An assessment of sampling methods and microbiological hygiene indicators for process verification in poultry slaughterhouses.

Studies to determine the appropriateness of the use of populations of indicator bacteria on poultry carcasses for process verification were undertaken in commercial slaughterhouses. Samples were collected from neck skin by excision or from whole carcass rinses and were examined for a range of presumptive process hygiene indicator bacteria. Coefficients of variation were calculated for each bacterial indicator and were significantly lower in excised samples, indicating more reproducible bacterial recovery by this sampling method. Total viable counts of aerobic bacteria, Enterobacteriaceae, and Pseudomonas in samples collected by excision had the lowest coefficients of variation when compared with other indicators and were therefore used for further study. The uncertainties associated with the quantification of each bacterial indicator were calculated and were lowest overall for total viable counts of aerobic bacteria. In general, uncertainty was higher for lower bacterial numbers. Results of microbiological testing on pooled excised neck skin samples were not significantly different from the mean of individually analyzed samples. Bacterial numbers increased by 1 log unit when cultures were stored under chilled conditions typical of those used for transporting samples to external laboratories, but the increases were not significant for Pseudomonas and aerobic bacteria when storage time was less than 17 h. Weak relationships were identified between bacterial indicator numbers and duration of processing, although cleanliness of the processing environment diminished visibly during this time. In the plants visited for this study, there was a poor relationship between presumptive bacterial indicator numbers and process hygiene. Consequently, bacterial analyses for process verification purposes may be of limited value.

Measurement of Campylobacter numbers on carcasses in British poultry slaughterhouses.

An assessment of the proposed new International Organization for Standardization quantitative method for Campylobacter was undertaken on poultry carcass samples collected after the chilling phase of processing. Using a critical differences method, we determined the uncertainty associated with log-transformed Campylobacter numbers by dual analyses of 346 samples collected from 22 processing plants located throughout the United Kingdom. Overall, using log-transformed Campylobacter numbers that ranged between -1 and 5 log, we calculated the expanded measurement of uncertainty (EMU) to be 3.889 for the new method. The EMU changed when ranges of bacterial numbers were grouped for analyses. For low numbers of Campylobacter (< 1 log), the EMU was calculated to be 5.622. There was less measurement error with higher bacterial numbers because the EMU was found to be 0.612 for samples containing Campylobacter numbers of 3 log or above. The draft method was used to measure numbers of Campylobacters on poultry carcasses collected from 18 United Kingdom processing plants in summer and winter. Numbers were significantly lower in winter. We conclude that, although the new method is adequate at quantifying high numbers of Campylobacter on poultry carcasses, further development is required to improve the measurement of small numbers of this causative agent of foodborne illness.

Principles involved in the detection and enumeration of clostridia in foods.

The clostridia are a group of anaerobic bacteria that vary considerably in their biochemical and physiological properties. Not surprisingly, attempts to develop a single isolation medium for all species that occur in foods have not been entirely successful, and the problem is compounded by the need to recover both vegetative cells and spores, some of the latter being unable to germinate without heat activation. Most available isolation media, except some of those used in the dairy industry, include sulphite and an appropriate iron salt, so that blackening due to sulphite reduction can serve as a differential test for clostridia. The limitations of this test in solid agar media are discussed and some advantages described in relation to its use in liquid media for Most Probable Number determinations. A medium favoured for the purpose is the Differential Reinforced Clostridial Medium of Gibbs and Freame (1965). An unresolved issue is whether or not special precautions are needed to exclude oxygen during food sample preparation and dilution, preparation of media, and in conditions used for anaerobic incubation. Although such stringency may be required for maximum recovery of sub-lethally damaged cells or spores, practical constraints in food control laboratories necessitate use of relatively simple procedures for detecting clostridia routinely.

Incorporation of elements of quantitative risk analysis in the HACCP system.

Foodborne bacterial diseases cause considerable morbidity and mortality throughout the world. Preventive measures such as good manufacturing practices (GMP), supplemented by the hazard analysis critical control point (HACCP) system, have been introduced as a means of ensuring the production of safe food. However, their use does not necessarily provide quantitative information on the risks associated with the consumption of a particular food product. To obtain such information, elements of quantitative risk analysis (QRA) need to be used. QRA is defined as a stepwise analysis of the health risks associated with a specific type of food product, resulting in an estimation of the probability of occurrence of adverse effects on health following consumption of the food in question. It also includes an analysis of the nature of the risks. Taking this definition, five successive steps can be recognized: hazard identification, exposure assessment, dose response assessment, risk characterization and risk management. Food production is a dynamic activity, involving changes in, e.g. the composition and microbial quality of raw materials due to seasonal variation. Also, there may be continuing changes in processing conditions and in product composition due to consumer demands. Therefore, it will be desirable to incorporate QRA in existing safety assurance systems, such as HACCP, when sufficient information is available to permit this approach.

Food products and consumer protection: a conceptual approach and a glossary of terms.

There is greatly increased activity in measures being taken to ensure the production of safe food. Several concepts, increasingly based on quantitative risk analysis, are being introduced and new terminology and definitions are being proposed. This article presents a general approach to the production of microbiologically safe food and a glossary of appropriate terms. Where possible, an attempt is made to provide a more adequate terminology, based on that used in risk analysis; background information is also presented.

Hygiene aspects of modern poultry chilling.

