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1.
The objectives of this study were to investigate the associations between antimicrobial resistance patterns in generic Escherichia coli and Salmonella spp. isolates recovered from identical pen pooled fecal samples, and to evaluate potential clustering of multiple isolates of these organisms within identical fecal samples. Up to 5 generic E. coli (n = 922 isolates) and Salmonella spp. (n = 922 isolates) isolates were obtained from each of 188 pen pooled fecal samples that had been collected from 45 finishing swine farms in Alberta in 2000, and tested for susceptibility to 15 antimicrobials. No isolates of either organism were resistant to 3rd generation cephalosporins or fluoroquinolones, which in Canada are considered antimicrobials of very high importance to human health. Approximately twice as many generic E. coli isolates as Salmonella spp. isolates were resistant to at least 1 antimicrobial. In addition, E. coli isolates showed more multidrug-resistance patterns. No significant association was observed between the resistance phenotypes of Salmonella spp. and E. coli at the fecal sample level. More clustering at the sample level was observed for proportions of antimicrobial resistance (AMR) in Salmonella spp. isolates than E. coli indicating that in future studies it might be sufficient to test fewer than 5 Salmonella spp. isolates per sample.  相似文献   

2.
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.  相似文献   

3.
The aims of this study were to investigate the incidence of Salmonella, verocytotoxigenic Escherichia coli (VTEC)/Escherichia coli O157 and Campylobacter on four mixed farms and to characterize the isolates in terms of a range of virulence factors. Eighty-nine composite (five different samples from the same animal species combined) faecal [cattle (24), pigs (14), sheep (4), poultry (4), horses (7), deer (4), dogs (9), rodents (2) and wild birds (20)] samples, 16 composite soil samples plus 35 individual water samples were screened using culture-based, immunomagnetic separation and molecular methods. Salmonella was detected in bovine faeces, cattle and poultry house water. Salmonella serotypes/phage types included Dublin, Kiel and Typhimurium DT193, and most isolates were spvC, invA and rck positive. The pefA and rck genes were found exclusively in the non-Typhimurium strains, while Salmonella Dublin and Salmonella Kiel strains carried Salmonella genomic island I marker(s). VTEC/E. coli O157 were found in deer and dog faeces only. The E. coli O157 isolate was an enteroinvasive E. coli, while the VTEC isolate was untypable but carried the vt1, eaeA, hlyA, tir and eptD genes. This article reports the first confirmed carriage of E. coli O157 in Irish deer. Campylobacter species were not detected over the course of this study. It was concluded that [1] Salmonella, VTEC and Campylobacter have low (<5%) prevalence or are absent on the farms in this study; [2] water was an important source of bacterial pathogens; [3] both dogs and deer may act as a source of pathogenic E. coli and [4] key virulence and resistance determinants are widespread in farm Salmonella strains. This study highlights the need to control water as a source of pathogens and suggests that the domestic pets and deer should be considered in any farm risk assessment.  相似文献   

4.
Surveillance is an important component of an overall strategy to address antimicrobial resistant bacteria in food animals and the food chain. The poultry market has many points of entry into the Canadian food chain, and some production practices are underrepresented in terms of surveillance. For example, pathogen carriage and antimicrobial resistance surveillance data are limited in smallholder chicken flocks raised for slaughter at provincially inspected abattoirs. In Canada, antimicrobial resistance in Escherichia coli and Salmonella isolated from commercial broiler chicken flocks, slaughtered at federally inspected abattoirs, is monitored by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS ). The objective of this study was to establish baseline information of antimicrobial resistance presence in E. coli and Salmonella isolated from smallholder flocks in Ontario, utilizing CIPARS collection and isolation methodologies, and to compare findings with CIPARS federally inspected abattoir data from Ontario, Canada. Five chickens per flock were sampled from 205 smallholder flocks. Of 1,025 samples, the E. coli prevalence was 99% (1,022/1,025), and 47% (483/1,022) of positive E. coli isolates were resistant to one or more of the 14 antimicrobials. Furthermore, as compared to results reported for the CIPARS commercial flocks, E. coli isolates from smallholder flocks had significantly lower resistance prevalence to six of 14 individual antimicrobials. Recovery of E. coli did not differ between federally inspected and provincially inspected flocks. Salmonella prevalence at the bird level in smallholder flocks was 0.3% (3/1,025), significantly lower (p  ? 0.0001, 95% CI 0.080%–0.86%) than federally inspected commercial flocks. The overall differences found between the commercial and smallholder flocks may be explained by differences in poultry husbandry practices and hatchery sources.  相似文献   

