Virulence factors of Escherichia cofi from cellulitis or colisepticemia lesions in chickens

This study was designed to compare virulence factors of cellulitis-derived Escherichia coli to colisepticemic E. coli in order to clarify whether E. coli associated with cellulitis comprise a unique subset of pathogenic E. coli. Isolates were tested for serotype, capsule, aerobactin production, colicin production, the presence of the iss gene, and serum resistance. Untypable isolates made up the greatest percentage of each group. Serotypes O2 and O78 were the most commonly identified among both groups of isolates. No statistical differences in the distribution of aerobactin or colicin production, capsule, or iss gene were observed between groups. Cluster analysis showed that 90% of the E. coli isolates had greater than 42% livability in serum-resistance tests. No separation of colisepticemic vs. cellulitis E. coli isolates was observed on the basis of SR. Colicin production by E. coli was highly correlated with serum resistance (P = 0.0029). These data suggest that cellulitis E. coli have virulence traits similar to those of colisepticemic E. coli.     

Antimicrobial resistance of Escherichia coli isolated from chickens

Faecal Escherichia coli isolated from healthy farm chickens, from farm chickens with avian influenza, and from chickens with diarrhoea were more resistant to antimicrobial agents (94-100%) than those isolated from healthy domestic chickens (20%). Transfer of drug resistance was readily achieved from strains isolated from both healthy and sick farm chickens, and from diarrhoeic chickens; it was more difficult to demonstrate in strains from domestic chickens. Resistant E. coli showing serotypes suspected to be enteropathogenic for man, i.e 0126:K71(B16), 044:K74 (L) and 0119:K69(B14), were isolated from faecal samples of healthy and sick farm chickens, but not from healthy domestic birds.     

Phenotypic and genotypic characterization of virulence factors of Escherichia coli isolated from broiler chickens with simultaneous occurrence of cellulitis and other colibacillosis lesions.

The objective of this study was to characterize virulence factors of Escherichia coli isolates from broilers with simultaneous occurrence of cellulitis and other colibacillosis lesions. Thirty flocks were sampled and 237 birds with cellulitis were examined. Eighty-two (34.6%) of 237 birds condemned for cellulitis had gross lesions in the heart, air sacs, joints, or liver. In 58 chickens, E. coli was isolated from both the cellulitis and other lesions of colibacillosis, and 18.9% of the E. coli isolates from the 2 types of lesions belonged to the same O group. Escherichia coli of serogroups O78, O1, and O2 predominated. Isolates of the same serogroup that were derived from different lesions in the same birds had similar patterns of biotype, aerobactin production, serum sensitivity profile, antibiotic sensitivity, and K1 capsule production. Escherichia coli derived from cellulitis lesions produced virulence factors similar to those found in E. coli isolated from other colibacillosis lesions in poultry.     

广东鸡致病性大肠杆菌对氟喹诺酮类药物的敏感性分析

以广东省21个地级市为单位,从鸡场病死鸡分离细菌,选取经生化和动物试验证明的鸡致病性大肠杆菌共115株,采用药敏纸片法测定其对氟喹诺酮类药物的敏感性.结果显示,72.2 %的试验菌对氟喹诺酮类药物产生抗药性;氟喹诺酮类药物之间交叉耐药严重,恩诺沙星与氟罗沙星交叉耐药率高达99%.     

鸡源耐安普霉素大肠杆菌耐药表型研究

进行了安普霉素耐药大肠杆菌耐药表型的研究.采用常规方法和生化鉴定管对有过安普霉素用药史的鸡场分离的鸡源病原性大肠杆菌进行鉴定,并用试管二倍稀释法测定其最低抑菌浓度(MIC),筛选出鸡源安普霉素耐药大肠杆菌;采用药敏纸片法研究了这些耐药菌对安普霉素等14种抗菌药物的敏感性.共筛选出7株对安普霉素耐药的鸡源性大肠杆菌,这些耐药菌株全部对安普霉素、妥布霉素、奈啶酸、多西环素和阿莫西林耐药;大部分对庆大霉素、链霉素、卡那霉素、壮观霉素也呈现耐药.对新霉素的耐药较低,对阿米卡星高度敏感.部分交叉耐药现象的存在揭示对安普霉素等氨基糖苷类药物产生耐药性的菌株,其他抗生素也可能对它们失去疗效.     

