Comparison of postmortem inspection procedures for detecting caseous lymphadenitis of Australian sheep and goats.

Alternative postmortem inspection procedures for the detection of gross abnormalities due to Caseous Lymphadenitis (CLA) of sheep and goats were compared quantitatively against the current Australian Standard (AS4696). Studies on sheep and goats in Australia during 2016 addressed data gaps regarding current prevalence, combinations of multiple lesions within affected carcases and sensitivity of inspection procedures enabling a comparison of alternative with current procedures. Using these contemporary inspection data from 54 915 sheep and 48 577 goats a desktop study estimated the effect of implementing alternative procedures of reduced palpation from eleven carcase sites to the four sites most commonly affected. Under current procedures it was estimated that 86 sheep and 34 goat carcases with CLA lesions are missed per 10,000 carcases. Under alternative procedures it is estimated that an additional 48.4 sheep and 10.5 goat carcases with CLA lesions would be missed per 10 000 carcases. Of these, 38.2 sheep and 5.6 goat per 10 000 carcases would contain CLA only in routinely discarded, non-edible tissue sites. Hence, only an additional 10.2 sheep and 4.9 goat carcases per 10 000 inspected, with CLA in edible tissue sites are estimated to be missed. These alternative procedures have now been officially implemented in the Australian domestic standard.

Listeria monocytogenes does not survive ingestion by Acanthamoeba polyphaga.

Listeria monocytogenes is a ubiquitous bacterium capable of infecting humans, particularly pregnant women and immunocompromised individuals. Although the intracellular invasion and pathogenesis of listeriosis in mammalian tissues has been well studied, little is known about the ecology of L. monocytogenes , and in particular the environmental reservoir for this bacterium has not been identified. This study used short-term co-culture at 15, 22 and 37 degrees C to examine the interaction of L. monocytogenes strains with Acanthamoeba polyphaga ACO12. Survival of L. monocytogenes cells phagocytosed by monolayers of trophozoites was assessed by culture techniques and microscopy. A. polyphaga trophozoites eliminated bacterial cells within a few hours post-phagocytosis, irrespective of the incubation temperature used. Wild-type L. monocytogenes and a phenotypic listeriolysin O mutant were unable to either multiply or survive within trophozoites. By contrast, Salmonella enterica serovar Typhimurium C5 cells used as controls were able to survive and multiply within A. polyphaga trophozoites. The data presented indicate that A. polyphaga ACO12 is unlikely to harbour L. monocytogenes, or act as an environmental reservoir for this bacterium.

Viability of Listeria monocytogenes in co-culture with Acanthamoeba spp.

Listeria monocytogenes is a human pathogen, ubiquitous in the environment, and can grow and survive under a wide range of environmental conditions. It contaminates foods via raw materials or food-processing environments. However, the current knowledge of its ecology and, in particular, the mode of environmental survival and transmission of this intracellular pathogen remains limited. Research has shown that several intracellular pathogens are able to survive or replicate within free-living amoebae. To examine the viability of L. monocytogenes in interaction with Acanthamoeba spp., bacteria were co-cultured with three freshly isolated amoebae, namely Acanthamoeba polyphaga, Acanthamoeba castellanii and Acanthamoeba lenticulata. The survival of bacteria and amoebae was determined using culture techniques and microscopy. Under the experimental conditions used, all amoebae were able to eliminate bacteria irrespective of the hly gene. Bacteria did not survive or replicate within amoeba cells. However, extra-amoebic bacteria grew saprophytically on materials released from amoebae, which may play an important role in the survival of bacteria under extreme environmental conditions.

Mechanism involved in phagocytosis and killing of Listeria monocytogenes by Acanthamoeba polyphaga.

