Congo red binding by Escherichia coli isolates from chickens

An attempt was made to use a recently reported special Congo red medium to determine the pathogenicity of Escherichia coli isolates obtained from chickens. The inclusion of bile salts in the Congo red medium as described in previous reports by others was found in the current experiments to cause the production of red colonies from almost all E. coli cultures tested, including known Congo red-negative control cultures. Cultures of E. coli, regardless of their pathogenic history, rarely produced red colonies on the Congo red medium without added bile salts. Numerous isolates of other bacterial genera were examined and found to produce red colonies on the Congo red medium with or without added bile salts.     

Virulence genes in bla(CTX-M) Escherichia coli isolates from chickens and humans

The aim of this study was to determine the presence of virulence genes in isolates of CTX-M Escherichia coli from diseased chickens, from healthy chickens and from urinary tract infections in people. Three CTX-M E. coli strains from three different instances of disease in poultry (two of which were E. coli related) were tested for bla(CTX-M) sequence type and replicon type. Additionally, they were tested for the presence of 56 virulence genes (encoding fimbriae, adhesins, toxins, microcins and iron acquisition genes) using a micro-array. Results were compared to the virulence genes present in isolates from 26 healthy chickens and from 10 people with urinary tract infections. All genes found in isolates from diseased birds, including the astA (heat stable toxin) and tsh (temperature sensitive haemagglutinin) genes which have previously been associated with colibacillosis in chickens, were also present in isolates from healthy birds. However, 6/10 of the virulence genes found were exclusive to isolates from humans. Genes exclusive to chicken isolates included ireA (sidephore receptor), lpfA (long polar fimbriae), mchF (microcin transporter protein) and tsh whilst genes exclusive to human isolates included ctdB (cytolethal distending toxin), nfaE (non-fimbrial adhesion), senB (plasmid encoded enterotoxin) and toxB (toxin B). The results support previous findings that CTX-M E. coli strains in chickens are generally different from those causing disease in humans, but genes such as astA and tsh in isolates from diseased birds with colisepticaemia were also present in isolates from healthy birds.     

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.     

Phylogenetic background and virulence genes of Escherichia coli isolates from colisepticemic and healthy broiler chickens in Iran

The purposes of this study were to determine the phylogenetic background and the virulence gene profiles of Escherichia coli isolates from colisepticemic and feces of healthy (AFEC) broiler chickens. In this study, 253 E. coli isolates including 141 avian pathogenic E. coli (APEC) and 112 AFEC isolates were examined by PCR. In general, 253 E. coli isolates distributed among group A (51.8%), B1 (15.8%), B2 (8.7%), and D (23.7%). Ten (8.9%) AFEC isolates segregated in to B1 phylo-group and 102 (91.1%) isolates fell into six different phylogenetic subgroups. Distribution of colisepticemic and fecal isolates differed significantly in their assignments to A and B1 phylo-groups. The three most prevalent virulence genes were crl, fimH, and aer in isolates between both groups. The four genetic markers aer, papC, afa, and sfa were detected significantly more often among colisepticemic isolates than in fecal isolates from healthy broilers. The presence of stx ₂ gene in fecal isolates were significantly differs among the colisepticemic isolates. F17 fimbrial family encoding gene and eae gene were detected in APEC and AFEC isolates, respectively. The colisepticemic and fecal isolates possessed the virulence genes were detected in all of the four phylogenetic groups. Several combination patterns of the virulence genes were detected in APEC and AFEC isolates. In colisepticemic isolates the combination of aer, crl, and fimH genes was the most prevalent pattern. None of the examined isolates harbored the cdt, cnf1, ipaH, and stx ₁ virulence gene sequences.     

广东地区2007～2009年禽源大肠杆菌的耐药性演变

通过对2007～2009年内从广东省10多个地市分离得到的378株禽源大肠杆菌进行15种兽医临床常用抗生素的药物敏感性试验(MIC),调查该区域禽类大肠杆菌的耐药性演变情况.采用琼脂稀释法对临床分离株开展MIC测试.结果显示临床分离株对多数兽医临床常用抗生素耐药率在30 ％以上,且有逐年上升的趋势,多数药物的半数抑菌浓度( MIC50)和有效抑菌浓度( MIC90)水平高且保持逐年升高的趋势;细菌的多重耐药情况严重,多集中在5～12耐,提示细菌的耐药能力逐渐提高.表明,广东地区禽源大肠杆菌的耐药水平已经达到了较为严重的程度,应加强食用动物源细菌耐药性的监测.     

