Survival of Campylobacter jejuni during in vitro culture with mixed bovine ruminal microorganisms in the presence of methanogen inhibitors

Foodborne pathogen Campylobacter jejuni has been associated with ruminants. The objectives of this experiment were to determine C. jejuni survivability in mixed in vitro rumen microbial populations and the impact on methane production with or without methane inhibitors 2-bromosulfonate (BES) and/or sodium nitrate. When inoculated into rumen microbial populations without or with 0.5 mM BES, 5.0 mM nitrate or their combination, C. jejuni viability decreased from 4.7 ± 0.1 log10 colony forming units (CFU)/mL after 24 h. Loss of C. jejuni viability was greater (P < 0.05) when incubated under 100% CO2 compared to 50% H2:50% CO2, decreasing 1.46 versus 1.15 log units, respectively. C. jejuni viability was also decreased (P < 0.05) by more than 0.43 log units by the anti-methanogen treatments. Rumen microbial populations produced less methane (P = 0.05) when incubated with than without C. jejuni regardless of whether under 100% CO2 or 50% H2:50% CO2. For either gas phase, nitrate was decreased (13.2 versus 37.9%) by the anti-methanogen treatments versus controls although not always significant. C. jejuni-inoculated populations metabolized 16.4% more (P < 0.05) nitrate under H2:CO2 versus 100% CO2. Apparently, C. jejuni can compete for H2 with methanogens but has limited survivability under rumen conditions.

Can probiotics mitigate age-related neuroinflammation leading to improved cognitive outcomes?

Changes in brain structure and cognitive function are a natural part of aging; however, in some cases these changes are more severe resulting in mild cognitive impairment (MCI) or Alzheimer's disease (AD). Evidence is mounting to show that neuroinflammation is an underlying risk factor for neurodegenerative disease progression. Age-related neuroinflammation does not appear to occur in isolation and is part of increased systemic inflammation, which may in turn be triggered by changes in the gut associated with aging. These include an increase in gut permeability, which allows immune triggering compounds into the body, and alterations in gut microbiota composition leading to dysbiosis. It therefore follows that, treatments that can maintain healthy gut function may reduce inflammation and protect against, or improve, symptoms of age-associated neurodegeneration. The aim of this mini review was to evaluate whether probiotics could be used for this purpose. The analysis concluded that there is preliminary evidence to suggest that specific probiotics may improve cognitive function, particularly in those with MCI; however, this is not yet convincing and larger, multilocation, studies focus on the effects of probiotics alone are required. In addition, studies that combine assessment of cognition alongside analysis of inflammatory biomarkers and gut function are needed. Immense gains could be made to the quality of life of the aging population should the hypothesis be proven to be correct.

Prevalence and Antimicrobial Resistance of Nontyphoidal Salmonella enterica from Head Meat and Trim for Ground Product at Pork Processing Facilities

ABSTRACT

Pork head meat may harbor Salmonella and contaminate other carcass by-products during harvest and fabrication. A large pork processing plant in the United States was sampled bimonthly for 11 months to determine the concentration, prevalence, seasonality, serotype diversity, and antimicrobial susceptibility of Salmonella enterica isolated from cheek meat and head trim of swine carcasses. Each collection consisted of 25 samples on two consecutive days in the morning and afternoon shifts, for a total of 100 cheek meat and 100 head trim samples each month. Tissues were cultured for Salmonella by using restrictive media and enrichment techniques, and a subset of isolates was serotyped, analyzed for antimicrobial susceptibility, and genome sequenced. Salmonella postenrichment prevalence did not differ (P = 0.20) between cheek meat (63%) and head trim (66%). Postenrichment prevalence differed (P < 0.05) by month (January, 94%; March, 80%; May, 54%; July, 59%; September, 47%; and November, 55%) and by processing shift (morning, 68%; afternoon, 62%). The subset (n = 618) of isolates selected for serotyping yielded 21 distinct serotypes: Typhimurium (49%), Infantis (10%), Heidelberg (8%), I 4,[5],12:i:- (8%), and 17 other types (≤5%). In total, 407 multidrug-resistant (MDR; resistance to three or more antibiotic classes) isolates were identified. There were 120 isolates that exhibited the penta-resistant ACSSuT phenotype. In addition, 113 isolates exhibited decreased susceptibility to ciprofloxacin (MIC ≥ 0.12 μg/mL). Resistance genes blaCARB, blaSHV, blaTEM, aac(6')-Ib-cr,qnrB, sul2, and dfrA were expressed in numerous MDR Salmonella isolates. The data herein suggest that pork products from the head, compared with data reported for carcasses, may have a relatively high prevalence of Salmonella with diverse serotypes and MDR.

HIGHLIGHTS

Evaluation of the Efficacy of Three Direct Fed Microbial Cocktails To Reduce Fecal Shedding of Escherichia coli O157:H7 in Naturally Colonized Cattle and Fecal Shedding and Peripheral Lymph Node Carriage of Salmonella in Experimentally Infected Cattle

Two experiments were conducted to evaluate the feeding of direct fed microbials (DFMs) on fecal shedding of Escherichia coli O157:H7 in naturally infected cattle (experiment I) and on Salmonella in the feces and peripheral lymph nodes (PLNs) of experimentally infected cattle (experiment II). Thirty cattle, 10 per treatment, were used in each experiment. Treatments in experiment I consisted of a control (lactose carrier only); DFM1, a 1:1 ratio of Enterococcus faecium and Lactobacillus animalis; and DFM2, a 1:1 ratio of Lactobacillus acidophilus and Pediococcus acidilactici. In Experiment II, DFM1 was replaced with DFM3, a 1:2 ratio of Lactobacillus reuteri and other Lactobacillus strains. Additives were mixed in water and applied as a top-dressing to each pen's daily ration for 50 days. Approximately half-way through each experiment, the DFM concentration was doubled for the remainder of the study. Fecal samples were collected throughout experiment I and cultured for E. coli O157:H7. Cattle in experiment II were inoculated intradermally with Salmonella Montevideo on days 32, 37, and 42 and then necropsied on days 49 and 50 (five cattle per treatment on each day). Innate immune function was assessed on days 29, 49, and 50. In experiment I, fecal concentration and prevalence of E. coli O157:H7 were not different (P > 0.10) nor was there an effect (P = 0.95) on the percentage of super shedders (cattle shedding ≥3.0 log CFU/g of feces). In experiment II, no treatment differences (P > 0.05) were observed for Salmonella in the PLNs except for the inguinal nodes, which had a significantly lower Salmonella prevalence in DFM-supplemented cattle than in the controls. Immune function, as measured by monocyte nitric oxide production and neutrophil oxidative burst, was decreased (P < 0.05) in the DFM treatment groups. Although results of this research indicate little to no effect of these DFMs on E. coli O157:H7 or Salmonella in cattle, an increase in the duration of administration to that similar to what is used for commercial cattle might elicit treatment differences.

