Escherichia coli challenge in chickens selected for high or low antibody response and differing in haplotypes at the major histocompatibility complex.

Relative sensitivity to Escherichia coli challenge was evaluated in white leg-horn chickens that had been selected for high antibody (HA) or low antibody (LA) response and that differed in haplotypes at the major histocompatibility complex (MHC). Assessments were made of relative body-weight change and of heart and air-sac lesions after inoculation of 10(6), 10(5), or 10(4) E. coli via the posterior thoracic air sac. As has previously been reported, chicks from line HA were more sensitive to E. coli than those from line LA. Lesion scores were 1.58 +/- 0.12 in line HA and 1.02 +/- 0.12 in line LA (mean +/- S.E.), and ranged from 0.99 +/- 0.14 with the lowest dose of E. coli to 1.79 +/- 0.15 for the highest dose. Relative body-weight change to 72 hours after inoculation was greater in line LA (7.5 +/- 0.5) than in line HA (4.4 +/- 0.8). There was no apparent resistance or susceptibility conferred to chickens in either the HA or LA genetic background as a result of haplotypes present at the MHC.     

Experimental Escherichia coli respiratory infection in broilers

This study determined optimal conditions for experimental reproduction of colibacillosis by aerosol administration of avian pathogenic Escherichia coli to 2-to-4-wk-old broiler chickens. The basic model for reproducing disease was intranasal administration of approximately 10(4) mean embryo infectious dose of infectious bronchitis virus (IBV) followed by aerosol administration of an 02 or an 078 strain of E. coli in a Horsfall unit (100 ml of a suspension of 10(9) colony-forming units/ml over 40 min). Scores were assigned to groups of infected chickens on the basis of deaths; frequency and severity of lesions in the air sacs, liver and heart; and recovery of the challenge E. coli 6 days post-E. coli infection. An interval of 4 days between the IBV and E. coli challenges was best whether the chickens received the IBV at 8 or 20 days of age. Typically, 50%-80% of the chickens developed airsacculitis and 0 to 29% of the chickens developed pericarditis or perihepatitis, with little or no mortality. Escherichia coli alone resulted in no deaths and 0 to 20% airsacculitis, but these percentages increased to 0 to 5% and 52%-60% when the E. coli aerosol was administered through a cone-shaped chamber. Administration of IBV alone failed to induce lesions. Recovery of the challenge E. coli from chickens did not correlate well with lesions. On the basis of these data, administration of IBV to 20-day-old chickens followed 4 days later by exposure to an avian pathogenic E. coli reproduces avian colibacillosis with the low mortality, high percentage of airsacculitis, and low percentage of septicemic lesions characteristic of the conditions seen in the natural disease.     

Turkey macrophage and heterophil bactericidal activity against Pasteurella multocida.

Bactericidal activity of turkey macrophages and heterophils was demonstrated in an in vitro colorimetric bactericidal assay. Two vaccine strains and one field isolate of Pasteurella multocida A:3,4 and a single isolate each of Escherichia coli and Staphylococcus aureus were compared for susceptibility to the bactericidal activity of turkey macrophages and heterophils. Only P. multocida A:3,4-strain M-9 (the least virulent strain) was susceptible to macrophage bactericidal activity in the absence of specific immune serum, whereas all three P. multocida A:3,4 organisms were killed when opsonized with specific immune serum. E. coli was susceptible to the bactericidal activity of macrophages, and S. aureus was resistant. All bacteria tested were highly sensitive to the bactericidal activity of intact turkey heterophils, regardless of the opsonin treatment. Electron microscopic findings suggested that heterophils may kill extracellular P. multocida. Only S. aureus and E. coli were killed by lysed heterophils.     

