Trends in Salmonella shedding by U.S. market hogs, swine 2000.

USDA’s National Animal Health Monitoring System’s (NAHMS) conducted a study of the health and management of swine as part of the Swine ‘95 study and Swine 2000 study. The studies were conducted in the top swine states in the U.S. A subset of participating farms allowed collection of fecal samples (50 samples per farm) from pens containing late finishers. The same methodology and laboratory was used in both studies so comparison of results provides a measure of change in on-farm Salmonella status between 1995 and 2000. Samples were tested for Salmonella and questionnaires were used to obtain management data regarding feed management, environmental conditions, vaccination policies, and other factors. The percent of farms with at least one positive sample was 38% in 1995 and 34% in 2000. The percent of samples positive was 6% in 1995 and 2000. The percent of pens positive was 17% in 1995 and 16% in 2000. In contrast to trends in slaughter HACCP Salmonella samples, the similarity in on-farm Salmonella status suggests that on-farm Salmonella intervention has yet to be initiated on a wide scale by producers and that on-farm Salmonella status is not directly related to slaughter Salmonella status

Mechanisms of host-agent interactions in subclinical salmonella infection in pig herds

Salmonella spp. are ubiquitous in nature and have been recovered from nearly all vertebrates (Taylor and McCoy, 1969) and there is little dispute that Salmonella is an intestinal pathogen (D\u27Aoust, 1991; Hsu, 1989). Typically, the organism is thought to pass through the stomach after oral exposure, enter into the intestine, replicate intraluminally, pass through the glycocalyx, undergo endocytosis through the cell cytoplasm, then exocytosis through the basement membrane (Hale and Formal, 1988). Malabsorption and/or the release of prostaglandins may play a role in the manifestation of diarrhea (Gianella et al., 1973). Other factors that may influence fluid loss include the presence of an enterotoxin or cytotoxin/hemolysin (Prasada et al., 1990; Libby et al., 1990; Reitmeyer, 1986)

Accelerated Calvarial Healing in Mice Lacking Toll-Like Receptor 4

The bone and immune systems are closely interconnected. The immediate inflammatory response after fracture is known to trigger a healing cascade which plays an important role in bone repair. Toll-like receptor 4 (TLR4) is a member of a highly conserved receptor family and is a critical activator of the innate immune response after tissue injury. TLR4 signaling has been shown to regulate the systemic inflammatory response induced by exposed bone components during long-bone fracture. Here we tested the hypothesis that TLR4 activation affects the healing of calvarial defects. A 1.8 mm diameter calvarial defect was created in wild-type (WT) and TLR4 knockout (TLR4-/-) mice. Bone healing was tested using radiographic, histologic and gene expression analyses. Radiographic and histomorphometric analyses revealed that calvarial healing was accelerated in TLR4-/- mice. More bone was observed in TLR4-/- mice compared to WT mice at postoperative days 7 and 14, although comparable healing was achieved in both groups by day 21. Bone remodeling was detected in both groups on postoperative day 28. In TLR4-/- mice compared to WT mice, gene expression analysis revealed that higher expression levels of IL-1β, IL-6, TNF-α,TGF-β1, TGF-β3, PDGF and RANKL and lower expression level of RANK were detected at earlier time points (≤ postoperative 4 days); while higher expression levels of IL-1β and lower expression levels of VEGF, RANK, RANKL and OPG were detected at late time points (> postoperative 4 days). This study provides evidence of accelerated bone healing in TLR4-/- mice with earlier and higher expression of inflammatory cytokines and with increased osteoclastic activity. Further work is required to determine if this is due to inflammation driven by TLR4 activation. © 2012 Wang et al

Salmonella prevalence and antimicrobial resistance in swine from 5 US states from 2003 to 2005

The Collaboration in Animal Health and Food Safety Epidemiology (CAHFSE), a USDA joint program of ARS, APHIS, and FSIS was established to track food borne pathogens and monitor animal health issues. Fecal samples (n=9020) were collected and cultured for Salmonella from pens of pigs near slaughter weight (generally~ 22 weeks old) from swine farms in five U.S. states. A prevalence of 8.0, 10.1, and 8.5% was observed in 2003, 2004, and 2005, respectively The top 10 serotypes accounted for 94% of the total Salmonella isolates with S. Derby (45%), S. Typhimurium var. 5- (15%), and S Heidelberg (9%) comprising the top three serotypes each year. Salmonella Give was found in 8% of samples in 2003, 3% of samples m 2004, but was not found in the top 10% of ISolates m 2005. The percentage of Salmonella isolates that were susceptible to all of the 16 antimicrobials tested increased from 6% in 2003 to 15% in 2005. At the same time, the percentage of isolates resistant to 10 or more antimicrobials increased from 1% to 15%. The increase in multiple drug resistance was coincident with an increase in the percentage of S. Derby isolates. Overall, frequency of resistance to individual antimicrobials was relatively stable from 2003 to 2005 and observed differences were related to changes in serotypes over time, which highlights the importance of reporting resistance data by individual serotype. CAHFSE provides a mechanism to monitor changes in serotypes of Salmonella as well as antimicrobial resistance patterns over time

