首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
食品动物源产CTX-M-14大肠杆菌传播分子机制的演变   总被引：1，自引：1，他引：0  
从保存的2002-2009年分离的食品动物源大肠杆菌中,挑选16株blaCTX-M-14阳性菌,用PCR方法检测超广谱β-内酰胺酶(ESBLs)编码基因、PMQR耐药基因及其他重要抗生素耐药基因(rmtB和floR);通过脉冲场凝胶电泳(PFGE)及种族进化关系分析16株细菌的亲缘关系;通过接合转移试验、复制子分型和blaCTX-M-14上下游插入元件的检测,分析产CTX-M-14大肠杆菌的传播分子机制。PCR检测结果表明,16株食品动物源产CTX-M-14大肠杆菌大多属于系统发育组A组,其次为B1和D组,没有B2组;PFGE分型结果表明,同一时间内不同动物间存在产CTX-M-14共生型大肠杆菌克隆的扩散传播,但养殖场内CTX-M-14主要是随质粒或其他元件进行水平传播;质粒复制子分型结果表明,携带blaCTX-M-14的质粒属于IncK(3/14)、 IncF(5/14)、 IncHI2(1/14)、IncFIB 和 IncF(1/14)、IncHI1和IncN(2/14)、 IncI1(2/14)等,且随着时间推移,复制子的种类呈增多趋势。2002-2007年的菌株blaCTX-M基因的上下游均检测到ISEcp1和IS903;但2009年菌株除了部分在上下游都可以检测到ISEcp1和IS903外,还有的只检测到上游的ISEcp1或下游的IS903;2002-2009年的菌均未检测到ISCR1。16株产CTX-M-14大肠杆菌除了携带其他ESBLs编码基因,如blaCTX-M79和blaTEM-135外,还携带其他重要抗生素耐药基因,如oqxA、floR、aac(6')-1b-cr及rmtB,而且2002-2009年大肠杆菌携带耐药基因的种类和数量逐年增多;接合转移试验发现,2002-2005年的菌株,blaCTX-M-14往往发生单独转移,而2009年分离菌blaCTX-M-14往往和floR或rmtB位于同一质粒上发生共同转移。这说明养殖场使用氨基糖苷类或氟苯尼考等任何一种抗生素,都可以筛选出产CTX-M-14大肠杆菌并促进其扩散,所以动物养殖过程中要慎用这些抗生素。  相似文献   

2.
The objective of this longitudinal study was to investigate the occurrence and genetic background of faecal Escherichia coli resistant to cefotaxime (CTX) in horses receiving broad-spectrum antimicrobial prophylaxis after admission to a veterinary teaching hospital. The ten horses enrolled in the study were treated with cefquinome either alone (n=4) or in combination with metronidazole (n=3) or other antimicrobial agents (n=3). CTX-resistant coliforms in faeces collected before, during and after treatment were quantified on selective MacConkey agar supplemented with CTX, and a colony isolated randomly from each positive sample was characterized by pulsed-field gel electrophoresis, and by PCR detection and sequencing of bla(TEM), bla(SHV), bla(CTX-M) and bla(CMY). All horses were negative for CTX-resistant coliforms at admission but became positive within the first three days of treatment. The average faecal densities of CTX-resistant coliforms increased significantly following antimicrobial prophylaxis (P<0.001). Genetic characterization of 29 faecal isolates revealed that this effect was due to proliferation of E. coli producing either CTX-M-1 (n=28) or CTX-M-14 (n=1). Five CTX-M-1 isolates produced additional β-lactamases (TEM-1, CMY-34 and the novel variant CMY-53). Shedding of CTX-M-producing E. coli appeared intermittent in four horses and persisted two weeks after antimicrobial treatments in five of six patients tested after discharge from hospital. Nosocomial transmission was suggested by finding five identical CTX-M-1-producing E. coli pulsotypes in multiple horses. The originality of the study lies in the unanticipated high frequency and genetic diversity of CTX-M-producing E. coli observed in the faecal flora of hospitalized patients receiving broad-spectrum antimicrobial prophylaxis.  相似文献   

