Antimicrobial-resistance trends in bacterial isolates from companion-animal community practice in the UK

We conducted a longitudinal, retrospective investigation of antimicrobial resistance in bacterial isolates obtained from canine and feline clinical cases in veterinary community practice in UK (1989–1997). Individual-drug resistance was examined using isolates of Escherichia coli and Staphylococcus spp. as Gram-negative and Gram-positive indicator organisms, respectively. The annual prevalence of resistance was calculated for each organism to each of nine (for E. coli) and 11 (for Staphylococcus spp.) selected antimicrobials. The annual prevalence of multiple-drug resistance (MDR) was calculated for E. coli, Proteus spp., Pseudomonas spp., staphylococci and streptococci.

Using a chi-square test for trend, significant rising trends were identified in individual resistance of E. coli to clavulanate-amoxycillin and streptomycin, and in MDR of E. coli, Proteus spp. and Pseudomonas spp.. Declining trends were identified in individual resistance of Staphylococcus spp. to ampicillin and penicillin. Comparison with previously reported results from a contemporaneous investigation of companion-animal hospital patients indicated that selection pressures acting on the two populations overlapped but were not identical.     

贵州省猪源大肠杆菌对四环素类药物的耐药性及耐药基因检测

为考察贵州省猪源大肠杆菌对四环素类抗菌药的耐药情况和耐药基因的流行情况,本试验采用微量肉汤稀释法测定783株分离于贵州省8个地区规模化养殖场的猪源大肠杆菌对6种四环素类药物的敏感性,并通过PCR方法检测其携带四环素耐药基因情况。结果显示,猪源大肠杆菌对土霉素、四环素、金霉素、多西环素、米诺环素和替加环素的耐药率分别为97.3%、97.6%、96.6%、89.3%、48.0%和34.2%;土霉素和四环素的耐药水平最高,其MIC₅₀分别为256 和128 μg/mL,而MIC₉₀均为512 μg/mL,四环素的耐药倍数高于土霉素;米诺环素和替加环素的耐药水平最低,其MIC₉₀分别为32和4 μg/mL,耐药倍数相同;耐药基因tetA、tetB、tetC、tetD和tetM的检出率分别为92.60%、41.50%、58.75%、58.62%和70.10%;耐药菌株中主要以tetA基因为主,且大多数以携带复合基因的形式存在;大肠杆菌对土霉素、四环素、金霉素、多西环素和米诺环素的耐药性分别与耐药基因tetB和tetM呈极显著相关（P<0.01）,tetD基因分别与对米诺环素和替加环素的耐药性呈极显著相关（P<0.01）。贵州省猪源大肠杆菌对四环素类药物的耐药情况十分普遍,尤其是四环素和土霉素,金霉素和强力霉素有高度耐药的趋势;外排泵是四环素类药物主要的耐药机制;在兽医临床上越来越严重的耐药情况与耐药基因的广泛存在有很大关系。     

Longitudinal study of antimicrobial-resistant commensal Escherichia coli in the faeces of horses in an equine hospital

The increasing prevalence of antimicrobial resistance in bacteria represents a considerable problem for human and veterinary medicine, causing complications in the treatment of infections. Resistance in Escherichia coli from horses has been documented in commensal and pathogenic strains, but little information exists regarding the prevalence of such bacteria in hospitalised horses or associated risk factors. A longitudinal cohort study was conducted of 103 horses admitted to a referral equine hospital for more than 48 h, with faecal samples collected on hospital admission and subsequently every two days until discharge. Horses undergoing radioactive gamma scintigraphic examination, un-weaned foals and mares with un-weaned foals were excluded. Data were collected from enrolled animals, including antimicrobial treatment history and hospitalisation details. Samples were cultured for resistant E. coli; isolates had their antimicrobial resistance profile determined. High sample prevalence for resistant E. coli was identified for all antimicrobials examined except co-amoxiclav. The prevalence of resistance was consistently lower at admission, rising to a peak 4 days post-admission. Risk factors were analysed using multilevel, multivariable modelling, which identified significant clustering of resistance outcomes within horses. For all outcomes except trimethoprim resistance, the day the sample was obtained was significant, with increased risk of resistance for samples taken on day 2 or later. Antimicrobial treatment in the previous seven days and increased total daily dosages of cotrimoxazole prescribed in the hospital in the previous 24-48 h were associated with increased risk. Location within the hospital and admission reason were significant risk factors for some resistance outcomes. High levels of multidrug-resistant E. coli (47.7% of samples) and extended spectrum β-lactamase-producing E. coli (27.3% of samples) were recovered; such bacteria could significantly complicate treatment if they were the cause of infection and may represent a risk to personnel in close contact with hospitalised horses.     