Inhibition of multidrug-resistant Staphylococci by sodium chlorate and select nitro- and medium chain fatty acid compounds

AIMS

Determine the antimicrobial effects of 5 μmol ml^-1 sodium chlorate, 9 μmol ml^-1 nitroethane or 2-nitropropanol as well as lauric acid, myristic acid and the glycerol ester of lauric acid Lauricidin^® , each at 5 mg ml^-1 , against representative methicillin-resistant staphylococci, important mastitis- and opportunistic dermal-pathogens of humans and livestock.

METHODS AND RESULTS

Three methicillin-resistant Staphylococcus aureus and two methicillin-resistant coagulase-negative staphylococci were cultured at 39°C in 5 μmol ml^-1 nitrate-supplemented half-strength Brain Heart Infusion broth treated without or with the potential inhibitors. Results revealed that 2-nitropropanol was the most potent and persistent of all compounds tested, achieving 58-99% decreases in mean specific growth rates and maximum optical densities when compared with untreated controls. Growth inhibition did not persist by cultures treated solely with chlorate or nitroethane, with adaptation occurring by different mechanisms after 7 h. Adaptation did not occur in cultures co-treated with nitroethane and chlorate. The medium chain fatty acid compounds had modest effects on all the staphylococci tested except the coagulase-negative Staphylococcus epidermidis strain NKR1.

CONCLUSIONS

The antimicrobial activity of nitrocompounds, chlorate and medium chain fatty acid compounds against different methicillin-resistant staphylococci varied in potency.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results suggest that differential antimicrobial activities exhibited by mechanistically dissimilar inhibitors against methicillin-resistant staphylococci may yield potential opportunities to combine the treatments to overcome their individual limitations and broaden their activity against other mastitis and dermal pathogens.

Interactions of organic acids with vancomycin-resistant Enterococcus faecium isolated from community wastewater in Texas

AIMS

Investigate the interactions of organic acids (OAs), acetic, butyric, citric, formic, lactic and propionic acid against 50 Gram-positive vancomycin-resistant Enterococcus faecium (VRE) strains to determine whether pH, undissociated or dissociated acid forms correlate with bacterial inhibition.

METHODS AND RESULTS

Concentrations of undissociated and dissociated OAs at the molar minimum inhibitory concentrations (MIC_M s) of the VRE were calculated using the Henderson-Hasselbalch equation. The pH at the MIC_M s of all VRE strains against acetic, butyric, formic and propionic acids was similar, 4·66 ± 0·07, but there was a 1·1 pH unit difference for all six OAs. Inhibition of VRE by all six OAs did not appear to be solely dependent on pH or on the undissociated OA species. The inhibition of VRE by all six dissociated acids was within Δ = 3·1 mmol l^-1 .

CONCLUSIONS

Vancomycin-resistant Enterococcus faecium inhibition correlated with the dissociated OA species. A small decrease in the concentration of the dissociated OAs from optimum may result in allowing VRE strains to escape disinfection.

SIGNIFICANCE AND IMPACT OF THE STUDY

When an OA is used to disinfect VRE strains, the concentration of the dissociated OA should be carefully controlled. A concentration of at least 20 mmol l^-1 dissociated OA should be maintained when disinfecting VRE.

Effect of kibble and raw meat diets on peripheral blood mononuclear cell gene expression profile in dogs

Peripheral blood mononuclear cell (PBMC) gene expression microarray profiling is a minimally invasive tool used in human diet intervention studies. In this study, PBMC gene expression was determined in dogs fed kibble or raw red meat diets for 9 weeks to test the hypothesis that diet influences canine immune cell gene expression profiles. The two diets were associated with differences in PBMC gene expression profiles, which corresponded with changes in plasma IgA concentrations. Analysis of PBMC gene expression profiles might provide useful insights into the long term effects of diet on health outcomes in dogs.

Effect of monensin inclusion on intake, digestion, and ruminal fermentation parameters by Bos taurus indicus and Bos taurus taurus steers consuming bermudagrass hay

Effects of monensin inclusion and cattle subspecies on utilization of bermudagrass hay (13.7% CP, 77.3% NDF, and 38.8% ADF) were evaluated using ruminally cannulated steers (5 [BI] and 5 [BT]; 398 kg BW). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments were 0 (CON) or 200 mg·steer·d monensin (MON) in 0.91 kg dried distillers' grains with solubles. Periods were 70 d in length: 20 d of adaptation, 22 d of sample collection, and 28 d for withdrawal of treatment. Steers were group housed during adaptation and moved to individual covered pens for sampling. Hay, ort, and fecal grab samples were collected d 21 through 25 for determination of intake and digestion. Ruminal fluid was collected with a suction strainer 0, 2, 4, 8, and 12 h after feeding on d 42 for pH, VFA, and ruminal NH-N (RAN) analysis. Additionally, at h 2, ruminal fluid and contents were collected for determination of rate of NH production and CH production rate. No subspecies × monensin interactions were observed ( ≥ 0.12). Monensin had no effect ( ≥ 0.16) on intake or digestibility parameters. No subspecies effect ( ≥ 0.11) was observed for forage OM intake, total OM intake, or OM digestion. Total digestible OM intake tended to be greater ( = 0.06) for BT steers than for BI steers (14.0 vs. 12.2 g/kg BW). There was an effect of hour after feeding ( ≤ 0.01) on pH, total VFA, acetate:propionate ratio, and molar percent acetate and propionate. Total VFA concentration was greater ( = 0.01) in CON steers than in MON steers (66.5 vs. 62.0 m). Monensin decreased molar percent acetate ( = 0.02) from 72.5 to 71.2% and increased molar percent propionate ( < 0.01) from 16.9 to 18.7%, resulting in a reduced ( < 0.01) acetate:propionate ratio (from 4.34 to 3.85). Although not significantly ( = 0.19), monensin numerically reduced the CH production rate by 15.8%. Greater ( = 0.07) CH production rate tended to be observed in BI steers than in BT steers (21.4 vs. 16.6 μmol CH·mL·h, respectively). Monensin had no effect ( ≥ 0.32) on pH, RAN, or rate of NH production. A subspecies × hour after feeding interaction was observed for RAN, with BT having greater RAN at h 0 and 4, whereas BI had greater RAN at h 2, 8, and 12. Overall, monensin decreased the acetate:propionate ratio and total VFA concentration but had no effect on forage utilization. steers consumed less digestible OM and had a greater CH production rate compared with BT steers, suggesting BT were better able to utilize the available forage resource than BI.