3.
The objective of this study was to isolate and characterize ESBL-producing Escherichia coli (ESBL-EC) from raw bovine and caprine milk samples, as well as from bovine faeces in Tunisia. Therefore, 120 bovine faecal samples and 9 caprine raw milk samples were collected from 2 extensive dairy-cow-farms and 5 ovine farms, respectively. In addition, 94 raw bovine milk samples, from containers and holding tanks from 50 small public-markets in the North of Tunisia, were processed for the isolation of cefotaxime-resistant E. coli (CTXR). Antimicrobial susceptibility testing was carried out by disc-diffusion/broth-microdilution methods. The presence of genes encoding ESBL, as well as those encoding colistin (mcr-1 to 5 genes)- sulfonamide-, tetracycline-, gentamicin-, quinolone and chloramphenicol-resistance and class 1 integrons were tested by PCR (and sequencing in some cases). ESBL-EC isolates were further characterized by phylogrouping and MLST/PFGE typing. Eight samples (3.6%) contained ESBL-EC isolates (3/2 from raw bovine/goat milk and 3 from cattle faeces) and one isolate/sample was characterized. Four ESBL-EC isolates, all of bovine origin (3 faeces/1 milk), were resistant to colistin (MIC: 8–16 μg/ml), harboured the mcr-1 gene and carried IncP- and IncFIB-type plasmids. The 8 ESBL-EC strains had the following characteristics: a) bovine faeces: mcr-1/CTX-M-1/D-ST1642 (3 strains); b) raw milk: mcr-1/CTX-M-1/A-ST10 (1 strain); CTX-M-15/B1-ST394 (3 strains), and CTX-M-15/A-ST46 (1 strain). Most of bovine ESBL-EC isolates were multidrug-resistant (4/5). Our results showed that ESBL-EC were detected in bovine and caprine samples (CTX-M-1/CTX-M-15 producers), being some of them colistin-resistant (associated with mcr-1 gene), and they belonged to international clonal lineages.  相似文献   

4.
The aim of the study was to compare the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli bovine isolates on a conventional dairy cattle farm with high consumption of parenteral and intramammary cephalosporins (farm A) and on an organic dairy farm with no cephalosporin use (farm B). ESBL-producing E. coli were isolated from rectal swabs and milk filters by selective cultivation on MacConkey agar with cefotaxime (2mg/l). ESBL genes were identified by polymerase chain reaction (PCR) and sequencing, and the genetic diversity of the isolates was determined by XbaI pulsed field gel electrophoresis (PFGE). Conjugative transfer, incompatibility group, and restriction fragment length polymorphism (RFLP) profiles of the ESBL-carrying plasmids were studied. Higher prevalence (39%, n(rectal samples in cows)=309) of CTX-M-1-producing E. coli isolates was found on farm A compared to farm B (<1%, n(rectal samples in cows)=154; 0%, n(rectal samples in calves)=46). Using PFGE, the isolates from farm A were divided into nine pulsotypes. In all ESBL-positive isolates, the bla(CTX-M-1) gene was carried on 40 kb IncN conjugative plasmids of three related HincII restriction profiles. Horizontal gene transfer through transmission of IncN plasmids harboring bla(CTX-M-1) as well as clonal dissemination of a particular clone seems to be involved in dissemination of CTX-M-1-producing E. coli isolates in cows on the farm using cephalosporins in treating bacterial infections. The study demonstrates a possible role of cephalosporin use in the widespread occurrence of CTX-M-1-producing E. coli on the conventional dairy cattle farm compared to the organic farm.  相似文献   

