The resistance to chemotherapeutic agents of Escherichia coli from domestic dogs and cats

The prevalence of antibiotic resistant Escherichia coli in the rectal flora of 168 healthy dogs and 93 cats in the Brisbane area was investigated. Rectal swabs were plated on MacConkey agar with and without antibiotics, and 690 isolates confirmed as faecal E. coli were tested for resistance to tetracycline, streptomycin, chloramphenicol, ampicillin, neomycin, furazolidone and sulphanilamide. Resistant isolates were obtained from 101 (60%) of the dogs and 24 (26%) of the cats sampled. A high percentage of the isolates was resistant to tetracycline, streptomycin, ampicillin and sulphanilamide. Multiple resistance to 3 or more of the drugs was exhibited by the majority of isolates and a total of 31 different multiple resistance patterns was demonstrated. Of the 50 strains tested for transfer of resistance, 30 (60%) transferred some or all of their resistance determinants to an E. coli K12F - recipient.     

Incidence of drug resistance and transmissible R factors in strains of E. coli isolated from faeces of healthy pigs

Two hundred and twenty-six strains of E. coli were isolated from faeces of 107 pigs at different ages and without clinical signs of infectious diseases. The resistance of the strains to sulphonamide, tetracycline, streptomycin, chloramphenicol, ampicillin, and nalidixic acid was determined. In 74 % of the animals the predominant E. coli flora was found to be resistant to one or more of the drugs mentioned. Fifty-three % of the strains were resistant. Multiple resistance was predominant among resistant strains (67 %). R factors transmissible to a sensitive strain of E. coli K12 W3132 were demonstrated in 28 %. The proportion of resistant strains was largest in young animals (0–14 weeks) accounting for 65 % of the strains isolated, as compared to 43 % of strains from pigs and sows (6 months or more). The incidence of resistance to sulphonamide, tetracycline, and streptomycin was high, whereas most of the strains were sensitive to ampicillin and chloramphenicol. All strains were sensitive to nalidixic acid.The incidence of resistance to antibiotics in a population of pigs to whom these drugs are not fed but applied as therapeutic agents solely seems rather high. When based on clinical findings only, the value is therefore questionable of sulphonamide, tetracycline and streptomycin treatment of infectious diseases caused by E. coli.     

Antimicrobial resistance and resistance gene determinants in clinical Escherichia coli from different animal species in Switzerland

Antimicrobial susceptibility testing was performed on a total of 581 clinical Escherichia coli isolates from diarrhea and edema disease in pigs, from acute mastitis in dairy cattle, from urinary tract infections in dogs and cats, and from septicemia in laying hens collected in Switzerland between 1999 and 2001. Among the 16 antimicrobial agents tested, resistance was most frequent for sulfonamides, tetracycline, and streptomycin. Isolates from swine presented significantly more resistance than those from the other animal species. The distribution of the resistance determinants for sulfonamides, tetracycline, and streptomycin was assessed by hybridization and PCR in resistant isolates. Significant differences in the distribution of resistance determinants for tetracycline (tetA, tetB) and sulfonamides (sulII) were observed between the isolates from swine and those from the other species. Resistance to sulfonamides could not be explained by known resistance mechanisms in more than a quarter of the sulfonamide-resistant and sulfonamide-intermediate isolates from swine, dogs and cats. This finding suggests that one or several new resistance mechanisms for sulfonamides may be widespread among E. coli isolates from these animal species. The integrase gene (intI) from class I integrons was detected in a large proportion of resistant isolates in association with the sulI and aadA genes, thus demonstrating the importance of integrons in the epidemiology of resistance in clinical E. coli isolates from animals.     

Salmonella-associated conjunctivitis in a cat.

Salmonella typhimurium-associated conjunctivitis in an adult female cat was characterized by epiphora and blepharospasm. The cat also harbored intestinal S typhimurium, as did one other cat in the same shipment of 7 cats obtained from a commercial cat dealer. The 3 isolates were resistant to ampicillin, cephaloridine, cephalothin, streptomycin, triple sulfonamides, and tetracycline. All 3 isolates were capable of transferring a part of the antibiotic resistance pattern to an Escherichia coli K-12 recipient. Salmonella were not recovered from the conjunctiva or fecal flora of either cat after 10 days of therapy with chloramphenicol.     

Drug resistance in strains of Escherichia coli isolated from the intestinal tract of pigs in Norway.

