Competitive exclusion of Salmonella from the gut of neonatal and weaned pigs

Our laboratory has developed a bacterial competitive-exclusion (CE) culture against enteropathogens (which are considered human foodborne pathogens) for use in swine. In this article, we document the effects of this CE culture, PCF1, on cecal colonization by and fecal shedding of Salmonella Choleraesuis in neonatal and weaned pigs and its effects on the horizontal transmission of this pathogen between weaned penmates. Piglets treated with the PCF1 culture twice within their first day of life and challenged with Salmonella 48 h after birth shed Salmonella at a significantly (P < 0.05) lower rate than did control pigs in experiment 1. Significant reductions of the pathogen were also observed in the cecum, the cecal contents, the ileocolic junction, and the colon contents (P < 0.05). In experiment 2, culture of the cecal contents and lymph nodes revealed a significant reduction in Salmonella isolated from PCF1-treated pigs (P < 0.05). Pigs in experiment 3 were treated as pigs in experiments 1 and 2 were: however, they were followed through day 10 postweaning. Significant reductions in shedding were noted for treated groups both pre- and postweaning (P < 0.05). Experiments 4 and 5 assessed the effects of PCF1 treatment on the horizontal transmission of Salmonella between littermates that were followed through day 14 postweaning. In these experiments, litters were divided into untreated contacts (UC), untreated seeders (US), treated contacts (TC), and treated seeders (TS). Overall, TC in experiment 4 shed Salmonella at a significantly lower rate than UC and US did (P < 0.05). In experiment 5, the transmission of Salmonella was significantly reduced for litters in which TS or TC were present, as evidenced by reduced shedding of Salmonella by both treated and untreated animals within these litters (P < 0.05). TS shed less often than US did, resulting in reduced levels of Salmonella shedding by both treated and untreated contacts (P < 0.05). Litters containing both TC and UC or both TC and US also shed Salmonella at lower rates than did litters in which only UC and US were present (P < 0.05).

Effects of the antibiotic ionophores monensin, lasalocid, laidlomycin propionate and bambermycin on Salmonella and E. coli O157:H7 in vitro

AIMS

To examine the effects of ionophores on Salmonella and Escherichia coli O157:H7 in pure and mixed ruminal fluid cultures.

METHODS AND RESULTS

Four Salmonella serotypes (Dublin, Derby, Typhimurium, and Enteriditis) and two strains of E. coli O157:H7 (ATCC 43895 and FDIU 6058) were cultured in the presence of varying concentrations of ionophores (monensin, lasalocid, laidlomycin propionate, and bambermycin) in pure and mixed ruminal fluid cultures. Bacterial growth rates in pure culture were not affected (P > 0.10) by ionophores at concentrations up to 10 times the approximate rumen ionophore concentration under normal feeding regimens. Likewise, ionophores had no effect (P > 0.10) on Salmonella or E. coli CFU plated from 24-h ruminal fluid incubations. Ionophore treatment decreased (P < 0.01) the acetate : propionate ratio in ruminal fluid cultures as expected.

CONCLUSIONS

Ionophores had no effect on the foodborne pathogens Salmonella and E. coli O157:H7 in vitro.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results suggest that ionophore feeding would have little or no effect on Salmonella or E. coli populations in the ruminant.

Sexually dimorphic expression of multiple doublesex-related genes in the embryonic mouse gonad

The only molecular similarity shown so far for sexual regulatory genes among different phyla involves doublesex (dsx) of Drosophila, mab-3 and mab-23 of Caenorhabditis elegans, and Dmrt1 of vertebrates. These genes encode DM domain transcription factors (DM = dsx and mab-3) and are required for sexual differentiation. In the case of dsx and mab-3, the two genes control analogous aspects of sexual development, bind similar DNA sequences, and are capable of functional substitution in vivo. All three phyla have multiple DM domain genes, but it is unknown how many of these are involved in sexual development. Mammals, for example, have at least seven DM domain genes, but embryonic expression has only been examined in detail for Dmrt1(dsx- and mab-3 related transcription factor 1). We have identified additional murine DM domain genes and have examined their expression in the mouse embryo, with emphasis on the developing gonad. At least three murine DM domain genes in addition to Dmrt1 are expressed in the embryonic gonad: Dmrt4 is expressed at similar levels in gonads of both sexes; Dmrt3 is more highly expressed in males; and Dmrt7 is more highly expressed in females. Expression of three other genes is low or absent in the embryonic gonad. Two of these, Dmrt5 and Dmrt6, are expressed primarily in the brain, and the third, Dmrt2, is expressed in presomitic mesoderm and developing somites. Our data suggest that multiple DM domain genes may be involved in mammalian sexual development, and that they may function in both testis and ovary development.

