The emergence of New Delhi metallo-beta-lactamase (NDM)-producing Escherichia coli (E. coli) in the food production chain poses a serious public health threat. This study aimed to investigate the prevalence and molecular characteristics of blaNDM-carrying E. coli along the chicken production chain (farms, slaughterhouses, and supermarkets) in Jiangsu Province, China. Between 2023 and 2025, 408 samples were collected, recovering 39 blaNDM-positive E. coli isolates (9.56%). Isolation rates were 10.4% (26/250) in farms, 10.1% (11/108) in slaughterhouses, and 4.0% (2/50) in supermarkets. Whole-genome sequencing (WGS) identified blaNDM-5 as the dominant variant, alongside the first detection of blaNDM-13 in local farm environments. All isolates exhibited high-level resistance to meropenem (MIC: 16-128 mu g/mL) and universal resistance (100%) to ampicillin, cefoxitin, ceftiofur, and sulfisoxazole. Notably, 41.03% and 7.69% of strains co-harbored the polymyxin resistance gene mcr-1.1 and the tigecycline resistance gene tet(X4), respectively. Isolates carried an average of 19.5 antimicrobial resistance genes, with IncFIB (AP001918) (82.05%) identified as the dominant plasmid replicon. Multilocus sequence typing (MLST) revealed 18 distinct sequence types (STs), with ST156 and ST155 being the most prevalent. Phylogenetic analysis confirmed slaughterhouses as critical hubs for cross-contamination, evidenced by shared STs (ST1158, ST155, ST162) and minimal SNP differences (1-11) between environment and carcass isolates. Furthermore, the detection of clinically relevant ST10 and ST69 clones in supermarket retail chicken meat underscores a direct foodborne transmission risk to humans. These findings highlight the poultry supply chain as a significant reservoir of multidrug-resistant blaNDM-positive E. coli. Accordingly, we recommend enhanced biosecurity protocols and stricter restrictions and controls on antimicrobial use in broiler farms.

Campylobacter is a major bacterial cause of gastroenteritis worldwide, and poultry meat is widely recognized as a principal reservoir for human Campylobacter infection. This study characterized the antimicrobial susceptibility profiles, genomic diversity, key antimicrobial-resistance determinants, and virulence genes of Campylobacter isolates collected from chicken farms and fresh retail poultry meat in ten regions of Jiangsu Province, China. The biofilm- forming capacity of selected strains was also evaluated. MLST identified CC-574 and CC-828 as the predominant clonal complexes of Campylobacter jejuni and Campylobacter coli, respectively. The isolates exhibited a broad range of sequence types (STs), including 21 previously documented STs in C. jejuni and 16 in C. coli, as well as six novel STs from C. jejuni and three novel STs from C. coli. Phylogenetic analysis revealed extensive genetic diversity among the Campylobacter isolates. Overall, 46.6 % of isolates were classified as MDR. The MDR proportion was significantly higher in C. coli (75.4 %) than in C. jejuni (17.5 %), and C. coli exhibited broader resistance across the ten antibiotics assessed. Among the detected resistance genes, the resistance-enhancing variant RE-CmeABC, which was primarily harbored by C. jejuni, had the highest prevalence (32.8 %), followed by tet(O) (31.3 %), the aminoglycoside resistance gene cluster aadEsat4-aphA-3 (21.9 %), and erm(B) (9.4 %). Virulence-gene profiling of the 128 Campylobacter isolates identified 10 virulence genes across five functional categories: adhesinon, invasion, immune modulation, motility, and toxin production. The wlaN gene, which is associated with Guillain-Barré syndrome, was detected in 7 (5.5 %) C. jejuni isolates. Among the 38 Campylobacter strains tested for biofilm formation, six C. coli isolates exhibited pronounce biofilm-forming capacity. These findings indicate that Campylobacter isolates from chicken farms and retail poultry meat pose potential public health risks, underscoring the need for targeted Campylobacter control strategies and providing a useful reference for future surveillance pograms.