Faecal samples from 95 healthy pigs and samples of jejunal content from 85 piglets suffering from colienterotoxaemia were tested for the presence of drug resistant E. coli strains. Practically all pigs in both groups harboured E. coli strains resistant to one or more of the 6 antibiotics/chemotherapeutic agents tested (Oxytetracycline, streptomycin, sulphaisodimidin, neomycin, ampicillin, chloramphenicol). Almost 100% of healthy and approx. 90% of diseased pigs harboured strains resistant to Oxytetracycline, streptomycin and sulphaisodimidin. Pigs with strains resistant to neomycin, ampicillin and chloramphenicol were less frequently found. The predominant coliform flora consisted of E. coli strains” resistant to Oxytetracycline, streptomycin and sulphaisodimidin in 71% to 81% of diseased pigs and in 47% to 69% of the healthy pigs. In diseased pigs ¾ of the animals had a coliform flora dominated by neomycinresistant E. coli strains.Of the 721 resistant E. coli strains isolated from healthy pigs, 11% were single resistant while the corresponding figure for the 518 resistant strains isolated from diseased pigs was 6%. Thus 89% and 94% of strains showed simultaneous resistance to 2 or more antibiotics. E. coli strains resistant to 3 or more drugs were found in approx. 60% and 70% of the isolates from healthy and diseased animals, respectively. Oxytetracycline/streptomycin/sulphaisodimidin resistance was most commonly found, approx. 22% and 38% of the strains from healthy and diseased pigs, respectively, showing this resistance pattern.Transmission of drug resistance which was examined in E. coli strains originating from the diseased pigs was demonstrated in approx. 76% of the isolates. The incidence of drug resistance transfer in single, double, triple and quadruple resistant strains was 11%, 68%, 97% and 98%, respectively.     

Associations of antimicrobial uses with antimicrobial resistance of fecal Escherichia coli from pigs on 47 farrow-to-finish farms in Ontario and British Columbia

This study assessed the associations between antimicrobial use and other management practices in pigs and antimicrobial resistance in generic Escherichia coli recovered from feces of weaner and finisher pigs on 39 purposefully selected farrow-to-finish farms in Ontario and 8 in British Columbia. Antimicrobials (n = 13), most frequently penicillins and tetracycline, wer dministered to different age groups of pigs on study farms through various routes of administration. Logistic regression was used to model risk factors to antimicrobial resistance in fecal E. coli of pigs for the following antimicrobials: ampicillin, apramycin, carbadox, cephalothin, chloramphenicol, kanamycin, neomycin, nitrofurantoin, spectinomycin, streptomycin, sulfamethoxazole tetracycline, and cotrimoxazole (trimethoprim and sulfamethoxazole). Use of antimicrobials in weaner pigs compared with use in finisher pigs was associated with resistance in most models. There was phenotypic evidence of different mechanisms of resistance selection, including direct selection [use of carbadox was associated with carbadox resistance (OR = 6.48)]; cross-resistance [use of spectinomycin was associated with streptomycin resistance (OR = 2.29)]; and possible co-selection [ceftiofu use was associated with tetracycline resistance (OR = 6.12)]. These results provide further evidence that use of antimicrobials in pigs selects for resistance among fecal E. coli within and between classes of antimicrobials.     

Susceptibility to antibiotics of Escherichia coli strains isolated from diarrhoeic and non-diarrhoeic livestock in Trinidad.

The sensitivity of strains of Escherichia coli isolated from calves, piglets, lambs and kids in Trinidad to seven antibiotics was determined. Two hundred and sixty-four (91.3%) of 289 strains isolated from diarrhoeic animals and 173 (87.4%) of 198 strains from non-diarrhoeic animals exhibited resistance to one or more antibiotics. The difference was not statistically significant (P > or = 0.05; X2). Regardless of health status, isolates from lambs were least resistant (75.0%) and those from piglets most resistant (96.7%) and the difference was significant (P < or = 0.001; X2). Strains of E. coli were most resistant to streptomycin (81.3%) and tetracycline (78.9%) and least resistant to chloramphenicol (4.3%) and gentamycin (4.7%). The predominant antibiotic resistance pattern for isolates from all sources was streptomycin-tetracycline (27.9%). It was concluded that the widespread prevalence of resistance to antibiotics reflects their misuse in the local environment.     