Forage feeding to reduce preharvest Escherichia coli populations in cattle, a review

Although Escherichia coli are commensal organisms that reside within the host gut, some pathogenic strains of E. coli can cause hemorrhagic colitis in humans. The most notable enterohemorrhagic E. coli (EHEC) strain is O157:H7. Cattle are asymptomatic natural reservoirs of E. coli O157:H7, and it has been reported that as many as 30% of all cattle are carriers of this pathogen, and in some circumstances this can be as high as 80%. Feedlot and high-producing dairy cattle are fed large grain rations in order to increase feed efficiency. When cattle are fed large grain rations, some starch escapes ruminal microbial degradation and passes to the hind-gut where it is fermented. EHEC are capable of fermenting sugars released from starch breakdown in the colon, and populations of E. coli have been shown to be higher in grain fed cattle, and this has been correlated with E. coli O157:H7 shedding in barley fed cattle. When cattle were abruptly switched from a high grain (corn) diet to a forage diet, generic E. coli populations declined 1000-fold within 5 d, and the ability of the fecal generic E. coli population to survive an acid shock similar to the human gastric stomach decreased. Other researchers have shown that a switch from grain to hay caused a smaller decrease in E. coli populations, but did not observe the same effect on gastric shock survivability. In a study that used cattle naturally infected with E. coli O157:H7, fewer cattle shed E. coli O157:H7 when switched from a feedlot ration to a forage-based diet compared with cattle continuously fed a feedlot ration. Results indicate that switching cattle from grain to forage could potentially reduce EHEC populations in cattle prior to slaughter; however the economic impact of this needs to be examined.

Effect of feeding the ionophores monensin and laidlomycin propionate and the antimicrobial bambermycin to sheep experimentally infected with E. coli O157:H7 and Salmonella typhimurium

Escherichia coli O157:H7 and Salmonella are widely recognized as important agents of foodborne disease with worldwide distribution. The use of ionophores in feeding growing ruminants is widespread in the United States and has attracted recent interest due to the apparent temporal relationship between initial ionophore use and the increase in human E. coli O157:H7 cases. Two experiments were conducted to evaluate the effects of short-term feeding of ionophores on fecal shedding, intestinal concentrations, and antimicrobial susceptibility of E. coli O157:H7 and S. typhimurium in growing lambs. Sixteen lambs were used in each experiment, four lambs per treatment group: monensin, laidlomycin propionate, bambermycin, and a control treatment. Lambs were fed a grain and hay (50:50) diet with their respective ionophore for 12 d before experimental inoculation with E. coli O157:H7 or S. typhimurium. Animals were maintained on their respective diets an additional 12 d, and fecal shedding of inoculated pathogens was monitored daily. Lambs were killed and tissues and contents were sampled from the rumen, cecum, and rectum. No differences (P > 0.05) in fecal shedding of Salmonella or E. coli O157:H7 were observed due to treatment. Occurrence of Salmonella or E. coli in luminal contents and tissue samples from the rumen, cecum, and rectum did not differ (P > 0.05) among treatments. Feeding monensin decreased (P < 0.05) the incidence of scours in sheep infected with Salmonella compared with the other treatments. No differences in antimicrobial susceptibility were found in any of Salmonella or E. coli O157:H7 isolates. Results from these studies indicate that short-term ionophore feeding had very limited effects on E. coli and Salmonella shedding or on antimicrobial susceptibility in experimentally infected lambs.