Effect of monensin withdrawal on intake, digestion, and ruminal fermentation parameters by Bos taurus indicus and Bos taurus taurus steers consuming bermudagrass hay

Effects of monensin withdrawal and cattle subspecies on the utilization of bermudagrass hay (14.3% CP, 72.3% NDF, and 36.9% ADF) were evaluated using ruminally cannulated steers (5 [BI] and 5 [BT]). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments consisted of either 0 mg·steer·d-1 monensin with no previous monensin feeding (CON) or withdrawal from 200 mg·steer·d-1 monensin (MON) fed individually in 0.91 kg dried distillers' grains with solubles for 42 d. Withdrawal was evaluated for a 28-d period. Ruminal fluid was collected 2 h after feeding on d 0, 1, 4, 7, 14, and 21 after withdrawal for determination of pH, VFA, ruminal NH-N (RAN), rate of NH production, and CH production rate. Hay, ort, and fecal grab samples were collected d 23 through 28 after withdrawal for determination of intake and digestion. No subspecies × monensin, subspecies × day, or subspecies × monensin × day interactions were observed ( ≥ 0.11). An effect of day after monensin withdrawal was observed ( < 0.01) for total VFA concentration, with an increase following withdrawal followed by a decrease and then stabilization. Monensin × day after monensin withdrawal interactions ( ≤ 0.01) were observed for the acetate:propionate (A:P) ratio and molar percent of acetate and propionate. There was a decrease in molar percent of propionate between d 1 and 4 from 19.1 to 18.0; however, it remained greater ( ≤ 0.10) for MON than CON through d 7. Withdrawal increased molar percent of acetate from 68.3 to 69.8 between d 0 and 4 for MON steers. The A:P ratio was less ( ≤ 0.01) on d 0 for MON than for CON (3.4 vs. 4.0), but by d 4, it increased to 3.8 and was not different ( = 0.14) from CON. By d 14, no differences ( ≥ 0.88) remained for acetate, propionate, or the A:P ratio. After monensin withdrawal, monensin reduced ( < 0.01) RAN by 12.3% (2.09 vs. 1.83 m for CON and MON, respectively). Monensin withdrawal and cattle subspecies had no effect ( ≥ 0.23) on rate of NH production or CH production rate. Monensin withdrawal had no effect ( ≥ 0.45) on intake or digestibility parameters. Greater forage OM intake ( = 0.09; 21.2 vs. 19.2 g/kg BW) and OM digestibility ( < 0.01; 72.4 vs. 63.0%) resulted in greater ( < 0.01) total digestible OM intake (16.8 vs. 13.2 g/kg BW) in BT steers than in BI steers. These results suggest that BT steers are better able to utilize bermudagrass hay than BI steers. Upon monensin withdrawal, steers previously fed monensin continue to have a reduced A:P ratio for at least 7 d.

In Vitro Effects of Thymol-β-D-Glucopyranoside on Salmonella enterica Serovar Typhimurium and Escherichia coli K88

Although thymol is bactericidal against many pathogens in vitro, its in vivo effectiveness against pathogens in the lower gastrointestinal tract is limited because of its rapid absorption in the proximal gut. Thymol-β-<small>D</small>-glucopyranoside (β-thymol), a conjugated form of thymol, can deliver thymol to the lower gastrointestinal tract and has shown antibacterial effects. In the present study, we examined the in vitro effects of β-thymol on Salmonella enterica serovar Typhimurium (ST) and Escherichia coli K88 (K88). We inoculated one-half strength Mueller-Hinton broth with 5.8 ± 0.09 log CFU/ml novobiocin- and naladixic acid-resistant (NN) ST (NVSL 95-1776) and 5.1 ± 0.09 log CFU ml(-1) NN-resistant K88, with or without porcine feces (0.1% [wt/vol]) (fecal incubations). The resultant bacterial suspensions were distributed under N2 to triplicate sets of tubes to achieve initial concentrations of 0, 3, 6, and 12 mM for ST treatments and 0, 3, 12, and 30 mM for K88 treatments. Samples were incubated at 39°C and then plated onto NN-containing brilliant green agar and NN-containing MacConkey agar; ST and K88 CFU concentrations were determined via 10-fold dilutions, and viable cell counts were performed at 0, 6, and 24 h. No differences in ST CFU counts were observed in β-thymol-treated tubes without the added porcine feces (i.e., pure culture) at 6 or 24 h. However, in tubes that contained fecal incubations, ST CFU counts were reduced (P < 0.05) from controls at 6 h in tubes treated with 6 and 12 mM β-thymol, whereas in tubes treated with 3, 6, and 12 mM β-thymol the CFU counts were reduced (P < 0.05) at 24 h. No differences were observed in K88 CFU counts in pure culture or in fecal incubations at 6 h, but K88 CFU counts were reduced (P < 0.05) in both pure and fecal incubations at 24 h. The results from this study demonstrate that β-thymol, in the presence of fecal suspensions, has anti-Salmonella and anti-E. coli effects, suggesting a role of β-glycoside-hydrolyzing microbes for the release of bactericidal thymol from β-thymol.