The role of first line of defence mechanisms in the pathogenesis of cellulitis in broiler chickens: skin structural, physiological and cellular response factors

The present study examined several basic attributes of first-line defence mechanisms in the skin as potential factors that may explain the susceptibility of broiler chickens to cellulitis. The variables including structural characteristics of the skin, physicochemical properties and cellular responses to the challenge with pathogens were compared between two categories of chickens, a strain of fast-growing commercial broiler chickens (susceptible to cellulitis) and leghorn chickens (resistant to cellulitis). There were substantial differences between leghorns and broilers with regard to physiological characteristics of the skin. Broiler skin was more amenable to injury and the wound-healing process was slow. Compared with leghorns, the lesions resulting from sub-dermal challenge in broilers were more severe and disseminated over a larger area. Mobilization of phagocytic cells (heterophils and macrophages) in leghorns was brisk even in the areas distant from the site of infection, whereas only few heterophils were recruited in the skin of broilers. The functional competence of heterophils in broilers was inferior when compared with leghorns. Based on the present finding, the predisposition of broilers to cellulitis appears to be primarily associated with the inferior first line of defence of their skin. Broilers in commercial situations may be at higher risk to succumb to even minor infection and eventually develop cellulitis because: (1) structural weaknesses of the skin may predispose broilers to skin injury and thus the risk of skin infection by pathogens is increased; (2) broiler skin surface is more likely to provide a conducive environment for colonization of Escherichia coli; (3) in the event of infection, poor recruitment of phagocytic cells to the site of infection may readily lead to widespread colonization of the tissue by pathogens causing cellulitis and (4) poor functional quality of the phagocytic cells that are mobilized compromise the ability of the host to contain the spread of infection.     

Association between the porcine Escherichia coli F18 receptor genotype and phenotype and susceptibility to colonisation and postweaning diarrhoea caused by E. coli O138:F18

Porcine postweaning Escherichia coli enteritis is a cause of significant morbidity and mortality in pigs worldwide, and effective prevention remains an unsolved problem. This study examined the correlation between susceptibility of pigs to experimental infection with an E. coli F18 strain and the porcine intestinal F18 receptor genotypes. Thirty-one pigs classified as either belonging to the susceptible or the resistant genotype were inoculated with cultures of an E. coli O138:F18 isolated from a pig with postweaning diarrhoea. Susceptibility to colonisation and diarrhoea was assessed by clinical observations, faecal shedding of the challenge strain, histopathology and microscopic adhesion tests. Ten of 14 (71.4%) genetically susceptible pigs and one of 17 (5.9%) resistant pigs developed diarrhoea attributable to the challenge strain. There was no difference in susceptibility between homozygotic and heterozygotic susceptible pigs. Faecal shedding of the challenge strain correlated with the genetic receptor profile. Twenty pigs examined immunohistochemically revealed focal to extensive small intestinal mucosal colonisation by E. coli O138:F18 in nine of 10 susceptible and three of 10 resistant pigs. Results of in vitro adhesion assays performed with F18 cells on enterocyte preparations from 24 pigs, showed complete concordance with the F18 genotypes. In conclusion, this study showed a high correlation between the porcine intestinal F18 receptor genotypes and susceptibility to disease. However, pigs of the resistant F18 receptor genotype were not entirely protected against intestinal colonisation by E. coli F18.     

Socialization as a factor in resistance to infection, feed efficiency, and response to antigen in chickens

Chickens were habituated to human beings (socialized) by being talked to, offered food, and handled gently. After 7 weeks of socialization, the birds were challenge exposed with Escherichia coli. When compared with ignored groups, the socialized birds showed more than a 60% reduction in the prevalence of death and pericarditis. Furthermore, small flocks of socialized birds were more uniform in their response to E coli than were similar nonsocialized flocks. Socialized chickens also had improved feed efficiency and increased antibody response to canine RBC. Socialization was also applied easily to larger flocks of chickens.     

Acute airsacculitis in untreated and cyclophosphamide-pretreated broiler chickens inoculated with Escherichia coli or Escherichia coli cell-free culture filtrate.