Intra-cellular pathogen, Listeria monocytogenes, is capable of invasion and survival within mammalian cells. However, Acanthamoeba polyphaga trophozoites phagocytose and rapidly degrade Listeria cells. In order to provide more information on amoeba phagocytosis and killing mechanisms, this study used several inhibitor agents known to affect the phagocytosis and killing of bacteria by eukaryotes. Amoebae were pre-treated with mannose, cytochalasin D, wortmannin, suramin, ammonium chloride, bafilomycin A and monensin followed by co-culture with bacteria. Phagocytosis and killing of bacterial cells by amoeba trophozoites was assessed using plate counting methods and microscopy. The data presented indicates that actin polymerisation and cytoskeletal rearrangement are involved in phagocytosis of L. monocytogenes cells by A. polyphaga trophozoites. Further, both phagosomal acidification and phagosome-lysosome fusion are involved in killing and degradation of L. monocytogenes cells by A. polyphaga. However, the mannose-binding protein receptor does not play an important role in uptake of bacteria by amoeba trophozoites. In conclusion, this data reveals the similar principles of molecular mechanisms used by different types of eukaryotes in uptake and killing of bacteria.

A qualitative assessment of Toxoplasma gondii risk in ready-to-eat smallgoods processing.

Toxoplasma gondii is one of the most common parasitic infections of humans and other warm-blooded animals. In most adults, it does not cause serious illness, but severe disease may result from infection in fetuses and immunocompromised people. Consumption of raw or undercooked meats has consistently been identified as an important source of exposure to T. gondii. Several studies indicate the potential failure to inactivate T. gondii in the processes of cured meat products, This article presents a qualitative risk-based assessment of the processing of ready-to-eat smallgoods, which include cooked or uncooked fermented meat, pâté, dried meat, slow cured meat, luncheon meat, and cooked muscle meat including ham and roast beef. The raw meat ingredients are rated with respect to their likelihood of containing T. gondii cysts and an adjustment is made based on whether all the meat from a particular source is frozen. Next, the effectiveness of common processing steps to inactivate T. gondii cysts is assessed, including addition of spices, nitrates, nitrites and salt, use of fermentation, smoking and heat treatment, and the time and temperature during maturation. It is concluded that processing steps that may be effective in the inactivation of T. gondii cysts include freezing, heat treatment, and cooking, and the interaction between salt concentration, maturation time, and temperature. The assessment is illustrated using a Microsoft Excel-based software tool that was developed to facilitate the easy assessment of four hypothetical smallgoods products.

Microbial profiles of carcasses and minced meat from kangaroos processed in South Australia.

The microbiological profiles of kangaroo carcasses and minced meat at game meat processing plants in South Australia were determined in surveys undertaken in 2002 and 2004. In 2002 mean values for log(10) total viable counts (TVC) on carcasses at individual plants ranged from 0.9 to 3.9 log(10) cfu/cm(2), with the mean for all plants being 2.3 log(10) cfu/cm(2). In 2004 the between plant range was narrower, by about 1 log unit, and the mean value for carcasses at all plants was 1.2 log(10) cfu/cm(2). Minced kangaroo meat, was sampled in 2002 only. The overall mean log(10) TVC was 3.9 log(10) cfu/g, with mean counts at individual plants ranging from 3.1 to 4.6 log(10) cfu/g. The overall prevalence of E. coli was 70%, with mean numbers of 2.1 log(10) cfu/g on positive samples. Salmonella was not detected in any of 60 samples from carcasses in 2002. However, in 2004 Salmonella was detected in 4/385 samples (1.04%, 95% CI: 0.28%-2.64%). In minced kangaroo meat, Salmonella was detected in 9/50 (18%, 95% CI: 9%-31%) samples. The abdominal cavity, sampled in 2004, was found to be highly contaminated, with E. coli isolated from 46% of samples and the mean number for positive samples being 2.7 log(10) cfu/cm(2); Salmonella was isolated from 14/120 (12%; 95% CI: 6.52%-18.80%) of abdominal cavities. The practice of collecting carcasses together and pushing grouped carcasses into the chiller likely leads to cross contamination of carcasses from the abdominal cavities of others. To align results of sampling by swabbing for domestic purposes with excision sampling, required for export purposes, both methods were used to sample opposite sides of each of the 50 carcasses sampled in 2004. The results obtained with the two methods of sampling were similar.

Effect of acidified sodium chlorite treatment on chicken carcases processed in South Australia.