This study aimed to evaluate the maternal genetic diversity and mitochondrial population structure of once endangered indigenous chicken breeds in China under current conservation conditions. The genetic characteristics of six endangered indigenous chicken breeds, namely the Bian chicken, Jinyang Silky chicken, Pudong chicken, Xiaoshan chicken, Zhongshan Shalan chicken, and Pengxian Yellow chicken, were analyzed based on mitochondrial DNA (mtDNA) D-loop region sequences. Blood samples were collected from the wing vein. The D-loop region was amplified by PCR, and genetic characteristics were analyzed using bioinformatics approaches. A total of 368 individuals were amplified and sequenced, yielding complete D-loop sequences of 1231 and 1232 bp. Sequence alignment identified 42 polymorphic sites, with a hypervariable region primarily located between 167 and 446 bp. The overall haplotype diversity, nucleotide diversity, and the average number of nucleotide differences were 0.876 ± 0.010, 0.00603 ± 0.00012, and 7.426, respectively, with significant inter-breed variation. Haplotype analysis identified 32 haplotypes belonging to haplogroups A, B, C, E, F, and G. The proportion of breed-specific and shared haplotypes varied among breeds, and several high-frequency haplotypes were widely distributed across populations. Analysis of molecular variance (AMOVA) indicated that the majority of genetic variation occurred within breeds (83.41%), whereas among-breed variation accounted for 16.59% (Fst = 0.166), suggesting moderate population differentiation. The median-joining haplotype network exhibited a radial pattern centered on several core haplotypes, with no evidence of breed-specific clustering of maternal lineages. Neutrality tests (Tajima’s D and Fu’s Fs) yielded non-significant results, consistent with neutral evolution. However, mismatch distribution analyses suggested possible population expansion in the Zhongshan Shalan chicken and Pengxian Yellow chicken. In summary, the six endangered indigenous chicken breeds retain a moderate level of maternal genetic diversity under current conservation conditions. However, differences among breeds were observed in the maintenance of genetic diversity and population structure.

Carbapenem-resistant bacteria, in particular NDM-producing Enterobacteriaceae, have become a great threat to the global public. The blaNDM-13 is a novel blaNDM variant with increasing dydrolytic activity against cefotaxime. This study aimed to investigate the molecular characteristics of blaNDM-13-positive E. coli in a chicken farm located in Jiangsu Province of China. Six blaNDM-13-positive E. coli strains were isolated from 83 samples, including cloacal samples (n = 4), cages (n = 1), and water dispensers (n = 1). Antimicrobial susceptibility testing showed that these isolates exhibited pan-resistance to β-lactams (meropenem MIC≥32 μg/mL), colistin, and six other antibiotic classes, retaining susceptibility only to tigecycline. Illumina sequencing showed that isolates harbored multiple resistance genes, with fosA3, aph(3′)-IIa, oqxA, oqxB, and aph(6)-Id being present in all strains. Notably, blaCTX-M-65 (extended-spectrum β-lactamase), mcr-1.1 (colistin resistance), and qacE (disinfectant genes) were detected in 50 %, 66.67 %, and 66.67 % of blaNDM-13-positive E. coli strains, respectively. MLST classified the isolates into ST155 (n = 3), ST93 (n = 2), and ST1158 (n = 1), with blaNDM-13-positive ST155 E. coli isolates found to be horizontal transmission between chicken and environmental surface samples. Three representative isolates were subjected to Nanopore long-read sequencing; the blaNDM-13 was located on the IncFII plasmid, which showed high homology with clinical (pB5-1) and poultry-derived plasmids (YZLc23-1-NDM-13-96k), harboring conserved resistance gene clusters (IS91-blaNDM-13-bleMBL-IS50R-aph(3′)-IIa-IS26-IS6-fosA3), and confirmed horizontal transfer via conjugation. The conjugants were stably inherited after 15 days of passage and exhibited no significant differences in growth rates when compared to E. coli J53. This study identifies blaNDM-13-carrying multidrug-resistant E. coli clones in poultry production systems, transmitted via poultry-environment interactions and plasmid-mediated gene transfer. Farm-level surveillance targeting high-risk transmission routes is essential to control antimicrobial resistance and protect poultry health.