Virulence plasmids of enterotoxigenic Escherichia coli isolates from piglets

Virulence plasmids of 68 ETEC isolates from piglets belonging to different pathotypes and six ETEC isolates from calves with pathotypes typical of porcine ETEC were identified with seven virulence probes for the heat-stable (STa and STb) and heat-labile (LT) enterotoxins, for the F4, F5, F6, and F41 fimbrial adhesin subunit, and also with five Rep probes for the RepFIA and RepFIB basic replicons, and the RepFIC family of basic replicons. With the exception of the F41 probe, the other virulence probes hybridized with at least one plasmid band of a size range from 65 to more than 100 Mda. Common associations of virulence factor-encoding genes on plasmid bands were: STb/LT, STa/F5, STa/F6, STa/STb. Other associations, STa/F4, STa/F4/F6, and STa/STb/LT/F6, were rarer. On the other hand the F4 adhesin-encoding genes were isolated on one plasmid band in all but three F4+ isolates. All but one of the 92 virulence plasmids which were studied have Rep probe hybridization profiles and replicon types typical of the uni- or multireplicon plasmids belonging to the various incompatibility groups of the F incompatibility complex.     

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.     

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.     

临床分离食品动物源多重耐药大肠杆菌耐药分子特征研究

本研究从主动外排机制、膜孔蛋白缺失及氟喹诺酮类药物作用靶位改变等几个方面探讨,临床分离的20株动物源性多重耐药大肠杆菌的耐药分子特征。实验结果表明,20株临床分离大肠杆菌gyrA83、gyrA87、parC80的突变率分别为95％、85％、55％。gyrA和parC共同突变的有11株,突变率为55％;20株多重耐药菌大肠杆菌普遍存在主动外排机制,主要介导对部分氨基糖苷类、四环素、氟苯尼考和氟喹诺酮类药物耐药,当添加外排泵抑制剂PAβN后多数菌株庆大霉素、新霉素、四环素、氟苯尼考及氟喹诺酮类药物的MIC都降低了2倍～256倍。利用建立的ELISA方法检测外排泵AcrA蛋白的表达水平,结果证实所有,临床分离菌外排泵表达都增高;20株分离大肠杆菌中,部分菌株缺失OmpC或OmpF蛋白,同时缺失这两个蛋白的只有3株。部分菌株OmpF蛋白条带附近存在有多重耐药相关蛋白（Mar）。本研究结果揭示多重耐药大肠杆菌对常用抗菌药物高水平的耐药表型是主动外排机制、药物作用靶位的改变、外膜通透性的改变及其它机制共同作用的结果。     

Comparative efficacy of enrofloxacin, oxytetracycline, and sulfadimethoxine for the control of morbidity and mortality caused by Escherichia coli in broiler chickens

The purpose of the present study was to compare the ability of enrofloxacin, oxytetracycline, and sulfadimethoxine to reduce morbidity and mortality caused by Escherichia coli (colibacillosis) in broiler chickens. The chickens were raised in 80 pens (20 birds per pen) with 20 pens representing each treatment group under simulated commercial conditions that produced a colibacillosis challenge scenario. Each group of 20 randomized pens (replicates) was given one of four water treatments. Chickens that received enrofloxacin had significantly less mortality (P < 0.01), lower average gross pathology (colibacillosis) scores (P < 0.01), and better feed-conversion ratios (P < 0.05) than did chickens that received either oxytetracycline or no medication. Chickens that received enrofloxacin had significantly less mortality and lower pathology scores than those that received sulfadimethoxine and numerically lower feed conversion than the sulfadimethoxine group. Results from the present study show that enrofloxacin is superior to oxytetracycline and sulfadimethoxine for the control of morbidity and mortality caused by E. coli in broiler chickens. Our findings will help veterinarians choose and prescribe the most efficacious antimicrobial when treating colibacillosis.     

氟喹诺酮类药物对大肠杆菌防突变浓度的测定

抗生素从临床使用至今已半个世纪,在防治感染性疾病、保障人类健康和养殖业持续发展做出巨大贡献的同时,耐药性问题已引起全球高度重视。各国政府和科研机构对耐药性研究十分重视,认为控制动物性病原菌耐药性的产生及传播是解决人类日趋严重的耐药问题中相当重要的一环。为了减     

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…     

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%.     

Virulence-associated genes in Escherichia coli isolates from poultry with colibacillosis

Avian pathogenic Escherichia coli, the causative agent of colibacillosis, harbors several putative virulence genes. In this study we examined by polymerase chain reaction (PCR) the presence of 16 of those genes in 200 colibacillosis isolates from our region. The seven virulence genes iutA, iss, cvaC, tsh, papC, papG and felA were detected significantly more often amongst colibacillosis isolates than in fecal isolates from healthy birds, thereby confirming their worldwide occurrence and possible pathogenic role in colibacillosis. However, several of those genes were not detected in many colibacillosis isolates, and none of them were detected in 27.5% of those isolates, which suggests that variants of those genes and yet undetected virulence factors should be searched for.     

