This study determined whether tributyrin and lactitol could synergistically facilitate the transition from milk to solid feed in nursery pigs. At 21 d after birth, 64 piglets were moved from the ...piggery to a production barn and fed a medicated diet. At 28 d after birth, the piglets were weighed and allotted into four groups and fed a standard nonmedicated diet (control) or the control diet with tributyrin (butanoic acid 1,2,3-propanetriyl ester; 10 g/kg), or with lactitol (beta-D-galactopyranosyl-(1-->4)-D-sorbitol; 3 g/kg), or with tributyrin (10 g/kg) plus lactitol (3 g/kg). On d 0, 14, and 42 after being fed the control or experimental diets, the animals were weighed, and animal health, feed intake, and feed conversion ratio were determined. On d 42, four piglets from each treatment were killed to measure the empty and full weight of the gut, as well as the weights of the liver and kidneys. The jejunum and cecum were sampled to analyze the luminal concentrations of lactic acid; short-chain fatty acids; and mono-, di-, and polyamines and to assess the mucosal status. Mortality after 42 d ranged from 19% for animals fed the control diet, to 6% for animals fed the tributyrin or lactitol diets, and to 0% for animals fed the tributyrin+lactitol diet. After 14 d, the ADG was 127% greater (P < 0.05) in animals fed the tributyrin+lactitol diet than in animals fed the control or tributyrin diets. After 42 d, animals fed the tributyrin+lactitol diet were heavier (P < 0.05) than animals fed the tributyrin diet. At slaughter, no differences (P > 0.05) in organ weights were observed. With the exception of animals fed the lactitol diet, wherein cecal lactic acid levels increased threefold (P < 0.01), the luminal concentrations of lactic acid and short-chain fatty acids were not different (P > 0.05). Among the various amines analyzed, the only response (P < 0.05) was a 66 and 49% decrease in histamine levels in the jejunum and cecum, respectively, in animals fed the tributyrin+lactitol diet compared to the control diet. In the jejunum of animals fed the lactitol or tributyrin+lactitol diets, the length of the villi was increased by 12% (P < 0.05) compared to animals fed the control diet, whereas the tributyrin diet did not have any effect on the villi (P > 0.05). In the cecum, the depths of the crypts were reduced (P < 0.001) by 18% in animals fed the lactitol diet and 45% in animals fed the tributyrin or tributyrin+lactitol diets compared to animals fed the control diet. In conclusion, a diet containing tributyrin and lactitol as nutribiotics resulted in lower histamine levels in the jejunum and cecum, as well as longer jejunal villi and shallower cecal crypts.
A total of 150 fecal and water samples from four swine farms were tested for the presence of Salmonella enterica using different enrichment techniques as follows: (i) 92 fecal samples from nursery ...and farrowing barns at three swine farms were preenriched overnight in tryptic soy broth (TSB) at 37 degrees C followed by overnight enrichment in Rappaport-Vassiliadis 10 broth (RV10) at 42 degrees C; (ii) 24 water samples from the third farm were preenriched overnight in 3MC broth at 37 degrees C followed by overnight enrichment in RV10 at 42 degrees C; and (iii) 34 fecal samples from a fourth farm, a finishing farm, were enriched overnight in RV10 at 42 degrees C with no additional enrichment. Following each of the enrichment techniques, samples were subcultured onto modified semisolid Rappaport-Vassiliadis (MSRV) agar prior to transfer to Hektoen Enteric agar plates for the recovery of viable Salmonella bacteria. Presumptive Salmonella isolates were biochemically and serologically confirmed. For the PCR detection of Salmonella, a 1-ml portion was removed from each sample after the first overnight enrichment and the DNA was extracted using a Sepharose CL-6B spin column. Amplicons (457 bp) derived from primers to the invA and invE genes were confirmed as Salmonella specific on ethidium bromide-stained agarose gels by Southern hybridization with a 20-mer oligonucleotide probe specific for the Salmonella invA gene. Neither the standard microbiological method nor the molecular method detected all of the 65 samples that tested positive by both methods or either method alone. Salmonella bacteria were detected by both cultivation and PCR-hybridization in 68% (17 of 25) of the positive samples that were preenriched in TSB, in 73% (11 of 15) of the positive samples preenriched in 3MC broth, and in 24% (6 of 25) of the positive samples enriched in RV10. Agreement between Salmonella detection using cultivation with preenrichment and detection by PCR was 76% using the kappa statistic. However, agreement between Salmonella detection using cultivation without preenrichment and detection by PCR was about 6%; the PCR assay detected 80% (20 of 25) of the 25 positive samples, while Salmonella bacteria were recovered from only 44% (11 of 25) by cultivation. Our results indicate that the PCR-hybridization approach is equivalent to or better than cultivation for detecting Salmonella in swine feces or water samples from swine farms when using the medium combinations evaluated in this study.
