Methylsulfonylmethane exhibits bacteriostatic inhibition of Escherichia coli, and Salmonella enterica Kinshasa, in vitro.

AIMS: To evaluate antibacterial properties of methylsulfonylmethane (MSM) on Escherichia coli (MDRE21) and Salmonella enterica serovar Kinshasa (SK132). METHODS AND RESULTS: Bacterial proliferation analysis was measured spectrophotometrically during log phase growth with 0, 3, 5, 7, 10, 12 and 16% MSM. To assess the mechanism of inhibition, cultures were grown overnight with 0-16% MSM and enumerated on unmedicated brain-heart infusion agar (BHIA) or BHIA with 0-16% MSM. The long-term viability studies were done to evaluate the impact of 10% MSM. Absorbance data indicated a dose-dependent inhibition from 0 to 16% MSM. There was no growth of MDRE21 or SK132 on BHIA in 10-16% MSM. Both strains enumerated on unmedicated BHIA from overnight cultures with 10-16% MSM were able to partially recover. CONCLUSIONS: Recovery after MSM removal may be indicative of a bacteriostatic mechanism of inhibition. The long-term viability studies illustrated that neither MDRE21 nor SK132 could be rescued from 10% MSM after 5 or 6 days respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Methylsulfonylmethane antibacterial activity may prove useful during pre or postharvest food safety as a disinfectant. The primary benefit being, its clinical safety to humans. Comparisons to other disinfectants would also need to be done to determine if MSM was superior to those already on the market and would be cost effective.

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 (MICM s) of the VRE were calculated using the Henderson-Hasselbalch equation. The pH at the MICM 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.

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.

Evidence supporting vertical transmission of Salmonella in dairy cattle.

We set out to investigate whether Salmonella enterica could be recovered from various tissues of viable neonatal calves immediately following parturition. Eleven samples were aseptically collected from each of 20 calves and consisted of both left and right subiliac and prescapular lymph nodes (LN), mesenteric LN, spleen and liver, as well as intestinal tissue (including luminal contents) from the small intestine, caecum, spiral colon and rectum. In addition, a faecal sample was collected from 19 of the dams. Salmonella was recovered from at least one sample from 10 of the 20 neonates. Across all calves, Salmonella was recovered from 12·7% of all samples and from LN in particular, Salmonella was recovered from 10·0%, 5·0%, and 5·0% of subiliac, prescapular, and mesenteric LN, respectively. Within calves, Salmonella was recovered from 0% to 73% of samples and across tissues, estimates of Salmonella prevalence were greatest in the caecum (30%) but was never recovered from the right pre-scapular LN. These data provide evidence of vertical transmission from a dam to her fetus such that viable calves are born already infected and thereby not requiring faecal-oral exposure for transmission. This new knowledge ought to challenge - or at least add to - existing paradigms of Salmonella transmission dynamics within cattle herds.

Characterization of antibiotic and disinfectant susceptibility profiles among Pseudomonas aeruginosa veterinary isolates recovered during 1994-2003.

AIMS: To evaluate susceptibility of Pseudomonas aeruginosa veterinary isolates to antibiotics and disinfectants. METHODS AND RESULTS: Pseudomonas aeruginosa isolates collected from dogs (n = 155) and other animals (n = 20) from sixteen states during 1994-2003 were tested for susceptibility. Most isolates were resistant to twenty-one antimicrobials tested, and the highest prevalence of resistance was to ß-lactams (93.8%) and sulphonamides (93.5%). Fluoroquinolone resistance did not increase from 1994 to 2003. Ciprofloxacin and enrofloxacin had a 5 and 16% prevalence of resistance, respectively, while sarafloxacin and nalidixic acid had a prevalence of resistance of 97 and 98%, respectively. Strains were pan-resistant to triclosan and chlorhexidine, were highly resistant to benzalkonium chloride and demonstrated high susceptibility to other disinfectants. Didecyldimethylammonium chloride was the most active ammonium chloride. Inducible resistance was observed to cetyl ammonium halides, chlorhexidine and benzyl ammonium chlorides, which formulate disinfectants used in veterinary clinics and dairies. Organic acid inhibition was associated with the dissociated acid species. CONCLUSIONS: Dissociated organic acids appear able to inhibit Ps. aeruginosa, and rates of fluoroquinolone resistance merit sustained companion animal isolate surveillance. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of Ps. aeruginosa susceptibility to 24 disinfectants and illustrates the high resistance of Ps. aeruginosa to both antibiotics and disinfectants.

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.

Competitive effect of commensal faecal bacteria from growing swine fed chlortetracycline-supplemented feed on ß-haemolytic Escherichia coli strains with multiple antimicrobial resistance plasmids.