Effects of feeding wet corn distillers grains with solubles with or without monensin and tylosin on the prevalence and antimicrobial susceptibilities of fecal foodborne pathogenic and commensal bacteria in feedlot cattle

Distillers grains, a coproduct of ethanol production from cereal grains, are composed principally of the bran, protein, and germ fractions and are commonly supplemented in ruminant diets. The objective of this study was to assess the effect of feeding wet distillers grains with solubles (WDGS) and monensin and tylosin on the prevalence and antimicrobial susceptibilities of fecal foodborne and commensal bacteria in feedlot cattle. Cattle were fed 0 or 25% WDGS in steam-flaked corn-based diets with the addition of no antimicrobials, monensin, or monensin and tylosin. Fecal samples were collected from each animal (n = 370) on d 122 and 136 of the 150-d finishing period and cultured for Escherichia coli O157. Fecal samples were also pooled by pen (n = 54) and cultured for E. coli O157, Salmonella, commensal E. coli, and Enterococcus species. Antimicrobial resistance was assessed by determining antimicrobial susceptibilities of pen bacterial isolates and quantifying antimicrobial resistance genes in fecal samples by real-time PCR. Individual animal prevalence of E. coli O157 in feces collected from cattle fed WDGS was greater (P < 0.001) compared with cattle not fed WDGS on d 122 but not on d 136. There were no treatment effects on the prevalence of E. coli O157 or Salmonella spp. in pooled fecal samples. Antimicrobial susceptibility results showed Enterococcus isolates from cattle fed monensin or monensin and tylosin had greater levels of resistance toward macrolides (P = 0.01). There was no effect of diet or antimicrobials on concentrations of 2 antimicrobial resistance genes, ermB or tetM, in fecal samples. Results from this study indicate that WDGS may have an effect on the prevalence of E. coli O157 and the concentration of selected antimicrobial resistance genes, but does not appear to affect antimicrobial susceptibility patterns in Enterococcus and generic E. coli isolates.     

广东水禽源大肠埃希菌耐药性及氨基糖苷类耐药基因研究

为了调查广东地区水禽源大肠埃希菌对氨基糖苷类药物耐药现状和耐药基因的流行情况,探索大肠埃希菌的氨基糖苷类耐药基因型与耐药表型之间的关系,本研究采用琼脂梯度稀释法测定251株广东地区水禽源大肠埃希菌对氨基糖苷类药物的耐药性和采用PCR方法检测耐药基因。药敏试验结果显示,大肠埃希菌对链霉素耐药较严重,鸭源和鹅源的耐药率分别为81.58%和75.43%,对庆大霉素和卡那霉素较敏感,耐药率分别为25%和54.86%,对阿米卡星最为敏感,其中鸭源的菌株耐药率仅为1.32%。PCR方法检测显示,aadA1和aph(3′)-1检出率较高,为84.6%和91.9%,表明携带aadA1和aph(3′)-1耐药基因的水禽源大肠埃希菌在广东地区呈流行趋势。耐药基因型与耐药表型相关性分析结果显示,耐药基因rmtB的携带与4种药物(庆大霉素、阿米卡星、卡那霉素和壮观霉素)耐药株的产生具有显著相关性,表明耐药基因rmtB对大肠埃希菌耐药株的产生起重要的作用。本试验结果可为指导广东地区水禽大肠埃希菌病的临床用药提供理论基础和研究大肠埃希菌的耐药基因提供相关的数据。     

Retrospective study on Escherichia coli infection in broilers subjected to postmortem examination and antibiotic resistance of isolates in Trinidad