The probiotic Escherichia coli Nissle 1917 inhibits propagating colonic contractions in the rat isolated large intestine

The objective of this research was to test an in vitro motility model by investigating whether a probiotic that reduces diarrhea in humans would reduce motility in the rat colon in vitro. The probiotic Escherichia coli Nissle 1917 (EcN) the active ingredient in Mutaflor® was used as an example probiotic because it is effective for treating infectious diarrheal diseases. The effect of EcN on motility was compared in two colonic preparations. In distal colon segments EcN extract decreased the tension of spontaneous contractions by 74% and frequency by 46% compared with pre-treatment controls. In the whole large intestine the number of synchronized spontaneous propagating contractions decreased by 86% when EcN extract was applied externally and 69% when applied via the lumen compared with pre-treatment. From the inhibition produced by EcN extract in the distal colon segment a myogenic action was inferred and in the whole large intestine neural involvement was implicated. Both are consistent with its anti-diarrheal effect in humans.

Typical versions of learned swamp sparrow song types are more effective signals than are less typical versions

The learned songs of songbirds often cluster into population-wide types. Here, we test the hypothesis that male and female receivers respond differently to songs depending on how typical of those types they are. We used computational methods to cluster a large sample of swamp sparrow (Melospiza georgiana) songs into types and to estimate the degree to which individual song exemplars are typical of these types. We then played exemplars to male and female receivers. Territorial males responded more aggressively and captive females performed more sexual displays in response to songs that are highly typical than to songs that are less typical. Previous studies have demonstrated that songbirds distinguish song types that are typical for their species, or for their population, from those that are not. Our results show that swamp sparrows also discriminate typical from less typical exemplars within learned song-type categories. In addition, our results suggest that more typical versions of song types function better, at least in male-female communication. This finding is consistent with the hypothesis that syllable type typicality serves as a proxy for the assessment of song learning accuracy.

Development of challenge models to evaluate the efficacy of a vaccine to reduce carriage of Salmonella in peripheral lymph nodes of cattle

Because challenge models to infect peripheral lymph nodes (PLNs) with Salmonella have not been reported, we performed a series of experiments to develop and refine challenge models to evaluate an intervention applied at the animal level and to provide initial estimates of efficacy of an intervention (i.e., a vaccine) to aid in the design of future studies. In each of four experiments, steers (control or vaccinated) were inoculated with Salmonella strains Montevideo or Newport, and in experiment IV, Salmonella Senftenberg was also used. Calves were euthanized 14 to 42 days postinoculation, and PLNs were collected. In the first experiment, calves were challenged with ∼10¹⁰ Salmonella cells, and few treatment differences were observed 14 days postchallenge. However, by day 21, Salmonella Newport was recovered from fewer vaccinated calves than control calves (P < 0.05). In experiment II, calves were challenged with ∼10⁷ Salmonella cells and, after two necropsies (14 and 28 days postchallenge), only one lymph node was Salmonella positive; therefore, the study was terminated. In experiment III, calves were again challenged with ∼10¹⁰ Salmonella cells, and no significant effect of vaccine was observed in calves challenged with Montevideo or Newport strains. A transdermal route of challenge was explored in experiment IV, using a 10-lancet, allergy testing instrument. Sixteen steers were challenged with either Salmonella Newport or Salmonella Montevideo (Salmonella Newport right legs; Salmonella Montevideo left legs), and all steers were challenged on the lower abdomen with Salmonella Senftenberg. Transdermal inoculation resulted in predictably Salmonella-positive PLNs, and a modest vaccine effect was detected. Because it is well tolerated by the calves and results in predictable and regionally specific Salmonella recovery from PLNs, the transdermal route of challenge may be preferred by researchers wishing to evaluate the impact of interventions designed to reduce the carriage of Salmonella in PLNs.

Development of a transdermal Salmonella challenge model in calves

Recent investigations have found that Salmonella can be routinely recovered from peripheral lymph nodes (PLNs) of cattle presented for harvest. When contained within the PLNs, this foodborne pathogen is protected from currently used postharvest, inplant intervention strategies and, therefore, PLNs harboring Salmonella may be a potential contaminant of ground beef. The objective of this work was to develop a challenge model that effectively and repeatedly results in Salmonella -positive PLNs. A 10-lancet skin-allergy instrument was inoculated with Salmonella, and calves were inoculated intra- and/or transdermally by applying the device over various ventral regions of the skin. Salmonella was successfully and predictably recovered from regionspecific PLNs up to 8 days postchallenge. Furthermore, serotypes inoculated within specific regions were only recovered from the PLNs draining those regions. This model provides a method to predictably infect PLNs with Salmonella. Further, this model makes it possible to determine the duration of infection and to evaluate candidate interventions that may shorten the duration of infection.

Glycerol inhibition of ruminal lipolysis in vitro

Supplemental glycerol inhibits rumen lipolysis, a prerequisite for rumen biohydrogenation, which is responsible for the saturation of dietary fatty acids consumed by ruminant animals. Feeding excess glycerol, however, adversely affects dry matter digestibility. To more clearly define the effect of supplemental glycerol on rumen lipolysis, mixed populations of ruminal bacteria were incubated with 6 or 20% glycerol (vol/vol). After 48-h anaerobic incubation of mixed culture rumen fluid, rates of free fatty acid production (nmol/mL per h) for the 6 and 20% glycerol-supplemented samples were decreased by 80 and 86%, respectively, compared with rates from nonsupplemented control cultures (12.4±1.0; mean ± SE). Conversely, assay of the prominent ruminal lipase-producing bacteria Anaerovibrio lipolyticus 5S, Butyrivibrio fibrisolvens 49, and Propionibacterium species avidum and acnes revealed no effect of 2 or 10% (vol/vol) added glycerol on lipolytic activity by these organisms. Supplementing glycerol at 6% on a vol/vol basis, equivalent to supplementing glycerol at approximately 8 to 15% of diet dry matter, effectively reduced lipolysis. However, the mechanism of glycerol inhibition of ruminal lipolysis remains to be demonstrated.