Ninety commercial broiler chickens were divided into three equal groups; 30 were injected with brain-heart-infusion broth into the cranial thoracic air sacs (controls), 30 were similarly inoculated with a culture of Escherichia coli, and 30 were similarly inoculated with E. coli cell-free culture filtrate. Birds were examined from 0 to 6 hours post-inoculation. E. coli-inoculated and cell-free culture filtrate-inoculated chickens reacted similarly, with exudation of heterophils into the air sac. Microscopically, heterophils were present in low numbers perivascularly 0.5 hour after inoculation and became more numerous by 3 hours post-inoculation. By 6 hours post-inoculation, there was severe swelling of air sac epithelial cells and thickening of the air sac by proteinaceous fluid and heterophils. Ultrastructurally, air sac epithelial cells were swollen and vacuolated, and interdigitating processes were separated. Histologically and ultrastructurally, all features in control chickens were normal, with only rare heterophils in the air sac interstitium. In E. coli-inoculated and cell-free culture filtrate-inoculated chickens, cell counts (predominantly heterophils) in air sac lavage fluids increased markedly at 3 and 6 hours, with only slight increases in counts from lavages of controls. Heteropenia was observed in E. coli-inoculated chickens, whereas heterophilia was observed in cell-free filtrate chickens and controls. Ninety additional chickens were pretreated with cyclophosphamide, subdivided into three equal groups, and inoculated and examined similarly as above. Cyclophosphamide pretreatment reduced inflammatory changes in air sacs, lowered cell numbers in lavage fluids, and abolished hematologic changes; however, it did not prevent epithelial cell changes. These results indicate that cell-free culture filtrate of E. coli induces changes similar to those induced by cultures of E. coli.     

Susceptibility of Escherichia coli and Enterococcus faecium isolated from pigs and broiler chickens to tetracycline degradation products and distribution of tetracycline resistance determinants in E. coli from food animals

One hundred Escherichia coli isolates from diseased and healthy pigs, cattle and broiler chickens were screened for the presence of tetracycline resistance genes tet(A), (B), (C), (D) or (E). The tet(A) gene was the most abundant (71% of the 100 isolates) followed by tet(B) (25%). The predominance of tet(A) and tet(B) applied to all three animal species, and there was no difference between the distribution of tet(A) and tet(B) genes among non-pathogenic and pathogenic E. coli in any of the animal species. The susceptibility of 20 of these isolates together with 10 tetracycline sensitive E. coli and 18 tetracycline resistant and 10 sensitive Enterococcus faecium to tetracyclines and tetracycline degradation products was determined. The resistant isolates showed reduced resistance to anhydrotetracycline, 4-epi-anhydrotetracycline, anhydrochlortetracycline and 4-epi-anhydrochlortetracycline. In general both the tetracycline resistant and susceptible E. faecium were more susceptible to the compounds tested than E. coli.     

Escherichia coli multiplication and lesions in the respiratory tract of chickens inoculated with infectious bronchitis virus and/or E. coli.

Escherichia coli numbers and histopathological changes were studied in the respiratory tract of line 151 chickens intranasally inoculated with infectious bronchitis virus (IBV) and/or virulent E. coli; this line is highly susceptible to IBV. Chickens inoculated with IBV alone showed increased numbers of E. coli in the trachea and had tracheitis, airsacculitis, and bronchiolitis. One of 17 chickens inoculated with IBV alone died with fibrinopurulent serositis. Chickens inoculated with IBV and E. coli had more severe and persistent respiratory lesions than those inoculated with IBV alone. E. coli was isolated from tracheas of chickens inoculated with IBV and E. coli more frequently than from chickens inoculated with IBV alone. In this group, 14 of 27 chickens died with tracheal plugs or with fibrinopurulent serositis. There was neither increased numbers of E. coli nor significant lesions in the respiratory tract of the group inoculated with E. coli alone. These results suggest that IBV may facilitate E. coli invasion into the lower respiratory tract of the chicken.     

Resistance of broiler chickens to Escherichia coli respiratory tract infection induced by passively transferred egg-yolk antibodies

Egg-yolk antibodies induced by immunizing hens with selected Escherichia coli antigens were evaluated for their ability to protect broiler chickens against respiratory/septicemic disease caused by avian pathogenic E. coli (APEC). Seven groups of broiler breeder hens were vaccinated three times, 1 week apart with live E. coli, killed E. coli, E. coli antigens [lipopolysaccharide (LPS), type 1 pilus adhesin (FimH), P pilus adhesin (PapG), aerobactin outer membrane receptor (IutA)] or phosphate buffered saline (PBS). An O78 APEC strain was used for preparation of all the antigens. Egg yolk immunoglobulins (IgY) were purified from eggs of each group and antibody activity in serum and purified IgY was determined by enzyme-linked immunosorbent assay (ELISA). IgY (100mg) was injected intramuscularly into 11-day-old broiler chickens, which were challenged 3 days later with homologous (O78) or heterologous (O1 or O2) E. coli by the intra-air sac route. Mortality was recorded and surviving chickens were euthanized 1 week after the challenge and examined for macroscopic lesions. Passive antibodies against all antigens except FimH were protective (90-100%) against the homologous challenge, but only anti-PapG and anti-IutA were effective against heterologous challenge. Anti-PapG IgY provided the greatest protection against the three serogroups of E. coli used for challenge. Hence vaccination of broiler breeders to induce anti-PapG and anti-IutA antibodies may provide passive protection of progeny chicks against respiratory/septicemic disease caused by APEC.     