Campylobacter is a major cause of bacterial foodborne diarrhea worldwide. Consumption of raw or undercooked chicken meat contaminated with Campylobacter is the most common causative agent of human infections. Given the high prevalence of contamination in poultry meat and the recent rise of multi -drug -resistant (MDR) Campylobacter strains, an effective intervention method of reducing bird colonization is needed. In this study, the Campylobacter-specific lytic phage CP6 was isolated from chicken feces. Phage CP6 exhibited a broad host range against different MDR Campylobacter isolates (97.4% of strains were infected). Some biological characteristics were observed, such as a good pH (3-9) stability and moderate temperature tolerance (<50 degree celsius). The com plete genome sequence revealed a linear double -stranded DNA (178,350 bp, group II Campylobacter phage) with 27.51% GC content, including 209 predicted open reading frames, among which only 54 were annotated with known functions. Phylogenetic analysis of the phage major capsid protein demonstrated that phage CP6 was closely related to Campylobacter phage CPt10, CP21, CP20, IBB35, and CP220. CP6 phage exerted good antimicrobial effects on MDR Campylobacter in vitro culture and reduced CFUs of the host cells by up to 1 -log compared with the control in artificially contaminated chicken breast meat. Our findings suggested the potential of CP6 phage as a promising antimicrobial agent for combating MDR Campylobacter in food processing.

Infectious bronchitis virus (IBV) restricts cell tropism. Except for the Beaudette strain, other IBVs cannot infect mammalian cell lines. The limited cell tropism of other IBVs has hindered IBV vaccine development and research on the mechanisms of IBV infection. A novel Vero cell-adapted strain, HV80, has been previously reported. In this study, we constructed recombinants expressing the chimeric S glycoprotein, S1 or S2 subunit of strain H120 and demonstrated that mutations on S2 subunit are associated with the strain HV80 Vero cell adaptation. R687P or P687R substitution recombinants were constructed with the genome backbone of strains HV80 or H120. We found that the RRRR690/S motif at the S2' cleavage site is crucial to the Vero cell adaptation of strain HV80. Another six amino acid substitutions in the S2 subunit of the recombinants showed that the Q855H mutation induced syncytium formation. A transient transfection assay demonstrated the S glycoprotein with the PRRR690/S motif at the S2' cleavage site induced low-level cell-cell fusion, while H855Q substitution hindered cell-cell fusion and blocked cleavage event with S20 product. This study provides a basis for the construction of IBV recombinants capable of replicating in Vero cells, thus contributing to the advancement in the development of genetically engineered cell-based IBV vaccines.

The prevalence of antimicrobial resistance originating from animals presents a significant threat to the treatment of animal disease, public health, and food safety. Researchers have focused on antibiotic resistance in Escherichia coli (E. coli), yet there are few reports on the resistance change during the feeding cycle. The purpose of this study was to investigate the prevalence and antibiotic resistance changes of E. coli in animal, environmental, and human samples during the broiler feeding cycle. Epidemiological surveys were performed in a farm with feeding AA broilers in Yangzhou, Jiangsu Province, China. Results showed that during a 42-days feeding cycle, 128 E. coli isolates were obtained from the cloaca of white-feathered broilers (n = 140), with an isolation rate of 91.4%, 27 E. coli isolates were obtained from Feed (n = 70) and 35 E. coli isolates were obtained from cage swabs (n = 70). A workers’ hands swabs sample isolation rate of 68.6% (24/35) was observed. Antibiotic susceptibility testing revealed that out of 214 E. coli isolates, varying degrees of resistance were observed against 14 antibiotics. Most strains were resistant to ampicillin, cephalothiophene, ciprofloxacin, tetracycline, sulfamisoxazole, sulfamethoxazole and florfenicol, with a resistance rate exceeding 80%. The resistant strains demonstrated relatively stable patterns in their resistance to various antibiotics. Of the six antibiotic resistance genes tested, the floR gene showed the highest detection rate (72.4%), followed by qnrS (43.0%), mcr-1 (35.0%), aadE-Sat4-aphA-3 (28.0%), blaNDM (8.4%), aac(6′)-lb (3.7%), and cfr (0). The highest detection rate for virulence genes was yijp. In summary, the isolation rate of E. coli and antibiotic resistance profile in broiler chickens remained stable throughout their feeding cycle. These findings can serve as a reference for the rational use of antibiotics in clinical settings, they can guide the use of veterinary drugs in poultry breeding.