A trial on the effectiveness of acidified sodium chlorite (ASC) on Salmonella and Campylobacter was undertaken on chicken carcases after they exited the screw chiller of a commercial premises in Adelaide, Australia. On untreated carcases mean log10 total viable count (25 degrees C) was 2.78/cm2 compared with 1.23/cm2 on treated carcases. Prevalence of E. coli, Salmonella and Campylobacter was 100%, 90% and 100% respectively, on untreated carcases and 13%, 10% and 23% respectively, on treated carcases. The distributions of E. coli, Salmonella and Campylobacter (mean log10 of positive samples) from untreated carcases were 1.55, -1.80 and 1.59/cm2 respectively, and -0.64, -1.85 and -2.21/cm2 respectively, on treated carcases. On untreated carcases S. Sofia and S. Infantis were isolated from 73% and 37% of carcases, respectively; only S. Sofia was isolated from treated carcases. The significant reductions in both prevalence and concentration demonstrated in the present trial indicate that ASC is a risk management option immediately available to the poultry industry.

Use of routine beef carcase Escherichia coli monitoring data to investigate the relationship between hygiene status of incoming stock and processing efficacy.

In Australian export-registered abattoirs microbiological monitoring is carried out within the E. coli and Salmonella Monitoring (ESAM) program. During the calendar year 2003, the ESAM database indicated a national prevalence of Escherichia coli of around 3.0% for steers/heifers and 7.1% for cows/bulls. An investigation was carried out to attempt to elucidate why some establishments had E. coli prevalence markedly higher or markedly lower than the national average. The investigation was based on a questionnaire completed by fifteen export establishments which provided data on livestock, processing, operator training and management. The responses were verified by site visits and then evaluated for their relationship with ESAM data on E. coli in two stages. In stage 1, E. coli prevalence for each abattoir was plotted against each variable recorded by the questionnaire; no single variable was a reasonable predictor for prevalence of E. coli on carcases. In stage 2, variables influencing contamination were grouped under two categories: contamination on incoming livestock (Problem variables) together with the ability of the plant's process to deal with such contamination (Process variables). The analysis prompted two main conclusions. Firstly, plants with a large incoming problem with livestock (long haul, high tag score and proportion of cows/bulls slaughtered) plus "poor" processes had higher than average E. coli prevalence. Secondly, plants with hot water decontamination systems had low E. coli prevalence even when there was a substantial incoming problem with livestock, such as a relatively high proportion of cows/bulls.

A risk microbiological profile of the Australian red meat industry: risk ratings of hazard-product pairings.

A risk profile of microbial hazards across the supply continuum for the beef, sheep and goat meat industries was developed using both a qualitative tool and a semi-quantitative, spreadsheet tool, Risk Ranger. The latter is useful for highlighting factors contributing to food safety risk and for ranking the risk of various product/pathogen combinations. In the present profile the qualitative tool was used as a preliminary screen for a wide range of hazard-product pairings while Risk Ranger was used to rank in order of population health risk pairings for which quantitative data were available and for assessing the effect of hypothetical scenarios. 'High' risk hazard-product pairings identified were meals contaminated with Clostridium perfringens provided by caterers which have not implemented HACCP; kebabs cross-contaminated by Salmonella present in drip trays or served undercooked; meals served in the home cross-contaminated with Salmonella. 'Medium' risk hazard-product pairings identified were ready-to-eat meats contaminated with Listeria monocytogenes and which have extended shelf life; Uncooked Comminuted Fermented Meat (UCFM)/Salami contaminated with Enterohaemorrhagic E. coli (EHEC) and Salmonella; undercooked hamburgers contaminated with EHEC; kebabs contaminated by Salmonella under normal production or following final "flash" heating. Identified 'low' risk hazard-product pairings included cooked, ready-to-eat sausages contaminated with Salmonella; UCFM/Salami contaminated with L. monocytogenes; well-cooked hamburgers contaminated with EHEC. The risk profile provides information of value to Australia's risk managers in the regulatory, processing and R&D sectors of the meat and meat processing industry for the purposes of identifying food safety risks in the industry and for prioritising risk management actions.