The outbreak of Escherichia coli O157:H7 linked with dry-cured salami in late 1994 prompted regulatory action that required manufacturers of fermented products to demonstrate a 5-log unit reduction ...in counts of this pathogen during processing. Therefore, pepperoni batter (75% pork:25% beef with a fat content of ca. 32%) was inoculated with a pediococcal starter culture and a five-strain mixture of E. coli O157:H7 (greater than or equal to 2 X 10(7) CFU/g) and stuffed into 55-mm diameter fibrous casings 47 cm in length. The viability of the pathogen was monitored before stuffing, after fermentation, after thermal processing, and/or after drying. Chubs were fermented at 96 degrees F (36 degrees C) and 85% relative humidity (RH) to pH less than or equal to 5.0 and then dried at 55 degrees F (13 degrees C) and 65% RH to a moisture/protein ratio of less than or equal to 1.6:1 (modified method 6 process). Counts of the pathogen decreased about 1.2 log units after fermentation and drying. In subsequent experiments, heating chubs after fermentation to internal temperatures of 145 degrees F (63 degrees C) instantaneous or 128 degrees F (53 degrees C) for 60 min resulted in a greater than or equal to 5-log unit decrease in numbers of strain O157:H7 without visibly affecting the texture or appearance of the product. These data revealed that a traditional nonthermal, process for pepperoni was only sufficient to eliminate relatively low levels (ca. 2 log CFU/g) of E. coli O157:H7, whereas heating to internal temperatures of 145 degrees F (63 degrees C) instantaneous or 128 degrees F (53 degrees C) for 60 min delivered a 5 to 6 log unit reduction in counts of the pathogen in pepperoni
The Escherichia coli O104 polysaccharide is an important antigen, which contains sialic acid and is often associated with EHEC clones. Sialic acid is a component of many animal tissues, and its ...presence in bacterial polysaccharides may contribute to bacterial pathogenicity. We sequenced the genes responsible for O104 antigen synthesis and have found genes which from their sequences are identified as an O antigen polymerase gene, an O antigen flippase gene, three CMP-sialic acid synthesis genes, and three potential glycosyl transferase genes. The E. coli K9 group IB capsular antigen has the same structure as the O104 O antigen, and we find using gene by gene PCR that the K9 gene cluster is essentially the same as that for O104. It appears that the distinction between presence as group IB capsule or O antigen for this structure does not involve any difference in genes present in the O antigen gene cluster. By PCR testing against representative strains for the 166 E. coli O antigens and some randomly selected Gram-negative bacteria, we identified three O antigen genes which are highly specific to O104/K9. This work provides the basis for a sensitive test for rapid detection of O104 E. coli. This is important both for decisions on patient care as early treatment may reduce the risk of life-threatening complications and for a faster response in control of food borne outbreaks.