Development of colonic microflora as assessed by pyrosequencing in dairy calves fed waste milk

The objective of the current study was to examine the effect of pasteurization of waste milk, used to feed dairy calves, on the bacterial diversity of their lower gut. Using 16S rDNA bacterial tag-encoded FLX amplicon pyrosequencing, fecal samples from dairy calves, ages 1 wk to 6 mo old and fed either pasteurized or nonpasteurized waste milk, were analyzed for bacterial diversity. Calves were maintained on 2 separate farms and, aside from how the waste milk was treated, were housed and cared for similarly. Fifteen calves were sampled from each age group (1, 2, and 4 wk, and 2, 4, and 6 mo of age; n=90 samples per milk treatment, 180 total samples) on each farm via rectal palpation and the samples shipped and frozen before analysis. In general, bacterial diversity, as represented by the total number of different species, was greater for the calves fed pasteurized waste milk at all ages (except 1 wk of age) and increased with increasing age in both treatments. Proteobacteria, Bacteroidetes, and Firmicutes were the predominant phyla. Differences in phyla and class were observed among treatments and age of calf but with no consistent trends. Salmonella were detected in 9 out of 14 (64%) of the 1-wk-old calves fed nonpasteurized milk. Treponema, an important beneficial bacterium in cattle rumen, was more prevalent in the pasteurized waste milk-fed animals and became higher in the older animals from this group. Escherichia-Shigella were detected among treatments at all ages, and highest at 1 wk of age, averaging approximately 21 and 20% of all bacteria for calves fed pasteurized and nonpasteurized waste milk, respectively, and decreasing as calves aged (2.6 and 1.3%). The consistent detection of Salmonella in the younger animals fed nonpasteurized milk and its absence in all other groups is an important finding related to this feeding practice.

Evaluation of the potential antimicrobial resistance transfer from a multi-drug resistant Escherichia coli to Salmonella in dairy calves

Previous research conducted in our laboratory found a significant prevalence of multi-drug resistant (MDR) Salmonella and MDR Escherichia coli (MDR EC) in dairy calves and suggests that the MDR EC population may be an important reservoir for resistance elements that could potentially transfer to Salmonella. Therefore, the objective of the current research was to determine if resistance transfers from MDR EC to susceptible strains of inoculated Salmonella. The experiment utilized Holstein calves (approximately 3 weeks old) naturally colonized with MDR EC and fecal culture negative for Salmonella. Fecal samples were collected for culture of Salmonella and MDR EC throughout the experiment following experimental inoculation with the susceptible Salmonella strains. Results initially suggested that resistance did transfer from the MDR E. coli to the inoculated strains of Salmonella, with these stains demonstrating resistance to multiple antibiotics following in vivo exposure to MDR EC. However, serogrouping and serotyping results from a portion of the Salmonella isolates recovered from the calves post-challenge, identified two new strains of Salmonella; therefore transfer of resistance was not demonstrated under these experimental conditions.

Lack of effect of feeding citrus by-products in reducing salmonella in experimentally infected weanling pigs

The objective of the current research was to determine if feeding the citrus by-products(D) -limonene (DL) and citrus molasses would reduce the concentration and prevalence of Salmonella in weanling pigs experimentally infected with Salmonella Typhimurium. Twenty crossbred weanling pigs (average body weight [BW], 19.9 kg) were randomly assigned to one of four treatments: control, low-dose DL (1.5 ml/kg of BW per day), high-dose DL (3.0 ml/kg of BW per day), and citrus molasses (0.05 kg/kg of BW per day). Treatments were administered in the feed (twice daily) for 7 days, with one-half of the dose administered at each feeding. Fecal samples were collected twice daily (prior to administration of treatment) and cultured for quantitative and qualitative determination of the challenge strain of Salmonella. Upon termination of the study, pigs were euthanized and tissues from the stomach, ileum, cecum, spiral colon, and rectum, as well as luminal contents, were collected. In addition, the popliteal and ileocecal lymph nodes and liver, spleen, and tonsil tissue were collected for qualitative Salmonella culture. No significant treatment differences (P > 0.05) were observed among treatments for fecal concentration or prevalence of Salmonella throughout the 7-day collection period. Likewise, no treatment differences (P > 0.05) were observed for any of the tissue or luminal content samples collected. Salmonella was not cultured from the muscle-bound popliteal lymph node but was cultured from the mesenteric ileocecal lymph nodes. While there were no effects in the current experiment, future research may examine the effect of a lower challenge dose and/or different administration (dose or duration) of the citrus by-products.

Evaluation of the effect of gallium maltolate on fecal Salmonella shedding in cattle

Strategies aimed at reducing fecal shedding of Salmonella and other foodborne pathogens may be effective for limiting transmission of pathogens from food animals to humans. The objective of this study was to determine the effectiveness of gallium maltolate (GaM) against Salmonella in vitro and to determine whether oral administration of GaM would reduce fecal shedding of Salmonella in cattle. Gallium is a semimetal exhibiting antimicrobial properties against some pathogenic bacteria, including Salmonella, by exploiting their need for iron to survive and replicate. In vitro growth studies were performed in pure cultures of Salmonella and in mixed cultures from ruminal fluid. Inclusion of GaM in culture medium or in mixed cultures of ruminal fluid resulted in a significant reduction in growth of Salmonella, suggesting that GaM may be effective for limiting growth and survival in vivo. Therefore, we subsequently administered two doses of GaM to Holstein steers, experimentally infected them with Salmonella, and quantitatively and qualitatively monitored fecal shedding at 12-h intervals. Sixty hours after beginning treatment, cattle were euthanized, and luminal contents and tissue were aseptically harvested from the rumen, jejunum, spiral colon, cecum, and rectum. The luminal contents were processed for quantitative and qualitative analysis of the challenge strains of Salmonella, and tissue samples were enriched and plated for qualitative analysis. We found no significant differences between control and treated animals in quantitative levels of Salmonella in the feces or the luminal contents. Likewise, we observed no pattern between control and treated animals in the frequency of positive or negative results from enriched feces, luminal contents, or tissue samples. These results suggest that GaM was not effective for reducing Salmonella in cattle.