5.
This study investigated the potential spread of CTX-M-14 Escherichia coli from a known ESBL E. coli positive farm and risk factors for the presence of CTX-M E. coli on dairy farms. Between November 2009 and March 2010, 65 farms in North West England and North Wales were visited and animals sampled for E. coli producing CTX-M ESBLs. Seventeen of these were known to have received animals from a known ESBL E. coli positive 'index' farm since 2005 (linked farms). The prevalence of CTX-M E. coli in the population of linked farms was 58.8% (10/17; CI(95%) 32.9-81.6%) and in the randomly selected control population was 35.4% (17/48; CI(95%) 22.2-50.5%). There was no significant (p>0.05) linkage for the detection of any CTX-M E. coli or specifically a CTX-M-14 E. coli to the index farm. Group 1 (CTX-M-15, CTX-M-55, CTX-M-1, CTX-M-32), group 2 (CTX-M-2) and group 9 (CTX-M-14, CTX-M-14B, CTX-M-27) CTX-M E. coli were identified on the study farms. Molecular analysis revealed that three plasmids from linked farms had similar sizes (95kbp), replicon type (IncK) and backbone genes as that from the index farm. Logistic regression analysis revealed that farms that had used a 3rd or 4th generation cephalosporin (ceftiofur, cefoperazone and cefquinome) in livestock in the last 12months were nearly 4times more likely to have ESBL E. coli present (p=0.037; OR=3.93). There was no significant association between presence of CTX-M E. coli and the use of any 1st or 2nd generation cephalosporins. Several other risk factors for the presence of CTX-M E. coli were identified, such as storage of slurry in a pit, operating an open herd policy and infrequent cleaning of calf feeding equipment.  相似文献   

6.
Wang Y  He T  Han J  Wang J  Foley SL  Yang G  Wan S  Shen J  Wu C 《Veterinary microbiology》2012,159(1-2):53-59
The aim of this study is to characterize the prevalence of extended-spectrum β-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR) genes in Escherichia coli from captive non-human primates. A total of 206 E. coli isolates were collected from primates in six zoos in China in 2009 and their susceptibility to 10 antimicrobials were tested by broth microdilution. The susceptibility patterns of E. coli strains varied greatly among different zoos reflecting different backgrounds of antimicrobial usage. Both the ESBL-encoding genes and the PMQR genes were detected by PCR. Of the 206 strains, 65 (32%) were confirmed as phenotypic ESBL producers with bla(CTX-M) (27%, bla(CTX-M-15), n=31, bla(CTX-M-3), n=23 and bla(CTX-M-14), n=2) mainly mediating the ESBL phenotype. qnrS1 (18%, n=36) and oqxAB (15%, n=31) were the predominant PMQR genes and the prevalence of PMQR genes was much higher among phenotypic ESBL producers than that among phenotypic non-ESBL producers from any zoo. Notably, the PMQR genes qnrS1 and oqxAB and β-lactamase genes bla(TEM-1) and bla(CTX-M-3) were found together in 23 E. coli isolates in two zoos in Shanghai. PFGE analysis of these 23 isolates demonstrated nearly identical PFGE profiles (similarity matrix >97%) indicating this specific E. coli genotype was prevalent in these two zoos. To the best of our knowledge, this is the first report of these four genes coexisting in an E. coli genotype and the first report of antimicrobial resistance profiles in E. coli isolated from primates in China.  相似文献   

7.
To evaluate the diversity of extended-spectrum β-lactamases (ESBL) genes among food-producing animals, 48 isolates of ESBL-producing Escherichia coli isolates were obtained from rectal samples of broilers, layers, beef cattle and pigs, at the slaughterhouse level. ESBL-carrying E. coli were isolated from 60.0% of individual broiler rectal samples, 5.9% of layers, 12.5% of beef cattle and 3% of pigs. One ESBL-producing Klebsiella pneumoniae was isolated from a broiler. The ESBL-positive E. coli isolates from broilers harbored various ESBL genes: bla (SHV-12), bla(CTX-M-2), bla(CTX-M-14), bla(CTX-M-15) and bla(CTX-M-44). The plasmid DNAs were analyzed by restriction patterns. Homogeneous band patterns were yielded in those of K. pneumoniae and E. coli isolates harboring the bla(CTX-M-2) gene from different farms. No genetic relation between the 2 CTX-M-14 ESBL-producing strains was found by pulsed-field gel electrophoresis, although 2 plasmids in these strains, obtained from different broiler farms, were similar to each other. This study provides evidence that the proliferation of CTX-M-producing E. coli is due to the growth of indigenous CTX-M-producing strains and the possible emergence of strains that acquired CTX-M genes by horizontal transfer in different broiler farms. CTX-M-producing coliforms in broilers should be controlled due to the critical importance of cephalosporins and the zoonotic potential of ESBL-producing bacteria.  相似文献   

