Genetic Diversity and Pathogenic Potential of Attaching and Effacing Escherichia coli O26:H11 Strains Recovered from Bovine Feces in the United States

Escherichia coli O26 has been identified as the most common non-O157 Shiga toxin-producing E. coli (STEC) serogroup to cause human illnesses in the United States and has been implicated in outbreaks around the world. E. coli has high genomic plasticity, which facilitates the loss or acquisition of virulence genes. Attaching and effacing E. coli (AEEC) O26 strains have frequently been isolated from bovine feces, and there is a need to better characterize the relatedness of these strains to defined molecular pathotypes and to describe the extent of their genetic diversity. High-throughput real-time PCR was used to screen 178 E. coli O26 isolates from a single U.S. cattle feedlot, collected from May to July 2011, for the presence or absence of 25 O26 serogroup-specific and virulence-associated markers. The selected markers were capable of distinguishing these strains into molecularly defined groups (yielding 18 unique marker combinations). Analysis of the clustered regularly interspaced short palindromic repeat 1 (CRISPR1) and CRISPR2a loci further discriminated isolates into 24 CRISPR types. The combination of molecular markers and CRISPR typing provided 20.8% diversity. The recent CRISPR PCR target SP_O26-E, which was previously identified only in stx 2-positive O26:H11 human clinical strains, was identified in 96.4% (161/167 [95% confidence interval, 99.2 to 93.6%]) of the stx-negative AEEC O26:H11 bovine fecal strains. This supports that these stx-negative strains may have previously contained a prophage carrying stx or could acquire this prophage, thus possibly giving them the potential to become pathogenic to humans. These results show that investigation of specific genetic markers may further elucidate our understanding of the genetic diversity of AEEC O26 strains in bovine feces

Twenty-four Hour Holter Monitoring in Finishing Cattle Housed Outdoors

Ambulatory electrocardiogram monitoring, in the form of Holter monitoring, has been used in human and veterinary medicine for decades as an aid in the diagnosis and determination of appropriate therapy of heart rhythm disturbances. Within veterinary medicine, Holter monitors have been primarily used in companion animal species, yet little attention has been given to food animal species. Moreover, the heart rhythm in clinically normal cattle fed high concentrate diets and housed outdoors in confined drylot facilities has not been previously reported. In order to properly identify pathologic arrhythmias in cattle, the normal rhythm and arrhythmia prevalence in healthy cattle should be defined. Most prior reports of arrhythmia in cattle have been recordings of relatively shorter duration and in animals that were hospitalized or being handled for various reasons. Therefore, the objective of this study was to determine normal Holter monitor registrations including heart rate, rhythm, number of ventricular premature complexes, and atrial premature complexes in unrestrained finishing Angus steers

Antimicrobials in animal agriculture: Parables and policy

In addition to the scientific, economic, regulatory and other policy factors that impact on antimicrobial decision-making in different jurisdictions around the world, there exist ethical, social and cultural bases for the contemporary use of these products in animal agriculture. Thus, the use of the word ‘parable’ to describe the contemporary moral stories that help to guide ethical antimicrobial use practices and broader policy decisions in animal agriculture is appropriate. Several of these stories reflect difficult decisions that arise from conflicting moral imperatives (i.e. both towards animal welfare and towards human health). Understanding the factors that combine to define the past and present paradigms of antimicrobial usage is crucial to mapping a path forward. There exist barriers, as well as opportunities, for advancing scenarios for reducing antimicrobial usage under a variety of voluntary, regulatory and legal policy frameworks. Any new approaches will ideally be structured to extend the use of present-day antimicrobials into the future, to provide novel alternatives for regulating any newly introduced antimicrobial products so as to maximize their useful life span and to ensure the optimal use of these products in animal agriculture to protect not only the health of animals and the interests of animal health/agriculture stakeholders, but also the human health and the interests of the public at large. A full range of policy approaches, which span the realm from strictly enforced regulations and laws to voluntary guidelines and compliance, should be explored with respect to their risks and benefits in a variety of worldwide settings and in full consideration of a range of stakeholder values

Effects of SRP Vaccine in Reducing E. coli O157:H7 in Cattle

Cattle are the main reservoir of Escherichia coli O157:H7, which is a foodborne pathogen that causes bloody diarrhea in adults and kidney damage in children . E. coli O157 is shed in the feces of cattle, which can be a contamination source of water, ground beef, fresh vegetables, and unpasterized milk and fruit juices. In 2003, shiga-toxin producing E. coli O157:H7 caused 73,000 illnesses, which resulted in over 2,000 hospitalizations and 60 deaths in the United States. The estimated annual cost of this illness was $405 million, which included$370 million for premature deaths, $30 million for medical care, and$5 million for lost productivity. Strategies to reduce this food borne illness must be further investigated. A new vaccine technology targeting E. coli O157:H7 in hopes of reducing the colonization of this pathogen in beef cattle has been developed (Epitopix, LLC, Wilmar, MN). This vaccine was designed to block the transport of iron into the bacterial cell, which is an essential nutrient needed for the survival of this microorganism. Previous trials showed that this vaccine elicited an immune response and reduced fecal shedding of the pathogen in five-month old Holstein steers. The purpose of this experiment was to further evaluate the efficacy of this new siderophore receptor/porin protein (SRP) technology by analyzing fecal shedding and immune responses of mixed-breed calves orally inoculated with E. coli O157:H7