Factors influencing the severity of Escherichia coli and avian adenovirus group II infections in chickens

Chickens from lines selectively bred for either a high (HH) or low (LL) antibody response to sheep erythrocytes were challenged intravenously with avian adenovirus group II (AA). Spleen size was determined 6 days later. In some experiments the responses of chickens to AA and Escherichia coli infections were compared. The level of corticosterone in the feed (15 mg/kg) which resulted in the lowest incidence of pericarditis in response to E. coli resulted in the greatest incidence of large spleens in response to AA infection. Incidence of enlarged spleens in response to AA infection was increased in fasted chickens and reduced in socialized LL-line chickens. Among ignored chickens harshly treated for 2 weeks before challenge, LL-line chickens had a higher incidence of enlarged spleens than HH-line chickens. Socialized HH-line chickens subjected to social stress 1 day before challenge had more severely affected spleens than socialized LL-line chickens. The HL cross was more severely affected by AA than the LH cross but was less severely affected by E. coli. Antibody responsiveness to sheep erythrocytes did not affect the severity of AA infection. Factors that increased the severity of AA infection seemed to result in a decreased severity of E. coli infection.     

Effect of environmental stress on the responses of ascorbic-acid-treated chickens to Escherichia coli challenge infection

As the stressfulness of the environment increased (measured as increasing heterophil/lymphocyte [H/L] ratios), resistance of chickens to Escherichia coli challenge infection increased. At a relatively low level of environmental stress (H/L ratio = 0.33), the incidence of severe lesions was 22% in chickens fed diets containing 330 mg of ascorbic acid (AA)/kg and 80% in undosed controls. As the level of environmental stress increased, the dose of AA required for maximum reduction of the incidence of severe lesions increased, and the difference in lesion incidence between AA-dosed and undosed chickens decreased. When environmental stress resulted in H/L ratios of 0.53 or more, AA did not ameliorate the severity of infection. At levels of stress characterized by H/L ratios between 0.39 and 0.44, increasing doses of AA resulted in increased susceptibility to E. coli until a dose associated with maximum susceptibility was reached. Further increases in the dose of AA resulted in decreased susceptibility until a dose associated with maximum resistance was reached. In chickens fed feed containing 15 mg corticosterone/kg, increasing doses of AA resulted in increasing susceptibility to E. coli.     

鸡大肠埃希氏菌菌毛表达、血凝谱及粘附特性研究

对６株具有不同致病性的鸡大肠埃希氏菌分离株体外菌毛的表达、对１３种不同红细胞血凝谱及血凝方式、对鸡胚成纤维细胞（ＣＥＦ）及在体内外对１日龄鸡气管组织的粘附特性进行了研究,结果表明,具有致病性的菌株,在体外适宜的条件下,能表达菌毛,非致病性菌株不表达。不同菌株的血凝谱及血凝方式具有差异,除中等致病性菌株ＭＧ３０e对大鼠红 细胞（ＲＢＣＦ）的凝集不能被Ｄ－甘露糖抑制,表现为抗甘露糖型血凝（ＭＲＨＡ）外,     