Antimicrobial resistance patterns of Campylobacter from feedlot cattle

Aims: This study examined 448 Campylobacter strains isolated in 1999 and 2000 from US feedlot cattle for resistance to 12 antimicrobials. Methods and Results: Isolates were tested for antimicrobial susceptibility using the E-test method. Approximately 60% (n = 267) were resistant to one or more antimicrobials, and 19·6% (n = 88) were resistant to two or more antimicrobials. Of the Campylobacter jejuni isolates, 49·1% (n = 187) were resistant to tetracycline, 10·2% (n = 39) were resistant to nalidixic acid, 8·4% were resistant to trimethoprim/sulfamethoxazole, and 1·8% (n = 7) were resistant to ciprofloxacin. Resistance to any of the other eight antimicrobials was 1·3% or less, but 14·4% (n = 55) were resistant to two or more antimicrobials. In the Campylobacter coli group, 65·7% (n = 44) were resistant to tetracycline, 52·2% (n = 35) were resistant to trimethoprim/sulfamethoxazole, 22·4% (n = 15) were resistant to nalidixic acid, and 9·0% (n = 6) were resistant to ciprofloxacin. Resistance to any of the remaining eight antimicrobials was 3·0% or less, although 49·3% (n = 33) were resistant to two or more antimicrobials. Conclusions: Although antimicrobials are widely used in US feedlot cattle production, our results demonstrate generally low levels of resistance to a broad range of commonly used antimicrobials relative to other recent studies. Significance and Impact of the Study: Resistance data on Campylobacter isolated from this major US livestock commodity is lacking. This overview enhances current knowledge and provides a basis for further studies

Control of Salmonella Virulence in the Natural Host

The long term goal of this research is to understand the mechanisms that govern Salmonella virulence in the natural host. Much of the genetic and pathogenesis studies have focused on using the murine model of salmonellosis. Although the results from using the model have been useful, there have been several cases where mutants of Salmonella not showing virulence in mice have been virulent in the natural host and visa versa. Therefore, virulence may be mediated by the host to some degree. We have chosen Salmonella choleraesuis which is host-adapted to swine, to study particular genes that may be crucial in causing disease. Specifically, we have begun a project to evaluate several mutants of Salmonella choleraesuis and test them for virulence. We will use strains containing separately or in pairs the following mutations: sly, rpoS, and spvR

Antimicrobial resistance patterns of Campylobacter from feedlot cattle

Aims: This study examined 448 Campylobacter strains isolated in 1999 and 2000 from US feedlot cattle for resistance to 12 antimicrobials. Methods and Results: Isolates were tested for antimicrobial susceptibility using the E-test method. Approximately 60% (n = 267) were resistant to one or more antimicrobials, and 19·6% (n = 88) were resistant to two or more antimicrobials. Of the Campylobacter jejuni isolates, 49·1% (n = 187) were resistant to tetracycline, 10·2% (n = 39) were resistant to nalidixic acid, 8·4% were resistant to trimethoprim/sulfamethoxazole, and 1·8% (n = 7) were resistant to ciprofloxacin. Resistance to any of the other eight antimicrobials was 1·3% or less, but 14·4% (n = 55) were resistant to two or more antimicrobials. In the Campylobacter coli group, 65·7% (n = 44) were resistant to tetracycline, 52·2% (n = 35) were resistant to trimethoprim/sulfamethoxazole, 22·4% (n = 15) were resistant to nalidixic acid, and 9·0% (n = 6) were resistant to ciprofloxacin. Resistance to any of the remaining eight antimicrobials was 3·0% or less, although 49·3% (n = 33) were resistant to two or more antimicrobials. Conclusions: Although antimicrobials are widely used in US feedlot cattle production, our results demonstrate generally low levels of resistance to a broad range of commonly used antimicrobials relative to other recent studies. Significance and Impact of the Study: Resistance data on Campylobacter isolated from this major US livestock commodity is lacking. This overview enhances current knowledge and provides a basis for further studies