Jeffrey T. Gray

Survey of Salmonella serotypes in feedlot cattle.

A national study of health and management of cattle in feedlots was conducted. Within this study, the prevalence of Salmonella spp. in fecal samples was determined. Fifty fecal samples were collected from each of 100 feedlots. Within each feedlot, 25 fresh fecal samples were collected from the floor of the pens of cattle which had been on feed the shortest and 25 from those on feed the longest periods of time. The total number of samples collected was 4,977; 2,484 and 2,495 from pens of cattle on feed the shortest and longest times, respectively. Salmonella spp. were recovered from 38% (38 of 100) of the feedlots. Salmonella spp. were recovered from 5.5% (273 of 4,977) of all samples and from 3.5% (88 of 2,484) and 7.4% (185 of 2,495) of samples from pens of cattle shortest and longest on feed, respectively. The most common serotype recovered was S. anatum (27.9%), followed by S. montevideo (12.9%), S. muenster (11.8%), S. kentucky (8.2%), and S. newington (4.3%). The most common serogroups identified were E1 (39.6%), C1 (20.7%), and B (10.4%). Shedding of the serotypes most commonly associated with human illness occurred infrequently (13 of 273: 4.8%). This study provides information on the status of Salmonella spp. from cattle in feedlots and may serve as baseline information for future studies.

Isolation of Escherichia coli O157:H7 from intact colon fecal samples of swine.

Escherichia coli O157:H7 was recovered from colon fecal samples of pigs. Polymerase chain reaction confirmed two genotypes: isolates harboring the eaeA, stx1, and stx2 genes and isolates harboring the eaeA, stx1, and hly933 genes. We demonstrate that swine in the United States can harbor potentially pathogenic E. coli O157:H7.

Survival and Infectivity of Salmonella Choleraesuis in Swine Feces

Many serotypes of Salmonella survive well in the environment. Conversely, it is believed that Salmonella Choleraesuis, the host-adapted serotype of swine, does not survive well outside the host. We examined the survival capability of Salmonella Choleraesuis in swine feces. Six pigs were infected with Salmonella Choleraesuis and feces were collected and pooled on days 2, 4, 7, and 10 postinoculation (PI). Feces were stored in a wet and a dry form, and survival was measured over 13 months. Salmonella Choleraesuis was recovered from wet feces through 3 months of storage. In a desiccated (dry) form, Salmonella Choleraesuis was recovered from at least 13 months. Salmonella Choleraesuis shed from swine prior to 4 days PI did not survive as well as that shed 4 days PI or later. We also examined the infectivity of Salmonella Choleraesuis resident in dry feces. Six- or 13-week-old pigs were inoculated with dry feces that had been stored either 2 months or 4 months, respectively. Pigs were inoculated either intranasally or by mixing dry feces with the swine ration. Although clinical signs were mild, Salmonella Choleraesuis was widely disseminated among the tissues of all the pigs inoculated. This study demonstrates that Salmonella Choleraesuis remains viable and infective in the environment. Therefore, contaminated fecal matter can serve as a reservoir for Salmonella Choleraesuis as well as other Salmonella spp. Control measures must consider this environmental reservoir as a source of new infections.

A diagnostic strategy to determine the Shiga toxin-producing Escherichia coli O157 status of pens of feedlot cattle.

Although cattle are reservoirs, no validated method exists to monitor Shiga toxin-producing Escherichia coli O157 (STEC O157) on farms. In 29 Midwestern United States feedlot pens we compared culturing faeces from the individual cattle to: (1) culturing rope devices that cattle rub or chew; and (2) culturing a composite of faecal pats. Eighty-six per cent (68-96%) of pens were classified correctly using rope devices to detect pens with at least 16% of the cattle shedding STEC O157 [sensitivity=82% (57-96%); specificity=92% (62-100%)]. Ninety per cent of pens (73-98%) were classified correctly using composite faeces to detect pens with at least 37% of the cattle shedding STEC O157 [sensitivity=86% (42-100%); specificity=91% (71-99%)]. Ranking pens into three risk levels based on parallel interpretation of the pen-test results correlated (Spearmans r=0.76, P<0.0001) with the pens prevalence. This strategy could identify pens of cattle posing a higher risk to food safety.

Extended-spectrum-cephalosporin resistance in Salmonella enterica isolates of animal origin

ABSTRACT A total of 112 out of 5,709 Salmonella enterica isolates from domestic animal species exhibited decreased susceptibilities to ceftiofur and ceftriaxone, and each possessed the blaCMY gene. Ten Salmonella serotypes were significantly more likely to include resistant isolates. Isolates from turkeys, horses, cats, and dogs were significantly more likely to include resistant isolates.

