Laura Hungerford

Ecological relationships between the prevalence of cattle shedding Escherichia coli O157:H7 and characteristics of the cattle or conditions of the feedlot pen.

This study was designed to describe the percentage of cattle shedding Escherichia coli O157:H7 in Midwestern U.S. feedlots and to discover relationships between the point prevalence of cattle shedding the organism and the characteristics of those cattle or the conditions of their pens. Cattle from 29 pens of five Midwestern feedlots were each sampled once between June and September 1999. Feces were collected from the rectum of each animal in each pen. Concurrently, samples of water were collected from the water tank, and partially consumed feed was collected from the feedbunk of each pen. Characteristics of the cattle and conditions of each pen that might have affected the prevalence of cattle shedding E. coli O157:H7 were recorded. These factors included the number of cattle; the number of days on feed; and the average body weight, class, and sex of the cattle. In addition, the temperature and pH of the tank water were determined, and the cleanliness of the tank water and the condition of the pen floor were subjectively assessed. The samples of feces, feed, and water were tested for the presence of E. coli O157:H7. E. coli O157:H7 was isolated from the feces of 719 of 3,162 cattle tested (23%), including at least one animal from each of the 29 pens. The percentage of cattle in a pen shedding E. coli O157:H7 did not differ between feedyards, but it did vary widely within feedyards. A higher prevalence of cattle shed E. coli O157:H7 from muddy pen conditions than cattle from pens in normal condition. The results of this study suggest that E. coli O157:H7 should be considered common to groups of feedlot cattle housed together in pens and that the condition of the pen floor may influence the prevalence of cattle shedding the organism.

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.

Prevalence, risk factors, O serogroups, and virulence profiles of shiga toxin-producing bacteria from cattle production environments

Shiga toxin (Stx)-producing bacteria are important human pathogens that have been linked with cattle and associated food products. We recovered Stx-producing bacteria from 27.5% of cattle, 6.8% of water, and 2.3% of wildlife samples from a cattle production area during an 11-month period. Positive samples were found during every month and on 98% of sampling days. We recovered isolates from all cattle operations sampled, and prevalence within operations ranged from approximately 5 to 33%. Cattle prevalence was associated with the presence of Stx-producing bacteria in water and the production group and environment of cattle, with an interaction between production group and environment. Odds of recovering isolates from cattle were highest for groups of adult cows and their unweaned calves in pasture environments. Overall, 49 O serogroups were identified from 527 isolates. Seventy of the isolates contained virulence genes that encoded intimin and enterohemorrhagic Escherichia coli hemolysin. These were serogroups O111, O157, O109, O103, O145, O172, O84, O26, O108, O117, O126, O159, O5, O69, O74, O98, and O-rough. Our results suggest that the prevalence of Stx-producing bacteria can be relatively high in cattle, and associated factors may not be entirely similar to those reported for serotype O157:H7. Although Stx-producing bacteria were frequently detected, the strains may not be equally pathogenic for humans given the wide variety of serogroups and virulence genes. However, focusing on O157:H7 in food safety and surveillance programs may allow other Stx-producing bacteria, which appear to be widespread in cattle, to go undetected.

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.

An economic risk assessment of the management of pregnant feedlot heifers in the USA

Pregnant heifers are undesirable in the feedyard. We applied simulation modeling to a partial-budget model to compare alternative strategies for managing pregnant heifers in feedyards. The model was developed with input costs (cattle, preventive medical care, morbidity, mortality, treatments, and performance), input benefits (sales of poorly performing heifers, baby calves, open (non-pregnant) heifers, recently calved heifers, and pregnant heifers), and net returns as the output. Predicted mean net returns for feeding either open heifers or aborted heifers were greater than

Influence of Diet on Total and Acid Resistant E. coli and Colonic pH

100 (live-basis sales) to

Method to detect the presence of a microorganism or agent in an animal

200 (rail-basis sales) higher than for pregnant heifers. However, there was substantial variability in net returns for all three types of heifers. Net returns were compared among three decision choices made upon arrival of the cattle at the feedyard: (1) palpate all heifers and inject with abortifacient only those pregnant (PALABT), (2) inject all heifers with abortifacient without determining pregnancy status (ABTALL), and (3) do not palpate or administer abortifacient to any of the heifers (NOTHING). Predicted returns for PALABT and ABTALL were equivalent when estimated pregnancy prevalence was 43% (median net returns=

Cleaning Coliform Bacteria from Feedlot Water Tanks

44.92 and

Longitudinal Patterns of Fecal Shedding of Escherichia coli O157:H7 by Feedlot Cattle

50.46, respectively). For heifer lots with pregnancy prevalences </=36%, PALABT yielded higher net returns than ABTALL but the opposite was true when the pregnancy prevalence was >/=49%. Net returns for PALABT and NOTHING were equivalent when the estimated prevalence of pregnancy was 2% on a live-basis sales (median net return=

A Diagnostic Strategy to Classify Pens of Feedlot Cattle by the Prevalence of Escherichia coli O157:H7 Fecal Shedding

50.05) and approximately 0.9% on a rail-basis sales (median net returns=