Study on Molecular Characterization of Class Ⅰ Integron and Integron-associated Antimicrobial Resistance in Escherichia coli from Beef Cattle

To investigate the prevalence and molecular characterization of class Ⅰ integron in Escherichia coli isolated from beef cattle, and analyze the relationship between integron and antimicrobial resistance, susceptibilities to 11 antimicrobials were conducted on 92 isolates, the presence and characterization of class Ⅰ integrons and inserted gene cassettes were performed using PCR combined with sequencing analysis. The results showed that 29 isolates had been detected positive for class Ⅰ integron integrase gene (intⅠ1) among 92 isolates, and aadA1 and dfrA17＋aadA5 were the most prevalent gene cassette arrays detected. The resistance rates of 92 isolates to ampicillin, streptomycin, sulfisoxazole and tetracycline were all more than 45.0%. As revealed by analyzing the association between resistance phenotypes and class Ⅰ integron, isolates that contained the class Ⅰ integron were significantly highly resistant to ampicillin, chloramphenicol, streptomycin, sulfisoxazole and sulfamethoxazole-trimethoprim (P<0.05), but not to quinolones and amoxicillin/clavulanic acid. The conclusion was that E.coli isolated from beef cattle were seriously resistant to antimicrobials,and integron/cassettes widely existed. The presence of integrons and the association of antimicrobial resistance determinants with transferable elements might play a crucial role in the dissemination of antibiotic resistance among E.coli. Data reported here clearly emphasized the need for a stricter application of antimicrobials restriction policies in feedlot setting.     

Antibiotic resistance among indicator bacteria isolated from healthy pigs in New Zealand

AIM: To determine the resistance to antibiotics among the indictor bacteria, Escherichia coli and Enterococcus spp, isolated from the faeces of healthy pigs on three conventional pig farms and one organic farm in the North Island of New Zealand. METHODS: Faecal samples, collected at intervals between March and October 2001, were plated onto MacConkey agar and Slanetz-Bartley agar and examined after 1-3 days incubation for colonies resembling E. coli and Enterococcus spp, respectively. Typical colonies were subcultured for further identification and storage. The isolates were tested for antibiotic resistance, using disc diffusion, to ampicillin, gentamicin, streptomycin, and tetracycline. Escherichia coli isolates were also tested for resistance to ciprofloxacin, cotrimoxazole and neomycin. Enterococcus spp isolates were also tested for resistance to vancomycin, erythromycin and virginiamycin. RESULTS: A total of 296 E. coli and 273 Enterococcus spp isolates were obtained from the three conventional farms, and 79 E. coli and 80 Enterococcus spp isolates were obtained from the organic farm. All the E. coli isolates from both the conventional and organic pig farms were susceptible to ciprofloxacin, and all the Enterococcus spp isolates were susceptible to ampicillin, gentamicin and vancomycin. Isolates of E. coli from conventional pig farms were resistant to gentamicin (0.7%), neomycin (0.7%), ampicillin (2.7%), cotrimoxazole (11%), streptomycin (25%) and tetracycline (60%). Enterococcus spp isolates from the same farms were resistant to erythromycin (68%), tetracycline (66%), streptomycin (54%) and virginiamycin (49%). By contrast, for the organic pig farm 相似文献   

Antimicrobial susceptibility of Escherichia coli isolates from dairy farms using organic versus conventional production methods

OBJECTIVE: To compare antimicrobial susceptibility patterns of Escherichia coli isolates cultured from fecal samples from cows and calves on dairy farms that used organic (ie, no or severely limited antimicrobial use) versus conventional production methods. DESIGN: Cross-sectional study. SAMPLE POPULATION: Fecal samples from 10 cows and 10 calves on each of 30 organic dairy farms and 30 neighboring conventional dairy farms in Wisconsin. PROCEDURE: E. coli isolates obtained from the fecal samples were tested for susceptibility to 17 antimicrobials by means of a microbroth dilution test. Prevalence of antimicrobial resistance was compared between organic and conventional dairy farms. RESULTS: E. coli was isolated from 1,121 (94%) fecal samples. Farm type (organic vs conventional) and animal age (cow vs calf) were significantly associated with odds that E. coli isolates would be resistant to various antimicrobials. After controlling for age, logistic regression analyses indicated that isolates from conventional dairy farms had significantly higher rates of resistance to ampicillin, streptomycin, kanamycin, gentamicin, chloramphenicol, tetracycline, and sulfamethoxazole than did isolates from organic dairy farms. However, no significant differences were detected for the 10 other antimicrobials that were tested. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that compared with isolates from conventional dairy farms, E. coli isolates from organic dairy herds have significantly lower prevalences of resistance to 7 antimicrobials; however, prevalence of resistance was not significantly different for 10 other antimicrobials. Resistance was more common for isolates from calves than for isolates from adult dairy cows.     