AIMS: To determine the differences in competitive fitness among Escherichia coli strains with different plasmid profiles when grown in suspension with commensal faecal bacteria from growing swine fed chlortetracycline-supplemented or unsupplemented diets. METHODS AND RESULTS: Five multiple drug-resistant (MDR) E. coli strains that possessed 0, 2, 6 or 8 plasmids were inoculated into anoxic faecal cultures from swine fed an unsupplemented (control) or chlortetracycline (50 g ton(-1))-supplemented (experimental) diet. On days 21 of chlortetracycline supplementation, faecal growth competition studies were performed. MDR E. coli were enumerated at 0, 6 and 24 h. The plasmid-free strain was below culturable limits in both the control and experimental cultures by 24 h. For each plasmid-bearing strain, there was no statistically significant difference in population CFU ml(-1) (P < 0.05) between the control and experimental cultures. CONCLUSIONS: There was no significant effect on the faecal microflora, owing to the inclusion of chlortetracycline, in the swine diets, that affected the growth of E. coli in the competition studies employed. Furthermore, these results suggest that the cost of maintaining plasmids in these E. coli strains had little influence on survivability. SIGNIFICANCE AND IMPACT OF STUDY: Mutations that led to antimicrobial resistance may have a greater impact on survivability than multiple plasmid carriage.

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.

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.

Effect of supplementation of prebiotic mannan-oligosaccharides and probiotic mixture on growth performance of broilers subjected to chronic heat stress.

The present study was aimed at elucidating the effects of supplementing mannan-oligosaccharides (MOS) and probiotic mixture (PM) on growth performance, intestinal histology, and corticosterone concentrations in broilers kept under chronic heat stress (HS). Four hundred fifty 1-d-old chicks were divided into 5 treatment groups and fed a corn-soybean diet ad-libitum. The temperature control (CONT) group was held at the normal ambient temperature. Heat stress broilers were held at 35 ± 2°C from d 1 until the termination of the study at d 42. Heat stress groups consisted of HS-CONT fed the basal diet; HS-MOS fed the basal diet containing 0.5% MOS; HS-PM fed the basal diet containing 0.1% PM; and HS-SYN (synbiotic) fed 0.5% MOS and 0.1% PM in the basal diet. Broilers were examined at d 21 and 42 for BW gain, feed consumption, feed conversion ratio (FCR), serum corticosterone concentrations, and ileal microarchitecture. The results revealed that the CONT group had higher (P < 0.01) feed consumption, BW gain, and lower FCR on d 21 and 42, compared with the HS-CONT group. Among supplemented groups, the HS-MOS had higher (P < 0.05) BW gain and lower FCR compared with the HS-CONT group. On d 21 and 42, the HS-CONT group had higher (P < 0.05) serum corticosterone concentrations compared with the CONT and supplemented groups. The CONT group had higher (P < 0.05) villus height, width, surface area, and crypt depth compared with the HS-CONT group. On d 21, the HS-PM had higher (P < 0.05) villus width and surface area compared with HS-CONT group. On d 42, the HS-SYN had higher (P < 0.05) villus width and crypt depth compared with the HS-CONT group. These results showed that chronic HS reduces broiler production performance, intestinal microarchitecture, and increases adrenal hormone concentrations. Also, supplementation of the MOS prebiotic and the PM can partially lessen these changes.

Evaluation of a Preharvest Bacteriophage Therapy for Control of Salmonella within Bovine Peripheral Lymph Nodes.

ABSTRACT: A series of proof-of-concept studies were developed to determine whether a commercial bacteriophage cocktail could be utilized for the mitigation of Salmonella in bovine peripheral lymph nodes (LNs). The first objective sought to determine whether exogenous phage could be isolated from the LNs following administration. If isolation were successful, the second objective was to determine whether the phage in the LNs could effectively reduce Salmonella. Salmonella Montevideo was inoculated intradermally at multiple sites and multiple times, followed by delivery of the phage cocktail subcutaneously in two injections around each of the right and left prescapular and subiliac LNs. At the conclusion of each study, animals were euthanized, and the popliteal, prescapular, and subiliac LNs were examined. The inoculated phage was successfully isolated from the LNs; transmission electron microscopy revealed phages in the LNs of the treated cattle, and these phages were identical to those in the cocktail. Levels of phage were higher (P < 0.01) in the prescapular and subiliac LNs in the phage-treated than in the control cattle. In subsequent studies, the protocols were modified to increase Salmonella and phage levels within the LNs. Compared with the first study, overall Salmonella levels were increased in the LNs, and phage treatment decreased (P < 0.01) Salmonella in the some of the LNs. Phage levels were numerically but not significantly increased (P = 0.12) in the treated cattle. The final study was modified, hypothesizing that a 48-h postmortem period before LN removal would facilitate phage-Salmonella interaction; however, no differences (P > 0.10) in Salmonella levels were found among treatments. Salmonella-specific phages administered to live cattle can translocate to the LNs; however, these phages had limited to no effect on Salmonella in these LNs under these experimental conditions.

