Objectives: The objective of this study was to determine the effectiveness of WGS in identifying resistance genotypes of MDR Escherichia coli and whether these correlate with observed phenotypes. ...Methods: Seventy-six E. coli strains were isolated from farm cattle and measured for phenotypic resistance to 15 antimicrobials with the Sensititrew system. Isolates with resistance to at least four antimicrobials in three classes were selected for WGS using an Illumina MiSeq. Genotypic analysis was conducted with in-house Perl scripts using BLAST analysis to identify known genes and mutations associated with clinical resistance. Results: Over 30 resistance genes and a number of resistance mutations were identified among the E. coli isolates. Resistance genotypes correlated with 97.8% specificity and 99.6% sensitivity to the identified phenotypes. The majority of discordant results were attributable to the aminoglycoside streptomycin, whereas there was a perfect genotype–phenotype correlation for most antibiotic classes such as tetracyclines, quinolones and phenicols. WGS also revealed information about rare resistance mechanisms, such as structural mutations in chromosomal copies of ampC conferring third-generation cephalosporin resistance. Conclusions: WGS can provide comprehensive resistance genotypes and is capable of accurately predicting resistance phenotypes, making it a valuable tool for surveillance. Moreover, the data presented here showing the ability to accurately predict resistance suggest that WGS may be used as a screening tool in selecting anti-infective therapy, especially as costs drop and methods improve.
Salmonella
occurs in all the major meat producing livestock species (ruminants, swine and poultry), most often residing within the gastrointestinal tract asymptomatically. While considerable success ...has been achieved post-harvest, the design of effective pre-harvest interventions to control
Salmonella
has lagged. A simplistic view of the extremely complex host/pathogen interaction suggests that the pathogen has a vested interest in not causing illness or death to the host. The former would initiate an immune response from the host and/or the application of therapeutic antibacterial agents, while the latter would require finding another suitable host. Due to the widespread prevalence of
Salmonella
within livestock and poultry, and the relatively few salmonellosis cases in comparison, it appears, and is supported by new research, that
Salmonella
has developed methods to avoid detection by the animal’s immune system and live essentially as a commensal organism within the gastrointestinal tract of the animal. Yet, for reasons that are not fully understood, this “commensal”
Salmonella
does on occasion become virulent, in young and mature animals alike. Indeed, these researchers have documented
Salmonella
carriage throughout the year in cattle, but only rarely, if at all, was salmonellosis observed. Further, evaluation of
Salmonella
isolates (serotype and antimicrobial resistance patterns) from sick and healthy cattle failed to explain that while
Salmonella
was present in the majority of cattle sampled on that farm, only a few developed salmonellosis. Virulence, as well as multi-drug resistance, in both livestock and humans appears to cluster within a few serotypes. As a result, petitions are circulating calling for the labeling of some
Salmonella
serotypes as adulterants, as was done with
Escherichia coli
O157:H7 and other enterohemorrhagic
E. coli
strains. Regulators are considering approaching the
Salmonella
problem by serotype, such as focusing specifically on the top 10 reported serotypes causing human illness. Herein, the authors will discuss the many challenges of controlling
Salmonella
pre-harvest, reflecting on the significant research portfolio that has been generated over the last 25 years, as well as challenging existing paradigms surrounding this pathogen and the experimental methods used to further our understanding of
Salmonella
and/or evaluate methods of control.
Bacteriophage CEV1 was isolated from sheep resistant to Escherichia coliO 157:H7 colonization. In vitro, CEV1 efficiently infected E.coli O157:H7 grown both aerobically and anaerobically. In vivo, ...sheep receiving a single oral dose of CEV1 showed a 2-log-unit reduction in intestinal E. coli O157:H7 levels within 2 days compared to levels in the controls.