鸡致病性大肠杆菌对头孢噻呋和氟喹诺酮类药物的敏感性

近年来,第三代动物专用头孢菌素类头孢噻呋和发展极为迅速的氟喹诺酮类药物均在兽医临床上广泛应用,取得了明显的治疗效果。但随着使用时间的延长和用药的增多,临床上细菌耐药性也开始出现并导致疗效下降。然而,目前尚缺乏系统资料说明其耐药性发生的程度。为了更好地控制鸡大肠杆菌病,本研究对2004-2005年河南省中北部9个地级市区大型养殖场收集的91株鸡源致病性大肠杆菌对头孢噻呋和氟喹诺酮类药物的耐药性情况进行了观查。1材料与方法1.1药品与试剂头孢噻呋、恩诺沙星、环丙沙星和沙拉沙星标准品均购自中国兽医药品监察所;细菌生化鉴定管…     

Molecular characteristics of ESBL-producing Escherichia coli isolated from chickens with colibacillosis

BackgroundAvian pathogenic Escherichia coli (APEC) causes colibacillosis, resulting in significant economic losses in the poultry industry.ObjectivesIn this study, the molecular characteristics of two extended-spectrum beta-lactamase (ESBL)-producing APEC isolates were compared with previously reported ESBL-producing E. coli isolates.MethodsThe molecular characteristics of E. coli isolates and the genetic environments of the ESBL genes were investigated using whole genome sequencing.ResultsThe two ESBL-producing APEC were classified into the phylogenetic groups C and B1 and ST410 and ST162, respectively. Moreover, the ESBL genes of the two isolates were harbored in different Inc plasmids. The EC1809182 strain, harboring the bla_CTX-M-55 gene on the plasmid, exhibited extensive homology to IncFIB (98.4%) and IncFIC(FII) (95.8%). The EC1809191 strain, harboring the bla_CTX-M-1 gene, was homologous to IncI1-I (Gamma) (99.3%). All chromosomes carried the multidrug transporter, mdf(A) gene. Mobile genetic elements, adjacent to CTX-M genes, facilitated the dissemination of genes in the two isolates, analogous to other ESBL-producing E. coli isolates.ConclusionsThis study clarifies the transmission dynamics of CTX-M genes and supports strengthened surveillance to prevent the transmission of the antimicrobial-resistant genes to humans via the food chain.     

Ocular lesions in chickens inoculated with Escherichia coli.

Specific-pathogen-free chickens (two, four and ten weeks of age) which were inoculated via the air sac with Escherichia coli developed ocular lesions. Histologically, the main ocular lesions consisted of hyphema, hemorrhages of the iris, hypopyon, keratitis and uveitis. Hyphema was associated with hemorrhages of the iris, and hypopyon with keratitis and uveitis. Cyclophosphamide treatment enhanced the incidence and severity of hyphema and hemorrhages of the iris in the chickens.     

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.     

信宜地区鸡大肠杆菌耐药性的调查

近几年来,由致病性大肠杆菌引起的鸡大肠杆菌病在广东省信宜市有明显上升趋势,由于多方面原因,特别是临床上随意及超量使用抗菌药物,致使大肠杆菌的耐药性不断加强,呈现难以控制的局面.     

Serotypes of Escherichia coli isolated from septicaemic chickens in Galicia (Northwest Spain)

The purpose of this study was to establish the serogroups of Escherichia coli that cause avian colibacillosis in Spain. The serogroups of 625 avian E. coli isolated between 1992 and 1993 were determined. The 458 E. coli from chickens with septicaemia belonged to 62 different O serogroups; however, 59% were of one of 18 serogroups (O1, O2, O5, O8, O12, O14, O15, O18, O20, O53, O78, O81, O83, O102, O103, O115, O116 and O132). These 18 serogroups were also determined as an important percentage (29%) of control isolates from faeces of healthy birds. Nevertheless, a significant difference (59% versus 29%; P<0.001) was observed. Furthermore, the serogroups O12, O14, O18, O53, O78, O81, O102, O115, O116 and O132 were almost exclusively identified among septicaemic E. coli (31% versus 3%; P<0.001). The high prevalence of O18, O81, O115, O116 and O132 isolates was not expected and may indicate the emergence of five new serogroups associated with avian colibacillosis not yet reported.     