Prevalence of resistance to 11 antimicrobials among Campylobacter coill isolated from pigs on 80 grower-finisher farms in Ontario.

We carried out a cross-sectional study to investigate antimicrobial resistance patterns of Campylobacter coli isolated from Ontario grower-finisher pigs. From January to June 2004, 1200 samples were collected from 80 farms by obtaining a constant number (15) of fecal samples per farm. Susceptibility of the isolates to 11 antimicrobial drugs was determined by the agar-dilution technique. The overall prevalence of resistance to 1 or more antimicrobials among the isolates was 99.2%. High levels of resistance were observed for azithromycin, clindamycin, erythromycin, streptomycin, and tetracycline: 91.7%, 82.5%, 81.4%, 70.7%, and 63.7%, respectively. For sulfamethoxazole, ampicillin, and nalidixic acid, resistance was observed in 40.3%, 26.6%, and 22.7% of the isolates, respectively. Although at very low levels, resistance was observed for ciprofloxacin (a fluoroquinolone), chloramphenicol, and gentamicin: in 2.4%, 1.7%, and 0.2%, respectively. Many of the isolates (29.7%) were resistant to 5 antimicrobials, the most common being azithromycin, clindamycin, erythromycin, streptomycin, and tetracycline. Isolates from the same farm showed at least 5 patterns of resistance. Results from this study indicate high levels of resistance to the antimicrobial drugs most commonly used in the Canadian swine industry (macrolides, lincosamides, and tetracyclines) among C. coli isolated from grower-finisher pigs in Ontario. Macrolides and fluoroquinolones are the drugs most commonly used to treat severe human campylobacteriosis. Fortunately, at present, there is little resistance to fluoroquinolones among C. coli from pigs in Ontario.     

Antimicrobial resistant Escherichia coli isolates in cattle and house sparrows on two Czech dairy farms

Rectal smears of calves, cows and young bulls, as well as cloacal smears of house sparrows (Passer domesticus), from farms at the villages of Sumice and Troskotovice, Czech Republic, were examined for E. coli resistant to 12 antimicrobials. The resistant isolates were tested for antimicrobial-resistance genes and integrons. Totals of 40% (n=183), 3% (n=95), 0% (n=33), and 9% (n=54) of Escherichia coli isolates from calves, cows, young bulls and house sparrows, respectively, were antimicrobial resistant. The following genes were identified in cattle E. coli isolates: tetA, tetB (isolates resistant to tetracycline), bla(TEM) (beta-lactams), strA, aadA (streptomycin), sul1, sul2 (sulphonamides), and cat, floR (chloramphenicol). Seven of 16 antimicrobial-resistant calf isolates from the Sumice farm possessed class 1 integrons with the aadA1 gene cassette integrated, 1 kb in size. On the Troskotovice farm, eight of 57 antimicrobial-resistant calf isolates possessed class 1 integrons. Integrons of 1.5kb with the dhfr1- aadA1 gene cassette were found in four isolates, followed by a 1kb integron with the aadA1 gene found in three isolates, and a 1.7kb integron with the dhfr17-aadA5 gene cassette and the phenotype ASSuTSxtNaCipCCfG. The prevalence of resistant E. coli in calves compared to adult cattle was much higher and probably was influenced by oral antimicrobial usage in calves, feeding with milk and colostrum from treated cows, as well as mechanisms unrelated to antimicrobial drug selection. Although house sparrows lived together with the cattle and came into contact with cattle waste on the farm, they were not infected by resistant E. coli isolates with the same characteristics as those found in cattle.     

