Pharmacokinetics of enrofloxacin and ceftiofur in plasma, interstitial fluid, and gastrointestinal tract of calves after subcutaneous injection, and bactericidal impacts on representative enteric bacteria.

This study's objectives were to determine intestinal antimicrobial concentrations in calves administered enrofloxacin or ceftiofur sodium subcutaneously, and their impact on representative enteric bacteria. Ultrafiltration devices were implanted in the ileum and colon of 12 steers, which received either enrofloxacin or ceftiofur sodium. Samples were collected over 48 h after drug administration for pharmacokinetic/pharmacodynamic analysis. Enterococcus faecalis or Salmonella enterica (5 × 10(5) CFU/mL of each) were exposed in vitro to peak and tail (48 h postadministration) concentrations of both drugs at each location for 24 h to determine inhibition of growth and change in MIC. Enrofloxacin had tissue penetration factors of 1.6 and 2.5 in the ileum and colon, while ciprofloxacin, an active metabolite of enrofloxacin, was less able to cross into the intestine (tissue penetration factors of 0.7 and 1.7). Ceftiofur was rapidly eliminated leading to tissue penetration factors of 0.39 and 0.25. All concentrations of enrofloxacin were bactericidal for S. enterica and significantly reduced E. faecalis. Peak ceftiofur concentration was bactericidal for S. enterica, and tail concentrations significantly reduced growth. E. faecalis experienced growth at all ceftiofur concentrations. The MICs for both organisms exposed to peak and tail concentrations of antimicrobials were unchanged at the end of the study. Enrofloxacin and ceftiofur achieved intestinal concentrations capable of reducing intestinal bacteria, yet the short exposure of ceftiofur in the intestine may select for resistant organisms.

Prevalence and relatedness of Escherichia coli O157:H7 strains in the feces and on the hides and carcasses of U.S. meat goats at slaughter.

We determined the prevalences of Escherichia coli O157:H7 in feces, hide, and carcasses of meat goats at a U.S. processing plant. Prevalences were 11.1%, 2.7%, and 2.7%, respectively. Sixteen pulsed-field gel electrophoresis (PFGE) subtypes were identified among 49 E. coli O157:H7 isolates, some of which were present on multiple sample types or collection days.

Refrigerated multi-dose insulin vials remain sterile through 6 months of use.

OBJECTIVES: To evaluate sterility in refrigerated multi-dose insulin vials through 6 months of routine aspiration. MATERIALS AND METHODS: Twelve vials of insulin, six of insulin glargine U100 (Lantus®, 10 mL multi-dose vial, Sanofi, Bridgewater, NJ) containing the preservative metacresol, and six of protamine zinc insulin U40 (ProZinc®, 10 mL multi-dose vial, Boehringer Ingelheim, Duluth, GA) containing the preservative phenol, were refrigerated and aspirated twice daily for 6 months, using a new insulin syringe each time. Three vials of each insulin type were wiped with a single-use alcohol swab before sampling. Three times weekly, aspirated samples were inoculated in Tryptic Soy Broth enrichment media and incubated for evidence of microbial growth. Positive broth was cultured and speciated. Endpoints were microbial vial contamination (defined as three consecutive positive cultures of the same organism) and completion of the six-month study period. RESULTS: Microbial contamination was not identified in any vial throughout the study period. A total of 454 aspirated samples were cultured, one of which exhibited non-repeatable growth of Staphylococcus epidermidis. This vial was prematurely lost to breakage after 59 culture samples (29 after the positive growth). CLINICAL SIGNIFICANCE: Refrigerated phenol- and metacresol-containing multi-dose insulin products carry minimal risk for iatrogenic infection through 6 months of use, regardless of alcohol swab preparation.

Grip Strength, Gait Speed and Plasma Markers of Neurodegeneration in Asymptomatic Middle-aged and Older Adults.