Escherichia coli O157:H7 populations in sheep can be reduced by chlorate supplementation

Ruminant animals are a natural reservoir of the foodborne pathogen Escherichia coli O157:H7. Some foodborne pathogens (e.g., E. coli) are equipped with a nitrate reductase that cometabolically reduces chlorate. The intracellular reduction of chlorate to chlorite kills nitrate reductase-positive bacteria; however, species that do not reduce nitrate are not affected by chlorate. Therefore, it has been suggested that ruminants be supplemented with chlorate prior to shipment for slaughter in order to reduce foodborne illnesses in human consumers. Sheep (n = 14) were fed a high-grain ration and were experimentally infected with E. coli O157:H7. These sheep were given an experimental product (XCP) containing the equivalent of either 2.5 mM NaNO3 and 100 mM NaCl (control sheep; n = 7) or 2.5 mM NaNO3 and 100 mM NaClO3 (chlorate [XCP]-treated sheep; n = 7). Control and XCP-treated sheep were treated for 24 h; XCP treatment reduced the population of inoculated E. coli O157:H7 (P < 0.05) from 10(2), 10(5), and 10(5) CFU/g in the rumen, cecum, and rectum, respectively, to < 10(1) CFU/g in all three sections of the gastrointestinal tract. The number of sheep testing positive for E. coli O157:H7 was significantly reduced by XCP treatment. In a similar fashion, total E. coli and coliforms were also reduced (P < 0.05) in all three compartments of the intestinal tract. Intestinal pH, total volatile fatty acid production, and the acetate/propionate ratio were unaffected by XCP treatment. On the basis of these results, it appears that chlorate treatment can be an effective method for the reduction of E. coli O157:H7 populations in ruminant animals immediately prior to slaughter.

Sodium chlorate supplementation reduces E. coli O157:H7 populations in cattle

Cattle are a natural reservoir of the food-borne pathogen Escherichia coli O157:H7. Therefore, strategies that reduce E. coli O157:H7 prior to slaughter will reduce human exposures to this virulent pathogen. When bacteria that can anaerobically respire on nitrate (e.g., E. coli) are exposed to chlorate, they die because the intracellular enzyme nitrate reductase converts nitrate to nitrite, but also co-metabolically reduces chlorate to cytotoxic chlorite. Because chlorate is bactericidal only against nitrate reductase-positive bacteria, it has been suggested that chlorate supplementation be used as a strategy to reduce E. coli O157:H7 populations in cattle prior to harvest. Cattle (n = 8) were fed a feedlot-style high-grain diet experimentally infected with three strains of E. coli O157:H7. Cattle were given access to drinking water supplemented with 2.5 mM KNO3 and 100 mM NaCl (controls; n = 4) or 2.5 mM KNO3 and 100 mM NaClO3 (chlorate-treated; n = 4). Sodium chlorate treatment for 24 h reduced the population of all E. coli O157:H7 strains approximately two logs (10(4) to 10(2)) in the rumen and three logs (10(6) to 10(3)) in the feces. Chlorate treatment reduced total coliforms and generic E. coli from 106 to 10(4) in the rumen and by two logs throughout the rest of the gastrointestinal tract (ileum, cecum, colon, and rectum). Chlorate treatment reduced E. coli O157:H7 counts throughout the intestinal tract but did not alter total culturable anaerobic bacterial counts or the ruminal fermentation pattern. Therefore, it appears that chlorate supplementation is a viable potential strategy to reduce E. coli O157:H7 populations in cattle prior to harvest.