8.
Recent data from the European and Hungarian Antimicrobial Resistance Monitoring Systems have indicated that the routine use of gentamicin in human and veterinary medicine frequently leads to the selection of gentamicin resistance in Escherichia coli. The aim of this study was to provide molecular characterization of gentamicin resistance in clinical and commensal E. coli strains representing humans and food producing animals by genotyping for antimicrobial resistance and virulence using a miniaturized microarray. All 50 strains tested proved to be multidrug resistant defined as resistance to three or more antimicrobial classes. Antimicrobial resistances genes such as aadA1-like, strB, bla(TEM), sul1 and tet(A) or tet(B), and corresponding phenotypes (streptomycin-, ampicillin-, sulfamethoxazole- and tetracycline resistance) were detected in >50% of isolates regardless of the host or clinical background. However, certain genes encoding gentamicin resistance such as aac(6')-Ib and ant(2″)-Ia as well as catB3-like genes for phenicol resistance were only detected in human isolates. Among virulence genes, the increased serum survival gene iss was predominant in all host groups. Although the majority of gentamicin resistant E. coli strains were characterized by diverse antimicrobial resistance, and virulence gene patterns, accentuated links between catB3-like, aac(6')-Ib, bla(CTX-M-1) and sat genes could be detected in human strains. Further resistance/virulence gene associations (tet(A) with iroN and iss) were detected in poultry strains. In conclusion, the simultaneous characterization of antimicrobial resistance and virulence genotypes of representative clinical and commensal strains of E. coli should be useful for the identification of emerging genotypes with human and or animal health implications.  相似文献   

9.
BackgroundKlebsiella spp. is an important conditional pathogen in humans and animals. However, due to the indiscriminate use of antibiotics, the incidence of antimicrobial resistance has increased.ObjectivesThe purpose of this study was to investigate antimicrobial resistance in strains of Klebsiella strains and the phylogenetic relatedness of extended-spectrum cephalosporin (ESC)-resistance among Klebsiella strains isolated from clinically ill companion animals.MethodsA total of 336 clinical specimens were collected from animal hospitals. Identification of Klebsiella species, determination of minimum inhibitory concentrations, detection of ESC resistance genes, polymerase chain reaction-based replicon typing of plasmids by conjugation, and multilocus sequence typing were performed.ResultsForty-three Klebsiella strains were isolated and, subsequently, 28 were identified as K. pneumoniae, 11 as K. oxytoca, and 4 as K. aerogenes. Eleven strains were isolated from feces, followed by 10 from ear, 7 from the nasal cavity, 6 from urine, 5 from genitals, and 4 from skin. Klebsiella isolates showed more than 40% resistance to penicillin, cephalosporin, fluoroquinolone, and aminoglycoside. ESCresistance genes, CTX-M groups (CTX-M-3, CTX-M-15, and CTX-M-65), and AmpC (CMY-2 and DHA-1) were most common in the K. pneumoniae strains. Some K. pneumoniae carrying CTX-M or AmpC were transferred via IncFII plasmids. Two sequence types, ST709 and ST307, from K. pneumoniae were most common.ConclusionsIn conclusion, this is the first report on the prevalence, ESCresistance genotypes, and sequence types of Klebsiella strains isolated from clinically ill companion animals. The combination of infectious diseases and antimicrobial resistance by Klebsiella in companion animals suggest that, in clinical veterinary, antibiotic selection should be made carefully and in conjunction with the disease diagnosis.  相似文献   