Genetic relationships among temperament, immune function, and carcass merit

Cattle producers historically have selected for docile temperaments simply for management convenience because calmer animals are conducive to safe environments for their peers as well as their handlers. As many producers would acknowledge, there seems to be a relationship between temperament and health, and calmer cattle tend to frequent the working chute for treatment of disease less often. Positive correlations have been found in cattle between temperament traits (chute scores, pen scores, and chute exit velocities) and cortisol concentration in the blood, suggesting that more excitable cattle are easily stressed (Curley et al., 2006; Cooke et al., 2009). In addition, Curley et al. (2007) found that easily excitable animals sustain elevated cortisol concentrations for a longer duration and had greater pituitary and adrenal responses following a stressor than calm cattle. Temperamental cattle have significantly higher mean temperament responses at all points (Oliphint, 2006). Higher basal serum cortisol concentrations may suggest that easily excitable cattle are chronically stressed (Curley et al., 2007), possibly resulting in a compromised immune system, illness, and decreased fat and protein deposition. Common measures of cattle temperament are pen scores, chute scores, and exit velocities. Temperament appears to be moderately heritable, with estimates ranging from 0.15 to 0.44 (Burrow and Corbet, 2000; Kadel et al., 2006; Schrode and Hammack, 1971; Stricklin et al., 1980; Fordyce et al., 1988). If genetic correlations are found between temperament and production traits or immunological factors, they may aid cattle breeders in producing profitable cattle. Such relationships have been found between exit velocity and hot carcass weight (r = -0.54), exit velocity and marbling score (r = 0.10), exit velocity and yield grade (r = -0.22) (Nkrumah et al., 2007), and post-weaning weight gain and exit velocity (Weaber et al., 2006). Bovine respiratory disease (BRD) susceptibility has been estimated to be lowly heritable (Muggli-Cockett et al., 1992; Snowder et al., 2005, 2006, 2007; Schneider et al., 2008). This study was conducted to further investigate the genetic relationships between cattle temperament measured by chute score and exit velocity, immunological factors, and a range of economically relevant performance traits

A Systematic Approach to Identify and Characterize the Effectiveness and Safety of Novel Probiotic Strains to Control Foodborne Pathogens

A total of 44 lactic acid bacteria (LAB) strains originally isolated from cattle feces and different food sources were screened for their potential probiotic features. The antimicrobial activity of all isolates was tested by well-diffusion assay and competitive exclusion on broth against Salmonella Montevideo, Escherichia coli O157:H7 and Listeria monocytogenes strain N1-002. Thirty-eight LAB strains showed antagonistic effect against at least one of the pathogens tested in this study. Improved inhibitory effect was observed against L. monocytogenes with zones of inhibition up to 24 mm when LAB overnight cultures were used, and up to 21 mm when cell-free filtrates were used. For E. coli O157:H7 and Salmonella maximum inhibitions of 12 and 11.5 mm were observed, respectively. On broth, 43 strains reduced L. monocytogenes up to 9.06 log10 CFU/ml, 41 reduced E. coli O157:H7 up to 0.84 log10 CFU/ml, and 32 reduced Salmonella up to 0.94 log10 CFU/ml 24 h after co-inoculation. Twenty-eight LAB isolates that exhibited the highest inhibitory effect among pathogens were further analyzed to determine their antimicrobial resistance profile, adhesion potential, and cytotoxicity to Caco-2 cells. All LAB strains tested were susceptible to ampicillin, linezolid, and penicillin. Twenty-six were able to adhere to Caco-2 cells, five were classified as highly adhesive with > 40 bacterial cells/Caco-2 cells. Low cytotoxicity percentages were observed for the candidate LAB strains with values ranging from -5 to 8%. Genotypic identification by whole genome sequencing confirmed all as members of the LAB group; Enterococcus was the genus most frequently isolated with 21 isolates, followed by Pediococcus with 4, and Lactobacillus with 3. In this study, a systematic approach was used for the improved identification of novel LAB strains able to exert antagonistic effect against important foodborne pathogens. Our findings suggest that the selected panel of LAB probiotic strains can be used as biocontrol cultures to inhibit and/or reduce the growth of L. monocytogenes, Salmonella, and E. coli O157:H7 in different matrices, and environments