Large-scale trials to study competitive exclusion of salmonella in chickens

Competitive exclusion of salmonella by native gut microflora was studied in 24 groups of 100 chickens each started in thoroughly cleaned and sanitized isolation facilities. During 53-day test periods, infection by both Salmonella infantis and S. typhimurium was greatly restricted in groups previously treated with native microflora compared with control groups. Feed and water starvation for 48 hours starting at either 23 or 51 days did not affect the incidence of infection in protected groups. The protective flora spread readily to adjacent untreated groups; infected groups given the protective flora at 11 days exhibited a more rapid elimination of infection than untreated control groups.     

Comparative studies on competitive exclusion of three isolates of Campylobacter fetus subsp. jejuni in chickens by native gut microflora

Resistance of young chicks to Campylobacter fetus subsp. jejuni was substantially increased by early exposure to native gut microflora. Protection was demonstrated against two human isolates and a chicken isolate of C. fetus subsp. jejuni. Significant protection against the chicken isolate was observed throughout a 91-day test period. Infection reached 100% (25/25) in the untreated group at 56 days of age and only 4% (1/25) in the group treated with native gut microflora. Campylobacter fetus subsp. jejuni was isolated from the ceca and less frequently from the gall bladder and liver of chicks that actively shed the bacteria. Cultures of feces from chicks reared on wood-shavings litter were often negative, suggesting that culturing litter as an indicator of infection has limited value.     

Influence of Mycoplasma gallisepticum, infectious bronchitis, and cyclophosphamide on chickens protected by native intestinal microflora against Salmonella typhimurium or Escherichia coli

Chickens that have considerable resistance to Salmonella typhimurium or Escherichia coli infection by early development of a native intestinal microflora shed these bacteria following aerosol exposure to Mycoplasma gallisepticum and/or infectious bronchitis virus. Administration of cyclophosphamide to similarly treated chickens induced slight shedding of these bacteria, and the combination of cyclophosphamide and respiratory agents magnified the shedding rate. These agents also influenced the isolation rate of E. coli and S. typhimurium from the trachea and air sacs.     

Virulence factors associated with Escherichia coli present in a commercially produced competitive exclusion product

In this study, we assessed the pathogenic potential of Escherichia coli associated with a commercial competitive exclusion (CE) product by examining the phenotypic characteristics associated with E. coli virulent for humans and domestic animals. Most E. coli isolates were capable of proliferating in iron-deplete chicken sera. Interestingly, none of the E. coli isolates from the commercial CE product contained the bacterial adhesin Tsh characteristic of avian pathogenic E. coli associated with airsacculitis and colisepticemia. In terms of virulence potential for humans, most E. coli isolates (78%) were sensitive to killing by 12.5% human sera. Because of their sensitivity to human sera, the E. coli in the CE product are not likely to cause a serious systemic infection in humans and, therefore, do not present a risk of causing septicemia in humans. Because these isolates also lack the gene tsh, they are also less likely to cause systemic disease or airsacculitis in poultry than pathogenic strains commonly isolated from diseased birds.     

Protection of chicks against salmonella infection induced by spray application of intestinal microflora in the hatchery

Summary

The efficacy of spray application of intestinal microflora of the adult bird in protection of broilers against salmonella infections was studied in 3 experiments under laboratory and field conditions.

In chicks treated soon after hatching (in the hatchers at approximately 30 per cent hatch or in the chick delivery boxes in the hatchery) with crop‐caecum homogenate or a mixture of aerobically and strict anaerobically cultured intestinal flora, very good results were achieved.

A very obvious protective effect against a high infection dose (3 × 10 c.f.u. S. infantis bacteria per chick) and complete protection against natural infection with different salmonella types was induced.

A significant improvement of growth rate was observed in broilers treated by spray in the hatchery and reared for 7 weeks under field conditions in an environment heavily contaminated with different salmonella types.     

Protection of chicks against salmonella infection induced by spray application of intestinal microflora in the hatchery

The efficacy of spray application of intestinal microflora of the adult bird in protection of broilers against salmonella infections was studied in 3 experiments under laboratory and field conditions. In chicks treated soon after hatching (in the hatchers at approximately 30 per cent hatch or in the chick delivery boxes in the hatchery) with crop-caecum homogenate or a mixture of aerobically and strict anaerobically cultured intestinal flora, very good results were achieved. A very obvious protective effect against a high infection dose (3 X 10(6) c.f.u.S. infantis bacteria per chick) and complete protection against natural infection with different salmonella types was induced. A significant improvement of growth rate was observed in broilers treated by spray in the hatchery and reared for 7 weeks under field conditions in an environment heavily contaminated with different salmonella types.     