BACKGROUND: Pragmatic biomarkers of preclinical dementia would allow for easy and large-scale screening of risk in populations. Physical function measures like grip strength and gait speed are potential predictive biomarkers but their relationship with plasma markers of Alzheimer's Disease and neurodegeneration have not been elucidated. OBJECTIVES: To examine association between physical function measures and plasma markers of Alzheimer's Disease (AD) and neurodegeneration. DESIGN: Cross-sectional and longitudinal analyses. SETTING: Community-based cohort in the city of Framingham, Massachusetts. PARTICIPANTS: 2336 participants of the Framingham Heart Study Offspring cohort with an average age of 61. MEASUREMENTS: Plasma Aß40 and Aß42 were measured in 1998-2001 (Exam-7) and plasma total tau measured 5 years later (Exam-8). Grip strength, fast walk speed and chair stand speed were measured at both exams. Quantification of Aß isoforms in plasma was performed using INNO-BIA assays and plasma total-tau was measured using Quanterix Simoa HD-1 assay. Confounder-adjusted linear regression models examined associations between physical function and plasma markers, Results: Grip strength at Exam-7 was associated with plasma Aß40 (ß -0.006, p-value 0.032) at Exam-7 and plasma total-tau (ß -0.010, p-value 0.001) at Exam-8. Grip strength and fast walk speed at Exam-8 were associated with plasma total-tau at Exam-8 (GS: ß -0.009, p 0.0005; FWS: ß -0.226, p-value <0.0001). Chair stand speed was not associated with plasma markers; Aß42 was not associated with function. CONCLUSION: Grip strength and fast walk speed are associated with plasma markers of neurodegeneration in dementia-free middle aged and older individuals. Both these measures could be used as potential screening tools for identifying individuals at a higher risk for AD and related dementias alongside other validated markers.

Effects of danofloxacin dosing regimen on gastrointestinal pharmacokinetics and fecal microbiome in steers.

Fluoroquinolones are a class of antimicrobial commonly used in human medicine, and deemed critical by the World Health Organization. Nonetheless, two formulations are approved for the treatment of respiratory disease in beef cattle. The objective of this study was to determine the gastrointestinal pharmacokinetics and impact on enteric bacteria of cattle when receiving one of the two dosing regimens (high: 40 mg/kg SC once or low: 20 mg/kg IM q48hr) of danofloxacin, a commonly utilized synthetic fluoroquinolone in veterinary medicine. Danofloxacin was administered to 12 steers (age 7 months) fitted with intestinal ultrafiltration devices at two different dosing regimens to assess the gastrointestinal pharmacokinetics, the shifts in the gastrointestinal microbiome and the development of resistant bacterial isolates. Our results demonstrated high intestinal penetration of danofloxacin for both dosing groups, as well as, significant differences in MIC values for E. coli and Enterococcus between dosing groups at selected time points over a 38 day period. Danofloxacin treatment consistently resulted in the Euryarchaeota phyla decreasing over time, specifically due to a decrease in Methanobrevibacter. Although microbiome differences were minor between dosing groups, the low dose group had a higher number of isolates with MIC values high enough to cause clinically relevant resistance. This information would help guide veterinarians as to appropriate dosing schemes to minimize the spread of antimicrobial resistance.

Inclusion of dried or wet distillers' grains at different levels in diets of feedlot cattle affects fecal shedding of Escherichia coli O157:H7.

Our objectives were to evaluate the prevalence of Escherichia coli O157:H7 in cattle fed diets supplemented with 20 or 40% dried distillers' grains (DG) (DDG) or wet DG (WDG) and assess whether removing DG from diets before slaughter affected fecal shedding of E. coli O157:H7. Eight hundred forty steers were allocated to 70 pens (12 steers/pen). Treatments were no DG (control), 20% DDG or WDG, and 40% DDG or WDG, and each was replicated in 14 pens. In phase 1, eight floor fecal samples were collected from each pen every 2 weeks for 12 weeks for isolation of E. coli O157:H7 and detection of high shedders. In phase 2, half of the pens with DG were transitioned to the no-DG control diet, and pen floor fecal samples were collected weekly from all pens for 4 weeks. During phase 1, prevalence of E. coli O157:H7 was 20.8% and 3.2% for high shedders. The form of DG had no significant effect on fecal E. coli O157:H7 shedding. The prevalence levels of E. coli O157:H7 and the numbers of high shedders were not different between diets with 0 or 20% DG; however, cattle fed 40% DG had a higher prevalence and more high shedders than cattle fed 0 or 20% DG (P ≤ 0.05). During phase 2, overall and high-shedder prevalence estimates were 3.3% and <0.1%, respectively, and there were no differences between those for different DG forms and inclusion levels or when DG was removed from diets. The form of DG had no impact on E. coli O157:H7; however, fecal shedding was associated with the DG inclusion level.