Prevalence of antimicrobial resistance among Salmonella on midwest and northeast USA dairy farms

The objective of this study was to determine the prevalence of antimicrobial resistance among Salmonella isolated from dairy herds in New York, Minnesota, Michigan, and Wisconsin, USA. Serogroup and antimicrobial susceptibility characteristics were determined for Salmonella from cattle and environmental samples collected during August 2000–October 2001 as part of a longitudinal study where 129 herds were visited at 2-month intervals. Salmonella isolates were tested (using a broth microdilution method) for susceptibility to amoxicillin/clavulanic acid, ampicillin, ceftiofur, ceftriaxone, cephalothin, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, nalidixic acid, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim/sulfamethoxazole. Of the 1506 isolates tested for minimum inhibitory concentrations to these 14 antimicrobial agents, 81.2% were pan-susceptible and for most herds (81.6%) the predominant antimicrobial resistance pattern was pan-susceptible. At least 1 Salmonella isolate resistant to 5 or more antimicrobial agents was found on 23.6% of herds. This resistance phenotype was most common among serogroups B and E1 and among samples from calves and farmer-designated sick cows. Resistant samples most frequently exhibited resistance to tetracycline, streptomycin, and/or ampicillin. No samples were resistant to ceftriaxone (though 13 were in the intermediate range), and very few samples were resistant to ciprofloxacin (n = 1), nalidixic acid (n = 5), or trimethoprim/sulfamethoxazole (n = 7).     

牛肉源大肠杆菌的耐药性检测及相关耐药基因分布

为了解牛肉源大肠杆菌的耐药性并检测其相关耐药基因分布,本研究选取了117株牛肉源大肠杆菌,经药敏纸片法对11种抗菌药物进行了药敏检测,并根据耐药表型利用普通和(或)多重PCR技术对耐四环素菌中tet(A)、tet(B)和tet(C)基因,耐氨苄西林菌中blaTEM1、blaPSE1和blaOXA1基因,耐链霉素菌中strA-strB、aadA1基因,耐磺胺类药菌中sul1、sul2和sul3基因进行了调查分析。结果显示,117株大肠杆菌对四环素、氨苄西林、链霉素和磺胺异恶唑的耐药率较高,分别为89%、42%、38%和22%。tet(A)基因是所有四环素耐药基因中最为流行的一种基因(55%);在检测的3个β-内酰胺类药物耐药基因中,最流行的为blaTEM1基因(73%);链霉素的耐药性主要由strA-strB基因(38%)编码;sul2基因在耐磺胺异恶唑菌中的检出率最高(77%)。结果表明本次分离的牛肉源大肠杆菌耐药非常严重,进一步肯定了肉牛业生产中抗菌药的使用对大肠杆菌耐药性的产生和发展所发挥的重要作用,提示食品动物养殖应严格控制饲料中抗菌药的滥用。     

Assessment of antibiotic resistance phenotype and integrons in Salmonella enterica serovar Typhimurium isolated from swine

Salmonella enterica serovar Typhimurium (S. Typhimurium) isolated and identified from swine were subjected for the analysis of antibiotic resistance pattern and clinically important class 1 and 2 integrons. In addition, S. Typhimurium isolates exhibiting ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline and florfenicol (ACSSuTF) resistance pattern as described in most Salmonella enterica serotype Typhimurium definitive type 104 (DT104) were characterized by polymerase chain reaction. All the isolates were resistant to more than four antibiotics and showed the highest resistance to streptomycin (94.1%), followed by tetracycline (90.1%), ampicillin (64.7%), chloramphenicol (56.8%) and gentamicin (54.9%). MIC value for the ten isolates ranged between 0.125-2 mug/ml for ciprofloxacin. Among the beta-lactams used, only one of the isolate exhibited resistance to ceftiofur (MIC 8 microg/ml). Sixty eight percent of these multi drug resistance (MDR) S. Typhimurium isolates carried clinically important class 1 integron with 1kb (aadA) and/or 2kb (dhfrXII-orfF-aadA2) resistance gene cassettes. This study reports the increasing trend of multi drug resistance (MDR) S. Typhimurium with clinically important class 1 integron in pigs. In addition, emergence of the ACSSuTF-type resistance in S. Typhimurium PT other than DT104 may limit the use of resistance gene markers in its detection methods by PCR.     

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.     

Escherichia coli isolates from young calves in Bavaria: in vitro susceptibilities to 14 anti-microbial agents

During the occasional testing of Escherichia coli from faecal samples of young calves we observed multi-resistant isolates. Because of the significance of E. coli as an indicator bacterium for resistance trends we tested E. coli populations of young calves over a longer period. Here we present the results of a retrospective study comparing isolates from 1998 to 2000. Moreover, we compared, in a clinical study, the resistance rates of E. coli populations from 67 hospitalized calves both before and after hospitalization (with or without anti-microbial therapy), and with their anamnestic data of antibiotic usage. The highest resistance rates were found to be more than 80% for tetracyclines, ampicillin, sulfonamide/trimethoprim combinations, and chloramphenicol. A significant increase or decrease over the years was not observed. In analysing the data of hospitalized calves, an increase of resistance to some anti-microbials had to be registered that seemed to be connected with the selective pressure due to agents used in the clinic. In comparing anamnestic data and resistance rates it became obvious that reliable data are not easily available and that a number of potential anti-microbial influence factors have to be taken into account.     