10.
Faecal samples of healthy dogs (n=39) and cats (n=36) obtained in Northern Portugal were seeded on Levine agar plates, and two Escherichia coli isolates per sample were recovered (78 of dogs and 66 of cats). The susceptibility to 16 antimicrobial agents was tested in this series of 144 E. coli isolates. Almost 20% of them showed tetracycline resistance and 12 and 15% presented ampicillin or streptomycin resistance, respectively. The percentage of resistance to the other antimicrobial agents was in all cases below 4%, and no resistant isolates were detected for ceftazidime, imipenem, cefoxitin or amikacin. Two isolates (from one dog) showed cefotaxime-resistance and harboured both the CTX-M-1 and OXA-30 beta-lactamases. A bla(TEM) gene was detected in 12 of 17 ampicillin-resistant isolates, the aac(3)-II gene in the three gentamicin-resistant isolates, aadA in 7 of 22 streptomycin-resistant isolates, and tet(A) and/or tet(B) gene in all 28 tetracycline-resistant isolates. The gene encoding class 1 integrase was detected in six E. coli isolates, including the four trimethoprim-sulfamethoxazole-resistant isolates and those two harbouring CTX-M-1 and OXA-30 beta-lactamases; different gene cassette arrangements were identified: dfrA1+aadA1 (two isolates), dfrA12+orfF+aadA2 (two isolates) and bla(OXA30)+aadA1 (two isolates). One amino acid change in GyrA protein (Ser83Leu or Asp87Tyr) was detected in four nalidixic acid-resistant and ciprofloxacin-susceptible isolates and two amino acid changes in GyrA (Ser83Leu+Asp87Asn) and one in ParC (Ser80Ile) were identified in one nalidixic acid- and ciprofloxacin-resistant isolate. Faecal E. coli isolates of healthy pets could be a reservoir of antimicrobial resistance genes.  相似文献   

11.
The objective of this clinical trial was to examine the effect of a single dose of florfenicol on antimicrobial resistance patterns in faecal E. coli of feedlot steers. Steers (n = 370), were purchased from two sources and housed in outdoor concrete floored pens. Two cattle from each pen (n = 42 pens, 84 cattle) were randomly selected for faecal sampling at study day 1, 14, 28, and 42. One sampled animal from each of 21 pens was randomly selected to receive a single 39.6 mg/kg dose of florfenicol subcutaneously at study day 11. Ten lactose positive colonies were isolated from faecal swabs and tested for antimicrobial resistance to 11 antimicrobials using the disk diffusion method. Zones of inhibition were grouped using cluster analysis and clusters were ordered by increasing multiple resistance. A cumulative logistic regression model using generalized estimating equations was used to assess factors associated with increasing levels of multiple resistance. Immediately post-treatment, all isolates obtained from treated cattle belonged to multiple resistant clusters containing chloramphenicol resistance. Though less pronounced in later sampling, resistance to chloramphenicol and other antimicrobials persisted. Antimicrobial treatment, sampling time and animal source, as well as interactions between these variables, were important predictors of the odds of E. coli belonging to a more resistant cluster. A very clear but transitory shift to increasingly multiple resistant faecal E. coli in response to florfenicol treatment was observed. There was no indication of horizontal transfer of resistant E. coli between steers. Level of resistance was influenced by complex interaction of animal source and previous management.  相似文献   