Immunogenic potency of an oil-emulsified Escherichia coli bacterin

Immunogenicity of an oil-emulsified Escherichia coli (O1:K1) bacterin with an aqueous-phase-to-oil-phase ratio of 1:4 was evaluated in chickens. Chickens were vaccinated subcutaneously with 0.5 ml of the bacterin at 4 and 6 weeks of age. At 8 weeks, the vaccinated chickens and unvaccinated controls were challenged via air sacs with 10(4) colony-forming units (CFU) of homologous E. coli. Vaccinated chickens were protected against active respiratory infection in that they (a) gained body weights comparable to those in unvaccinated, unchallenged chickens, (b) suffered no morbidity or mortality, (c) had gross lesions so mild that the scored values were comparable statistically to the 0 lesion scores of the negative controls, and (d) did not yield E. coli when their heart blood, pericardial sacs, livers, and air sacs were cultured. Unvaccinated challenged chickens had severe respiratory distress, suffered 36% mortality, and had average air sac, pericardial sac, and liver lesion scores significantly (P less than or equal to 0.05) different from both the vaccinated and negative control chickens. Also, the challenge strain of E. coli only was isolated from the affected tissues of 5 of 14 chickens. Protection against active respiratory infection was again demonstrated in a second experiment, though the challenge dose was 1.06 X 10(6) CFU of E. coli. The immunity, however, was partially overcome, as the vaccinated chickens gained less body weight and the scored values for lesions in the air sacs, pericardial sacs, and livers were significantly higher than those of the negative controls (P less than or equal to 0.05).     

Protection of chickens from Newcastle disease and infectious laryngotracheitis with a recombinant fowlpox virus co-expressing the F, HN genes of Newcastle disease virus and gB gene of infectious laryngotracheitis virus

A recombinant fowlpox virus (rFPV) coexpressing the Newcastle disease virus (NDV) fusion and hemagglutinin-neuraminidase genes and infectious laryngothracheitis virus (ILTV) glycoprotein B gene was constructed. This virus was then evaluated for its ability to protect specific-pathogen-free (SPF) chickens against clinical symptoms and death after challenge by virulent NDV and ILTV. SPF chickens were grouped and vaccinated with the rFPV and commercial NDV (La Sota) and ILTV attenuated live vaccine (Nobilis ILT), respectively. After challenge with NDV 10 days postvaccination, 70% of chickens vaccinated with rFPV were protected from death, whereas 100% of the commercial NDV-vaccinated chickens were protected from death. In contrast, 100% of the unvaccinated chickens died after challenge. After challenge with ILTV, both the rFPV and commercial ILTV-vaccinated chickens were completely protected from death and 70% of chickens were protected from respiratory signs. In comparison, 100% of the unvaccinated chickens developed severe respiratory disease and 10% of chickens died. The protective efficacy was also measured by the antibody responses and isolation of challenge viruses. Results showed that this rFPV could be a potential vaccine for preventing NDV and ILTV by a single immunization.     

Response to Eimeria tenella of chickens selected for high or low antibody response and differing in haplotypes at the major histocompatibility complex.

Sublines of chickens selected for high antibody (HA) or low antibody (LA) response that differed at the major histocompatibility complex (MHC) were tested for response to Eimeria tenella. In Expt. 1, the first exposure to E. tenella was natural (in floor pens), and chicks were challenged orally 21 days later with 0, 928, or 1855 oocysts. In Expt. 2, chicks were reared in wire-floored batteries, vaccinated orally with 928 oocysts, and challenged orally 12 days later with 15,844 oocysts. Corticosterone (20 mg/kg) was mixed with feed from 24 hr before vaccination to 120 hr after vaccination in Expt. 2. In Expt. 1, LA chicks had more-severe cecal lesions but gained relatively more body weight after challenge than did HA chicks. In Expt. 2, cecal lesions were least severe in HA chicks that had been fed corticosterone, most severe in LA chicks fed corticosterone, and intermediate in chicks that were not fed corticosterone. No differences in response to E. tenella occurred as a result of haplotypes at the MHC.     

Comparative infectivity for axenic and specific-pathogen-free chickens of O2 Escherichia coli strains with or without virulence factors

Adhesion to epithelial respiratory cells, iron acquisition, and production of K1 polysaccharide capsules have been proposed as potential virulence factors of avian Escherichia coli. These factors were studied by inoculating groups of axenic or specific-pathogen-free (SPF) chickens intratracheally with O2 E. coli strains after previous challenge with a wild strain of infectious bronchitis virus (IBV). In all experiments, the association between IBV and an E. coli strain endowed with the three virulence factors previously mentioned resulted in the most severe pathological effects, as measured by mortality, weight gains, lesions, and reisolation of E. coli from internal organs. An E. coli strain devoid of virulence factors was able only to induce mild pathological effects restricted to the respiratory tract when combined with IBV. Both E. coli strains were more invasive in axenic chickens than in SPF chickens. These results confirm the probable involvement of the three factors studied in the pathogenic properties of avian E. coli. This model can be used to assess the role of virulence factors, by comparing pairs of positive and negative isogenic strains.     