Salmonella
is a significant food safety concern in commercial beef production, and some contamination is thought to occur by inclusion of
Salmonella
-infected peripheral lymph nodes (LN) in ground ...beef and through fecal contamination. Surveillance in processing plants assists packers in risk management of
Salmonella
by understanding seasonal trends and risks associated with different cattle types. Approximately 25 fecal samples and 20 LN were collected from animals representing each of five cattle types (cull beef cattle, cull dairy cows, conventional feedlot cattle, all-natural feedlot cattle raised without pharmaceuticals, and grass-finished cattle) and each of five climate regions (mixed-temperatures and dry, mixed-temperatures and humid, hot and humid, hot and dry, cold) during each of three seasons (summer, fall, winter) to better characterize
Salmonella
inputs into a commercial cattle processing facility. In total, 1,840 fecal samples and 1,550 LN samples were collected. Fecal samples and LN were cultured for
Salmonella
, and select isolates were serogrouped and screened for antimicrobial resistance. Conventional feedlot cattle had the highest LN
Salmonella
concentrations (1.17 log10 CFU/g LN) in this data set, while cull dairy cows had the highest fecal
Salmonella
concentrations (1.96 log10 CFU/g feces). Conventional feedlot cattle and cull dairy cows had the greatest
Salmonella
prevalence in both LN (32 and 18%, respectively) and feces (37 and 49%, respectively), while all-natural feedlot cattle had the lowest prevalence in the LN (3%) and feces (7%). As expected,
Salmonella
prevalence and concentration was lowest for all cattle types during winter compared to warmer seasons. When examined by climate region, a greater
Salmonella
prevalence in both feces and LN was observed in climate region 4 (hot-dry), than the other regions. Only 21 of 50
Salmonella
isolates examined for antimicrobial susceptibility were identified as multidrug resistant (MDR); cull dairy cows were responsible for 48% of MDR isolates, cull beef cattle were responsible for 38%, and conventional feedlot, grass-fed, and all-natural feedlot cattle were each responsible for 4.8%. These results indicate that different production schemes, season, and climate region may influence which cattle are most likely to introduce
Salmonella
to the abattoir, allowing for greater risk awareness during the slaughter process.
The objective of the current research was to determine if pasteurization of nonsaleable waste milk influences fecal Salmonella concentrations and prevalence, or antimicrobial susceptibility and ...serotype of the cultured isolates. Holstein dairy calves (n = 211) were housed on a single commercial dairy in the southwestern United States and randomly allotted to be fed either pasteurized (PWM; n = 128 calves) or nonpasteurized waste milk (NPWM; n = 83 calves). Fecal samples were collected via rectal palpation or from freshly voided, undisturbed fecal pats, weekly during the first 4 wk of the animal's life and then again at weaning. Eight total collections were made and 1,117 fecal samples cultured for Salmonella. One isolate from each culture-positive fecal sample was preserved for antimicrobial susceptibility screening and serotyping. Sixty-nine percent of the fecal samples were culture positive for Salmonella with no difference due to treatment (67.7 and 69% Salmonella positive for PWM and NPWM treatments, respectively). Few fecal samples (178/1,117; 15.9%) contained Salmonella concentrations above the limit of detection (∼1 cfu/g of feces) with concentrations ranging from 1.0 to 6.46 cfu (log10)/g of feces. Concentration was not affected by treatment. Seventeen different serotypes were identified, the majority of which were Montevideo and Anatum. A greater percentage of Typhimurium (87 vs. 13%), Muenchen (88 vs. 12%), and Derby (91 vs. 9%) were recovered from calves fed PWM compared with NPWM-fed calves. Conversely, Newport (12.5 vs. 86%), Bredeney (22.2 vs. 77.8%), and Muenster (12.5 vs. 87.5%) were lower in PWM compared with NPWM treatments. The majority (66.7%) of isolates were susceptible to all of the antibiotics examined. Results from this one commercial dairy suggest that milkborne Salmonella is not an important vector of transmission in dairy neonates, nor does pasteurization of waste milk influence fecal shedding of this pathogen. Caution should be used, however, when extrapolating results to other farms as Salmonella contamination of milk on farm is well documented. The potential benefits of pasteurization in disease prevention outweigh the potential risks of feeding a nonpasteurized product and warrants incorporation into any calf-rearing program using nonsaleable waste milk for feeding young dairy neonates.