An 8-yr retrospective study was conducted to evaluate the rate of Escherichia coli infection and antibiotic resistance of isolates from diseased broilers submitted for diagnosis in Trinidad from 1990 to 1997. Of a total of 906 cases of diseased birds subjected to postmortem examination, 603 (66.6%) had E. coli infection. The number of cases increased over the years from 16 in 1990 to a peak of 294 in 1996. For every year, at least 50% of all broiler cases had E. coli infection. The rate of infection was significantly higher during the rainy season (74.1 +/- 6.9%) than during the dry season (57.8 +/- 7.0%). Approximately 50% of all E. coli isolates were resistant to 9 out of a total of 11 antimicrobial drugs selected for the study. The isolates showed an increasing trend of resistance to amoxicillin, apramycin, gentamicin, nitrofurantoin, norfloxacin, and sulfamethoxazole-trimethoprim. However, only the trends of resistance to apramycin and norfloxacin were statistically significant. Overall, of the antimicrobial drugs selected, norfloxacin relatively appeared as the best choice for treatment. From this study, we conclude that the high rate of E. coli infection in broilers submitted for diagnosis along with the high resistance of isolates to antimicrobial drugs constitute a threat to the poultry industry on the island.     

CNS species and antimicrobial resistance in clinical and subclinical bovine mastitis

Coagulase-negative staphylococci (CNS) are often associated with bovine mastitis. Knowledge about the relative importance of specific CNS species in different types of mastitis, and differences in antimicrobial resistance among CNS species is, however, scarce. Therefore, the aims of this study were to compare prevalence and antimicrobial susceptibility of CNS species in clinical and subclinical mastitis using material from two national surveys. Overall, Staphylococcus chromogenes and Staphylococcus epidermidis were the most common CNS species found followed by Staphylococcus simulans and Staphylococcus haemolyticus. S. epidermidis was significantly more prevalent in subclinical than in clinical mastitis, and a similar trend was observed for Staphylococcus saprophyticus, while Staphylococcus hyicus was significantly more common in clinical mastitis. The prevalence of β-lactamase producing isolates varied markedly between CNS species, and was significantly higher in S. epidermidis and S. haemolyticus (～ 40%), than in S. simulans and S. chromogenes where none or a few of the isolates produced β-lactamase. Resistance to more than one antimicrobial substance occurred in 9% and 7% of the clinical and subclinical isolates, respectively. In conclusion, the distribution of CNS species differed between clinical and subclinical mastitis indicating inter-species variation of pathogenicity and epidemiology. Overall, the prevalence of antimicrobial resistance was low, but some variation between CNS species was observed.     

Antimicrobial resistance in commensal faecal Escherichia coli of hospitalised horses

The objective of this study was to examine the impact of hospitalisation and antimicrobial drug administration on the prevalence of resistance in commensal faecal E. coli of horses. Faecal samples were collected from ten hospitalised horses treated with antimicrobials, ten hospitalised horses not treated with antimicrobials and nine non-hospitalised horses over a consecutive five day period and susceptibility testing was performed on isolated E. coli. Results revealed that hospitalisation alone was associated with increased prevalence of antimicrobial resistance and multidrug resistance in commensal E. coli of horses. Due to the risk of transfer of resistance between commensal and pathogenic bacteria, veterinarians need to be aware of possible resistance in commensal bacteria when treating hospitalised horses.     

Quantitative resistance level (MIC) of bacterial pathogens (Escherichia coli, Pasteurella multocida, Pseudomonas aeruginosa, Salmonella sp., Staphylococcus aureus) isolated from chickens and turkeys: national resistance monitoring by the BVL 2004/2005

In the study 2004/2005, the current quantitative resistance level of Escherichia coli, Pasteurella multocida, Pseudomonas aeruginosa, Salmonella sp. and Staphylococcus aureus from chickens and turkeys was determined for the first time within the framework of the National Resistance Monitoring of the Federal Office of Consumer Protection and Food Safety (BVL).The objective was to implement a valid database on the basis of which the development and spread of resistance can be evaluated and monitored. During the investigation period from January 2004 to February 2005,927 strains were collected and 857 (92%) bacteria strains which corresponded to the specifications of the study protocol were tested with the broth microdilution method to determine the in vitro susceptibility (minimum inhibitory concentration) to 22 to 28 antimicrobial agents or antibiotic combinations. The results document a prevalence of resistance that exceeds that of bacterial pathogens of other animal species, especially in the case of tetracycline. Apart for S. aureus, clinical resistance to fluoroquinolones can still be considered low in poultry pathogens (E. coli approx. 2%). By applying the MICG of 4 mg/L for enrofloxacin, a susceptibility of approximately 78 % was calculated for S. aureus. A comparison of the prevalence of resistance between chickens and turkeys, showed that a slightly higher prevalence of resistance can be expected in turkeys. Differences between the susceptibility data of chicks and adult animals could only be found in turkeys. In the case of E. coli, the prevalence of resistance of strains isolated from adult turkeys was up to 10% higher than those isolated from chicks for the corresponding antimicrobial agents. It must be pointed out that the number of E. coli strains from adult turkeys was much higher (n = 194) than the number from turkey chicks (n = 21). The results indicate clearly that in a resistance monitoring system it is necessary to categorise poultry by animal species (chicken, turkey) as well as by production stage and type (broiler, laying hen), so that the epidemiology of resistance can be correctly represented and evaluated. This information is the basis for the development of long-term management options for minimizing antibiotic resistance. Furthermore, the knowledge of prevailing resistance levels in Germany is a valuable tool for veterinary practitioners when determining an empirical therapy.The data collected by the BVL make an important contribution to the optimisation of the safety of food from animals, and thus to improving consumer protection.     