12.
The aim of the present study was to contribute to the knowledge on extended-spectrum beta-lactamases (ESBL's), AmpC beta-lactamases and integrons in Enterobacteriaceae isolated from horses, which is still limited. The susceptibility of 1581 clinical isolates from animals to ceftiofur was tested. Most of these isolates (n=1347) originated from horses. Seven ceftiofur-resistant equine isolates (four Escherichia coli and three Klebsiella pneumoniae) were identified and all seven were multidrug-resistant. These isolates were further studied for the presence of ESBL's, AmpC beta-lactamases and class 1 integrons. The potential for the horizontal transfer of resistance genes among these clinical isolates was also studied. ESBL-type resistance genes were found in five isolates, AmpC-type genes in one isolates and integrons in six isolates. Nucleotide sequence analysis revealed that the isolates carried the bla(CTX-M-1), bla(CMY-2), bla(TEM-1) and/or bla(SHV-1) genes. This is the first report describing the in vitro conjugal transfer of the bla(CTX-M-1) genes from a clinical E. coli isolate to Salmonella isolates. Gene cassettes encoding resistance to aminoglycosides (aadA1, aadA2 and aadA5), and trimethoprim (dfrA1, drfA12 and dfrA17) were found on the integrons present in the isolates. The cassette arrays of the dfrA17-aadA5 and dfrA1-aadA1 genes in the two integrons of a single E. coli isolate have not yet been described before. To our knowledge this is the first report on ESBL's and AmpC beta-lactamases in equine E. coli and Klebsiella isolates.  相似文献   

13.
The objectives of this study were to determine the prevalence of antimicrobial resistance (AMR) in faecal Campylobacter spp. from lambs and adult sheep and associations between antimicrobial use (AMU) and AMR. A total of 275 faecal samples collected during initial and final visits from 51 sheep flocks, including one feedlot, across southern Ontario were tested for the presence of Campylobacter spp. Campylobacter jejuni was detected in 52% (143/275) of the faecal samples, Campylobacter coli in 7% (19/275), Campylobacter lari in 1% (2/275) and 2% (4/275) were non-speciated Campylobacter. Broth microdilution was used to test antimicrobial susceptibility of 162 isolates to nine antimicrobials. Campylobacter jejuni isolates (n = 142) were resistant to tetracycline (39%), ciprofloxacin (4%), nalidixic acid (4%) and telithromycin (1%). C. coli isolates (n = 19) were resistant to tetracycline (74%), and azithromycin, clindamycin, erythromycin, and telithromycin (5%). The C. lari isolate displayed resistance to nalidixic acid. No statistically significant associations were found between AMU and AMR during multivariate modelling in this study.  相似文献   

14.
A total of 318 Escherichia coli isolates obtained from different food-producing animals affected with colibacillosis between 2001 and 2006 were subjected to phylogenetic analysis: 72 bovine isolates, 89 poultry isolates and 157 porcine isolates. Overall, the phylogenetic group A was predominant in isolates from cattle (36/72, 50%) and pigs (101/157, 64.3%) whereas groups A (44/89, 49.4%) and D (40/89, 44.9%) were predominant in isolates from poultry. In addition, group B2 was not found among diseased food-producing animals except for a poultry isolate. Thus, the phylogenetic group distribution of E. coli from diseased animals was different by animal species. Among the 318 isolates, cefazolin resistance (minimum inhibitory concentrations: ≥32 μg/ml) was found in six bovine isolates, 29 poultry isolates and three porcine isolates. Of them, 11 isolates (nine from poultry and two from cattle) produced extended spectrum β-lactamase (ESBL). The two bovine isolates produced blaCTX-M-2, while the nine poultry isolates produced blaCTX-M-25 (4), blaSHV-2 (3), blaCTX-M-15 (1) and blaCTX-M-2 (1). Thus, our results showed that several types of ESBL were identified and three types of β-lactamase (SHV-2, CTX-M-25 and CTX-M-15) were observed for the first time in E. coli from diseased animals in Japan.  相似文献   