In order to reveal the changes in the microbial communities in chilled chicken during partially frozen storage, and to provide a theoretical basis for partially frozen preservation, 16S RNA high-throughput sequencing was used to analyze the bacterial diversity and community composition of the chilled chicken during storage at-3 ℃. The results showed that Shannon index decreased, Simpson index increased, which indicates the bacterial diversity of chilled chickens reduced during storage at-3 ℃. The Ace index and Chao1 index first decreased, and then increased and reached a peak on the 4th day of storage, and then gradually decreased to the lowest level on the 28 th day of storage. At the phylum level, the dominant microorganisms of chilled chicken during storage were Proteobacteria, Firmicutes, Bacteroidetes,Actinobacteriota and Chloroflexi. The relative abundance of Proteobacteria increased with storage time, while the other Phylum decreased. At the genus level, the dominant taxa of chilled chickens were Pseudomonas, Acinetobacter, Shewanella and Psychrobactera. With the extension of partially frozen storage time, the microbial composition changed. The relative abundance of Pseudomonas increased, and the relative abundance of Acinetobacter, Shewanella, and Psychrophilic decreased. At the 28 th day of storage under freezing storage conditions at-3 ℃, the microbial composition was mainly Pseudomonas. The relative abundance of Acinetobacter, Shewanella and Psychrobacter decreased, accounting for less than 1%, respectively. These results showed that Pseudomonas is the dominant spoilage bacteria of chilled chickens in the partially frozen storage.

《中华人民共和国生物安全法》于2021年4月15日起正式实施,生物安全被提升到国家战略高度.肉鸡养殖的生物安全技术是阻断病原微生物进入鸡群而采取的相应措施,主要包括养殖场的选址、总体布局等结构性方面的生物安全措施和投入品、消毒防疫、粪污及病死鸡无害化处理等管理性方面的生物安全措施,其目的是"阻止传染源、切断传播途径和保护易感动物".

Infectious bronchitis virus (IBV) has restricted cell and tissue tropism. IBVs, except the Beaudette strain, can infect and replicate in chicken embryos, primary chicken embryo kidneys, and primary chicken kidney cells, only. The limited viral cell tropism of IBV substantially hinders in vitro cell-based research on pathogenic mechanisms and vaccine development. Herein, the parental H120 vaccine strain was serially passaged for five generations in chicken embryos, 20 passages in CK cells and 80 passages in Vero cells. This passaging yielded a Vero cell-adapted strain designated HV80. To further understand viral evolution, serial assessments of infection, replication, and transmission in Vero cells were performed for the viruses obtained every tenth passage. The ability to form syncytia and the replication efficiency significantly after the 50th passage (strain HV50). HV80 also displayed tropism extension to DF-1, BHK-21, HEK-293 T, and HeLa cells. Whole genome sequencing of viruses from every tenth generation revealed a total of 19 amino acid point mutations in the viral genome by passage 80, nine of which occurred in the S gene. The second furin cleavage site appeared in viral evolution and may be associated with cell tropism extension of HV80.

[Background] Campylobacter is a common group of foodborne pathogens that can cause gastroenteritis in the world. It is increasingly resistant to clinically important antibiotics and poses a serious threat to food safety and public health. [Objective] To investigate the resistance phenotype and genes of a Campylobacter coli strain carrying both optrA and cfrC， the whole genome characteristics of the strain， the distribution of virulence genes， and the gene environments of optrA and cfrC. [Methods] Agar dilution method was employed to determine the minimal inhibitory concentrations （MIC）. Whole genome sequencing （WGS） was carried out to sequence the DNA of the strain. [Results] The strain was highly resistant to tetracycline， clindamycin， azithromycin， florfenicol， and linezolid， and sensitive to ciprofloxacin and gentamicin. WGS identified a circular DNA with a size of 1 436 486 bp （GC content of 31.63%）， which carried 12 resistance genes involving four major categories of antibiotics. All of the 12 genes were detected on the chromosome， most of which were aminoglycoside resistance genes. A total of 83 virulence genes involved in adherence， invasion and motility were identified， and most of them were associated with motility. The gene islands GIs002 and GIs003 contained resistance genes. CfrC was located on the GIs002， linked with aph（3’）-Шaand flanked by two transposons. OptrA was located on chromosome and connected to the insertion sequence Integrase/IS607 family at upstream and downstream sides. Transposon and insertion sequence could mediate the horizontal transfer of resistance genes. [Conclusion] The genome information， resistance genes， and virulence genes of a multiresistant C. coli strain were analyzed by WGS. The mobile genetic elements （transposase and insertion sequence） played an important role in the transmission of antibiotic resistance of C. coli. The findings provide basic information for risk assessment of antibiotic resistance of Campylobacter.