Cross-sectional study of antimicrobial-resistant bacteria in horses. Part 1: Prevalence of antimicrobial-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus

Reasons for performing study: The increasing prevalence of antimicrobial‐resistant bacteria such as methicillin‐resistant Staphylococcus aureus (MRSA) and antimicrobial‐resistant Escherichia coli represents a significant problem. However, the carriage of such bacteria by horses in the UK has not been well characterised. Objectives: To estimate the prevalence of nasal carriage of MRSA and faecal carriage of antimicrobial‐resistant E. coli amongst horses in the general equine community of the mainland UK. Methods: A cross‐sectional study of horses recruited by 65 randomly selected equine veterinary practices was conducted, with nasal swabs and faecal samples collected. Faecal samples were cultured for antimicrobial‐resistant E. coli. Nasal swabs were cultured for staphylococcal species; methicillin‐resistant isolates identified as S. aureus were characterised by SCCmec and spa gene typing. Multilevel logistic regression models were used to calculate prevalence estimates with adjustment for clustering at practice and premises levels. Spatial variation in risk of antimicrobial resistance was also examined. Results: In total, 650 faecal samples and 678 nasal swabs were collected from 692 horses located on 525 premises. The prevalence of faecal carriage of E. coli with resistance to any antimicrobial was 69.5% (95% CI 65.9–73.1%) and the prevalence of extended‐spectrum β‐lactamase (ESBL)‐producing E. coli was 6.3% (95% CI 4.1–9.6%). The prevalence of nasal carriage of MRSA was 0.6% (95% CI 0.2–1.5%). Spatial analysis indicated variation across the UK for risk of carriage of resistant and multidrug‐resistant (resistant to more than 3 antimicrobial classes) E. coli. Conclusions and potential relevance: Carriage of MRSA by horses in the community appears rare, but the prevalence of antimicrobial‐resistant E. coli (including ESBL‐producing E. coli) is higher. A high prevalence of antimicrobial‐resistant bacteria could have significant health implications for the horse population of the UK.     

Comparison of Drug Resistance of Escherichia coli from Different Cattle Farms in Kuitun Area of Xinjiang

In order to understand the resistance of E.coli to clinical antimicrobial drugs from different farms in Kuitun area of Xinjiang,the bovine fecal samples were collected using the anal swab and E.coli was isolated from 123 (30),127 (30) and 128 (30) farms,respectively.The minimum inhibitory concentrations of E coli isolated from fecal samples to 10 antimicrobial drugs were determined by agar dilution method and the difference of resistance rate of E.coli from different farms was compared by chi square test.The results showed that the resistance rates of 128 farm to amoxicillin/clavulanic acid (33.3%) and apramycin (23.3%) were relatively high;The resistance rates of 127 farm to ampicillin (20.0%),amoxicillin/clavulanic acid (16.7%) and florfenicol (16.7%) were relatively high;The resistance rates of 123 farm to ampicillin (13.3%) and the apramycin (13.3%) were relatively high.The chi square test results showed that resistance rates of E.coli to florfenicol and enrofloxacin from 127 farm were significantly higher than that from 123 and 128 farms (P<0.05);The resistance rates of E.coli to amoxicillin/clavulanic acid and apramycin from 128 farm were significantly higher than that from 123 and 127 farms (P<0.05),respectively.The most of the antibiotics resistance pattern of E.coli from different farms was 1 to 2 resistant.The results showed that the drug resistance rates of bovine E.coli in Kuitun was not high,while the resistance rates to commonly used drugs such as amoxicillin/clavulanic acid and apramycin were high.It suggested that this kinds of antimicrobial drugs should be replaced or avoid using to treat bacterial diseases.In addition,the antimicrobial resistance between farms was different,indicating the farms medicine would impact the drug resistance in bacteria.     