Animal- and truckload-level associations between Escherichia coli O157:H7 in feces and on hides at harvest and contamination of preevisceration beef carcasses.

Cattle feces and hides contribute to carcass contamination with Escherichia coli O157:H7, ultimately impacting beef safety. Primary objectives of our cross-sectional study were to evaluate associations among fecal, hide, and preevisceration carcass prevalence of E. coli O157:H7 and to assess factors affecting carcass contamination. Fecal, hide, and preevisceration carcass samples were collected from up to 32 cattle on each of 45 truckloads presented to a midwestern U.S. abattoir. Enrichment and selective culture were used to assess fecal, hide, and carcass prevalence, and direct plating was used to identify cattle shedding high levels of E. coli O157:H7 in feces. Fecal, hide, and carcass prevalence of E. coli O157:H7 within truckload were significantly correlated (P < 0.05) with each other. Enriched fecal sample prevalence was 13.8%, and high shedder prevalence was 3.3%; 38.5% of hides and 10.5% of carcasses were positive for E. coli O157:H7. We used logistic regression to assess animal- and truckload-level variables affecting the probability of carcasses testing positive for E. coli O157:H7. All truckload-level predictors significantly affected the probability of an E. coli O157:H7-positive carcass, including presence of a high shedder within the truckload (odds ratio [OR] = 4.0; confidence interval [CI], 1.6 to 10.1), high (>25%) within-truckload fecal prevalence (OR = 19.3; CI, 4.7 to 79.0), and high (>50%) within-truckload hide prevalence (OR = 7.7; CI, 3.1 to 19.6). The only significant animal-level predictor was having a positive hide (OR = 1.6; CI, 1.0 to 2.6). Our results suggest that preharvest interventions for reducing E. coli O157:H7 contamination of carcasses should focus on truckload (cohort)-level and hide mitigation strategies.

Neuromuscular Attributes are Associated with Poor Mobility in Older Adults with Vascular Risk Conditions.

BACKGROUND: The mobility of older adults is limited by the compounding effects of vascular health conditions, or vascular risk burden. However, little is known about the role of neuromuscular attributes among those in which vascular risk burden contributes to mobility limitations. OBJECTIVE: We investigated (1) the relationship between the absence/presence of type 2 diabetes, hypertension, and/or obesity and mobility measures and neuromuscular attributes, and (2) whether the association between vascular risk burden and mobility is mediated by lower limb neuromuscular attributes. DESIGN: Cross-sectional analysis of baseline data from 430 older adults within the Boston RISE Study. MEASUREMENTS: Measures of mobility were the Short Physical Performance Battery, habitual gait speed, and functional mobility as measured by the Late Life Function Instrument. We also evaluated lower limb neuromuscular attributes, namely leg strength, leg velocity, trunk extensor muscle endurance, knee and ankle range of motion, and sensory loss. RESULTS: Participants self-reported the presence of None (n=93), One (n=179), Two (n=114), or Three (n=44) of the following conditions: diabetes, hypertension, and obesity. Multivariable regression models indicated that those with a greater vascular risk burden had worse performance on the Short Physical Performance Battery (p=0.01), slower gait speed (p=0.0003) and lower Basic and Advanced Late Life Function Instrument scores (p<0.003). These associations were independent of multiple covariates. Vascular risk burden was also found to be negatively associated with leg strength (p=0.0002) and knee flexion range of motion (p<0.0001) and an associated non-significant trend was observed with leg velocity (p=0.06). In addition, the association between vascular risk burden and mobility outcomes were found to be partially mediated by leg strength, leg velocity, and knee flexion range of motion. CONCLUSIONS: Among older adults with vascular risk burden and mobility problems, neuromuscular impairments in attributes such as leg strength, leg velocity, and knee range of motion may need to be treatment priorities.