Infectious bronchitis virus (IBV) has restricted cell tropism. Apart from the Beaudette strain, other IBVs cannot infect mammalian cell lines. The limited cell tropism of other IBVs has hindered the development of IBV vaccines and research on mechanisms of IBV infection. In a previous study, a new Vero-cell-adapted strain HV80 was obtained via serial chicken embryo and cell passaging of strain H120 and 17 mutations leading to amino acid substitutions occurred in replication gene 1a, S gene and E gene. This study, we constructed recombinants that expressed chimeric S glycoprotein, S1 or S2 subunit of strain H120, and demonstrated that mutations in S2 subunit were related to the Vero cell adaption of strain HV80. With a genome backbone of strain HV80 or H120, and expression of chimeric S2′ cleavage site of H120 or HV80, two recombinants demonstrated that the RRRR690/S motif at the S2′ cleavage site played a key role in Vero cell adaption of strain HV80. Another six amino acid substitutions in the S2 subunit of the recombinants showed that F692V enhanced the capability of invasion of HV80 strain, and Q855H induced the formation of syncytia. A transient transfection assay demonstrated different mechanisms for virus-to-cell fusion and cell-to-cell fusion induced by S glycoprotein. The PRRR690/S motif at the S2′ cleavage site could be activated by proteases in the process of cell-to-cell fusion, while H855Q substitution did not affect the cell invasion of HV80, but hindered the cell-to-cell fusion by blocking activation of the S2′ cleavage site.IMPORTANCE Infectious bronchitis is an acute respiratory disease that has caused large economic losses to the poultry industry. As a member of the gamma-coronaviruses, the restricted cell tropism of infectious bronchitis virus (IBV) limits the development of cellular vaccines and research on infection mechanisms. As a strain that can replicate effectively in mammalian cell lines, studies of HV80’s adaptive mechanisms point a way for engineering other IBVs for adaptation in mammalian cell lines. In our study, different recombinants were constructed by reverse genetic techniques, and demonstrated the different mechanism between virus-to-cell and cell-to-cell fusion induced by HV80 S glycoprotein. The acquisition of a highly efficient S2′ cleavage site enabled the virus to invade Vero cells. The Q855H substitution played a key role in cell-to-cell fusion, and provided a more efficient model of infection in Vero cells. Our study provides new theoretical insights into mechanisms of IBV adaptation in mammalian cell lines.

AmpC β-lactamase genes are clinically important because they often confer resistance to most β-lactams other than 4th-generation cephalosporins and carbapenems. However, traditional and existing detection methods are expensive, labor-intensive and range-limited. We established an efficient multiplex PCR method to simultaneously identify six families of ampC β-lactamase genes, ACC, EBC, CIT, DHA, MOX and FOX, and evaluated the sensitivity and specificity of this assay. The multiplex method could accurately identify ACC, EBC, CIT, DHA, MOX and FOX variants among a total of 175 ampC β-lactamase genes. The minimum concentration of genomic DNA that could be detected was 1.0×103 copies/μL. We subsequently used this method to analyze 2 Salmonella spp. with carrying CMY-2 and DHA-1, and 167 Enterobacteriaceae isolates in blinded PCR testing. Positive isolates produced bright bands that corresponded with their genotype. Results were in concordance with those of the traditional method but showed increased sensitivity and accuracy. This indicates that the newly developed multiplex PCR system could be used as a diagnostic tool to accurately distinguish the six families of ampC β-lactamase genes with high efficiency, wide range, easy operation and good discrimination.

The microneutralization test is a sensitive and specific technique used for quantitation of virus-specific neutralizing antibodies in serum samples of infected or vaccinated chickens. Because of the characteristic of viral strictly cell tropism, the neutralization test for infectious bronchitis virus (IBV) is generally based on chicken embryos, tracheal organ cultures, and primary chicken kidney (CK) cells. In recent years, we have serially passaged the H120 vaccine strain in CK cells and obtained a Vero-cell-adapted strain HV80. Based on this strain, we developed a new neutralization test for anti-IBV antibody detection using Vero cells. In addition to having the advantages of neutralization assay, compared with the use of chicken embryos and primary tissue cells, the microneutralization test using Vero cells is easy to perform, does not need special equipment, and is suitable for use with large quantities of serum samples.