Effect of oral sodium chlorate administration on Escherichia coli O157:H7 in the gut of experimentally infected pigs

Strategies are sought to reduce pathogenic Escherichia coli concentrations in food animals. Because E. coli possess respiratory nitrate reductase activity, which also reduces chlorate to cytotoxic chlorite, we tested and found that oral sodium chlorate administration reduced gut concentrations of E. coli O157:H7 in experimentally infected pigs and wildtype E. coli concentrations in nonchallenged pigs. Mean +/- S.E. concentrations (log10 CFU/g) of E. coli O157:H7 in ileal, cecal, colonic and rectal contents from placebo-treated pigs were 4.03 +/- 0.66, 3.82 +/- 0.24, 4.42 +/- 0.25 and 4.03 +/- 0.16, respectively. In contrast, E. coli O157:H7 concentrations were reduced (P < 0.05) in ileal (1.56 +/- 0.22) cecal (2.65 +/- 0.38), colonic (3.05 +/- 0.38) and rectal (3.00 +/- 0.29) contents from pigs orally administered three successive (8 h apart) 10-ml doses of 100 mM chlorate. Wildtype E. coli concentrations in gut contents of non-E. coli O157:H7-challenged pigs likewise treated with chlorate were reduced by 1.1 to 4.5 log10 units compared to concentrations in placebo-treated pigs, which exceeded 6.0 log10 CFU/g. As before, the reductions were greater in anterior regions of the gut than regions more caudal. Similar treatment of E. coli O157:H7-challenged pigs with 200 mM chlorate caused reductions in gut concentrations of E. coli O157:H7; however, the reductions were not necessarily greater than those achieved with the 100 mM chlorate treatment.

Early temperamental traits in an octopus (Octopus bimaculoides)

During their 3rd week of life, 73 Octopus bimaculoides were observed to test whether discrete behaviors could be grouped reliably to reflect dimensions of temperament. Frequencies of behaviors during Week 3 were subjected to principal-components analysis (PCA), resulting in 4 components (active engagement, arousal/readiness, aggression, and avoidance/disinterest) that explain 53% of the variance. Levels of temperamental traits were then evaluated for 37 octopuses using composite scores at 3 time points across the first 9 weeks of life. Profile analysis revealed significant change for the testing group as a whole in trait expression levels from Week 3 to Week 6. Results also suggest a significant effect of relatedness on developing temperamental profiles of octopuses. Discussion focuses on how results apply to the life history of O. bimaculoides and what temperament can reveal about adaptive individuality in a protostome.

Attenuation of somatosensory evoked potentials during positioning in a patient undergoing suboccipital craniectomy for Chiari I malformation with syringomyelia

Intraoperative electrophysiologic monitoring can diminish the risk of neurologic injury by enabling the detection of injury at a time when it can be reversed or minimized. This report describes a 14-year-old girl with a Chiari's malformation type I and syringomyelia who underwent a suboccipital decompression and dural patch grafting with concurrent somatosensory evoked potentials. When the patient was turned into the prone position and the neck was flexed, the left-sided somatosensory evoked potential deteriorated. After the patient's neck was repositioned, the left median nerve potential improved but did not return to baseline. Postoperatively, the patient had decreased proprioception of her left arm, which completely resolved at 2-week follow-up. This single case report does not establish the need for routine somatosensory evoked potential monitoring. Nevertheless, deterioration of the potential in this case led directly to a change in the surgical positioning, which may have significantly reduced the chances of a permanent neurologic injury.

Escherichia coli O157:H7 becomes resistant to sodium chlorate in pure culture, but not in mixed culture or in vivo

AIMS

Chlorate kills Escherichia coli O157:H7 and may be an effective feed additive for use in food animals. This study was designed to determine if development of chlorate-resistant E. coli O157:H7 strains was likely.

METHODS AND RESULTS

Escherichia coli O157:H7 was chlorate-sensitive, but became chlorate-resistant in pure batch culture and in sterilized faecal fluid; it was killed in mixed culture and did not become resistant. Addition of chlorate to continuous pure cultures caused chlorate resistance, but chlorate addition to mixed continuous culture eliminated E. coli O157:H7 and no resistance occurred. Piglets challenged with E. coli O157:H7 were treated with chlorate; populations were reduced and colonies were always chlorate-sensitive.

CONCLUSION

Chlorate-resistant E. coli O157:H7 can be selected in pure, but not mixed culture, and results suggest that terminal chlorate feeding will not select for chlorate-resistance in vivo.

SIGNIFICANCE AND IMPACT OF THE STUDY

Chlorate can reduce food-borne pathogens prior to harvest, but development of resistance does not appear likely in vivo.