Transmission of Salmonella enterica serotype Typhimurium in poultry with and without antimicrobial selective pressure

Aims:  To determine the effect of antimicrobial selective pressure on the transmission of antimicrobial resistant and sensitive strains of Salmonella in poultry.

Escherichia coli O157:H7 prevalence in fecal samples of cattle from a southeastern beef cow-calf herd.

The proportion of fecal samples culture-positive for Escherichia coli O157:H7 was determined for samples collected from 296 beef cows on pasture in a single Florida herd in October, November, and December 2001. The overall proportion of samples that cultured positive was 0.03. The proportion of cows that were culture-positive on at least one occasion was 0.091. No effect of pregnancy status or nutritional regimen on the proportion of culture-positive samples for E. coli O157:H7 was detected. We detected a breed effect on the shedding of E. coli O157, with Romosinuano cows having a lower (P < 0.01) proportion of samples culture-positive than Angus or Brahman cows. This difference might have resulted from the presence of confounding variables; however, it also might represent evidence of breed-to-breed genetic variation in E. coli O157 shedding. Further research is warranted to evaluate breed as a possible risk factor for shedding of this important foodborne pathogen. Further substantiated findings could indicate that breed is a cow-calf-level critical control point of E. coli O157:H7.

Effects of Moraxella (Branhamella) ovis Culture Filtrates on Bovine Erythrocytes, Peripheral Mononuclear Cells, and Corneal Epithelial Cells

ABSTRACT Infectious bovine keratoconjunctivitis (IBK) is a highly contagious ocular disease that affects cattle of all ages and that occurs worldwide. Piliated hemolytic Moraxella bovis is recognized as the etiologic agent of IBK. According to data from the Nebraska Veterinary Diagnostic Laboratory System, however, Moraxella (Branhamella) ovis has been isolated with increasing frequency from cattle affected with IBK. The objective of this study was, therefore, to examine M. ovis field isolates for the presence of the putative virulence factors of M. bovis. Culture filtrates from selected M. ovis field isolates demonstrated hemolytic activity on bovine erythrocytes and cytotoxic activity on bovine peripheral blood mononuclear cells and corneal epithelial cells. The hemolytic activity of the culture filtrates was attenuated after heat treatment. Polyclonal antibodies raised against the M. bovis hemolysin-cytotoxin also recognized a protein of approximately 98 kDa in a Western blot assay. These data indicate that the M. ovis field isolates examined produce one or more heat-labile exotoxins and may suggest that M. ovis plays a role in the pathogenesis of IBK.

Testing of swine feces obtained through the national animal health monitoring system's swine 2000 study for the presence of Escherichia coli O157:H7

Fecal samples collected from healthy pigs from 13 of the top 17 swine-producing states were tested for Escherichia coli O157:H7 as part of the National Animal Health Monitoring System Swine 2000 study. Serogroup O157 strains were isolated from 106 of 2,526 fecal samples. None of the isolates were positive by PCR for the fliCh7 (H7 flagellin) gene or for the hly933 (hemolysin) gene; however, one isolate was positive for the stxl gene (Shiga toxin 1), an additional four isolates were positive for the stx2 gene (Shiga toxin 2), and three isolates possessed the eae gene (intimin).

Fecal Shedding of Foodborne Pathogens by Florida-Born Heifers and Steers in U.S. Beef Production Segments

The objective in this study was to assess breed effects in fecal prevalence of Escherichia coli O157:H7 in heifers on a development program in Florida and in their steer half siblings in stocker and feedlot phases in Oklahoma. A secondary objective was to characterize fecal shedding of Campylobacter and Salmonella in subsets of the same samples. After weaning, heifers (n = 501; purebreds and F1 crosses of Angus, Brahman, and Romosinuano) were preconditioned and placed in a local development program. Steers (n = 481) were transported to Oklahoma, where they grazed wheat for 6 months and then were placed in feedlot pens. Fecal samples were obtained at least every 28 days for 12 months on most animals. None of the 10,982 samples tested positive for E. coli O157:H7. Overall fecal prevalences of Campylobacter and Salmonella in heifers were 1.7 and 0.04%, respectively. Corresponding overall prevalences in steer samples were 27.2 and 0.6%. Campylobacter isolates were mostly C. jejuni and were tetracycline resistant. Eight Salmonella isolates were Salmonella Typhimurium that were either quad or penta resistant, most often to ampicillin, chloramphenicol, sulfamexathole, and tetracycline. Feedlot steers had greater odds of positive detection of Campylobacter (odds ratio, 8.5; confidence interval, 3.7, 19.5) than when grazing winter wheat. No breed effect was detected for fecal prevalence of these pathogens.