Inhibition of Salmonella typhimurium in the chicken intestinal tract by a transformed avirulent avian Escherichia coli.

An avirulent, wild-type avian Escherichia coli (E. coli Av) was electrotransformed with a plasmid coding for the production of microcin 24 (pGOB18) and was designated E. coli AvGOB18. The transformant inhibited the growth of seven serotypes of Salmonella commonly associated with colonization and contamination of poultry products and seven strains of E. coli O157:H7 in the in vitro colicin/microcin assay. The transformant did not inhibit the replication of multiple isolates of Listeria monocytogenes or Campylobacter jejuni in similar assays. The transformant is nonconjugative, indicating that the plasmid would not be transmitted to other intestinal microflora in the environment. The transformant also survived in sterile tap and deionized water incubated at 25 C and 37 C in the laboratory for 30 days and was recovered from drinkers and birds in in vivo floor pen studies. In in vivo studies, E. coli AvGOB18 did not colonize the intestinal tract of broiler chicks when given as a single or multiple dose and did not reduce the Salmonella load in the broilers. But Salmonella typhimurium was reduced significantly in the intestinal tracts of broiler chickens when E. coli AvGOB18 was administered continually in the water supply.     

Reduction of salmonella infection of broilers by spray application of intestinal microflora: a longitudinal study

The Nurmi concept for diminishing salmonella infection of poultry by application of gastrointestinal microflora from adult birds into newly hatched chicks was tested in a field study in which 8 million broilers were involved. Half of the 284 flocks was treated in the hatchery by spray application of an undefined microflora propagated in SPF chicks. A significant reduction in salmonella-contaminated flocks, as well as in the number of infected broilers in these flocks was demonstrated. No undesirable side effects were detected. It was concluded that hygienic improvements in transportation and slaughtering of broilers are needed in order to maintain the reduced salmonella contamination rate.     

Efficacy of different microbial preparations for controlling Salmonella colonisation in chicks and turkey poults by competitive exclusion.

1. Control by competitive exclusion of intestinal colonisation by Salmonella infantis was studied in domestic chicks and turkey poults given a commercial product developed for use with chickens, compared with two similar preparations containing intestinal microorganisms from turkeys. 2. Each type of material protected both avian species when given orally before challenge; the degree of protection depended at least as much on the type of preparation as its host origin.     

Carriage of Shiga-toxigenic Escherichia coli by native marsupials in Australia

Shiga-toxigenic strains of Escherichia coli (STEC) are zoonotic pathogens with human health, meat processing and trade impacts. Cattle are the principal reservoirs of STEC, although other animals can be carriers. The STEC status of Australian native marsupials has not been formatively described to date. The aim of the current study was to investigate carriage of STEC by native Australian marsupials in Southeast Queensland. Faeces from a variety of marsupial species, stratified by gastrointestinal morphology and dietary type, were screened for stx(1), stx(2) and other STEC virulence genes by PCR. Positive samples were cultured to isolate STEC for characterisation. A number of macropods from both captive and wild habitats had evidence of STEC in their faeces. Rates of stx carriage by macropods (8.6%) were comparable, though generally low, compared to cattle. Eastern grey kangaroos had the highest rate of stx presence in faeces (10.3%). Hindgut-fermenting and monogastric marsupials had no evidence of STEC shedding. Based on virulence marker possession and serotype, the human pathogenic potential of isolates was low. This is the first report of Australian marsupials carrying STEC. Australian native macropods may act as reservoirs for STEC strains, but the potential significance to public health and/or livestock epidemiology remains questionable.     

Interaction of turkey complement with Escherichia coli isolated from turkeys

The role of turkey complement in a serum bactericidal reaction was determined using serum-sensitive and serum-resistant Escherichia coli isolated from turkeys. Inactivation of complement by heating serum (56 C for 40 minutes) or by treating serum with 10 mM EDTA eliminated bactericidal activity. Serum-sensitive E coli organisms were killed by turkey serum treated with 10 mM ethylene glycol-bis-beta-(aminoethyl ether)-N,N,N',N'-tetraacetic acid and 5 mM MgCl2. Exposure of normal turkey serum to serum-sensitive or serum-resistant E coli resulted in equivalent reductions in hemolytic activity of serum. Treatment of serum-resistant E coli with antibody rendered the bacteria sensitive to bactericidal effects of normal turkey serum. Serum-sensitive E coli organisms were readily killed by an alternative complement pathway, serum-sensitive and serum-resistant E coli activated the complement system equally well, and antibody was required for complement-mediated killing of certain serum-resistant E coli organisms from turkeys.     