目的 了解江苏地区肉鸡屠宰生产链中弯曲菌分离菌株毒力基因分布及不同环节分离菌株遗传相关性.方法 利用特异性引物对肉鸡屠宰过程不同环节分离所得的96株弯曲菌分离菌株的10种致病相关毒力基因进行聚合酶链式反应(polymerase chain reaction,PCR)检测,应用多位点序列分型(multilocus sequence typing,MLST)方法对分离菌株进行分子分型研究,通过与弯曲菌MLST数据库比对获得各株菌等位基因值、序列型(sequence types,STs)及克隆复合体.结果 96株分离菌株中,flaA、cadF和cdtB毒力基因携带率均为100％,其次为cdtC、iam和cdtA毒力基因,携带率较高,分别为96.9％、86.5％和84.4％,另外3个毒力基因flhA、virB11、ciaB携带率均较低,分别为25.0％、15.6％、11.5％;格林-巴利综合症相关毒力基因wlaN在所有菌株中均无检出.MLST分型结果显示,96株弯曲菌可分为10个STs,其中2个为新STs,形成1种优势克隆复合体CC828(56株)和4种未定义的克隆复合体,表现为较低的遗传多样性.结论 肉鸡屠宰生产链中弯曲菌毒力基因分布广泛,不同环节弯曲菌分离菌株遗传多样性较低,表明弯曲菌在肉鸡屠宰生产链中存在交叉污染.

为了对鸡传染性支气管炎(IB)疫苗的免疫效果进行有效评估,研究以QX型IBV的Vero细胞适应株为包被抗原,对检测条件进行优化,建立了IBV抗体间接ELISA检测方法.结果显示:抗原最佳包被浓度为160μg/mL,最佳包被条件为37℃、2 h,封闭条件为5％脱脂奶粉、37℃封闭2 h,最佳抗体稀释液选择2％脱脂奶,一抗的最佳反应条件为37℃、60 min,二抗的最佳稀释度为1:10000,作用时间为60 min,底物显色时间为15 min;特异性、重复性试验证明,该方法与其他病原无交叉反应,特异性好,批内、批间变异系数较低,重复性好.研究初步建立了IBV抗体间接ELISA检测方法,可应用于免疫鸡群后抗体水平监测及早期感染预警.

本试验旨在从鸡肠道中分离筛选出耐镉(Cd)的乳酸菌,为将其开发应用于防控家禽饲料重金属Cd污染提供理论基础.取鸡肠道内容物的样品进行乳酸菌分离,以耐受100 mg/L的Cd为标准筛选乳酸菌,采用分子生物学方法鉴定菌株.对筛选出的乳酸菌株进行生长性能、耐Cd性能及Cd吸附性能等测定.结果表明:本试验共筛选出5株耐Cd乳酸菌,分别为1株约氏乳杆菌Cd3?1和4株卷曲乳杆菌Cd1?1、Cd5?2、Cd4?5和Cd8?2.其中Cd3?1、Cd5?2和Cd8?2菌株最高可耐受1000 mg/L的Cd,而Cd1?1和Cd4?5菌株最高可耐受400 mg/L的Cd.各菌株对50 mg/L Cd的吸附率随溶液pH的升高而增加,在pH为6.0和7.0时Cd的吸附率均显著高于pH为2.6时Cd的吸附率(P<0.05).5株乳酸菌均可耐受0.3％的胆盐,且可抑制金黄色葡萄球菌的生长.综合上述结果,本试验从鸡肠道中分离筛选鉴定出5株耐Cd乳酸菌,包括1株约氏乳杆菌和4株卷曲乳杆菌,在pH接近中性的条件下,对Cd的吸附率可达30％.