Antimicrobial resistance in fecal Escherichia coli isolated from growing chickens on commercial broiler farms

To investigate the effects of rearing practices of commercial broiler chickens on the incidence of antimicrobial resistance in commensal Escherichia coli isolates, fecal E. coli isolates obtained in 4 farms were screened for anitimicrobial resistance. Ten E. coli isolates were recovered from each of the fecal samples collected from 10 birds in the farms at the ages of 2 days, 14-17 days, and 47-50 days. In 2 out of the 4 farms, no antimicrobials were used during the rearing period. In the other two farms, following collection of the fecal samples at 14 and 15 days of age, oxytetracycline (OTC), sulfadimethoxine (SDMX), and tylosin were given to birds on one farm and SDMX was used in the other. Isolates resistant to ampicillin and OTC that were obtained from an untreated flock at different sampling times were closely related to each other by pulsed-field gel electrophoresis patterns (PFGE) of XbaI-digested chromosomal DNA. PFGE analysis together with in vitro conjugation experiments suggested that diversity of resistance phenotypes within a clone may be resulted from the acquisition and loss of R-plasmids in an untreated and a treated flock. The numbers of resistance phenotypes observed among fecal isolates increased during the growth of the chickens in all the farms. The results in the present study suggest that persistence of commensal E. coli strains resistant to antimicrobials even in the absence of antimicrobial administration. It is also hypothesized that horizontal transmission of resistance determinants resulted in the emergence of different resistance phenotypes in those farms.     

Anti-enteropathogenic Escherichia coli immunoglobulin Y isolated from eggs laid by immunised Leghorn chickens

IgY, the egg yolk immunoglobulin, equivalent to the IgG from mammals, has been used in veterinary practice for passive immunisation against bacterial or viral infectious diseases. Enteropathogenic Escherichia coli (EPEC) is the main etiological agent of infantile diarrhoea in Brazil and other developing countries. Our aims were to isolate immunoglobulin IgY from egg yolk laid by EPEC -immunised Leghorn chickens and to study its reactivity to the antigens from this pathogen, including some virulence factors. Leghorn chickens were immunised with a bacterial suspension intramuscularly (three hens) or intravenously (three hens) or with PBS (two hens). Eggs were collected over a period of 17 weeks. IgY isolation procedures were carried out by salt precipitation (ammonium sulphate, in solid form) followed by centrifugations and dialysis. Final preparations were submitted to sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS - PAGE), enzyme-linked immunosorbent assay (ELISA) and immunoblotting. All immunised animals developed good levels of antibodies reactive to whole bacteria or lipopolysaccharide (LPS), in contrast to the control ones. Immunoblottings allowed the recognition of several antigenic fractions of bacterial antigens, some of which had a molecular weight compatible with bacterial virulence factors, confirming the efficacy of the immunisation and the adequacy of the method.     

Persistence of cellulitis-associated Escherichia coli DNA fingerprints in successive broiler chicken flocks

Avian cellulitis in broiler chickens is primarily caused by Escherichia coli. Previous research found that the E. coli isolates of cellulitis origin were unique to each ranch, suggesting that these E. coli were endemic within the ranch environment. To test the hypothesis that the E. coli associated with cellulitis are endemic in the litter of the broiler house, we designed a study to determine whether E. coli DNA fingerprints associated with cellulitis persist over successive flocks that are grown in the same house. In addition, we assessed the impact of different cleaning and disinfection strategies on this persistence. Two broiler houses were followed on each of five farms over 3-4 flocks. A total of 353 E. coli isolates from cellulitis lesions were analyzed in this study, and 314 of these isolates (89%) were DNA fingerprinted by PFGE. In each ranch, there were several DNA fingerprint patterns that were present over successive flocks, regardless of the cleaning and disinfection strategy utilized. Isolates persisted as long as 191 days, implying that these E. coli are capable of persisting in the broiler house environment for long periods of time. In addition, these E. coli isolates were associated with cellulitis lesions in successive flocks. Thus, the isolates of E. coli that are associated with cellulitis in broiler chickens appear to be endemic in the litter environment of the broiler house.     