鸡源大肠杆菌在亚抑菌浓度头孢菌素诱导下的体外耐药表型

为了解在亚抑菌浓度单一药物的持续诱导下,鸡源大肠杆菌(E.coli)对临床常见药物的耐药表型变化,本实验采用亚抑菌浓度的头孢曲松或头孢噻肟持续诱导培养LG30鸡源E.coli和O78标准菌至30代,并采用微量稀释法检测各不同诱导代次的菌株对常见药物的耐药表型.结果表明在亚抑菌浓度的头孢曲松或头孢噻肟持续诱导培养下,受试菌对药物的敏感性持续下降,当诱导至20代,各诱导菌已成为多重耐药菌株,继续诱导至30代,各诱导菌对药物的耐药程度加重,但各药的最小抑菌浓度值升高速率变慢.表明细菌在单一药物诱导下可以较快进化为多重耐药菌.     

Antimicrobial susceptibilities of Escherichia coli strains from a turkey operation

OBJECTIVE: To measure minimum inhibitory concentrations (MIC) of 17 antimicrobials for Escherichia coli isolates from a turkey operation and assess whether small samples provide precise estimates of geometric mean MIC. DESIGN: Prospective study. SAMPLE POPULATION: 105 clinical isolates from birds and 1,104 fecal isolates from 20 flocks (poults and finisher hens). PROCEDURE: A Mueller-Hinton broth dilution panel was used to measure MIC, and MIC of fecal and clinical isolates were compared. We drew random samples of 5,10, 15, 20, 25, 30, 35, 40, and 45 isolates from each finisher flock and between 100 and 105 isolates from 5, 7, 10, and 20 flocks. Antimicrobial usage was determined for enrolled flocks. RESULTS: Six of 12 poult and 18 of 20 finisher flocks had been treated with antimicrobials, often for respiratory illnesses consistent with colibacillosis. All birds received gentamicin at the hatchery. More fecal than clinical isolates were resistant to ampicillin; however, more clinical isolates were resistant to ciprofloxacin, gentamicin, and sulfamethoxazole. Precise estimates of geometric mean MIC for flocks were obtained when > or = 15 fecal isolates were obtained per flock and, for the operation, when 105 isolates were obtained from > or = 7 flocks. CONCLUSION AND CLINICAL RELEVANCE: Antimicrobial usage was common and may have contributed to the resistance patterns of isolates. With a modest allocation of laboratory resources, producers can monitor antimicrobial susceptibilities of clinical and fecal E coli to manage risks of antimicrobial usage and resistance.     

鸡大肠杆菌致病机制研究

鸡大肠杆菌病（Chicken Colibacillosis）是由埃希氏大肠杆菌（Escherichia coli）的某些血清型引起的一种常见细菌性传染病,表现为雏鸡脐炎、败血症、大肠杆菌性肉芽肿、腹膜炎、气囊炎和输卵管炎等,发生于鸡的胚胎期至产卵期^[1]。其发病率为11％～69％,死亡率为3．8％-72．9％,致死率为40．2％-90．3％^[2]。     

Enhancement of enteropathogenic Escherichia coli pathogenicity in young turkeys by concurrent turkey coronavirus infection

In a previous study, turkey coronavirus (TCV) and enteropathogenic Escherichia coli (EPEC) were shown to synergistically interact in young turkeys coinfected with these agents. In that study, inapparent or mild disease was observed in turkeys inoculated with only TCV or EPEC, whereas severe growth depression and high mortality were observed in dually inoculated turkeys. The purpose of the present study was to further evaluate the pathogenesis of combined TCV/EPEC infection in young turkeys and determine the role of these agents in the observed synergistic interaction. Experiments were conducted to determine 1) effect of EPEC dose, with and without concurrent TCV infection, and 2) effect of TCV exposure, before and after EPEC exposure, on development of clinical disease. Additionally, the effect of combined infection on TCV and EPEC shedding was determined. No clinical sign of disease and no attaching and effacing (AE) lesions characteristic of EPEC were observed in turkeys inoculated with only EPEC isolate R98/5, even when turkeys were inoculated with 10(10) colony forming units (CFU) EPEC (high dose exposure). Only mild growth depression was observed in turkeys inoculated with only TCV; however, turkeys inoculated with both TCV and 10(4) CFU EPEC (low dose exposure) developed severe disease characterized by high mortality, marked growth depression, and AE lesions. Inoculation of turkeys with TCV 7 days prior to EPEC inoculation produced more severe disease (numerically greater mortality, significantly lower survival probability [P < 0.05], increased frequency of AE lesions) than that observed in turkeys inoculated with EPEC prior to TCV or simultaneously inoculated with these agents. Coinfection of turkeys with TCV and EPEC resulted in significantly increased (P < 0.05) shedding of EPEC, but not TCV, in intestinal contents of turkeys. These findings indicate that TCV infection predisposes young turkeys to secondary EPEC infection and potentiates the expression of EPEC pathogenicity in young turkeys.     