Evaluation of feeding glycerol on free-fatty acid production and fermentation kinetics of mixed ruminal microbes in vitro

Ruminant-derived foods contain high proportions of saturated fats as a result of ruminal biohydrogenation that rapidly saturates and thus limits the availability of free unsaturated fatty acids for assimilation. The objective of this study was to evaluate the effects of glycerol on ruminal free-fatty acid (FFA) production rates and in vitro fermentation kinetics of alfalfa hay. In vitro incubations demonstrated 48% and 77% reductions in rates of FFA accumulation in incubations supplemented with 2% and 20% glycerol as compared to controls. In vitro incubations with alfalfa hay demonstrated that increasing levels of glycerol did not affect NDF digestibility of the hay. Additionally, increasing amounts of glycerol decreased the acetate to propionate ratio in the rumen. These results suggest that inhibiting bacterial fat degradation may promote ruminal passage of total lipid, thereby providing greater proportions of beneficial unsaturated fat for incorporation into beef products.

Evaluation of bacterial diversity in the rumen and feces of cattle fed different levels of dried distillers grains plus solubles using bacterial tag-encoded FLX amplicon pyrosequencing

Dietary components and changes cause shifts in the gastrointestinal microbial ecology that can play a role in animal health and productivity. However, most information about the microbial populations in the gut of livestock species has not been quantitative. In the present study, we utilized a new molecular method, bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP) that can perform diversity analyses of gastrointestinal bacterial populations. In the present study, cattle (n = 6) were fed a basal feedlot diet and were subsequently randomly assigned to 1 of 3 diets (n = 2 cows per diet). In each diet, 0, 25, or 50% of the concentrate portion of the ration was replaced with dried distillers grain (DDGS). Ruminal and fecal bacterial populations were different when animals were fed DDGS compared with controls; ruminal and fecal Firmicute:Bacteroidetes ratios were smaller (P = 0.07) in the 25 and 50% DDG diets compared with controls. Ruminal pH was decreased (P < 0.05) in ruminal fluid from cattle fed diets containing 50% compared with 0% DDGS. Using bTEFAP, the normal microbiota of cattle were examined using modern molecular methods to understand how diets affect gastrointestinal ecology and the gastrointestinal contribution of the microbiome to animal health and production.

Decreased competiveness of the foodborne pathogen Campylobacter jejuni during Co-culture with the hyper-ammonia producing anaerobe Clostridium aminophilum

Campylobacter spp. are a leading bacterial cause of human foodborne illness. When cocultured in anaerobic Bolton broth with the hyper-ammonia producing bacterium, Clostridium aminophilum, ammonia accumulation was greater and final growth of Campylobacter jejuni was reduced (CFU>or=1.4 log10/mL) compared to that obtained by pure culture controls. Co-culture with the less active ammonia-producing saccharolytic Prevotella albensis had no effect on final C. jejuni concentrations. When co-cultured similarly except with the addition of 10 micromol/L monensin, monensin-susceptible Cl. aminophilum was reduced by 2 to 4 log10 CFU/mL and concentrations of C. jejuni, which is insensitive to monensin, did not differ from its pure culture control. These results suggest that in the absence of added monensin, the hyper ammonia-producing Cl. aminophilum may be able to outcompete asaccharolytic C. jejuni for amino acid substrates and that this competitive ability was eliminated by addition on monensin.

Effects of the methane-inhibitors nitrate, nitroethane, lauric acid, Lauricidin and the Hawaiian marine algae Chaetoceros on ruminal fermentation in vitro

The effects of several methane-inhibitors on rumen fermentation were compared during three 24h consecutive batch cultures of ruminal microbes in the presence of nonlimiting amounts of hydrogen. After the initial incubation series, methane production was reduced greater than 92% from that of non-treated controls (25.8+/-8.1 micromol ml(-1) incubation fluid) in cultures treated with nitroethane, sodium laurate, Lauricidin or a finely-ground product of the marine algae, Chaetoceros (added at 1, 5, 5 and 10 mg ml(-1), respectively) but not in cultures treated with sodium nitrate (1 mg m1(-1)). Methane production during two successive incubations was reduced greater than 98% from controls (22.5+/-3.2 and 23.5+/-7.9 micromol ml(-1), respectively) by all treatments. Reductions in amounts of volatile fatty acids and ammonia produced and amounts of hexose fermented, when observed, were most severe in sodium laurate-treated cultures. These results demonstrate that all tested compounds inhibited ruminal methane production in our in vitro system but their effects on fermentation differed.

Effects of nitrocompounds on uric acid-utilizing microorganisms, nitrogen retention, and microbial community in laying hen manure

A study was conducted to evaluate effects of nitrocompounds on growth of uric acid-utilizing microorganisms, nitrogen retention, and microbial community in laying hen manure. There were three treatments: control, 100 mM nitropropanol (NPL), and 100 mM nitropropionic acid (NPC). The mixed laying hen manure was divided into 3 groups and incubated at 23 degrees C for 7 days. On Days 0, 3, and 7, samples were collected to measure the quantity of uric acid-utilizing microorganisms, total nitrogen retention, and microbial community changes. Both nitrocompounds significantly reduced growth of the uric acid-utilizing microorganisms on Day 3 (P < 0.05). Inhibitory effects of both nitrocompounds remained until Day 7 when the experiment was terminated. NPL treatment retained significantly more manure nitrogen compared to the control on both Days 3 and 7. Manure nitrogen levels of NPC treatment were also significantly higher than the control on Day 7. We further investigated the effects of NPL and NPC on microbial community changes during a 7-day incubation. NPC treatment and control on Day 7 exhibited 94% community similarity. NPC on Day 3 and NPL on Day 7 also showed high community similarity (approximately 94%). Control on Day 0 and Day 7 yielded less than 80% community similarity. Control and NPL treatment groups on Day 3 gave the lowest community similarity (approximately 64%) compared to the other groups. This result indicated that incubation time and treatment moderately influenced microbial community changes. In summary, these results indicate that both nitrocompounds increased manure nitrogen retention by inhibiting the growth of uric acid-utilizing microorganisms, and that NPL and NPC could be used as manure treatments in order to reduce ammonia volatilization and nitrogen retention in poultry manure. Moreover, nitrocompounds may have potential as feed additives to reduce ammonia volatilization.