15.
Sixty Actinobacillus pleuropneumoniae (App) strains from pigs in Taiwan were examined. Serotyping revealed that these belonged to serovars 1 (n=53), 2 (n=3), and 5 (n=4). Agar disk diffusion susceptibility testing of the isolates showed 55 (92%) were resistant to three or more antimicrobial agents. Six resistance patterns were observed. Ampicillin-chloramphenicol-flumequine-nalidixic acid-streptomycin-sulfonamide/trimethoprim-tetracycline was the most common multi-resistance pattern. Minimal inhibitory concentration of 14 antimicrobial agents was determined. The isolates were highly susceptible to ceftiofur and trimethoprim in vitro. Isolates were resistant to streptomycin, ampicillin, and nalidixic acid. All isolates were examined for the presence of plasmids using the alkaline lysis method. Forty three (72%) isolates had four plasmid bands with an approximate sizes of 3.5, 4.3, 5.8 and 6.0 kb; 12 (20%) had three bands at 3.5, 4.3 and 5.2 kb, and 5 (8%) had no plasmid bands. Antimicrobial resistance plasmids were detected in resistant strains of App. Three antimicrobial resistance plasmids were transformed into E. coli DH5 alpha. pTMY1 (4.3 kb) encoded a streptomycin kinase and a dihydropteroate synthase; pTMY2 (6.0 kb) encoded ROB-1 beta-lactamase and aminoglycoside 3'-phosphotransferase; pTMY3 (5.2 kb) encoded only ROB-1 beta-lactamase. The 4.3 kb plasmid was sequenced and consisted of 4242 bp with 42.9% GC content. The 4.3 kb plasmid DNA sequence was 98% homologous to a plasmid previously isolated from Pasteurella haemolytica.  相似文献   

16.

Background

Sulfonamide resistance is very common in Escherichia coli. The aim of this study was to characterize plasmids carrying sulfonamide resistance genes (sul1, sul2 and sul3) in E. coli isolated from pigs and humans with a specific objective to assess the genetic diversity of plasmids involved in the mobility of sul genes.

Methods

A total of 501 E. coli isolates from pig feces, pig carcasses and human stools were tested for their susceptibility to selected antimicrobial. Multiplex PCR was conducted to detect the presence of three sul genes among the sulfonamide-resistant E. coli isolates. Fifty-seven sulfonamide-resistant E. coli were selected based on presence of sul resistance genes and subjected to conjugation and/or transformation experiments. S1 nuclease digestion followed by pulsed-field gel electrophoresis was used to visualize and determine the size of plasmids. Plasmids carrying sul genes were characterized by PCR-based replicon typing to allow a comparison of the types of sul genes, the reservoir and plasmid present.

Results

A total of 109/501 isolates exhibited sulfonamide resistance. The relative prevalences of sul genes from the three reservoirs (pigs, pig carcasses and humans) were 65%, 45% and 12% for sul2, sul1, and sul3, respectively. Transfer of resistance through conjugation was observed in 42/57 isolates. Resistances to streptomycin, ampicillin and trimethoprim were co-transferred in most strains. Class 1 integrons were present in 80% of sul1-carrying plasmids and 100% of sul3-carrying plasmids, but only in 5% of sul2-carrying plasmids. The sul plasmids ranged from 33 to 160-kb in size and belonged to nine different incompatibility (Inc) groups: FII, FIB, I1, FIA, B/O, FIC, N, HI1 and X1. IncFII was the dominant type in sul2-carrying plasmids (52%), while IncI1 was the most common type in sul1 and sul3-carrying plasmids (33% and 45%, respectively). Multireplicons were found associated with all three sul genes.

Conclusions

Sul genes were distributed widely in E. coli isolated from pigs and humans with sul2 being most prevalent. Sul-carrying plasmids belonged to diverse replicon types, but most of detected plasmids were conjugative enabling horizontal transfer. IncFII seems to be the dominant replicon type in sul2-carrying plasmids from all three sources.  相似文献   

17.
In order to evaluate the genetic variability of the causative agent of cold water disease (CWD), plasmid profiling was used to characterize Flavobacterium (F.) psychrophilum isolates (n = 169). Size analysis of plasmids in F. psychrophilum isolates (n = 128) from several fish species demonstrated that six kinds of plasmids were harbored, and ayu isolates had different profiles compared to other isolates. Moreover, multiple isolates (n = 41) from CWD outbreaks in 2002 to 2003 at a single ayu farm were examined to determine differences between isolates from successive outbreaks and showed different profiles by the sources of seedlings.  相似文献   

