores in England, Scotland and Northern Ireland for between 18 and 216 weeks was assessed in two surveys carried out during 1993 (120 cuts) and 1994 (166 cuts). Overall the aerobic plate count at 25°C and the presumptive pseudomonad counts were <10(5)cm(2) on 269 (94%) and 273 (95·5%) of the cuts, respectively. Similarly the coliform and enterococcal counts were <10(3)cm(2) on 98·3% and 97·9% of the cuts, respectively. These findings suggest that the quality of dressing and butchery of the carcasses was of a generally satisfactory standard although on occasions there may have been suboptimum hygiene control during slaughter and butchery or some delay before freezing. The bacterial numbers were higher on average on the cuts obtained from the lower part of the carcass while there was a tendency for the number of aerobic spoilage organism to decrease slightly with increasing storage time. Evidence was obtained in the second survey which indicated differences between microbiological quality of meat coming from different boning plants although it was not possible to make a detailed evaluation of this point as the number of cuts available for sampling from each plant differed in each year.