Cryopreservation of Salmonella enterica in porcine fecal samples

Fecal samples are normally tested for Salmonella soon after collection because storage at any temperature, including refrigeration or freezing, can reduce detection. To evaluate several cryopreservation techniques, autoclaved porcine feces with and without additives were inoculated with 103 CFU S. Derby (UW -9)/g with autoclaved feces pnor to freezing. The mixtures and % of the CFU inoculum that was recovered was as follows: Feces only, 11 %; 50% feces plus 50% glycerol, 45%, 25% feces, 50% glycerol, 25% tetrathionate broth, 63%, 25% feces, 50% glycerol, 25% buffered peptone water (BPW), 66%; 50% feces, 50% glycyceroi/Tris buffer, 58%; 50 % feces, 50% BPW, 30%. When fresh (not autoclaved) feces were used, inoculated with a nalidixic acid resistant S Typhimurium (WI-73), 4% of the inoculum was recovered from undiluted frozen feces wh1le the add1tlon of 50% BPW before freezmg mcreased recovery to 27%

The association between herd characteristics and salmonella prevalence in slaughter age pigs

Many factors have the potential to result in exposure of pigs to Salmonella and/or to increase the potential shedding at the time of slaughter. Observation of selected production systems has suggested that control of Salmonella may not occur using common disease management strategies, such as batch pig flow, as do many other diseases.\u27 A rational approach to Salmonella reduction would be to rank risk factors, to aid in selecting. We designed this study to assess risk factors of Salmonella status at slaughter

Farm-level Risk Factor Assessment for Infection with Salmonella spp.

We are focusing on the factors that predispose to Salmonella spp. infection in commercial pig production systems. Our current project aims to accomplish two primary goals. First, we will define the herd-level and pig-level prevalence for Salmonella infection. Second, we will quantify the farm-level risk factors for Salmonella herd- and pig-level prevalence. The determination of Salmonella infection is species and serotype specific. Twenty-five pigs will be sampled on the farm and 15 at slaughter from each of 70 herds that participate in an ongoing slaughter monitoring project (PigMON). Risks will be assessed by a survey of farms at the time of the slaughter inspection

The association of antimicrobial resistance patterns and reported usage of antimicrobials in commercial growing pig production

The relationship between into microbial use and the development of resistance to antimicrobials has been demonstrated through both external models and has been observed clinically. However, the strength of this relationship in practical production systems has not been clearly quantified. We designed this study to examine the strength of the relationship between use of antimicrobials and the occurrence of antimicrobial resistence among Salmonella spp. collected from the same groups of growing pig

Repeated observations on the Salmonella culture status of midwest U.S. herds

Mesenteric lymph nodes were collected from pigs from 115 Midwest U.S. swine herds at slaughter on two occasions separated by 6-9 months. These herds were sampled up to three additional times during a three-year period, with 30 herds sampled five times. Thirty pigs were sampled at each collection. Herds were categorized positive if one or more samples revealed Salmonella spp. While culture status at collection one was associated with the second sampling collection (p \u3c 0.01), the association was only moderate in strength (OR = 2.6). Herds with three consecutive positive tests (9 of 38) were all positive on sample four. Prevalence estimates were weakly or not correlated between samplings. In conclusion, Salmonella culture status of these swine herds was weakly predictive of future culture results. Accurate description of Salmonella status based on bacterial culture appears to require repeated or ongoing testing

Antimicrobial resistance patterns of Salmonella isolates collected from slaughter age pigs

Salmonellae are ubiquitous in nature and are recovered from many animal species including swine. However, prevalence of specific serotypes can vary. Although carriage is often observed, fecal shedding can be sporadic (2). Salmonella, as well as other food borne pathogens, can be transferred from animals to the human population. However, since the federally mandated HACCP program has been implemented, a reduction in Salmonella among the major food animals has been observed

The effect of buffered peptone water pre-enrichment on detected prevalence of Salmonella in swine feces

Sensitive and specific detection methods are important to understand the epidemiology of Salmonella and to develop appropriate control strategies. The risk of Salmonella contamination of pork is associated with subclinical Salmonella infections in pigs. In most epidemiological investigations, microbiological culture has been used to deterimine Salmonella infection status for infections on swine farms or at slaughter plants. However, identification of Salmonella by culture among subclinically infected pigs may be highly influenced by the intermittent shedding status of pigs. The types and volume of samples used for culture as well as culture protocol used in microbiological examination can influence the sensitivity of the method

Reservoirs of Salmonella infection on swine farms in lllinois

An ecological study was conducted to identify possible reservoirs of Salmonella on swine farms in Dlinois. In 1998, 6 single-site farrow-to-finish swine farms with at least 100 sows, identified previously at slaughter as having a high prevalence of Salmonella infection, were selected for study. Between March and October 1998, each farm was visited 4 times. On each visit, 60- 150 pigs were sampled, from various age groups (pre-weaning pigs, nursery, grower, finisher, sows). Overnight trapping was conducted to collect rodents, cats, and arthropods. Fecal samples were obtained from pigs, rodents and cats. Environmental samples of water, feed, boots and pen floor material were also obtained. Samples were cultured for Salmonella using tetrathionate broth, followed by Rappaport\u27s medium for enrichment. Salmonella was detected in every reservoir for which at least 20 samples were available. Salmonella was detected in the feces of sows and finishing pigs on each farm, and in pen floor samples on 5 of the 6 farms. The overall prevalence of Salmonella in swine fecal samples was 2.8%; the prevalence of Salmonella shedding by pigs increased with increasing age (1.4% in suckling pigs, 3.5% in near market weight finishing pigs, 6.2% in sows). Boot samples had the highest prevalence of infection (17% ), suggesting a likely mode of transntission; on one farm, 81% of boot samples were positive. The prevalence of infection also was relatively high in cats (14%), ntice (10%), and flies (7%). The overall prevalence of Salmonella in floor samples was 7%, with one farm having 20% of floor samples positive, thereby implicating pen floors as a source for transntission. Feed samples had a low prevalence of salmonella (2%), suggesting that feed played a lesser role in Salmonella transntission

Spatial and temporal patterns of the distribution of Salmonella on swine farms in Illinois

An ecological study was conducted to identify possible reservoirs of Sa/monelln. From March to November 1998 there were 4 visits to each of 6 selected swine farms in lllinois. Fecal samples were collected from swine in longitudinal and cross-sectional groups on each visit to each farm. Fecal samples were also collected from chickens, cattle, cats, dogs, rodents, and other wildlife. Overnight trapping and hand capture techniques were used to obtain samples from wildlife, cats, and arthropods. Environmental samples including feed, water, pen floor material, bootdebris, and bird feces were collected. All samples were evaluated as Salmonel/n positive or negative by culture. A total of 3564 samples representing 40 sample types were collected and cultured. Of 2442 swine fecal samples, 935 were from longitudinal cohorts, and 1507 were from cross sectional groups. Non-swine fecal samples and environmental samples comprised the remaining 1123 samples. Salmonella was cultured from 157 samples in 19 different sample types. All positive samples are mapped with representation of location and time of collection on the farm

Herd-level risk for Salmonella culture positive status in slaughtered pigs.

Quantitative definition of risk factors is needed for farms to develop programs and procedures to reduce Salmonella shedding economically and reliably. It is essential that this information be available to producers before full implementation of proposed Salmonella reduction regulations. Producers should then be able to retain market access and choose informed interventions while avoiding unnecessary costs