Electrophoretic analysis of Antarctic fish from South Georgia

White muscle samples of Antarctic fish (Notothenia rossii, N. neglecta, N. gibberifrons and Chaenocephalus aceratus) were subjected to electrophoretic tests. Isoelectric focusing of general muscle proteins provides a quick method of identifying species. Six muscle enzymes were resolved by horizontal starch gel electrophoresis. These are presumed to be the products of ten independent gene loci. Coefficients of genetic distance were calculated and substantially agree with the conventional taxonomy. Levels of genetic variability are within the normal range for marine teleosts. Two polymorphic enzymes. GPI and PGM, might prove useful as 'genetic tags' for stock identification.

Evaluation of the bacterial diversity in cecal contents of laying hens fed various molting diets by using bacterial tag-encoded FLX amplicon pyrosequencing

Laying hens are typically induced to molt to begin a new egg-laying cycle by withdrawing feed for up to 12 to 14 d. Fasted hens are more susceptible to colonization and tissue invasion by Salmonella enterica serovar Enteritidis. Much of this increased incidence in fasted hens is thought to be due to changes in the native intestinal microflora. An alternative to feed withdrawal involves feeding alfalfa meal crumble to hens, which is indigestible by poultry but provides fermentable substrate to the intestinal microbial population and reduces Salmonella colonization of hens compared with feed withdrawal. The present study was designed to quantify differences in the cecal microbial population of hens (n=12) fed a typical layer ration, undergoing feed withdrawal, or being fed alfalfa crumble by using a novel tag bacterial diversity amplification method. Bacteroides, Prevotella, and Clostridium were the most common genera isolated from all treatment groups. Only the ceca of hens undergoing feed withdrawal (n=4) contained Salmonella. The number of genera present was greatest in the alfalfa crumble-fed group and least in the feed withdrawal group (78 vs. 54 genera, respectively). Overall, the microbial diversity was least and Lactobacillius populations were not found in the hens undergoing feed withdrawal, which could explain much of these hens' sensitivity to colonization by Salmonella.

Influence of sprinklers, used to alleviate heat stress, on faecal shedding of E. coli O157:H7 and Salmonella and antimicrobial susceptibility of Salmonella and Enterococcus in lactating dairy cattle

AIMS

To determine the effect of sprinklers on faecal shedding of Escherichia coli (E. coli) O157:H7 and Salmonella in lactating dairy cattle.

METHODS AND RESULTS

Sprinklers were applied to lactating dairy cattle on two farms at either the feedbunk or in the holding pen prior to milking. Faecal samples were collected approx. 1 and 4 weeks following initiation of sprinkler treatments for culture of E. coli O157:H7, Salmonella and Enterococcus. No treatment differences were observed for E. coli O157:H7. Salmonella was higher (P = 0.11) in the control treatment on day-7 whereas on day-28, the bunk sprinklers increased the number of Salmonella positive cows. Salmonella prevalence decreased (P = 0.0001) on day-5 and when examined across days in cows exposed to sprinklers prior to milking. Antimicrobial susceptibility screening found very few isolates that were multi-drug resistant. All Enterococcus isolates were susceptible to vancomycin.

CONCLUSIONS

This study demonstrated a significant decrease in faecal prevalence of Salmonella in lactating cattle following exposure to sprinklers administered prior to milking.

SIGNIFICANCE AND IMPACT OF THE STUDY

Identification of current dairy management techniques that are also effective in reducing on-farm prevalence of pathogenic bacteria could have significant food safety and environmental implications.

Acyl-homoserine-lactone autoinducer in the gastrointestinal [corrected] tract of feedlot cattle and correlation to season, E. coli O157:H7 prevalence, and diet

Acyl-homoserine-lactone autoinducer (AHL) produced by nonenterohemorrhagic Escherichia coli species in cattle appears to be required for enterohemorrhagic E. coli (EHEC) colonization of the gastrointestinal tract (GIT). The current research aimed to examine the effect of season, diet, EHEC shedding, and location within the GIT on AHL prevalence in the ruminant. Luminal content samples were collected from the rumen and rectum of feedlot cattle at slaughter in the spring, summer, fall, and winter for culture of E. coli O157:H7 and AHL determination. During the spring collection, samples were additionally collected from the cecum and small intestine, but these samples all were AHL negative and therefore not examined again. To assess the influence of diet on AHL prevalence, 14 lambs were fed either 100% forage or 80% concentrate diets and experimentally inoculated with EHEC. At 8 days after infection, all the lambs were killed, and necropsies were taken, with luminal contents collected from the GIT. The collections from the feedlot cattle had AHL in 100% of the rumen content samples from the spring, summer, and fall, but not in any of the winter samples. No other GIT samples from feedlot cattle were AHL positive, and all the samples from the sheep study were AHL negative. The cattle seemed to show a weak correlation between ruminal AHL and EHEC prevalence. This research found AHL only in the rumen and not in the lower GIT of feedlot cattle. However, it is unclear whether this is because the pH of the lower gut destroys the AHL or because a lack of certain bacteria in the lower gut producing AHL.

Incidence and ecology of Campylobacter jejuni and coli in animals

Since its initial emergence in the 1970s, Campylobacter has become one of the most common causative agents of bacterial foodborne illness. Campylobacter species readily colonize the gastrointestinal tracts of domestic, feral and wild animals and while they rarely cause clinical disease in food animals, they can produce severe acute gastroenteritis in humans. Prevalence of Campylobacter in food animals can exceed 80% thus challenging processors to employ post-harvest pathogen reduction strategies. Reduction of pathogens before arrival to the abattoir is also of interest because the implementation of pre-harvest interventions may compliment existing post-harvest control techniques to further diminish possible retail sources of infection. Such multiple hurdle approaches that simultaneously utilize pre- and post-harvest control techniques are expected to be the most effective approach for decreasing human illness associated with foodborne pathogens.

