Salmonella diversity and burden in cows on and culled from dairy farms in the Texas High Plains.

The objective of this study was to characterize the epidemiology of Salmonella carried by dairy cows culled from herds in the Texas High Plains. Feces were collected from a convenience sample of 706 animals culled from nine dairy farms. In addition, individually paired fecal and hide samples were collected from 70 healthy milking cows on three of the dairies. Samples were cultured for Salmonella using routine methods; isolates were serotyped and subjected to a panel of antimicrobial drugs to determine susceptibility. Salmonella was recovered from 32.6% of culled cows. Whole-herd use of a vaccine containing siderophore receptors and porin proteins was associated (p=0.05) with reduced Salmonella prevalence in that the prevalence among herds that practiced whole-herd vaccination was 8.0% compared to 36.8% among herds that did not use this vaccine. The majority (88.6%) of isolates were pansusceptible or resistant to one drug. Of the 3.1% of isolates resistant to more than four drugs, all were Salmonella Newport and were recovered from one dairy. Various serotypes were recovered from individual fecal and hide samples. Salmonella Montevideo was recovered more frequently (p<0.01) from hide samples, whereas Salmonella Cerro was recovered more frequently (p<0.01) from feces. Salmonella was recovered from at least one cow on all dairies. While our study was not a priori designed to address herd-level factors, we found evidence that the whole-herd use of a siderophore receptor and porin protein-containing vaccine might be a useful aid in the control of Salmonella in groups of cattle. As this is a nonrandomized evaluation of an intervention, other herd-level factors that may be correlated with vaccine use, such as biosecurity, might have been responsible for the observed association.

The role of disinfectant resistance of Salmonella enterica serotype enteritidis in recurring infections in Pennsylvania egg quality assurance program monitored flocks.

The Pennsylvania egg quality assurance program (PEQAP) has made major gains in the reduction of Salmonella enterica serotype enteritidis (S. enteritidis). However, S. enteritidis continues to be a major food safety concern for the commercial egg laying industry. Despite intensive control efforts through PEQAP, some commercial egg layer houses still remain positive for S. enteritidis. The primary objective of this study was to determine whether S. enteritidis isolates obtained from historically environmentally S. enteritidis-positive houses were resistant to commonly used disinfectants. Archived S. enteritidis isolates (environmental, rodent, or egg) were compared with recently obtained isolates from the environment, rodents, or eggs from the same S. enteritidis-positive house. In addition, the isolates were compared with archived isolates from those premises that appeared to have eliminated S. enteritidis from their layer facilities. The official methods of the use-dilution analysis of the Association of Official Analytical Chemists were used to evaluate each disinfectant product. Two phenolic, one quaternary ammonium, and one combination product containing quaternary ammonium and formaldehyde were evaluated, in addition to one sodium hypochlorite detergent. All products diluted according to the manufacturers' recommendations killed the S. enteritidis isolates in this test system. There was no difference in susceptibility or resistance to the disinfectants used between the isolates from those facilities that remained S. enteritidis-positive and those that appeared to have eliminated S. enteritidis from their facility.