The current antimicrobial resistance situation in Swiss veterinary medicine]

Antimicrobial susceptibility data (n = 1501) and bacterial isolates (n = 258) of important bacterial pathogens from animals were collected in collaboration with eight Swiss laboratories from May 1999 to February 2000. Using these data, the antimicrobial resistance situation could be assessed for the following bacterial species: Escherichia coli, Salmonella, Haemophilus parasuis, Actinobacillus pleuropneumoniae, Pasteurella multocida, Mannheimia haemolytica, Bordetella bronchiseptica, Campylobacter jejuni, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus intermedius, Streptococci, and enterococci. Differences in the distribution of resistance between animal species could be evidenced in E. coli and salmonella. Some resistance frequency data were compared with those obtained in 1980. A significant increase of resistance frequency was observed for several antibiotics. This includes in particular an increase of ampicillin, gentamicin, and cotrimoxazole resistance in E. coli. A similar increase was observed in salmonella for ampicillin, streptomycin, sulfonamides, and nalidixic acid. Staphylococci from dogs (S. intermedius and S. aureus) also presented a clear increase of resistance for penicillin, neomycin, sulfonamides, cotrimoxazole, and erythromycin. Finally, a comparison with data from abroad shows that the antibiotic resistance situation in Switzerland is relatively favorable.     

Molecular characterisation of bovine faecal Escherichia coli shows persistence of defined ampicillin resistant strains and the presence of class 1 integrons on an organic beef farm

Antimicrobial use is heavily restricted on organic farms; however, few studies have been conducted to investigate the impact this has on the epidemiology of resistance in pathogenic and commensal bacteria. We investigated the persistence of antimicrobial resistant Escherichia coli within an organic beef herd over a period of 28 months. Faecal samples collected monthly from three calf cohorts and annually from adult cattle and environmental samples, were screened for the presence of ampicillin, apramycin and nalidixic acid resistant E. coli. The prevalence of ampicillin resistance ranged from 27.3 to 40.7% in the annual herd and environmental samplings (n=22-55) and was greater in the calf cohorts, with a peak cohort prevalence of >47% in all 3 years (n=16-18). Apramycin and nalidixic acid resistant E. coli were rare. Pulsed-field gel electrophoresis (PFGE) identified 10 main genotype groups within the herd, with evidence of strain transmission between different livestock groups, animal species and years. Multiple resistance was found in >44% of isolates tested, with ampicillin, neomycin, sulphamethoxazole and tetracycline carriage the commonest phenotype identified. PCR detected the presence of class 1 integrons in <5% of resistant isolates, 6/7 of which were of cattle origin. These data demonstrate that ampicillin resistant E. coli was common on the farm despite restricted antimicrobial use, although strain diversity was low. Persistence of defined genotype groups was observed between years, together with the transmission of resistant strains between different animal species on the farm.     

猪大肠杆菌和葡萄球菌的分离鉴定及耐药性分析

对湘西北地区某猪场患病的仔猪的粪便及病变的脾脏、肝脏、淋巴结、肺脏、肾水肿液进行病原菌分离鉴定,并用Kirby-Bauer法测定分离菌株对15种抗菌药的敏感性。结果表明,患病仔猪分离到大肠杆菌和猪葡萄球菌两种细菌。其中大肠杆菌对庆大霉素、头孢呋肟、丁胺卡那霉素、四环素、先锋必素敏感,对氯霉素、氧哌嗪青霉素、先锋五号、头孢曲松钠、新霉素中介,对羧苄青霉素、强力霉素、青霉素、氨苄青霉素、红霉素有较高的耐药性。葡萄球菌对先锋霉素Ⅴ、丁胺卡那霉素敏感,对头孢曲松钠中介,对其他抗生素耐药。其中大肠杆菌对药物敏感率、中介率、耐药率均为33.33%;葡萄球菌的敏感率为13.33%,中介率为6.67%,耐药率为80.00%。     

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.     