Effects of dried distillers' grain on fecal prevalence and growth of Escherichia coli O157 in batch culture fermentations from cattle.

Distillers' grains (DG), a by-product of ethanol production, are fed to cattle. Associations between Escherichia coli O157 prevalence and feeding of DG were investigated in feedlot cattle (n = 379) given one of three diets: steam-flaked corn (SFC) and 15% corn silage with 0 or 25% dried distillers' grains (DDG) or SFC with 5% corn silage and 25% DDG. Ten fecal samples were collected from each pen weekly for 12 weeks to isolate E. coli O157. Cattle fed 25% DDG with 5 or 15% silage had a higher (P = 0.01) prevalence of E. coli O157 than cattle fed a diet without DDG. Batch culture ruminal or fecal microbial fermentations were conducted to evaluate the effect of DDG on E. coli O157 growth. The first study utilized microbial inocula from steers fed SFC or dry-rolled corn with 0 or 25% DDG and included their diet as the substrate. Ruminal microbial fermentations from steers fed DDG had higher E. coli O157 contents than ruminal microbial fermentations from steers fed no DDG (P < 0.05) when no substrate was included. Fecal fermentations showed no DDG effect on E. coli O157 growth. In the second study with DDG as a substrate, ruminal fermentations with 0.5 g DDG had higher (P < 0.01) E. coli O157 concentrations at 24 h than ruminal fermentations with 0, 1, or 2 g DDG. In fecal fermentations, 2 g DDG resulted in a higher concentration (P < 0.05) at 24 h than 0, 0.5, or 1 g DDG. The results indicate that there is a positive association between DDG and E. coli O157 in cattle, and the findings should have important ramifications for food safety.

Epidemiology for the clinical neurologist.

Epidemiology is a foundation of all clinical and public health research and practice. Epidemiology serves seven important uses for the advancement of medicine and public health. It enables community diagnosis by quantifying risk factors and diseases in the community; completes the clinical picture of disease by revealing the entire distribution of disease and presenting meaningful population averages from representative samples; identifies risk factors for disease by detecting and quantifying associations between exposures and disease and evaluating causal hypotheses; computes individual risk to identify high-risk groups to whom preventive interventions can be targeted; evaluates historic trends that monitor disease over time and provide clues to etiology; delineates new syndromes and disease subtypes not previously apparent in clinical settings, helping to streamline effective disease management; and investigates the effects of health services on population health to identify effective public health interventions. The clinician with a grasp of epidemiologic principles is in a position to critically evaluate the research literature, to apply it to clinical practice, and to undertake valid clinical epidemiology research with patients in clinical settings.

Feeding wet distillers grains plus solubles with and without a direct-fed microbial to determine performance, carcass characteristics, and fecal shedding of O157:H7 in feedlot heifers.

The inclusion of wet distillers grains plus solubles (WDGS) in feedlot diets has become a common practice in many regions of the United States due to the expanded production of byproducts and fluctuating corn prices related to ethanol production and other factors. In addition, societal concerns over the continued use of antimicrobials in agriculture production combined with an enhanced interest in disease and pathogen prevention in the food supply have led to an increased interest in use of direct-fed microbials (DFM) in growing and finishing cattle. Direct-fed microbials have been shown to improve ADG and feed efficiency, alter ruminal fermentation, and decrease fecal shedding of potential harmful pathogens in feedlot cattle in some experiments. The objective of this experiment was to evaluate the effects of WDGS inclusion with or without a DFM containing (1 × 10 cfu ∙ heifer ∙ d) combined with (1 × 10 cfu ∙ heifer ∙ d) on the performance, carcass characteristics, and O157:H7 shedding in feedlot heifers. In early August, 288 crossbred heifers (initial BW = 295 ± 28 kg) were assigned to 1 of 4 treatments (12 pens per treatment; 6 heifers per pen) in a randomized complete block design with a 2 × 2 factorial arrangement of treatments. Body weights and fecal grab samples were obtained at approximately 28-d intervals throughout the experiment. Across the feeding period, heifers fed 30% WDGS tended ( = 0.09) to have greater ADG and had greater carcass-adjusted ADG ( = 0.05) compared with heifers fed dry-rolled corn (DRC). Dry matter intake was not affected ( = 0.65) by diet, although carcass-adjusted G:F tended ( = 0.10) to be improved for heifers fed WDGS. Heifers fed 30% WDGS tended ( ≤ 0.10) to have greater fat thickness at the 12th rib, lower marbling scores, and higher yield grades. The inclusion of . combined with . in the diet had no effect ( > 0.10) on performance or carcass merit in the present experiment. The incidence of O157:H7 throughout the experiment was low, with only 18 positive samples across all sampling periods. Neither WDGS inclusion nor the inclusion of . combined with . in the diet had any effect ( > 0.10) on O157:H7 shedding in this experiment. Feeding 30% WDGS to feedlot heifers improved animal performance compared to the DRC-based control diet.