Virulence factors of avian pathogenic Escherichia coli strains isolated from chickens with colisepticemia in Japan

The virulence factors of avian pathogenic Escherichia coli (APEC) isolated in Japan were investigated. Serogroups O, serotypes K1 and K5, and genes cva C, iss, iutA, papA, tsh, and usp, which have been thought to be related to virulence, were examined for their association with E. coli strains isolated from diseased and healthy chickens. The frequently recognized serogroups O1, O2, and O78 were found in 56 of 125 (44.8%) strains of diseased chickens (APEC) versus 13 of 100 (13.0%) strains of healthy chickens (commensal E. coli), a significant difference at risk ratio < 0.01. Although iss, iutA, and tsh were widely distributed in the APEC irrespective of O serogroup, papA, usp, and the K1 serotype were detected in serogroup O2 of APEC. The kfiD gene related to the K5 capsule and VT, LT, and ST genes related to exotoxins were not detected in any strains examined.     

Isolation of Escherichia coli from cellulitis and other lesions of the same bird in broilers at slaughter.

Cellulitis results in substantial losses to the broiler industry due to condemnations at slaughter. This study was conducted to clarify the association between Escherichia coli isolated from cellulitis and other lesions caused by E. coli in individual birds. Fourteen flocks were sampled and 118 birds with cellulitis were examined. Escherichia coli was isolated from all but 2 of the cellulitis lesions, and serogroups O78, O1, and O2 predominated. Thirty-six birds had at least 1 other lesion in addition to the cellulitis lesion. Isolation of E. coli from cellulitis and other lesions occurred in 7 of the 14 flocks. Escherichia coli of the same serogroup were isolated from cellulitis and other lesions in some birds, suggesting that a single E. coli may sometimes be responsible for both types of lesions.     

Assessing cellulitis pathogenicity of Escherichia coli isolates in broiler chickens assessed by an in vivo inoculation model.

The purpose of this study was to identify Escherichia coli isolates that could be characterized as cellulitis pathogens. Twelve E. coli isolates from diagnostic cases of cellulitis or mixed infections with various serotypes were compared for ability to produce cellulitis and internal lesions indicative of systemic infection. Ranking of isolates was based on the premise that E. coli isolates that were "cellulitis-type" would cause cellulitis lesions without causing systemic infection. A quantitative scoring system was also used so both the time required for a lesion to develop and lesion severity could be evaluated as determinants of virulence. Escherichia coli isolates were inoculated by subcutaneous injection of a standardized dose in 24 broiler chickens per isolate. Necropsy was performed on four birds per group at 6, 12, 24, 36, 48, and 60 hr postinoculation (PI). Cellulitis lesions were scored on a 0 to 5 scale based on size, migration from the inoculation site, and gross characteristics. Lesions of the pericardium, liver, joint, or body cavity were evaluated. Gross lesion scores of 1 or 2 were evident by 6 hr PI with all isolates. Mortality occurred in 4 of 12 experimental groups. Internal lesions were observed in 3 to 12 birds per group. Escherichia coli was reisolated from all lesions. The four isolates with the highest lesion score and highest lesion points as determined by the quantitative scoring system did not vary. However, the rankings of two other isolates were affected. Four isolates that were below average for mean internal lesion score and above average for mean cellulitis points were characterized as cellulitis-type. Three isolates that were above average for internal lesion score and below average for mean cellulitis points were characterized as systemic-type. The E. coli serotype was not a determining factor for cellulitis-type pathogenicity. Isolates discriminated as cellulitis-type or septicemic-type E. coli in this study are being used to further investigate virulence factors involved in the pathogenesis of cellulitis in broiler chickens.     

Cytotoxin produced by Escherichia coli isolated from chickens with swollen head syndrome (SHS)

This study was conducted to determine the presence of selected virulence factors in Escherichia coli recovered from swollen head syndrome (SHS) in chickens. Thirty-six (72%) of 50 isolates of E. coli from SHS were shown to produce a cytotoxin that was active on Vero and HeLa but not on Y-1 cells. The toxin was called VT2y because the cytotoxic effect on Vero cells was morphologically similar to that produced by E. coli verotoxins (VTs), and this effect was neutralized by antiserum against VT2 but not by antiserum against VT1. Interestingly, DNA probes for VT1 and VT2 failed to hybridize the VT2y-positive isolates with total DNA. Although the role of this toxin in SHS has yet to be demonstrated, the marked edema which characterizes affected chickens is consistent with the action of a toxin such as verotoxin which targets vascular endothelium.