Antimicrobial resistance in generic fecal Escherichia coli from 29 beef farms in Ontario

The occurrence of antimicrobial resistance in generic Escherichia coli can serve as an indicator of the pool of resistance genes potentially available for transfer to pathogenic organisms. This study was conducted on 29 volunteer beef farms in Ontario to describe the prevalence and patterns of antimicrobial resistance in E. coli, and to describe changes in the prevalence of resistance during the feedlot stage of production. From the pooled fecal samples on 28 of the 29 farms, 31% of isolates from feedlots (n = 993) and 12% of isolates from cow-calf farms (n = 807) were resistant to one or more of 16 antimicrobials tested. No isolates were resistant to ceftriaxone, ciprofloxacin, gentamicin, or nalidixic acid, and < 1% of the pooled isolates were resistant to ceftiofur. Two percent of both feedlot and cow-calf isolates were resistant to > or = 5 antimicrobials. Cow-calf farms were at significantly lower risk than feedlots for having E. coli isolates that were resistant to streptomycin, sulfamethoxazole, and tetracycline. On average, the prevalence of sulfamethoxazole resistant E. coli isolates was significantly higher in calves than in cows. No resistance was observed to ceftriaxone or ciprofloxacin among isolates (n = 1265) obtained from individually sampled feedlot animals on 2 farms. Less than 1% of these isolates were resistant to gentamicin, nalidixic acid, and ceftiofur. From the individually sampled feedlot animals, resistance to streptomycin (on 1 farm), sulfamethoxazole, and tetracycline increased significantly from arrival to mid-point during the feeding period, and these levels persisted until market-readiness.     

In vitro susceptibility of Escherichia coli strains isolated from diarrhoeic lambs and goat kids to 14 antimicrobial agents

The in vitro activities of 14 anti-microbial agents were determined against 92 strains of E. coli isolated from lambs (60 strains) and kids (32 strains) affected by neonatal diarrhoea. The overall percentage of resistant strains to streptomycin, sulphadimethoxine and tetracycline was very high (above 70%). A high level of resistance (from 30% to 50%) to ampicillin, kanamycin, neomycin and chloramphenicol was also detected. The E. coli strains were highly susceptible to cephalosporins, polymyxin and quinolones. Most of the strains showed multiresistance: 77.2% of isolates were resistant to at least two antibiotics, 55.4% were resistant to at least four antibiotics and 33.7% were resistant to at least six antibiotics. A total of 34 antibiotypes could be distinguished.     

High prevalence and widespread distribution of multi-resistant Escherichia coli isolates in pigs and poultry in China

Escherichia coli play an important ecological role within resistant bacteria populations, and can be used as a bio-indicator of antimicrobial resistance. The aim of the present study was to use this feature of E. coli to investigate the prevalence of antimicrobial resistance and the degree of cross-species transmission of bacteria in pigs and poultry in China. A total of 592 E. coli strains, isolated from pigs and poultry (healthy and diseased animals), were tested for resistance to 22 antimicrobials representing eight antimicrobial drug types.E. coli isolates had high rates of resistance to ampicillin (99.5%), doxycycline (95.6%), tetracycline (93.4%), trimethoprim–sulfamethoxazole (74.3%), amoxicillin (65.1%), streptomycin (54.7%), and chloramphenicol (50.2%). Resistance to cephalosporins, quinolones, and aminoglycosides was also quite prevalent. The majority (81%) of isolates demonstrated multi-antimicrobial resistance, most commonly to 5–6 different antimicrobial types. One isolate was resistant to all 22 antimicrobials. Twenty-two cultures exhibiting multi-antimicrobial resistance were analysed by pulsed-field gel electrophoresis (PFGE) to assess their distribution between farms. Three distinct PFGE types were identified, indicating inter-farm transmission of multi-antimicrobial resistant bacteria. The study confirmed the presence and transmission of multi-antimicrobial-resistant E. coli strains amongst pigs and poultry in China and highlights the urgent need for appropriate monitoring programmes.