Comparing real-time and conventional PCR to culture-based methods for detecting and quantifying Escherichia coli O157 in cattle feces.

Detection of Escherichia coli O157 in cattle feces has traditionally used culture-based methods; PCR-based methods have been suggested as an alternative. We aimed to determine if multiplex real-time (mq) or conventional PCR methods could reliably detect cattle naturally shedding high (≥10(4) CFU/g of feces) and low (∼10(2) CFU/g of feces) concentrations of E. coli O157. Feces were collected from pens of feedlot cattle and evaluated for E. coli O157 by culture methods. Samples were categorized as (i) high shedders, (ii) immunomagnetic separation (IMS) positive after enrichment, or (iii) culture negative. DNA was extracted pre- and postenrichment from 100 fecal samples from each category (high shedder, IMS positive, culture negative) and subjected to mqPCR and conventional PCR assays based on detecting three genes, rfbE, stx1, and stx2. In feces from cattle determined to be E. coli O157 high shedders by culture, 37% were positive by mqPCR prior to enrichment; 85% of samples were positive after enrichment. In IMS-positive samples, 4% were positive by mqPCR prior to enrichment, while 43% were positive after enrichment. In culture-negative feces, 7% were positive by mqPCR prior to enrichment, and 40% were positive after enrichment. The proportion of high shedder-positive and culture-positive (high shedder and IMS) samples were significantly different from mqPCR-positive samples before and after enrichment (P < 0.01). Similar results were observed for conventional PCR. Our data suggest that mqPCR and conventional PCR are most useful in identifying high shedder animals and may not be an appropriate substitute to culture-based methods for detection of E. coli O157 in cattle feces.

Vaginal microbiota of spayed dogs with or without recurrent urinary tract infections.

BACKGROUND: Limited information is available regarding the vaginal microbiota of normal spayed dogs and spayed dogs with recurrent UTIs. Vaginal lactic acid-producing bacteria (LAB) have been associated with decreased frequency of recurrent urinary tract infection in women and may have a protective role within the urinary tract of female dogs. HYPOTHESIS/OBJECTIVES: Spayed dogs with historical recurrent UTI will have decreased prevalence of LAB and increased prevalence of uropathogenic bacterial populations in the vaginal microbiota when compared with the vaginal microbiota of healthy, spayed dogs. ANIMALS: Twenty-one client-owned adult spayed female dogs with historical recurrent UTI and 23 healthy, spayed female dogs without a history of recurrent UTI. METHODS: Dogs were placed into a recurrent UTI group or control group in this prospective study. Bacterial populations were isolated and characterized from vaginal swabs obtained from each dog. RESULTS: The most common bacterial isolates obtained from the vaginal tract of all dogs were Escherichia coli (11/44) and S. pseudintermedius (13/44). E. coli was isolated from the vaginal tract of 8 of 21 (38%) dogs in the rUTI group and 3 of 23 (13%) dogs in the control group (P = .08). LAB were isolated from 7 of the 44 dogs. Two of these 7 dogs were in the rUTI group and 5 of the 7 dogs were in the control group. CONCLUSIONS AND CLINICAL IMPORTANCE: The vaginal microbiota of spayed female dogs with recurrent UTI was similar to the control population of normal, spayed female dogs.

The effect of an oral probiotic containing lactobacillus, bifidobacterium, and bacillus species on the vaginal microbiota of spayed female dogs.

