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Aims: To (i) monitor the presence of Enterobacteriaceae as indicators of faecal contamination on pig carcasses, (ii) examine the potential use of chilling as a critical control point (CCP) and establish its influence on pig carcass categorization by Decision 471/EC and (iii) determine the incidence of E. coli O157:H7 in pigs., Methods and Results: Porcine faecal samples and carcass swabs were collected before and after chilling at four Irish pig abattoirs and examined for Enterobacteriaceae and E. coli O157:H7. Chilling generally reduced Enterobacteriaceae counts on carcasses, but increases were also observed, particularly in one abattoir. E. coli O157:H7 was absent from carcasses before chilling, present on 0.21% after chilling and was recovered from 0.63% of faecal samples. All of the isolates were found to contain virulence genes associated with clinical illness in humans., Conclusions: The data show that overall chilling had the capacity to reduce the numbers of carcasses positive for the presence of Enterobacteriaceae., Significance and Impact of Study: The influence of chilling on the categorization of pig carcasses suggests that it has the potential to improve the numbers of acceptable carcasses and the process could be used as a CCP within a HACCP plan.

An investigation was carried out in a pig abattoir to determine the microbiological status of carcasses being produced after slaughter and dressing. The carcasses were sampled in accordance with EC Decision 471 in relation to the application of hazard analysis critical control point (HACCP) criteria to the slaughter of animals. In this regard, four sites on the animals were examined on five consecutive carcasses during each of 10 visits for the presence of total viable counts and Enterobacteriaceae. A comparison of the EC four-site method, with a whole-body swab technique, as a means of measuring carcass contamination found that the two methods gave significantly different results for both groups of organisms. A comparison of the mean of the individual data from the four sites with the data from the pooled samples revealed that there was a poor relationship between the two. Samples may be taken by excision or swabbing and allocated to three categories of process control, which, in turn, are based on microbiological criteria that are different, depending on whether sampling is by excision or swabbing. The influence of these changes in microbiological criteria is discussed in relation to the categorization of samples as acceptable, marginal, or unacceptable and the influence this has on process control. Finally, the proposed introduction of Salmonella as a safety indicator in the EC HACCP system is discussed.

Thirty-six carcasses were sampled over a 12-month period at an Irish beef abattoir. Between one and five carcass sites (including the hock, brisket, cranial back, bung, inside round and outside round) were sampled after hind leg skinning, hide removal, bung tying, evisceration, splitting, washing, chilling for 24 h and boning, using a wet and dry, cotton wool swab technique. For each sample, total viable counts (TVC), Escherichia coli, total coliforms and Enterobacteriaceae were enumerated. The results are considered in relation to European Union Decision 2001/471/EC which sets performance criteria for TVCs and Enterobacteriaceae in samples taken by excision. Though not explicitly stated in the Decision, it has been proposed that microbiological performance criteria for samples taken by swabbing be set at 20% of the values set for excision samples. Therefore, log mean TVCs in carcass swab samples taken before chilling are acceptable, marginal and unacceptable when they are <2.8, 2.8-4.30 and >4.30 cm(-2), respectively. By these criteria, TVCs on carcasses in the present study were in the marginal range. The marginal result for TVCs was due in the most part to hide removal operations, particularly at the hock and brisket sites. Bacterial contamination on post-chill carcasses was similar or lower to that on pre-chill carcasses, while boning resulted in general increases in TVCs and in E. coli, total coliform and Enterobacteriaceae numbers. In Decision 2001/471/EC, the effects of chilling and boning are not included in the assessment of process control. Data from this study indicate that performance criteria based on log mean Enterobacteriaceae values are unsuitable because of the infrequent occurrence of these organisms on the carcass.

Aims: To investigate the influence of aerobic or vacuum pack storage of beef trimmings on the microbiology, colour and odour of subsequently produced mince. Methods and Results: Trimmings stored aerobically for 7 or 10 days and in vacuum packs for 7, 10, 14 or 22 days at 0 or 5°C were minced, stored aerobically at 0 or 5°C for up to 7 days and examined daily to determine Total viable, Pseudomonas, Lactic acid bacteria, Brochothrix thermosphacta, and Enterobacteriaceae counts, colour and odour. Mincing reduced counts, particularly of Pseudomonas, B. thermosphacta and Enterobacteriaceae, probably because of the action free radicals released from muscle and bacterial cells. Storage of vacuum-packed trimmings for 22 days resulted in improved mince colour and inhibition of the growth of Pseudomonas. Conclusions: The shelf life of mince from trimmings is directly influenced by the trimmings storage conditions, and longer-term vacuum storage of trimmings produced improvements in mince quality. Significance and Impact of the Study: There appears to be no scientific rationale for limiting the storage of vacuum packaging beef trimmings to 15 days, prior to mince production, as stated in EU 835/2004. This study identifies advantages in storing trimmings in vacuum packs for at least 21 days prior to mincing, in terms of improved mince quality. [ABSTRACT FROM AUTHOR]