This study was conducted to determine if feeding a
fermentation product (SCFP) to calves would alter the acute phase response to a lipopolysaccharide (LPS) challenge. Crossbred steer calves
= 32; ...274 ± 1.9 kg body weight (BW) were randomly allotted to two treatment diets for 21 d: 1) control, fed RAMP (Cargill, Dalhart, TX) and 2) SCFP, fed the control ration supplemented with NaturSafe at 12 g/hd/d mixed into the TMR (NaturSafe, Diamond V, Cedar Rapids, IA). On day 22, steers were fitted with indwelling jugular catheters and rectal temperature monitoring devices and placed in individual bleeding stalls. On day 23, steers were challenged i.v. with 0.25 µg/kg BW LPS. Blood samples were collected at 0.5-h (serum) or 2-h (complete blood counts) intervals from -2 to 8 h and again at 24 h relative to the LPS challenge at 0 h. Sickness behavior scores (SBS) were recorded after the collection of each blood sample. Rectal temperatures were greater in SCFP steers from 6 to 11 h, at 13 h, from 15 to 20 h, and from 22 to 24 h following the LPS challenge compared to Control steers (treatment × time:
= 0.01). Additionally, SCFP-supplemented steers had reduced (
< 0.01) SBS compared to Control steers. Platelet concentrations remained greater in SCFP-supplemented steers compared to Control steers throughout the study (
= 0.05), while there was a tendency (
= 0.09) for SCFP steers to have greater white blood cells and eosinophils concentrations than Control steers. There was a treatment × time interaction for serum cortisol and glucose (
< 0.01). Specifically, cortisol was greater at 0.5 and 2 h postchallenge but was reduced at 3 h for SCFP steers compared to Control steers. Glucose was greater in SCFP steers at -0.5, 2, and 7.5 h compared to Control steers. Serum amyloid A was reduced in SCFP steers at 0.5 h, yet greater at 1 and 7.5 h postchallenge compared to Control steers (treatment × time:
< 0.01). Fibrinogen concentrations were greater (
< 0.01) in SCFP compared to Control steers. There was a treatment × time interaction (
< 0.01) for tumor necrosis factor-α (TNF-α) such that concentrations were reduced in SCFP steers from 1 to 2 h postchallenge compared to Control steers. Overall, these data suggest that supplementing calves with SCFP may have primed the innate immune response prior to the challenge, particularly platelets, which resulted in an attenuated sickness behavior and TNF-α response to LPS.
Zoonotic enteric pathogenic bacteria can live in the intestinal tract of birds and can be transmitted to food animals or humans via fecal contact. In the present study, cecal samples were collected ...from 376 migratory birds from species often associated with cattle during the fall migration in the Central Flyway of the United States. Brown-headed cowbirds (n = 309, Molothrus ater), common grackles (n = 51, Quiscalus quiscula), and cattle egrets (n = 12, Bubulcus ibis) contained foodborne pathogenic bacteria in their ceca. Salmonella enterica was isolated from 14.9% of all samples, and Escherichia coli O157:H7 from 3.7%. Salmonella serotypes isolated included the following: Muenster, Montevideo, and Typhimurium. Our data suggest that migratory birds associated with cattle could be a vector for zoonotic enteric pathogenic bacteria to be disseminated across long distances.
We set out to describe the prevalence of
Salmonella enterica
in three large, adjacent cattle operations in the southern High Plains of the United States. Operations included two dairies (one of which ...routinely administers a commercially available
Salmonella
vaccine) and one feedlot. Samples were collected monthly for 12 months. At each sample collection, 25 freshly voided fecal pats and a sample from each of the water troughs were collected from each of five pens of cattle within an operation. Each monthly collection included a total of 375 fecal and ~32 water samples for a yearly total of 4,500 and 379 samples, respectively (note that the number of water troughs per pen varied within an operation).
Salmonella
was commonly recovered from fecal (71.3%) and water (28.5%) samples and tended to follow somewhat similar temporal patterns over time. However, its prevalence varied among operations despite being adjacent properties in that
Salmonella
was recovered from 61.3, 80.1, and 75% of fecal samples from dairy 1, dairy 2 and the feedlot, respectively.