5.
The use of antimicrobial drugs in livestock is suspected to contribute to bacterial antimicrobial resistance (AR) development. Dairy farms experiencing recent outbreaks of salmonellosis involving multi-resistant (MR) Salmonella strains were compared to control farms with respect to AR among bovine commensal E. coli isolates. For most antimicrobials tested, the percentage of AR E. coli isolated from salmonellosis-affected farms was significantly higher than that from control farms. Calf E. coli from both case and control farms had greater levels of AR than cow isolates. Commensal E. coli isolates from case farms and calves tended to more frequently be MR. These data are consistent with the existence of higher antimicrobial selection pressure on farms with recent salmonellosis outbreaks, however, the directionality of the relationship remains to be elucidated. An improved understanding of the epidemiology of AR bacteria in livestock production, both at the herd and molecular level, is essential to mitigate risk to public health and food safety.  相似文献   

6.
The main objectives of this study were to determine the prevalence and patterns of antimicrobial resistance in pigs on farms that medicated swine ration and those that did not. A total of 940 isolates of Escherichia coli from 188 pooled fecal samples obtained from weaner and finisher pigs on 47 farrow-to-finish swine farms (34 farms used in-feed medication and 13 did not) were tested for susceptibility to 21 antimicrobials using a breakpoint concentration method. The prevalence of resistance varied widely (0.0% to 81.3%) among the antimicrobials tested. Ninety percent of all the isolates tested were resistant to one or more antimicrobials. The most common multi-drug resistance patterns were to 2 to 6 antimicrobials. Resistance was significantly more frequent (P < 0.01) on farms that used in-feed medication compared to those that did not, and significantly more frequent (P < 0.01) in weaner pigs compared to finisher pigs. These findings indicate that resistance to a broad range of antimicrobials was prevalent among fecal E. coli isolates of pigs on study farms, and that this constitutes a potential reservoir for resistance genes that could spread to pathogens. The findings also provide further evidence that use of medication in swine rations provides selective pressure for antimicrobial resistance in E. coli in pigs.  相似文献   

7.
To investigate the effects of rearing practices of commercial broiler chickens on the incidence of antimicrobial resistance in commensal Escherichia coli isolates, fecal E. coli isolates obtained in 4 farms were screened for anitimicrobial resistance. Ten E. coli isolates were recovered from each of the fecal samples collected from 10 birds in the farms at the ages of 2 days, 14-17 days, and 47-50 days. In 2 out of the 4 farms, no antimicrobials were used during the rearing period. In the other two farms, following collection of the fecal samples at 14 and 15 days of age, oxytetracycline (OTC), sulfadimethoxine (SDMX), and tylosin were given to birds on one farm and SDMX was used in the other. Isolates resistant to ampicillin and OTC that were obtained from an untreated flock at different sampling times were closely related to each other by pulsed-field gel electrophoresis patterns (PFGE) of XbaI-digested chromosomal DNA. PFGE analysis together with in vitro conjugation experiments suggested that diversity of resistance phenotypes within a clone may be resulted from the acquisition and loss of R-plasmids in an untreated and a treated flock. The numbers of resistance phenotypes observed among fecal isolates increased during the growth of the chickens in all the farms. The results in the present study suggest that persistence of commensal E. coli strains resistant to antimicrobials even in the absence of antimicrobial administration. It is also hypothesized that horizontal transmission of resistance determinants resulted in the emergence of different resistance phenotypes in those farms.  相似文献   

