FoodProductionDaily, USA, France 10-24-06 Research helps cut Salmonella contamination By George Reynolds Government researchers are helping to dramatically reduce Salmonella on pig farms, part of a bid by the US agriculture department to prevent the pathogen from showing up at processing plants. The strategy seems to be working, according to the US Department of Agriculture (USDA). In 1998, only 65 per cent of samples of pork intended for processing plants met the USDA's minimum standards for Salmonella contamination. Since then, work by a number of USDA agencies, which combined efforts in 2003, has helped to push the pass rate beyond 90 per cent in 2005. Pathogens such as Salmonella can can spark off an expensive recall for a food company, which would also have to deal with damage to its brand and the subsequent loss of sales. The work is being done by USDA's Agricultural Research Service (ARS), the Animal and Plant Health Inspection Service (APHIS), and the Food Safety and Inspection Service (FSIS), which joined forces to create the Collaboration in Animal Health and Food Safety Epidemiology (CAHFSE) program. CAHFSE was set up to routinely track critical diseases in animal food production. The research also aims to help smaller producers and processors, who usually do not have the resources to conduct investigations themselves. CAHFSE chose pork as its first food animal to research. During the initial twoyear period, samples were taken from 48 farms across five states. FSIS also funded a pilot study to collect samples from pork-processing plants to be sent for analysis. “It's important to compare microbial data from both the farms and the processing plants to determine the impact each has on movement of pathogens,” said USDA researcher Paula Fedorka-Cray. “The data can also give information about the effects of plant operating speeds and temperatures on pathogen occurrence in swine." A study by the National Animal Disease Centre (NADC) and Iowa State University found that Salmonella infection in hogs waiting in pre-slaughter holding pens shot up 40 per cent from about seven per cent after just a few hours. “We need to find out which pathogens are moving from the farm to the processor and then on to retail,” Fedorka-Cray stated in a USDA report highlighting the research. Researchers are also doing detailed sampling, testing, and analytical work to determine the on-farm and in-plant prevalence of Salmonella, Campylobacter, Escherichia coli, and Enterococcus bacteria. “Because pathogens are fluid over time, we need to gather information over a long period—and across the production spectrum—to find out the impact any particular change in animal health issues or plant operations will have,” stated Fedorka-Cray. So far, the data indicate how variable results can be over time. This highlights the importance of a continual sampling program on the farm and in the processing plant she stated. For example, there are regional, seasonal, and farm effects in play. Sampling only one time, as many studies do, only gives us a snapshot of events. "CAHFSE gives us a history of events," she stated. "One other thing that certainly stands out is that resistance to antibiotics seems to be serotypedependent. In other words, not all types of Salmonella become resistant to antibiotics the same way. Some serotypes will be resistant to one antibiotic and not another. This makes studying antibiotic resistance very complicated.” Meanwhile other USDA researchers are also working on cutting pathogen contamination in pigs destined for the processing plant. In one study, microbiologist Thad Stanton and his team found that normal, commensal bacteria in the swine intestinal tract are not only reservoirs for microbial resistance, but are also, possibly, places where this resistance evolves. Commensal bacteria feed off their hosts without harming them. Some offer protection from infection by interacting with the host's immune system, while others directly benefit the host by digesting feedstuffs and providing nutrients. “One bacterium in particular, Megasphaera elsdenii, showed extremely high levels of resistance to chlortetracycline, an antibiotic used to treat a variety of infections,” stated Stanton. He is researching whether the bacterium can be used as a barometer species to evaluate management strategies and efforts aimed at reducing resistance among intestinal bacteria. In other work, microbiologist Shawn Bearson and colleagues are using microarray technology and other techniques to take research on Salmonella in pigs to the molecular level. Microarrays are microscope slides containing bacterial or host DNA that make it possible to examine thousands of genes in a single experiment. Bearson says she and others on the team want to identify the basis for swine's resistance to colonization by S. enterica serovar Typhimurium by characterizing aspects of the animal's immunity to infection. “Ultimately, we want to produce a genetic profile of the Salmonella-carrier pig,” she stated. Bearson says this will decrease preharvest disease and perhaps lead to diagnostic tests for resistance. “The research will also help the pork industry in breeder pig selection and will help control reemergence of Salmonella on the farm and during transportation and marketing,” she stated.