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.

Effects of thymol and diphenyliodonium chloride against Campylobacter spp. during pure and mixed culture in vitro.

AIMS: To determine if the purported deaminase inhibitors diphenyliodonium chloride (DIC) and thymol reduce the growth and survivability of Campylobacter. METHODS AND RESULTS: Growth rates of Campylobacter jejuni and Camp. coli were reduced compared to unsupplemented controls during culture in Muellar-Hinton broth supplemented with 0.25 micromol DIC or thymol ml(-1) but not with 0.01 micromol monensin ml(-1) or 1% ethanol. Recovery of Camp. jejuni and Camp. coli was reduced >5 log(10) CFU from controls after 24 h pure culture in Bolton broth supplemented with 0.25 or 1.0 micromol DIC ml(-1) or with 1.0 micromol thymol ml(-1). Similarly, each test Campylobacter strain was reduced >3 log(10) CFU from controls after 24 h mixed culture with porcine faecal microbes in Bolton broth supplemented with 0.25 or 1.0 micromol DIC ml(-1) or with 1.0 micromol thymol ml(-1). Treatments with 0.25 micromol thymol ml(-1), 0.01 micromol monensin ml(-1) or 1% ethanol were less effective. Ammonia production during culture or incubation of cell lysates was reduced by 0.25 or 1.0 micromol DIC ml(-1) but only intermittently reduced, if at all, by the other treatments. CONCLUSIONS: Diphenyliodonium chloride and thymol reduced growth, survivability and ammonia production of Camp. jejuni and Camp. coli. SIGNIFICANCE AND IMPACT OF THE STUDY: Results suggest a potential physiological characteristic that may be exploited to develop interventions.

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.

Planktonic and biofilm communities from 7-day-old chicken cecal microflora cultures: characterization and resistance to Salmonella colonization.

Information implicating bacterial biofilms as contributory factors in the development of environmental bacterial resistance has been increasing. There is a lack of information regarding the role of biofilms within the microbial ecology of the gastrointestinal tract of food animals. This work used a continuous-flow chemostat model derived from the ceca of 7-day-old chicks to characterize these communities and their ability to neutralize invasion by Salmonella enterica serovar Typhimurium. We characterized and compared the biofilm and planktonic communities within these microcosms using automated ribotyping and the Analytical Profile Index biotyping system. Eleven species from eight different genera were identified from six culture systems. Klebsiella pneumoniae was isolated from all planktonic communities and four of the biofilm communities. Three of the communities resisted colonization by Salmonella enterica serovar Typhimurium, two communities suppressed growth, and one community succumbed to colonization. In cultures that resisted colonization, no Salmonella could be isolated from the biofilm; in cultures that succumbed to colonization, Salmonella was consistently found within the biofilms. This study was one of a series that provided a molecular-based characterization of both the biofilm and planktonic communities from continuous-flow culture systems derived from the cecal microflora of chicks, ranging in age from day-of-hatch to 14 days old. The one common factor relating to successful colonization of the culture was the presence of Salmonella within the biofilm. The capacity to sequester the introduced Salmonella into the biofilm appears to be a contributing factor to the inability of these cultures to withstand colonization by the 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.

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.

Foodborne Salmonella ecology in the avian gastrointestinal tract.

Foodborne Salmonella continues to be a major cause of salmonellosis with Salmonella Enteritidis and S. Typhimurium considered to be responsible for most of the infections. Investigation of outbreaks and sporadic cases has indicated that food vehicles such as poultry and poultry by-products including raw and uncooked eggs are among the most common sources of Salmonella infections. The dissemination and infection of the avian intestinal tract remain somewhat unclear. In vitro incubation of Salmonella with mammalian tissue culture cells has shown that invasion into epithelial cells is complex and involves several genetic loci and host factors. Several genes are required for the intestinal phase of Salmonella invasion and are located on Salmonella pathogenicity island 1 (SPI 1). Salmonella pathogenesis in the gastrointestinal (GI) tract and the effects of environmental stimuli on gene expression influence bacterial colonization and invasion. Furthermore, significant parameters of Salmonella including growth physiology, nutrient availability, pH, and energy status are considered contributing factors in the GI tract ecology. Approaches for limiting Salmonella colonization have been primarily based on the microbial ecology of the intestinal tract. In vitro studies have shown that the toxic effects of short chain fatty acids (SCFA) to some Enterobacteriaceae, including Salmonella, have resulted in a reduction in population. In addition, it has been established that native intestinal microorganisms such as Lactobacilli provide protective mechanisms against Salmonella in the ceca. A clear understanding of the key factors involved in Salmonella colonization in the avian GI tract has the potential to lead to better approach for more effective control of this foodborne pathogen.

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.

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.