BACKGROUND: Recurrent urinary tract infections (UTIs) are often difficult to treat. Vaginal colonization with lactic acid-producing bacteria (LAB) is associated with reduced frequency of recurrent UTIs in women. Oral probiotics might help increase the prevalence of vaginal LAB and decrease the frequency of recurrent UTIs in dogs. HYPOTHESIS: Administration of an oral probiotic supplement containing Lactobacillus, Bifidobacterium, and Bacillus species will increase the prevalence of LAB in the vagina of dogs. ANIMALS: Thirty-five healthy, spayed female dogs without history of recurrent UTIs. METHODS: Prospective, controlled study. Enrolled dogs received an oral probiotic supplement for 14 or 28 days. A vaginal tract culture was obtained from each dog before and after oral probiotic administration. Twenty-three dogs received the oral probiotic supplement daily for a period of 14 days and 12 dogs received the oral probiotic supplement daily for a period of 28 days. RESULTS: Lactic acid-producing bacteria were isolated from 7 of 35 dogs prior to probiotic administration. After the treatment course, 6 of 35 dogs had LAB isolated. Only one of these dogs had LAB (Enterococcus canintestini) isolated for the first time. Enterococcus canintestini was the most common LAB isolated from all dogs in this study, although it was not included in the probiotic supplement. CONCLUSIONS AND CLINICAL IMPORTANCE: Lactic acid-producing bacteria are not a common isolate from the vaginal vault of dogs. Administration of this oral probiotic supplement for a 2- or 4-week period did not increase the prevalence of vaginal LAB in dogs.

Evidence of non-O157 Shiga toxin-producing Escherichia coli in the feces of meat goats at a U.S. slaughter plant.

Shiga toxin-producing Escherichia coli (STEC) are important human pathogens, and attention to non-O157 serogroups has increased in recent years. Although cattle are normally considered the primary reservoir for STEC, recent illnesses associated with goat contact have indicated that these animals are important potential reservoirs for the organisms. The prevalence of STEC, particularly non-O157 serogroups, in U.S. goats has not been well described. Our objective was to determine the prevalence of six major non-O157 STEC serogroups in the feces of meat goats. Rectal contents from 296 goats were collected postevisceration at a slaughter plant in the southeastern United States over 9 days during a 12-week period from August through October 2012. Samples were enriched in E. coli broth, and DNA was extracted and used as template in an 11-gene multiplex PCR that detected six non-O157 serogroups (O26, O45, O103, O121, O111, and O145) and virulence genes. Samples were considered positive when at least one non-O157 STEC serotype was present with either stx1 or stx2. All six non-O157 serogroups were detected by PCR in our samples, and 14.5% of samples were positive for at least one serogroup. Prevalence of O26 was highest, with 6.4% of goat fecal samples positive. The prevalence of O45 was 3.4%, O103 was 4.4%, O111 was 4.1%, O121 was 1.4%, and O145 was 3.0%. Twenty-two (7.4%) of 296 fecal samples had more than one non-O157 serogroup detected in the feces. Two samples had evidence of three non-O157 STEC serogroups. Goats appear to be an important reservoir for non-O157 STEC, and further work to understand the characteristics, epidemiology, and ecology of STEC in these animals is warranted.

Escherichia coli O157:H7 genetic diversity in bovine fecal samples.

Escherichia coli O157:H7 causes foodborne illness in humans; cattle are considered a primary reservoir for the organism, and transmission is often through contaminated food products or water. The objective of this study was to determine the genetic diversity of E. coli O157:H7 within a single individual bovine fecal sample based on pulsed-field gel electrophoresis (PFGE) typing. Fecal samples (n=601) were collected from dairy and beef cattle at three separate facilities, and E. coli O157:H7 was isolated by enrichment, immunomagnetic separation, and plating on selective medium. The prevalence of E. coli O157:H7 was 46 (7.7%) of 601. From each positive fecal sample, up to 10 putative colonies were tested, and isolates from samples with at least seven positive colonies were subtyped using PFGE and tested for six major virulence genes by multiplex PCR. A total of 254 E. coli O157:H7 isolates from 27 samples met these criteria and were included in PFGE analysis. Fifteen PFGE subtypes (<100% Dice similarity) were detected among the 254 isolates, and there were no common subtypes between the three locations. Seven (26%) of 27 fecal samples had E. coli O157:H7 isolates with different PFGE subtypes (mean=2.1) within the same sample. The virulence gene profiles of different isolates from the same sample were always identical, regardless of the number of PFGE types. The results of this study suggest that determining the PFGE pattern of a single isolate from a bovine sample may not be sufficient when comparing isolates from feces, hides, or carcasses, because multiple PFGE subtypes are present.