Salmonella
prevalence in water samples across collection times averaged 36.1, 70.2, and 46.1% for dairy 1, dairy 2, and the feedlot, respectively. While it is uncertain why the
Salmonella
prevalence varied from operation to operation, the higher observed prevalence of
Salmonella
in water on dairy 2 and/or the use of a commercial
Salmonella
vaccine by dairy 1 may offer a partial explanation.
Abstract
The objective of this study was to determine the difference between two dietary Saccharomyces cerevisiae fermentation products (SCFP) on performance characteristics of young, captive ...white-tailed deer. Pregnant does were randomly assigned to one of two dietary treatment groups. Does were offered a commercially available pelleted deer feed (Record Rack, Cargill, Inc., Wayzata, MN) ad-libitum formulated to provide 10g SCFP/kg feed (XPC; n=52) or the same basal pellet containing the other product at 8.8g SCFP/kg feed (NaturSafe; n=52) to provide approximately 12.5g XPC or 11g NaturSafe per animal daily (Diamond V Mills, Cedar Rapids, IA). Does were on diets for 86±19d prior to fawning and through lactation. Upon discovery of a newborn fawn, BW and morphological measurements were obtained using a soft tape measure. Fawns were weaned at 90d of age and remained on trial for 270-d post-weaning. Fawns were provided with the same diet as their dam throughout the study. Body weights were recorded every 90d during the post-weaning period. Antlers of yearling bucks were scored and weighed after removal of antlers the subsequent fall. Data were analyzed using the MIXED procedure of SAS with main effects of treatment and sex with age of fawn as a covariate. There were no differences in morphological measurements of fawns at birth. Fawns in the NaturSafe group had a greater (P=0.02) weaning weight than fawns in the XPC group, but there were no differences in post-weaning weights. There was a tendency (P=0.11) for a lower mortality rate for fawns in the NaturSafe group. Yearling bucks in the NaturSafe group had a greater antler score (P< 0.01) and antler mass (P=0.02) than bucks in the XPC group. Results indicate a reduction in fawn mortality, improvement in weaning weight, and increased antler growth in yearling bucks supplemented with NaturSafe compared to those supplemented with XPC.
Salmonella is a foodborne pathogenic bacterium that causes human illnesses and morbidity and mortality in swine. Bacteriophages are viruses that prey on bacteria and are naturally found in many ...microbial environments, including the gut of food animals, and have been suggested as a potential intervention strategy to reduce Salmonella levels in the live animal. The present study was designed to determine if anti-Salmonella phages isolated from the feces of commercial finishing swine could reduce gastrointestinal populations of the foodborne pathogen Salmonella Typhimurium in artificially inoculated swine. Weaned pigs (n = 48) were randomly assigned to two treatment groups (control or phage-treated). Each pig was inoculated with Salmonella Typhimurium (2 × 10(10) colony forming units/pig) via oral gavage at 0 h and fecal samples were collected every 24 h. Swine were inoculated with a phage cocktail via oral gavage (3 × 10(9) plaque forming units) at 24 and 48 h. Pigs were humanely killed at 96 h, and cecal and rectal intestinal contents were collected for quantitative and qualitative analysis. Fecal Salmonella populations in phage-treated pigs were lower (p < 0.09) than controls after 48 h. Phage treatment reduced intestinal populations of inoculated Salmonella Typhimurium in pigs compared to controls at necropsy. Cecal populations were reduced (p = 0.07) by phage treatment >1.4 log(10) colony forming units/g digesta, and rectal populations were numerically reduced. The number of pigs that contained inoculated Salmonella Typhimurium was reduced by phage treatment, but a significant (p < 0.05) reduction was only observed in the rectum. We conclude that phages can be a viable tool to reduce Salmonella in swine. Further research needs to be performed to determine the most efficacious dosing regimens and the most effective combinations of phages targeting the diverse Salmonella population found in swine before they can enter the food supply.
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