An evaluation was made of six commercial poultry chilling systems in relation to factors affecting microbial-contamination of carcasses. These systems included water immersion chilling, air chilling and air chilling with evaporative cooling using water sprays. Samples of neck skin and body cavity were taken from carcasses, together with samples from the chilling environment. These were examined for total aerobic mesophilic microbes and counts of presumptive coliform bacteria and Pseudomonas spp. at specific points in the chilling process. Physical measurements included surface and deep-muscle temperatures of carcasses, water temperatures and chlorine concentrations in the immersion system and air speed and temperature during air chilling. The results obtained for water immersion chilling confirmed previous experience that the washing effect reduces microbial contamination of carcasses, although initially the numbers of pseudomonads tended to increase. The air chillers varied in design and mode of operation, but had little overall effect on microbial contamination of the skin. When a completely dry process was used, microbial numbers were reduced approximately ten-fold in the body cavity. However, the use of water sprays tended to increase contamination of the cavity, while relatively heavy spraying using non-chlorinated water, resulted in a substantial increase in the numbers of pseudomonads.

Comparison of three commercial competitive-exclusion products for controlling Salmonella colonization of broilers in Brazil.

In this study, a new competitive-exclusion (CE) product, Mucosal Starter Culture (MSC), was compared with two other CE products (Aviguard and Avifree) commercially available in Brazil to evaluate their ability to protect newly hatched chicks against colonization by a strain of Salmonella Kedougou. This study was based on a previously published and recommended method for such products. Separate groups of the chicks were dosed orally with the respective treatment materials and challenged 24 h later, and their ceca were examined for Salmonella 5 days after challenge. Under the test conditions, only MSC and Aviguard gave statistically significant (P < 0.05) protection to the chicks, but the MSC treatment yielded the lowest mean level of cecal carriage and the smallest proportion of Salmonella-positive birds.

Distribution of Campylobacter spp. in selected U.S. poultry production and processing operations.

A study was conducted of 32 broiler flocks on eight different farms, belonging to four major U.S. producers. The farms were studied over I complete calendar year. Overall, 28 (87.5%) of the flocks became Campylobacter positive, and only four (12.5%) remained negative throughout the 6- to 8-week rearing period. In the majority of flocks, sampled every 2 weeks throughout production, Campylobacter-positive fecal and cecal samples were not detected until 4 to 8 weeks of age. In only six of the flocks were environmental samples found to be positive before shedding of Campylobacter was detected in the birds. Even in some of the Campylobacter-negative flocks, contamination of the rearing environment was positive for Campylobacter but did not result in the birds subsequently excreting the organism. These findings are discussed in relation to U.S. husbandry practices and present uncertainty about sources of Campylobacter infection for poultry flocks. Birds were often transported to the processing plant in coops that were already contaminated with Campylobacter, and the organisms were sometimes found in samples of scald water and chill water. After chilling, the proportions of Campylobacter-positive carcasses from different producers ranged from 21.0 to 40.9%, which is lower than in other studies, and possible reasons are considered.

Prospects for 'competitive exclusion' treatment to control salmonellas and other foodborne pathogens in poultry.

In newly hatched chicks, the rapid establishment of an adult-type intestinal microflora, via the oral route, produces almost immediate resistance to colonization by any food poisoning salmonellas that gain access to the rearing environment. Exploitation of the 'competitive exclusion' (CE) effect is now an accepted part of the overall strategy by which poultry-associated salmonellas are being controlled in some countries. This review covers practical aspects of CE treatment and factors affecting efficacy in both laboratory-scale trials and field studies. It also considers possible applications in preventing colonization of poultry with Escherichia coli O157 and Campylobacter jejuni. For the latter, evidence suggests that the 'protective' organisms are different from those involved in salmonella control.

Meat inspection: an overview of present practices and future trends.

This is a review of meat inspection literature, its history, current concerns and needs for the future. The value and limitations of meat inspection are discussed, along with the possible modifications or changes that are being developed to modernize an increasingly outdated method of safeguarding public health. The potential of on-farm risk assessment of slaughter animals and the practical considerations that need to be overcome are outlined. The needs of the consumer and subsequent challenges to the meat and farming industry are proposed as the driving force behind the changes occurring in veterinary public health. The current risk to consumers, from such microbial pathogens as Salmonella, Escherichia coli O157:H7 and Campylobacter infection, are highlighted.

The bacteriological quality of British beef 1. Carcasses sampled prior to chilling.

During a survey of 11 beef abattoirs in England 2200 swab samples were taken from carcasses just before chilling. Geometric mean aerobic plate counts at 30°C on each of four carcass sites ranged from log(10) 2·45 to 4·29cfu cm(2) with the brisket and flank samples tending to be more highly contaminated than those from the fore-rib and groin. Presumptive coliforms were isolated from 24% of the samples and the proportion of positive samples among the abattoirs varied between 1·5% and 43%. Analysis of variance confirmed that the bacteriological status of beef carcasses may be influenced by a number of interacting factors, including abattoir, visit, and sampling site. However, the results showed that working methods alone were not critical factors in the production of beef of superior bacteriological quality.

Factors affecting the survival of Campylobacter jejuni in relation to immersion scalding of poultry.

Potential measures for reducing the survival of campylobacters during commercial scalding of poultry have been evaluated in a series of laboratory trials. At 50 degrees C, the lower temperature limit of commercial scalding, raising the pH of a buffered heating medium from 6.0 to 9.0 markedly increased the heat sensitivity of Campylobacter jejuni but the effect was largely nullified in the presence of 1 per cent 'organic material' (50:50 horse blood and milk). Either in the presence or absence of organic material a more rapid rate of kill was observed at 60 degrees C and it was again enhanced by raising the pH to 9.0. Use of a mild detergent at a concentration of 1000 ppm had little effect on the survival of C jejuni at 50 degrees C, but the addition of a cationic quaternary ammonium product at 50 to 100 ppm was highly effective in enhancing the rate of kill, even in the presence of organic material. It is suggested that such products should be evaluated in commercial scalding systems as a possible means of preventing the spread of campylobacters and other organisms of significance to public health.

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.

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.