Beef carcass quarters and fat-covered subprimal cuts were suspended vertically and inoculated with a bovine manure slurry containing a five-strain mixture of Escherichia coli O157:H7 to deliver about ...4 to 5 log10 CFU/cm2. To identify treatments that would improve the effectiveness of spraying with lactic acid (LA), the inoculated quarters and cuts were treated as follows: experiment A, (i) not treated (control), (ii) sprayed with 2% (vol/vol) LA, (iii) tempered at 21 degrees C for 4 h, and (iv) tempered and then sprayed with LA; experiment B, (v) sprayed with water, (vi) sprayed with LA, (vii) sprayed with LA containing 0.5% (vol/vol) sodium benzoate (SB), and (viii) sprayed with LA containing SB and 5% (vol/vol) Tween 20 (TW20); and experiment C, (ix) sprayed with water (no prespray), (x) presprayed with TW20 and then sprayed with LA, and (xi) presprayed with TW20 and then sprayed with LA containing SB. In experiment A, spraying carcasses with LA significantly (P < 0.05) reduced the numbers of E. coli Biotype I and serotype O157:H7 after 1 and 3 days of storage, respectively. The tempering process employed did not affect the effectiveness of the LA spray on either type of E. coli. In experiment B, there was no significant difference in the reduction of E. coli O157:H7 on subprimal cuts sprayed with water and that on cuts sprayed with LA alone or with LA in combination with SB and TW20 after 1 or 3 days of storage (total reductions ranged from about 1.6 to 2.8 log10 CFU/cm2). In experiment C, prespraying subprimal cuts with TW20 significantly (P < 0.05) increased the effectiveness of LA (reductions of 2.8 and 3.2 log10 CFU/cm2, respectively) and that of LA with SB (reductions of 2.6 and 3.3 log10 CFU/cm2, respectively) compared with spraying with water alone (reductions of ca. 1.0 and 2.0 log10 CFU/cm2, respectively) after I and 3 days of storage, respectively. In a separate experiment, the incorporation of TW20 (0.1 or 0.25%) into buffered peptone water prior to the maceration of excised carcass surface samples resulted in the recovery of significantly larger numbers (ca. 5.1 to 5.2 log10 CFU/cm2) of E. coli O157:H7 cells than did the control treatment without added TW20 (ca. 3.8 to 4.6 log10 CFU/cm2). These results demonstrate that the treatment of beef carcasses with LA reduces the number of viable E. coli O157:H7 cells and that this inactivation or removal by LA is enhanced by prespraying of the carcass with a 5% solution of TW20.
A total of 689 co-grazing small ruminants along with 446 wild-living birds were tested during two springs and autumns (2007–2009) under two management systems at two Mid-Atlantic locations (~187km in ...aerial distance) of the U.S. Fecal shedding of Campylobacter jejuni and Salmonella spp. were, respectively, detected in 9.3% and 3.5% of small ruminants and in 7.4% and 0.2% of wild-living birds. Sheep had a significantly higher prevalence of C. jejuni and Salmonella than goats, but there were no differences due to season, location, or management. Pulsed field gel electrophoresis (PFGE) of isolated strains revealed geographic specificity and genomic diversity of both pathogens from small ruminants. However, C. jejuni strains with indistinguishable PFGE profiles were isolated from one Rock Dove and two European Starlings caught at separate locations. Matching C. jejuni or Salmonella strain profiles were not found between small ruminants and wild-living birds. This study found that sheep pose a greater risk than goats in C. jejuni and Salmonella contamination at co-grazing small ruminant farms. Wild-living birds also are potential carriers of C. jejuni and Salmonella although no evidence of cross-contamination with small ruminants was established.
ABSTRACT
The validity of a cross‐flow microfiltration (MF) process for separation of an avirulent strain of Bacillus anthracis (BA) spores from commercial unpasteurized liquid egg white (LEW) was ...examined. Unpasteurized LEW was inoculated with BA to a level of approximately 106 spores/mL and microfiltered using a 1.4‐micron ceramic membrane. Permeate flux increased at a rate of 50 L/h m2 per unit pH decrease, which is almost 30 times greater compared with the rate of increase in flux due to a unit increase in temperature. Spore removal efficiency was at least 6.14 log10 spores/mL. In a storage stability study, microfiltered LEW showed no outgrowth of spores for 21 days at 4C. Egg white protein permeation, and hence the functional properties, were unaffected during MF.