Effects of feeding wet corn distillers grains with solubles with or without monensin and tylosin on the prevalence and antimicrobial susceptibilities of fecal foodborne pathogenic and commensal bacteria in feedlot cattle.

Distillers grains, a coproduct of ethanol production from cereal grains, are composed principally of the bran, protein, and germ fractions and are commonly supplemented in ruminant diets. The objective of this study was to assess the effect of feeding wet distillers grains with solubles (WDGS) and monensin and tylosin on the prevalence and antimicrobial susceptibilities of fecal foodborne and commensal bacteria in feedlot cattle. Cattle were fed 0 or 25% WDGS in steam-flaked corn-based diets with the addition of no antimicrobials, monensin, or monensin and tylosin. Fecal samples were collected from each animal (n = 370) on d 122 and 136 of the 150-d finishing period and cultured for Escherichia coli O157. Fecal samples were also pooled by pen (n = 54) and cultured for E. coli O157, Salmonella, commensal E. coli, and Enterococcus species. Antimicrobial resistance was assessed by determining antimicrobial susceptibilities of pen bacterial isolates and quantifying antimicrobial resistance genes in fecal samples by real-time PCR. Individual animal prevalence of E. coli O157 in feces collected from cattle fed WDGS was greater (P < 0.001) compared with cattle not fed WDGS on d 122 but not on d 136. There were no treatment effects on the prevalence of E. coli O157 or Salmonella spp. in pooled fecal samples. Antimicrobial susceptibility results showed Enterococcus isolates from cattle fed monensin or monensin and tylosin had greater levels of resistance toward macrolides (P = 0.01). There was no effect of diet or antimicrobials on concentrations of 2 antimicrobial resistance genes, ermB or tetM, in fecal samples. Results from this study indicate that WDGS may have an effect on the prevalence of E. coli O157 and the concentration of selected antimicrobial resistance genes, but does not appear to affect antimicrobial susceptibility patterns in Enterococcus and generic E. coli isolates.

Feeding supplemental dried distiller's grains increases faecal shedding of Escherichia coli O157 in experimentally inoculated calves.

Escherichia coli O157 is an important foodborne pathogen and asymptomatic cattle serve as major reservoirs for human infection. We have shown a positive association between feeding distiller's grains and E. coli O157 prevalence in feedlot cattle. The objective of this study was to determine the effect of feeding dried distiller's grain (DDG) on faecal shedding of E. coli O157 in calves experimentally inoculated with E. coli O157. Holstein calves (five per treatment group), fed steam-flaked corn-based high-grain diets supplemented with 0% (control) or 25% DDG, were orally inoculated with a five-strain mixture (6 x 10(9) CFU/calf) of nalidixic acid-resistant (NalR) E. coli O157. Faecal samples were taken three times per week for 6 weeks to determine the prevalence and concentration of Nal E. coli O157. At the end of the study (day 43), calves were euthanized and necropsied. Ruminal, caecum, colon, and rectal contents, and rectoanal mucosal swab (RAMS) samples were collected at necropsy to determine NalR E. coli O157 concentration. There was a trend for an interaction between treatment and faecal sampling day. The concentration of NalR E. coli O157 in the faeces was significantly higher in faecal samples from calves fed DDG compared with control calves on days 35, 37, 39 and 42. At necropsy, the concentration of NalR E. coli O157 was higher in the caecum (P = 0.01), colon (P = 0.03) and rectum (P = 0.01) from calves fed DDG compared with control animals. The number of sites at necropsy positive for NalR E. coli O157 was higher in calves fed DDG compared with calves in the control treatment (P < 0.001). Our results indicate that E. coli O157 gut persistence and faecal prevalence increased in calves fed DDG, which potentially have important implications for food safety.