18.
Between November 5, 2007 and November 4, 2008, faecal samples from cattle and sheep submitted for diagnostic purposes to the Aberystwyth and Shrewsbury Veterinary Laboratories Agency (VLA) (now AHVLA) regional laboratories (covering North Wales and the West Midlands) were screened for the presence of Escherichia coli that produces CTX-M extended-spectrum β-lactamase (ESBL) using the selective medium CHROMagar CTX. Samples from 113 farms were tested and eight ESBL-positive farms identified. Of these, six farms were identified via submissions of cattle faeces and two from sheep. Gene sequencing revealed both group 1 and group 9 CTX-M enzymes corresponding to CTX-M-14, CTX-M-14B (group 9) and CTX-M-15/28 (group 1). Analysis of these isolates by nanoarray revealed that some were carrying a range of virulence genes including ireA, iroN and prfB, which have been associated with extraintestinal pathogenic E coli, and were multidrug resistant. Geographical analysis with choropleth maps suggested that these CTX-M genes are relatively widespread in the North Wales and West Midlands study area. This work was carried out concurrently with the running of a VLA ESBL surveillance system, which has subsequently identified many more CTX-M positive farms in the UK.  相似文献   

19.
Duplex real-time PCR assays were used as modules to cover partially automated detection of 12 genes encoding adhesins, enterotoxins and Shiga toxins in faecal E. coli isolates. For this a total of 194 E. coli isolates from pigs suffering from post-weaning diarrhoea (PWD), including 65 isolates with haemolytic activity, and 83 isolates from calves with diarrhoea were examined. Data obtained by PCR were compared with O-typing and with haemolytic activity as indirect virulence markers. E. coli O-types O139:K82, O141:K85, and O149:K91 accounted for 43.8% (n = 85) of all porcine strains and for 55.4% (n = 36) of the porcine strains, which exhibited haemolytic activity. These strains carried virulence genes by 65.9% (n = 56) and 80.6% (haemolytic E. coli, n = 29), respectively. The E. coli O-types O139:K82 and O141:K85 were significantly associated with the adhesin gene F18, and O149:K81 with the F4 gene. In this context, detection of the gene encoding F18 was coupled predominantly with the genes responsible for the production of the toxins ST-I, ST-II and Stx2, and the F4 gene with those of the enterotoxins ST-I, ST-II and LT. Both virulence patterns were detected more pronounced in E. coli strains with haemolytic activity. Fifty-six of a total of 83 E. coli isolates originating from calves were O-typed as O101 (O101:K28, O101:K30, O101:K32; n = 29), O78:K80 (n = 23), and O9:K35 (n = 4). Most of the E. coli O78:K80 strains carried the F17 gene (69.6%, n = 16). Virulence genes encoding for F4, F5 or ST-I were detected only in single cases. Intimin and Shiga toxin genes that are present in enterohaemorrhagic E. coli (EHEC) were not detected.  相似文献   

20.
The antimicrobial sensitivities of 78 recent (1995-1998) canine isolates of Bordetella bronchiseptica from 13 separate sources were determined. Minimum inhibitory concentrations were assessed using the E-test method or by agar dilution. All 78 isolates were sensitive to tetracycline, doxycycline, enrofloxacin, and amoxycillin/clavulanic acid; the majority were sensitive to ampicillin (63/78; 81%), trimethoprim (57/78; 73%), and sulphadiazine (63/78; 81%). Plasmids were detected in 14 out of the 24 isolates tested. There was no correlation between the presence of plasmids and antibiotic resistance, but there was some correlation between the presence of plasmids and the origin of the isolates. Three sizes of plasmid were found: 20, 14, and 5.5 kb. Eight of the isolates contained all three plasmids, the remainder one or two, Thirteen isolates demonstrated beta-haemolysis, of which six produced a soluble haemolysin. Except for one isolate, haemolysin production correlated with plasmid carriage. Pulsed-field gel electrophoresis showed that all except one isolate could be grouped in the same genotype. Within this genotype isolates could be divided into three subtypes, generally corresponding to their place of origin.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号