Recombinant human bone morphogenetic protein-2 for grade III open segmental tibial fractures from combat injuries in Iraq

This article has been retracted, an editorial will follow.

In vitro bacterial growth and in vivo ruminal microbiota populations associated with bloat in steers grazing wheat forage

The role of ruminal bacteria in the frothy bloat complex common to cattle grazing winter wheat has not been previously determined. Two experiments, one in vitro and another in vivo, were designed to elucidate the effects of fresh wheat forage on bacterial growth, biofilm complexes, rumen fermentation end products, rumen bacterial diversity, and bloat potential. In Exp. 1, 6 strains of ruminal bacteria (Streptococcus bovis strain 26, Prevotella ruminicola strain 23, Eubacterium ruminantium B1C23, Ruminococcus albus SY3, Fibrobacter succinogenes ssp. S85, and Ruminococcus flavefaciens C94) were used in vitro to determine the effect of soluble plant protein from winter wheat forage on specific bacterial growth rate, biofilm complexes, VFA, and ruminal H2 and CH4 in mono or coculture with Methanobrevibacter smithii. The specific growth rate in plant protein medium containing soluble plant protein (3.27% nitrogen) was measured during a 24-h incubation at 39 degrees C in Hungate tubes under a CO2 gas phase. A monoculture of M. smithii was grown similarly, except under H2:CO2 (1:1), in a basal methanogen growth medium supplemented likewise with soluble plant protein. In Exp. 2, 6 ruminally cannulated steers grazing wheat forage were used to evaluate the influence of bloat on the production of biofilm complexes, ruminal microbial biodiversity patterns, and ruminal fluid protein fractions. In Exp. 1, cultures of R. albus (P < 0.01) and R. flavefaciens (P < 0.05) produced the most H2 among strains and resulted in greater (P < 0.01) CH4 production when cocultured with M. smithii than other coculture combinations. Cultures of S. bovis and E. ruminantium + M. smithii produced the most biofilm mass among strains. In Exp. 2, when diets changed from bermudagrass hay to wheat forage, biofilm production increased (P < 0.01). Biofilm production, concentrations of whole ruminal content (P < 0.01), and cheesecloth filtrate protein fractions (P < 0.05) in the ruminal fluid were greater on d 50 for bloated than for nonbloated steers when grazing wheat forage. The molecular analysis of the 16S rDNA showed that 2 different ruminal microbiota populations developed between bloated and nonbloated animals grazing wheat forage. Bloat in cattle grazing wheat pastures may be caused by increased production of biofilm, resulting from a diet-influenced switch in the rumen bacterial population.

Smart Foods from the pastoral sector - implications for meat and milk producers

Smart Foods, or foods with functions that confer health benefits, are the future of the food and nutrition sectors. Pastoral products such as milk and meat are easily manipulated to improve the health benefits of these products. Therefore, there is the potential for farmers to add value to their current products. Additionally, the identification of key nutrients for health and the prevention of disease using nutrigenomic and nutritional epigenetic approaches may identify new ways to manipulate milk and meat products. However, consumer perceptions of product efficacy and the marketing of foods with health claims will be drivers behind the uptake of Smart Foods in the future.

Detection of methane and quantification of methanogenic archaea in faeces from young broiler chickens using real-time PCR

AIMS

To detect the presence of methanogens in the faeces of broiler chicks during the first 2 weeks of age.

METHODS AND RESULTS

Chicken faecal samples from 120 broiler chicks were incubated for methane gas formation and methanogenic archaea were analysed using real-time PCR. The copy number of the order Methanobacteriales 16S rDNA gene in chicken faeces when the broilers were 3-12 days of age, litter and house flies collected in the bird house ranged from 4.19 to 5.51 log(10) g(-1) wet weight. The number of positive methane culture tubes increased from 25% to 100% as the birds aged.

CONCLUSIONS

Methanogens were successfully detected in faecal samples from 3- to 12-day-old broilers, as well as litter and house flies using real-time PCR. The copy number of methanogenic 16S rDNA gene in these samples was also similar to the number observed in litter and house flies.

SIGNIFICANCE AND IMPACT OF THE STUDY

The same methanogens consistently appeared in chicken faeces a few days after birth. Detection of the methanogenic bacteria in litter and house flies implicated them as potential environmental sources for methanogen colonization in broiler chicks.

Gastrointestinal microbial ecology and the safety of our food supply as related to Salmonella

Salmonella causes an estimated 1.3 million human foodborne illnesses and more than 500 deaths each year in the United States, representing an annual estimated cost to the economy of approximately $2.4 billion. Salmonella enterica comprises more than 2,500 serotypes. With this genetic and environmental diversity, serotypes are adapted to live in a variety of hosts, which may or may not manifest with clinical illness. Thus, Salmonella presents a multifaceted threat to food production and safety. Salmonella have been isolated from all food animals and can cause morbidity and mortality in swine, cattle, sheep, and poultry. The link between human salmonellosis and host animals is most clear in poultry. During the early part of the 20th century, a successful campaign was waged to eliminate fowl typhoid caused by Salmonella Gallinarum/Pullorum. Microbial ecology is much like macroecology; environmental niches are filled by adapted and specialized species. Elimination of S. Gallinarum cleared a niche in the on-farm and intestinal microbial ecology that was quickly exploited by Salmonella Enteritidis and other serotypes that live in other hosts, such as rodents. In the years since, human salmonellosis cases linked to poultry have increased to the point that uncooked chicken and eggs are regarded as toxic in the zeitgeist. Salmonellosis caused by poultry products have increased significantly in the past 5 yr, leading to a USDA Food Safety and Inspection Service "Salmonella Attack Plan" that aims to reduce the incidence of Salmonella in chickens below the current 19%. The prevalence of Salmonella in swine and cattle is lower, but still poses a threat to food safety and production efficiency. Thus, approaches to reducing Salmonella in animals must take into consideration that the microbial ecology of the animal is a critical factor that should be accounted for when designing intervention strategies. Use of competitive exclusion, sodium chlorate, vaccination, and bacteriophage are all strategies that can reduce Salmonella in the live animal, but it is vital to understand how they function so that we do not invoke the law of unintended consequences.