Effect of a commercial competitive exclusion culture on reduction of colonization of an antibiotic-resistant pathogenic Escherichia coli in day-old broiler chickens

One-day-of-age broiler chickens were administered a commercial competitive exclusion (CE) product and then challenged by three different methods with an Escherichia coli O78:K80 that was pathogenic for poultry and resistant to six antibiotics. Three challenge methods were used on 2-day-old broilers: direct challenge, precolonized seeder, and instant seeder. Direct challenge was accomplished by administering the challenge E. coli per os. The precolonized seeder challenge had two chicks that had received the challenge E. coli 24 hr previously, whereas the instant seeder challenge had two chicks given the challenge E. coli per os with immediate placement with the experimental birds. One oral dose of the commercial CE product significantly reduced the colonization of the small intestine, large intestine, and ceca by the highly antimicrobial resistant poultry pathogenic E. coli O78:K80 at 7 and 14 days postchallenge by all three challenge methods. The overall mean reductions in colonization were 3.0 log10 for the large intestine, 3.0 log10 for the small intestine, and 4.0 log10 for the cecum. The most severe challenge method, on the basis of the least amount of reduction of colonization of the challenge E. coli by the CE, was by the direct oral gavage at 2 days of age.     

Drug use and antimicrobial resistance among Escherichia coli and Enterococcus spp. isolates from chicken and turkey flocks slaughtered in Quebec,Canada

An observational study was conducted of chicken and turkey flocks slaughtered at federal processing plants in the province of Quebec, Canada. The objectives were to estimate prevalence of drug use at hatchery and on farm and to identify antimicrobial resistance (AMR) in cecal Escherichia coli and Enterococcus spp. isolates and factors associated with AMR. Eighty-two chicken flocks and 59 turkey flocks were sampled. At the hatchery, the most used antimicrobial was ceftiofur in chickens (76% of flocks) and spectinomycin in turkeys (42% of flocks). Virginiamycin was the antimicrobial most frequently added to the feed in both chicken and turkey flocks. At least 1 E. coli isolate resistant to third-generation cephalosporins was present in all chicken flocks and in a third of turkey flocks. Resistance to tetracycline, streptomycin, and sulfisoxazole was detected in > 90% of flocks for E. coli isolates. Antimicrobial resistance (AMR) was observed to bacitracin, erythromycin, lincomycin, quinupristin-dalfopristin, and tetracycline in both chicken and turkey flocks for Enterococcus spp. isolates. No resistance to vancomycin was observed. The use of ceftiofur at hatchery was significantly associated with the proportion of ceftiofur-resistant E. coli isolates in chicken flocks. In turkey flocks, ceftiofur resistance was more frequent when turkeys were placed on litter previously used by chickens. Associations between drug use and resistance were observed with tetracycline (turkey) in E. coli isolates and with bacitracin (chicken and turkey), gentamicin (turkey), and tylosin (chicken) in Enterococcus spp. isolates. Further studies are needed to provide producers and veterinarians with alternative management practices and tools in order to reduce the use of antimicrobial feed additives in poultry.     

Use of competitive exclusion to protect newly-hatched chicks against intestinal colonisation and invasion by Salmonella enteritidis PT4.

1. The recommended dose of a commercial competitive exclusion (CE) product (BROILACT) was given orally to newly-hatched broiler chicks to protect them against oral challenge by Salmonella enteritidis PT4. 2. In 5 replicate trials, half of the birds thus treated and half from untreated control groups were examined for salmonellas at 5 d and the other half at 12 d after challenge. 3. Caecal contents were examined quantitatively while heart, liver and spleen samples were examined qualitatively by enrichment. 4. The treatment effectively prevented both colonisation of the caeca and invasion of the other organs by S. enteritidis PT4; the average number of salmonellas was less than 10 colony forming units (cfu)/g of caecal contents in the treated birds and more than 10 million cfu/g in the untreated birds. 5. Infection of organs other than the caeca was completely prevented by protective treatment, whereas 38% of the untreated birds were still infected at the end of the trial.