Comparison of necrotoxigenic Escherichia coli isolates from farm animals and from humans

Necrotoxigenic Escherichia coli (NTEC) isolated from animals and humans can belong to the same serogroups/types and produce or carry the genes coding for fimbrial and afimbrial adhesins of the same family, P, S, F17, and/or AFA, raising the question of a potential zoonotic source of human infection. The main purpose of this study was to compare 239 NTEC1 strains (45 from cattle, 65 from humans and 129 from piglets) and 98 NTEC2 strains from cattle, using a uniform and standardized typing scheme. The O serogroups and the biotypes recognized amongst NTEC1 and NTEC2 strains were quite varied, although some were more frequently observed (serogroups O2, O4, O6, O8, O18, O78, and O83 and biotypes 1, 2, 5, 6, and 9). Hybridization, results with gene probes for the P family (PAP probe), S family (SFA probe), AFA family (AFA probe), F17 family (F17 probe) of fimbrial and afimbrial adhesins, could differentiate most NTEC1 strains, which are PAP-, SFA- and/or AFA-positive, from NTEC2 strains, which are mainly F17- and/or AFA-positive, but were of no help in differentiating between NTEC1 strains from cattle, humans, and piglets. All but seven (98%) NTEC1 and NTEC2 strains were serum resistant, 199 (59%) produced an aerobactin, and colicin (I, V, or unidentified) was produced by 22-34% of them. On the other hand, more than 90% of the NTEC1 strains were haemolytic on sheep blood agar compared with only 40% of the NTEC2 strains. Production of a classical haemolysin, active on sheep erythrocytes, and hybridization with the PAP probe were associated in a majority of NTEC1 strains (63-81%), but very rarely in NTEC2 strains (3%). Production of enterohaemolysin and hybridization with the PAP probe were much less frequently associated in NTEC strains (1-9%). It was thus possible neither to completely differentiate NTEC1 strains from cattle, humans, and pigs, nor to define a signature for the NTEC strains. Necrotoxigenic E. coli must still be identified on the basis of the production of the Cytotoxic Necrotizing Factors 1 or 2 (or of their encoding genes) and complete differentiation of NTEC1 strains from cattle, humans, and piglets, use additionnal methods.     

Pharmacokinetic evaluation of enrofloxacin in chickens

1. The pharmacokinetics and bioavailability of enrofloxacin in chickens were investigated following intravenous, intramuscular, subuctaneous and oral administration of 10 mg/kg body weight. A rapid distribution phase was followed by a slower elimination phase.

2. The apparent volume of distribution was 2.2 1/kg. Absorption half lives were 0.37, 0.36 and 0.92 h; elimination half lives were 4.06, 4.48 and 4.29 h and bioavailabilities were 87.5%, 80.8% and 59.6% after intramuscular, subcutaneous and oral administration, respectively. The drug completely disappeared from all tissues after 3 days following oral administration.

3. Based on the bioavailability and disposition kinetics of enrofloxacin, administration of one dose per day should both be practical and adequate to maintain plasma enrofloxacin concentrations within the pharmacologically active but lower than tolerance limit.     

Antibiotic resistance in Escherichia coli and Enterococcus spp. isolates from commercial broiler chickens receiving growth-promoting doses of bacitracin or virginiamycin

Antibacterial agents such as zinc bacitracin (ZB) and virginiamycin (VG) are used as growth promoting agents (GP) in broiler chicken production. The objective of this study was to evaluate the effect of the use of ZB and VG on the emergence of antibacterial resistance in a commercial broiler chicken farm. Three trials were conducted using 3 different diets: one without antibacterial agents, one containing VG, and one with ZB. Escherichia coli and Enterococcus spp. strains were isolated and tested for their susceptibility to various antibacterial agents. The occurrence of the resistance genes vatD, ermB, and bcrR in Enterococcus spp. isolates was determined by polymerase chain reaction (PCR). Comparative quantification of vatD and bcrR genes in total deoxyribonucleic acid (DNA) extracts from litter was done by SYBR Green Real-Time PCR (QPCR). Escherichia coli and Enterococcus spp. isolates from diet groups had different levels of resistance to various antibacterial agents over time. These GPs did not select for specific antibacterial agent resistance (AAR) in Enterococcus spp. The use of GPs seemed to lower the percentage of E. coli isolates resistant to some antibacterial agents. The presence of the bcrR gene could not explain all resistant phenotypes to ZB. Genes other than vatD and ermB might be involved in the resistance to VG in Enterococcus spp. Use of GPs was not associated with presence of the bcrR gene in DNA extracts from litter, but use of VG was associated with vatD presence.