8.
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.  相似文献   

9.
Escherichia coli (n = 1439), isolated from the feces of apparently healthy grow-finish pigs in 20 herds in Alberta and Saskatchewan, were tested for susceptibility to 16 antimicrobials. All isolates were susceptible to amikacin, ceftriaxone, and ciprofloxacin and less than 1% was resistant to amoxicillin-clavulanic acid, cefoxitin, ceftiofur, gentamicin, and nalidixic acid. Resistance was most common to tetracycline (66.8%), sulfamethoxazole (46.0%) and streptomycin (33.4%). Twenty-one percent of the isolates were susceptible to all drugs, while 57% were resistant to 2 or more antimicrobials. Unconditional associations between resistances provided insight into the potential for co-selection. Every resistance-outcome was associated with at least 2 other drug-resistances. These associations illustrate the propensity for resistance phenotypes to occur together and the importance of considering co-selection in antimicrobial use decisions. A 2nd analysis explored the associations between resistance phenotypes in E. coli and Salmonella spp. from the same herd. Only 2 resistances in Salmonella were associated with herd-level E. coli resistance, indicating that E. coli is a poor sentinel for Salmonella AMR within herds. Herd-level management, including antimicrobial use, could affect antimicrobial resistance. The intra-class correlation between isolates within herds ranged from 0.1 to 0.46, which confirmed resistance clustered within herds. This suggests herd-level interventions might mitigate antimicrobial resistance. Overall, these results reflect the on-farm selection pressure for resistance and the potential food-safety risk from near-market animals. These data provide a baseline for comparisons with future on-farm monitoring of antimicrobial resistance in E. coli.  相似文献   

10.
Point prevalence studies have reported carriage rates of enteric pathogens in healthy horses, but longitudinal data are lacking. Commensal E. coli is an indicator organism to evaluate antimicrobial resistance of enteric bacteria, yet there are limited data for horses. The objectives of this study were to investigate and molecularly characterize isolates of Clostridium difficile, Clostridium perfringens and Salmonella, collected sequentially over a one year period, and to determine the antibiotic susceptibility profile for E. coli. Fecal samples were collected monthly from 25 adult horses for one year. Selective cultures were performed for all above bacteria. C. difficile isolates were characterized via PCR toxin gene profiling and ribotyping. Broth microdilution was performed to assess antimicrobial susceptibility profiles of E. coli. Toxigenic Clostridium difficile was isolated from 15/275 (5.45%) samples from 10/25 (40%) horses. Four horses were positive at multiple sampling times but different ribotypes were found in three. Ribotypes included 078 (n=6), 001 (n=6) and C (n=3). C. perfringens was not isolated, nor was Salmonella. E. coli was isolated from 232/300 (77%) fecal samples. Resistance to ≥1 and ≥ 3 antimicrobials was present in 31/232 (13.4%) and 6/232 (2.6%) respectively. Only two horses shed the same strain of toxigenic C. difficile for more than one month, indicating that shedding is transient. The high number of ribotype 078 is consistent with recent emergence of this strain in the local horse population. The low prevalence of antibiotic resistance in commensal E. coli suggests that healthy horses are not likely a major reservoir of resistance for enteric bacteria.  相似文献   

11.
为了解种鹅致病性大肠杆菌病的病原及其药物敏感性,2012年从广东地区患病种鹅器官和粪便中分离鉴定了62株大肠杆菌,采用琼脂稀释法测定了大肠杆菌对17种抗菌药物的敏感性。结果发现大肠杆菌耐药性严重,对大部分药物的耐药率超过60.0%,仅对头孢西丁、头孢他啶和黏菌素较敏感。联合药敏试验结果显示多西环素和氟苯尼考联用对耐药大肠杆菌产生协同抑菌作用,FIC指数为0.375～0.75。采用脉冲场凝胶电泳（PFGE）法对24株大肠杆菌进行分型,结果分为17种不同的PFGE型别。大肠杆菌系统进化分群结果显示43.5%属于系统进化组群的D组,其次是A组和B1组,分别为34.8%和21.7%,B2组未检测到。通过对种鹅大肠杆菌耐药性、PFGE分型及其系统发育群进行综合分析,为临床用药提供了参考依据。  相似文献   