Antimicrobial susceptibility and distribution of antimicrobial-resistance genes among Enterococcus and coagulase-negative Staphylococcus isolates recovered from poultry litter

Data on the prevalence of antimicrobial resistant enterococci and staphylococci from the poultry production environment are sparse in the United States. This information is needed for science-based risk assessments of antimicrobial use in animal husbandry and potential public-health consequences. In this study, we assessed the susceptibility of staphylococci and enterococci isolated from poultry litter, recovered from 24 farms across Georgia, to several antimicrobials of veterinary and human health importance. Among the 90 Enterococcus isolates recovered, E. hirae (46%) was the most frequently encountered species, followed by E. faecium (27%), E. gallinarum (12%), and E. faecalis (10%). Antimicrobial resistance was most often observed to tetracycline (96%), followed by clindamycin (90%), quinupristin-dalfopristin (62%), penicillin (53%), erythromycin (50%), nitrofurantoin (49%), and clarithromycin (48%). Among the 110 staphylococci isolates recovered, only coagulase-negative staphylococci (CNS) were identified with the predominant Staphylococcus species being S. sciuri (38%), S. lentus (21%), S. xylosus (14%) and S. simulans (12%). Resistance was less-frequently observed among the Staphylococcus isolates for the majority of antimicrobials tested, as compared with Enterococcus isolates, and was primarily limited to clarithromycin (71%), erythromycin (71%), clindamycin (48%), and tetracycline (38%). Multidrug resistance (MDR) phenotypes were prevalent in both Enterococcus and Staphylococcus; however, Enterococcus exhibited a statistically significant difference in the median number of antimicrobials to which resistance was observed (median = 5.0) compared with Staphylococcus species (median = 3.0). Because resistance to several of these antimicrobials in gram-positive bacteria may be attributed to the shuttling of common drug-resistance genes, we also determined which common antimicrobial-resistance genes were present in both enterococci and staphylococci. The antimicrobial resistance genes vat(D) and erm(B) were present in enterococci, vgaB in staphylococci, and mobile genetic elements Tn916 and pheromone-inducible plasmids were only identified in enterococci. These data suggest that the disparity in antimicrobial-resistance phenotypes and genotypes between enterococci and staphylococci isolated from the same environment is, in part, because of barriers preventing exchange of mobile DNA elements.     

Study on the Drug-resistance of Escherichia coli Isolated from Sheep in Inner Mongolia

In order to determine the drug resistance phenotype and prevalence of drug resistance genes in Escherichia coli (E.coli) isolated from sheep in Inner Mongolia, the minimum inhibitory concentrations (MICs) of the isolates to antibiotics commonly used in veterinary clinical were detected by micro-dilution method in vitro. The results showed that the highest resistance rates of the isolates to amoxicillin,cephalothin,sulfamethoxazole and polymyxin were up to 100.0%,respectively.To amoxicillin-clavulanic, tetracycline and ciprofloxacin were 50% to 80%. These isolates were sensitive to cefotaxime, meropenem trihydrate, neomycin, and their resistance rates were all less than 10%. Among the 108 strains of E.coli from sheep, 94.4% of them were resistant to more than 7 antimicrobial agents,15.6% of them were resistant to 13 antimicrobial agents, only one strain was sensitive to all antimicrobial agents. Six kinds of resistance genes among the 108 E.coli isolates were detected by PCR method.The results showed that detection rates of 4 kinds of drug resistance genes including bla_TEM, proP-2, sul-Ⅰ and ampG were all over 50%,the detection rate of resistance gene aph (3')-Ⅰ was up to 40%, only resistance gene aac(3)-Ⅱ detection rate was 5.5%. Thus, the sheep E.coli isolates in Inner Mongolia produced various degrees of resistance to 13 kinds of antibiotics, and their multi-drug resistances were very serious. They carried aph(3')-Ⅰ, sul-Ⅰ, ampG, bla_TEM, proP-2 and aac(3)-Ⅱ resistance genes.     