Aim: To investigate the influence of reducing beef surface water activity ( a w) on the survival of Salmonella Typhimurium DT104 during heating. Methods and Results: Beef discs were surface inoculated with S. Typhimurium DT104 and either untreated or dried to achieve surface a w values of 0·95, 0·85 and 0·70. The samples were vacuum packed, heat-treated at 60°C and removed at predetermined times. The inactivation curves were influenced by a w and treatment time. Biphasic inactivation curves were observed for S. Typhimurium DT104 heat-treated on beef samples with altered a w values, which were characterized by an initial decline in cell numbers at commencement of heating followed by a much slower rate of inactivation during the remaining treatment period. Point estimates of the heating time required to achieve a 1 log reduction on beef surfaces with a w of 0·99, 0·95, 0·85 and 0·70 were 0·5, 1·55, 11·25 and 17·79 min, respectively. Conclusions: A decrease in beef surface a w can substantially enhance the survival of S. Typhimurium DT104 after heating. Significance and Impact of the Study: Caution needs to be taken using dry air as a decontamination method as this may rapidly decrease product surface and pathogen a w values resulting in enhanced survival. [ABSTRACT FROM AUTHOR]

Aims: To determine the prevalence, seasonal variation and virulence characteristics of Escherichia coli O157:H7 in lambs presented for slaughter in Ireland. Methods and Results: Over a 13-month period, pre- and postchill carcass swabs, faeces and fleece samples from 1600 lambs were examined for the presence of E. coli O157:H7. Escherichia coli O157:H7 was isolated from 5·75% (23/400) of fleece samples, 1·5% (6/400) of pre- and 1% (4/400) of postchill carcass swabs but was not isolated in faeces (0/400). The present study detected no evidence of seasonal variation. Polymerase chain reaction analysis showed that both the vt1 and vt2 genes associated with clinical illness were carried by five of the E. coli O157:H7 isolates, while 24 of the remaining isolates carried the vt2 gene only. Phage typing detected four different subtypes: PT 32 (48·48%), PT 8 (12·12%), PT 31 (12·12%) and PT 21/28 (12·12%). Conclusions: Escherichia coli O157:H7 is present in lambs at slaughter in Irish abattoirs and the virulence profiles of these isolates reveals that they are potentially harmful to humans. Significance and Impact of the Study: The present study provides crucial information indicating that sheep may be a significant contributing source to human E. coli O157:H7 infection. [ABSTRACT FROM AUTHOR]

Aims: To investigate the effects of storage and the presence of a beef microflora on the thermal resistance of Salmonella serotype Typhimurium DT104 on beef surfaces and in a broth system during subsequent heat treatments after extended low-temperature storage (4°C for 14 days) or mild temperature abuse (10°C for 7 days). Methods and Results: Surviving Salm. Typhimurium DT104 cells were estimated after heating in a water bath (55°C) by plating beef and broth samples on tryptone soya agar and overlaying with xylose–lysine–deoxycholate agar. In beef and broth systems, D55 values for Salm. Typhimurium DT104 stored at 4°C or 10°C in the presence or absence of a beef microflora were significantly lower ( P < 0·01) than the D values for this organism heat-treated immediately after inoculation. In beef systems, the D55 values were significantly lower ( P < 0·05) in the presence of a beef microflora than the D55 values obtained in ‘pure’ culture under all temperature/storage combinations. However, in broth systems, there was no significant difference between the D55 values obtained in ‘pure’ culture and the D55 values obtained from systems containing beef microflora. Conclusions: Storage of Salm. Typhimurium DT104 significantly reduced the thermal resistance of the pathogen in beef and broth systems. In the presence of high numbers of a Gram-negative beef microflora, the heat sensitivity of the pathogen was further increased on beef surfaces but not in broth. Significance and Impact of the Study: Studies investigating the survival of Salm. Typhimurium DT104 in different food systems will help define safe food preservation processes and will aid in the elimination this pathogen from the food production environments. [ABSTRACT FROM AUTHOR]

Ruminant livestock, particularly cattle, is considered the primary reservoir of Escherichia coli O157:H7. This study examines the transmission of E. coli O157:H7 within groups of cattle during winter housing. Holstein Friesian steers were grouped in six pens of five animals. An animal inoculated with and proven to be shedding a marked strain of E. coli O157:H7 was introduced into each pen. Fecal (rectal swabs) and hide samples (900 cm2 from the right rump) were taken from the 36 animals throughout the study. Water, feed and gate or partition samples from each pen were also examined. Within 24 h of introducing the inoculated animals into the pens, samples collected from the drinking water, pen barriers, and animals hide were positive for the pathogen. Within 48 h, the hides of 20 (66%) of 30 cohort animals shed the marked E. coli O157:H7 strain in their feces on at least one occasion. Animal behavior in the pens was monitored during a 12-h period using closed circuit television cameras. The camera footage showed an average of 13 instances of animal grooming in each pen per hour. The study suggest that transmission of E. coli O157:H7 between animals may occur following ingestion of the pathogen at low levels and that animal hide may be an important source of transmission. [ABSTRACT FROM AUTHOR]