12.
A longitudinal study was conducted of the prevalence and characteristics of Escherichia coli in mammals, birds, and reptiles housed at the Emperor Valley Zoo, Trinidad. During a 6-mo study period, swabs were obtained from fecal samples that were randomly collected from the enclosures of animals from these three taxonomic groups every 3 wk. With snakes, both cloacal and fecal swabs were obtained. Fecal and cloacal swabs were cultured for E. coli on eosin methylene blue agar. The production of mucoid colonies and hemolytic colonies and non-sorbitol fermenter status were identified. The occurrence of O157 strains was determined amongst E. coli isolates that were non-sorbitol fermenters, and the disc diffusion method was used to determine the antibiograms of isolates. The frequency of E. coli isolation was significantly higher in mammals compared with birds and reptiles. Overall, the frequencies of isolation of E. coli from omnivores. herbivores, and carnivores, 87.2%, 70.0%, and 57.3%, respectively, regardless of animal class, were significantly different. Most (99.6%) of the E. coli isolates tested for antibiotic sensitivity exhibited resistance to one or more of the eight antimicrobial agents used. The possession of phenotypic virulence markers by the E. coli isolates studied and the generally high resistance to antimicrobial agents may have health implications for the zoological collection.  相似文献   

13.
Feed has been reported as a vehicle for transmission of Salmonella enterica in cattle and several lines of evidence suggest that feed can be a vehicle for transmitting Escherichia coli O157:H7 as well. To show whether microbial contamination of feeds could contribute to the populations of S. enterica and E. coli O157:H7 on a farm, we compared isolates from feed samples to bovine fecal isolates from the same farm using pulsed-field gel electrophoresis (PFGE). Four of 2365 component feed samples (0.2%) and 1 of 226 feed mill samples (0.4%) were positive for E. coli O157:H7. Twenty of 2405 (0.8%) component feed samples and none of 226 feed mill samples were positive for Salmonella. PFGE profiles from E. coli O157:H7 isolated from a component feed sample closely resembled that from a fecal isolate collected later from the same farm, and a similar observation was made of a Salmonella Tyhpimurium isolate from component feed on another farm. There were indistinguishable PFGE profiles from component feed Salmonella Tyhpimurium DT104 isolates and fecal isolates from the same farm. These results provide evidence for a role of cattle feed in transmission of E. coli O157:H7; S. enterica; cattle-bacteria.  相似文献   

14.
In the period October 1996 through December 2000, a total of 7163 pooled faecal samples of laying hen and broiler flocks, finishing-pig herds and veal herds were examined for the presence of Salmonella spp., Campylobacter spp. and verocytotoxin-producing Escherichia coli O157 as part of a national monitoring programme in The Netherlands. Isolates were tested for eae and VT genes. Risk factors for Dutch veal herds were quantified. For all herd/flock types, faecal samples were cultured for E. coli O157. Of broiler flocks, laying flocks and finishing pig herds, respectively, 1.7%, 0.5% and 0.4% were E. coli O157 positive. In total, 42 of the 454 veal herds (9.3%) showed at least one positive pooled sample. E. coli O157-positive herds were compared (with logistic regression) to negative herds, regarding variables obtained from the questionnaire taken from the farm manager. To account for season, a sine function was included in the logistic regression as offset variable. In the final model, 'pink-veal production' (compared to white-veal production), 'group housing of the sampled herd' (compared to individual housing), 'more than one stable present' (compared to one stable present), 'hygienic measures regarding visitors' (compared to no hygienic measures), 'interval arrival-sampling of a herd of >20 weeks' (compared to < or =10 weeks), and 'presence of other farms within 1 km' (compared to no presence of farms <1 km) showed associations (P<0.05) with the presence of E. coli O157. These results need careful interpretation; they should be considered as indications for further (experimental or cohort-based) research rather then causal associations.  相似文献   

15.
食品动物源大肠杆菌多重耐药性监测   总被引：1，自引：0，他引：1  
为掌握畜禽源大肠杆菌的耐药情况,了解其对各种抗菌药物的敏感程度,自广东地区临床分离鉴定出294株食品动物源大肠杆菌,采用琼脂稀释法测定294株大肠杆菌对14种抗菌药物的敏感性。结果显示,食品动物源大肠杆菌对各抗菌药的敏感性不同,且多重耐药现象较严重;受试大肠杆菌对四环素和复方新诺明的耐药率较高,均达到80%以上;对第3代头孢菌素类耐药率相对较低。  相似文献   