内蒙古地区羊源大肠杆菌耐药性研究

为确定内蒙古地区羊源大肠杆菌的耐药表型及其耐药基因的流行情况,本研究采用微量稀释法测定了内蒙古地区108株羊源大肠杆菌对13种临床常用抗菌药物的最小抑菌浓度。结果显示,分离菌株对阿莫西林、头孢噻吩、磺胺甲唑、黏菌素的耐药率最高,均达100.0%,对阿莫西林/克拉维酸、四环素、环丙沙星的耐药率在50%~80%之间,对头孢噻肟、美洛培南、新霉素的耐药率均低于10%,较为敏感。108株羊源大肠杆菌中耐7种以上药物的菌株占94.4%,其中15.6%菌株对13种抗菌药物耐药,只有1株菌对所有抗菌药物敏感。采用PCR方法对羊源大肠杆菌分离株所携带的6种相关耐药基因进行检测,结果显示,6种耐药基因中的4种耐药基因bla_TEM、proP-2、sul-Ⅰ、ampG检出率超过50%,耐药基因aph（3'）-Ⅰ携带率达40%,只有耐药基因aac（3）-Ⅱ检出率仅为5.5%。由此可见,内蒙古地区羊源大肠杆菌对13种抗菌药物产生了不同程度的耐药性,且存在严重的多重耐药情况,羊源大肠杆菌分离株携带aph（3'）-Ⅰ、sul-Ⅰ、ampG、bla_TEM、proP-2、aac（3）-Ⅱ耐药基因。     

宠物源菌株的分离鉴定及耐药性分析

为了解河南郑州市常见宠物携带菌株组成以及耐药情况,本试验采集了郑州地区不同宠物医院患病及健康犬、猫共计76个样本的肛拭子、眼拭子、耳拭子。试验通过细菌分离培养、形态学观察、生化试验、16s rRNA基因测序完成细菌鉴定,确定分离菌株种类,采用微量肉汤稀释法测定分离菌株耐药表型。结果共分离得到大肠杆菌50株、肠球菌27株、奇异变形杆菌24株、葡萄球菌46株、绿脓杆菌4株。奇异变形杆菌耐药最为严重,对多西环素、替米考星两种药物耐药率高于90.0%;大肠杆菌对替米考星的耐药率高达94.0%,对阿莫西林耐药率为62.0%,对多西环素、多粘菌素E、庆大霉素、环丙沙星、恩诺沙星、头孢噻呋的耐药率在4.0%~24.0%之间。肠球菌对多西环素、庆大霉素、头孢噻呋三种药物的耐药率在29.6%~40.7%之间;对阿莫西林、恩诺沙星、环丙沙星三种药物的耐药率在7.4%~14.8%之间,对替米考星的耐药率为66.7%。葡萄球菌对替米考星的耐药率为39.1%,对阿莫西林、多西环素、庆大霉素、环丙沙星、恩诺沙星、头孢噻呋的耐药率均低于20.0%。上述试验结果表明:大肠杆菌和葡萄球菌在宠物菌群组成中占比较大;大肠杆菌和奇异变形杆菌的耐药情况较为严重。     

Antimicrobial susceptibility of hazard analysis critical control point Escherichia coli isolates from federally inspected beef processing plants in Alberta, Saskatchewan, and Ontario

A survey to estimate the prevalence of antimicrobial resistance in Escherichia coli was conducted in 7 Canadian federally inspected processing plants during 2001. Escherichia coli isolates were recovered during routine hazard analysis critical control point sampling from beef carcasses and trim and subsequently tested for their antimicrobial susceptibility by using susceptibility panels. Of the 2653 isolates analyzed, 68% were sensitive to all 18 antimicrobials tested. For 14 of the 18 antimicrobials evaluated, the percentage of resistant isolates was < or = 1. Twenty-five percent of the isolates were resistant to tetracycline, 9% to sulfamethoxazole, 7% to streptomycin, and 3% to ampicillin. Multiple resistance was found in 12% of the isolates, with 7% showing resistance to 2 antimicrobials, 2% to 3 antimicrobials, 2% to 4 antimicrobials, and 1% to 5 or more antimicrobials. Forty-five different antimicrobial resistance patterns were observed. The reasons for the development of the antimicrobial resistance were not investigated in this study. This study was useful as a pilot to help to develop a national antimicrobial resistance surveillance program in Canada. This study indicates that laboratory standardization is possible for consistent results across the country and that the indicator organism, E. coli, is fairly easy to obtain for surveillance but Salmonella are not, due to their low prevalence in beef.