Clinical and microbial efficacy of antimicrobial treatments of experimental avian colibacillosis

The clinical and microbial efficacy of antimicrobial treatments of avian colibacillosis was studied, using an experimental model on chickens previously inoculated with multiresistant commensal Escherichia coli strains. One E. coli with pMG252 plasmid containing bla(FOX5) and qnrA1 genes and another E. coli with pMG298 plasmid containing bla(CTX-M15) and qnrB1 genes were first orally inoculated to chickens Both isolates were also resistant to chloramphenicol, sulphamethoxazole, trimethoprim, streptomycin, gentamicin, kanamycin, and tetracycline. The birds were then experimentally infected with an avian pathogenic E. coli (APEC), via the air sac. Treatments (oxytetracycline (OTC), trimethoprim-sulfadimethoxin (SXT), amoxicillin (AMX) or enrofloxacin (ENR) were then offered at the therapeutic doses. Symptoms, lesions in dead or sacrificed birds, and isolation and characterization of APEC from internal organs were studied. Results showed that OTC, SXT or ENR treatments could control the pathology. AMX worsened the disease, possibly due to endotoxin shock. All APEC re-isolated from internal organs showed the same antimicrobial susceptibility as the APEC inoculated strain, except for one APEC isolate from an infected OTC-treated bird, which acquired tetracycline resistance only, and one APEC isolate recovered from the air sacs of a chicken in the infected SXT-treated group, which acquired the pMG252 plasmid and became multi-resistant. Thus three antimicrobials could control the disease but the experimental model enabled, to our knowledge, the first observation of plasmid transfer from a bacterium of the intestinal tract to a pathogenic isolate from the respiratory tract.     

Immunogenicity of a temperature sensitive mutant Mycoplasma gaffisepticum vaccine

The immunogenicity of the ts-11 vaccine strain of Mycoplasma gallisepticum was assessed following eye drop or coarse aerosol administration in chickens of various ages. Protection was evalualted following intra-abdominal (IA) or fine droplet aerosol administration of virulent M. gallisepticum, usually the Ap3AS strain and was measured mainly by the scoring of gross air sac lesions or by egg production. Vaccination of chickens with ts-11 did not elicit a substantial serum antibody response as measured by rapid serum agglutination test, or ELISA. Protection was never demonstrated when no M. gallisepticum serum antibody response was detected in a vaccinated group of chickens. Failure to protect occurred usually, although not invariably, following aerosol administration of the vaccine. Vaccination by eye drop usually, although not invariably provided protection against challenge. In one experiment, chickens vaccinated by eye drop at 8-weeks were as susceptible as non vaccinated controls when challenged by IA inoculation at 13-weeks-of-age. Yet other birds from the same vaccinated group were resistant when challenged in an identical way at 23-weeks. No measurable increase in M. gallisepticum specific serum antibody concentrations occurred in the intervening period. Equally surprising was the response of another group of birds in the same experiment that had been vaccinated with a higher dose of ts-11. An antibody response was detected in this group, but they were susceptible to challenge at 23-weeks. Interestingly, a drop in egg production commenced 4 weeks after challenge, 2 weeks later than that observed in a non vaccinated group challenged at the same time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibiotic resistance of Escherichia coli strains isolated from chickens with colisepticaemia in Morocco

Sixty-two strains of Escherichia coli were isolated in 58 farms from broiler chickens showing respiratory signs and lesions characteristic of avian colibacillosis. Serological examination of these strains showed that the types 078, 01 and 02 (for the somatic antigen) and K1 (for the capsular antigen) were the most frequently found. Newcastle disease virus was also isolated in two cases. All the strains of E. coli isolated were sensitive to colistin, flumequine and gentamicin. A few strains were resistant to neomycin, nalidixic acid and trimethoprim. The frequency of strains resistant to nitrofurans, sulfonamides, chloramphenicol, spectinomycin and ampicillin was intermediate. Most strains were resistant to tetracycline. Multiple resistance was common.