PRACTICAL APPLICATIONS
Bacillus anthracis (BA), a spore‐forming bacterium and a potential biothreat agent, could be used as an atypical foodborne pathogen for intentional contamination of the food supply. Thermal pasteurization is effective only for pathogens that are in vegetative forms such as Salmonella, but ineffective for destroying spore‐forming pathogens, such as BA. Also, egg proteins' ability to form foam or gel is severely destroyed during pasteurization, since egg albumin is highly heat sensitive. There is a serious need in the agri‐industry to develop an effective intervention strategy for removal of B. anthracis from high value foods such as liquid eggs. The current study describes a microfiltration process that is capable of removing almost 99.9999% BA spores from liquid egg white (LEW) without affecting egg white's ability to form foam or gel, and hence may provide an option for safety and security of liquid foods such as LEW.
A whole-genome sequence analysis of
Listeria monocytogenes strain F2365 revealed 15 potential members of the Crp/Fnr family of transcriptional regulatory proteins. Each gene and the flanking regions ...were cloned, subjected to in vitro transpositional mutagenesis, and recombined into strain F2365. Mutant strains, produced for 14 of the family members, were compared to strain F2365 for differences in carbon utilization, resistance to oxidative stress, and growth under reduced oxygen conditions that would signal an Fnr- or Crp-like function for these proteins. There were no differences among strain F2365 and the 14 mutant strains in the utilization of the carbon sources readily utilized by
L. monocytogenes. Although strain KO2 had a reduced growth rate compared to strain F2365 and the other mutant strains at 30° but not at 37
°C, there were no differences in growth rates among strain F2365 and the mutant strains when incubated at either 30 or 37
°C under reduced oxygen conditions. However, when compared for differences in response to oxidative stress, mutants KO2 and KO5 showed reduced oxidative stress tolerance compared to the wild-type strain F2365. These results suggest that certain members of the putative Crp/Fnr family in
L. monocytogenes may function in response to oxidative stress similar to the Fnr-like protein (Flp) of other Gram-positive bacteria.
The pulsed-field technique of clamped homogeneous electric field electrophoresis was employed to characterize and size genomic DNA of three pediocin-producing (Ped+) and two non-pediocin-producing ...(Ped-) strains of Pediococcus acidilactici. Comparison of genomic fingerprints obtained by digestion with the low-frequency-cleavage endonuclease AscI revealed identical restriction profiles for four of the five strains analyzed. Summation of results for 10 individually sized AscI fragments estimated the genome length to be 1,861 kb for the four strains (H, PAC1.0, PO2, and JBL1350) with identical fingerprints. Genomic analysis of the pediocin-sensitive, plasmid-free strain P. acidilactici LB42 with the unique fingerprint revealed nine AscI fragments and a genome length of about 2,133 kb. Ped- (JBL1350) and Ped+ (JBL1095) starter cultures (one each) were used to separately prepare turkey summer sausage coinoculated with a four-strain Listeria monocytogenes mixture (ca. 10(5) CFU/g). The starter cultures produced equivalent amounts of acid during fermentation, but counts of L. monocytogenes were reduced to a greater extent in the presence of the Ped+ starter culture (3.4 log10 unit decrease) than in the presence of the Ped- starter culture (0.9 log10 unit decrease). Although no listeriae were recovered from sausages following the cook/shower, appreciable pediocin activity was recovered from sausages prepared with the Ped+ strain for at least 60 days during storage at 4 degrees C. The results of this study revealed genomic similarities among pediococcal starter cultures and established that pediocins produced during fermentation provide an additional measure of safety against listerial proliferation in turkey summer sausage
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