Radiosurgery for the treatment of recurrent central neurocytomas

OBJECTIVE

Central neurocytomas are benign neoplasms with neuronal differentiation typically located in the lateral ventricles of young adults. Although the treatment of choice is complete surgical excision, patients may experience local recurrence. Adjuvant therapy for patients with residual or recurrent tumor has included reoperation, radiotherapy, or chemotherapy. To avoid the side effects of conventional radiotherapy in young patients, we present a series of patients with clear evidence of tumor progression who were treated with gamma knife radiosurgery.

METHODS

Four patients (ages 20-49 yr; mean, 28 yr) who presented with an intraventricular mass on magnetic resonance imaging scans and underwent craniotomy for tumor resection were reviewed retrospectively. Histopathological analysis confirmed central neurocytoma in all cases. Each patient was followed up clinically and radiographically with serial magnetic resonance imaging. When radiographic signs of tumor progression were evident, patients were treated with radiosurgery.

RESULTS

Complete radiographic tumor resection was achieved in all patients. There were no major postoperative complications. Local tumor progression was detected on magnetic resonance imaging scans 9 to 25 months after surgery (median, 17.5 mo). All patients achieved complete response to radiosurgery with reduction in tumor size. There have been no complications from radiosurgery. Follow-up ranged from 12 to 28 months (mean, 16.5 mo) after radiosurgery, and from 24 to 84 months (mean, 54.5 mo) after initial presentation.

CONCLUSION

Radiosurgery with the gamma knife unit provides safe and effective adjuvant therapy after surgical resection of central neurocytomas. Radiosurgery may eliminate the need for reoperation and avoid the possible long-term side effects from conventional radiotherapy in young patients.

Effects of feed withdrawal and transport on cecal environment and Campylobacter concentrations in a swine surgical model

The objective of the present study was to evaluate how feed withdrawal and transportation influenced the cecal environment and cecal populations of Campylobacter in swine. Four miniature Yucatan gilts (8.8 kg), naturally infected with Campylobacter jejuni, were surgically implanted with cecal cannulas. The gilts were fasted for 48 h. Samples of cecal contents were collected for 7 days prior to and for 7 days after the fast, and mean values were determined for pH, volatile fatty acids (VFA), and CFU enumeration of C. jejuni. This was replicated three times. In another trial, gilts (full-fed) were transported in a livestock trailer for 4 h and cecal samples were collected before and after transport and analyzed for pH, VFA, and CFU. Following a 48-h fast, cecal pH increased (P < 0.05) by 1 unit; acetic and propionic acids decreased (P < 0.05) by 61% and 71%, respectively; and there was a twofold log10 increase (P < 0.05) in CFU/g cecal content of C. jejuni. Values of pH, VFA, and CFU of C. jejuni did not change in cecal samples from gilts following transportation. These data are important for food safety considerations because feed withdrawal, commonly associated with shipping and slaughter, can increase Campylobacter concentrations in the pig intestinal tract.

Comparison of GN Hajna and tetrathionate as initial enrichment for salmonellae recovery from swine lymph nodes and cecal contents collected at slaughter

An epidemiologic survey was conducted to determine the prevalence of salmonellae in swine from 5 farms of an integrated swine operation. The purpose of this study was to evaluate the recovery efficiencies for salmonellae from swine lymph nodes and cecal contents when GN Hajna and tetrathionate were compared as initial enrichments. Salmonellae were isolated from 61% of 645 pigs at slaughter; 324 positive cultures were from lymph nodes, and 224 were from cecal contents. Frequently, pigs had salmonellae isolated from both the lymph nodes and cecal contents. Total isolations, regardless of source, were similar for GN Hajna (247) and tetrathionate (301). There was no difference (P > 0.05) in the number of isolations from lymph nodes when GN Hajna enrichment was compared with tetrathionate enrichment (174 vs. 150). However, there was a significant (P < 0.05) advantage of utilizing tetrathionate when compared with GN Hajna for isolations from cecal contents (151 vs. 73).