为了解江苏地区鸡源弯曲杆菌的分子特征,应用多位点序列分型方法(Multilo?cus squence typing,MLST)对2016—2018年分离的225株鸡源弯曲杆菌进行分子分型,采用BURST和BioNumerics软件进行聚类分析.结果显示:225株弯曲杆菌共获得89种序列型,包括32种新序列型,57种已知序列型,其中38种已知序列型归属12种同源复合体(CC-828、CC464、CC-21、CC-45、CC-1150、CC-443、CC-460、CC-354、CC-52、CC-353、CC-179和CC-574),其中结肠弯曲杆菌和空肠弯曲杆菌分别以同源复合体CC-828和CC-464为主;BURST分析结果显示,179株57种已知序列型共分为2个克隆复合体和7个克隆群以及18个克隆单体;聚类分析结果显示,结肠弯曲杆菌主要聚为两个分支,菌株之间在进化上相对比较保守,而空肠弯曲杆菌分支比较复杂,具有丰富的遗传多样性.表明江苏省鸡源弯曲杆菌具有丰富的ST型,结肠弯曲杆菌和空肠弯曲杆菌流行具有明显的优势复合体,存在克隆传播,该结果为了解江苏省鸡源弯曲杆菌遗传特性提供了参考依据.

[目的]通过开展5个品种白羽肉鸡养殖过程中大肠杆菌流行病学研究及耐药性差异情况调查,了解不同品种肉鸡大肠杆菌耐药现状及其差异,为科学指导肉鸡相关疾病诊治和兽药监管提供参考依据.[方法]选用5个品种白羽肉鸡(2个为江苏养殖量较大的国外引进品种,3个为我国自主选育配套系)为研究对象,分别采集0日龄胎粪样品及4、8、12、16、20、24、28、32、36和40日龄的泄殖腔棉拭子,经麦康凯培养基分离大肠杆菌后进行PCR鉴定,并采用Kirby-Bauer(K-B)法进行药敏试验.[结果]从1075份样品中共分离获得978株大肠杆菌,总分离率为91.0％.其中,广明2号(A品种)和圣泽901(C品种)的大肠杆菌分离率最高,均为93.0％;WOD168(E品种)的分离率最低,为88.4％.5个品种白羽肉鸡的胎粪样品分离率、2个重复的分离率、5个品种白羽肉鸡大肠杆菌总分离率及不同日龄的分离率均无显著差异(P>0.05).5个品种白羽肉鸡大肠杆菌对氨苄西林(AMP)、阿莫西林(AML)、红霉素(E)、四环素(TE)和氯霉素(C)已产生较强的耐药性,对阿米卡星(AK)、磷霉素(FOS)、阿奇霉素(AZM)和头孢曲松(CRO)仍然较敏感;5个品种白羽肉鸡大肠杆菌分离株产生明显的多重耐药,但不同品种的优势耐药谱有所差异.[结论]不同品种白羽肉鸡大肠杆菌耐药情况受用药习惯、饲养方式及条件状况等环境因素的多重影响,但其多重耐药性具有一定的遗传稳定性.因此,在实际生产中应从动物饲养的源头抓起,鼓励和发展集约化养殖,加强饲料安全检测,改善饲养和防疫条件,严格进行合理规范用药,减少同一药物的使用频率,降低细菌耐药性,有效保障动物产品安全及维护人类健康.

A study on florfenicol (FF) and florfenicol amine (FFA) residue depletion raws was conducted in eggs. After the chickens were administered successively florfenicol (FF) powder of 15 mg/kg (prevention group) and 30 mg/kg (treatment group) of body mass in the form of premix for 5 d, the eggs of each group were collected at administration period and 1, 2, 3, 5, 7, 10, 12, 15, 18 d at withdrawal period. Then FF and FFA residues of egg, egg yolk and egg white were detected using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that the limits of detection (LOD) of FF and FFA in egg, egg yolk and egg white were 2 μg/kg, and the limits of quantitation (LOQ) were 5 μg/kg. The average recoveries were in the range of 78.9%-105.0% when the egg samples were added with FF in the range of 1.0-5.0 μg/kg, and the intraday precision and the interday precision was 2.22%-4.22% and 4.22%-6.54%, respectively. The peak values of FF residues (520.70, 797.12 μg/kg) of egg white in prevention group and treatment group, respectively, were higher than those of egg yolk (285.96, 442.40 μg/kg), while the peak values of FFA residue (218.40, 646.14 μg/kg) of egg yolk in prevention group and treatment group, respectively, were higher than those of egg white (87.36, 36.89 μg/kg). The elimination rates of FF and FFA in egg white were faster than those in egg yolk. FF and FFA residues and their total residues were positively correlated with the dosage. FF and FFA mainly existed in the egg yolk, and FF mainly existed in the egg white. The FF residual time of egg yolk in different dosage groups was 18 d.