16.
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.  相似文献   

17.
Minimum inhibition concentrations (MICs) were determined for ampicillin, ceftiofur, cephalothin, chloramphenicol, enrofloxacin, gentamicin, lincomycin, lincospectin (lincomycin/spectinomycin), neomycin, premafloxacin, spectinomycin, sulfamethoxazole/trimethoprim, and tetracycline against a total of 180 isolates of Actinobacillus pleuropneumoniae, Escherichia coli, and Salmonella choleraesuis (60 each) clinically isolated from pigs on farms in Taiwan from 1994 to 1996. No more than 3 isolates per farm were used. Ceftiofur had the highest activity in vitro against isolates of A. pleuropneumoniae, E. coli, and S. choleraesuis, with MIC90 values of 0.03, 2, and 1 microg/ml, respectively. Premafloxacin was highly active against isolates of A. pleuropneumoniae, E. coli, and S. choleraesuis, with MIC90 values of 2, 8, and 0.5 microg/ml, respectively, which were lower than those with enrofloxacin (MIC90 8, 32, and 2 microg/ml, respectively). Neomycin was moderately active against A. pleuropneumoniae and E. coli, with MIC90 values of 8 and 64 microg/ml, respectively, but was inactive with S. choleraesuis. Gentamicin showed high activity against A. pleuropneumoniae (MIC90 of 2 microg/ml) but was only moderately active with E. coli and S. choleraesuis (MIC90 of 64 and 32 microg/ml). Cephalothin was highly active against isolates of A. pleuropneumoniae (MIC90 of 1 microg/ml) but was inactive with E. coli (MIC90 of 128 microg/ml). Lincomycin had moderate activity (MIC90 of 32 microg/ml) against A. pleuropneumoniae. Chloramphenicol, lincomycin, and tetracycline were inactive with E. coli and S. choleraesuis (MIC90 > 128 microg/ml). In conclusion, ceftiofur and premafloxacin were highly active against isolates of A. pleuropneumoniae, E. coli, and S. choleraesuis, enrofloxacin and gentamicin were highly to moderately active; cephalothin was highly active against A. pleuropneumoniae and moderately active against S. cholearesuis; chloramphenicol, lincomycin, and tetracycline were active only with A. pleuropneumoniae; neomycin was moderately active against A. pleuropneumoniae and E. coli. The other antimicrobials tested were inactive.  相似文献   

18.
Short-term stability of measurements of antimicrobial susceptibility of Escherichia coli isolated from feces of feedlot cattle is important in developing monitoring and surveillance programs. Frequent evaluations (i.e., daily) are resource intensive and in some situations may be impractical for long-term sampling protocols. Consequently, a point-in-time measurement will need to be used to represent conditions in the perisampling period. In this study, 30 fecal samples were collected from each of 6 cattle pens on a commercial cattle feedlot on 2 occasions separated by 48 hours. Escherichia coli was isolated from single and pooled samples. The isolates were tested for antimicrobial susceptibility against a panel of 17 antimicrobials. Resistance to 5 antimicrobials (ampicillin, nalidixic acid, streptomycin, sulfamethoxazole, and tetracycline) was detected in single and pooled samples from both sampling periods (days 1 and 3). The prevalence of isolates resistant to these 5 antimicrobials was 2% or higher in all treatment combinations except for pools obtained from day 3 samples. Lower levels of resistance to 6 more antimicrobials were detected inconsistently across the single and pooled samples. Logistic models constructed for the antimicrobials to which the E. coli isolates were most commonly resistant demonstrated that there were no significant differences between periods (P > 0.10) and between single and pooled samples (P > 0.20). The distribution of the number of antimicrobials to which isolates were resistant was consistent for the single samples across periods, but there appeared to be a lower prevalence of any resistance in day 1 pooled samples. A larger number of resistant phenotypes were detected in the single samples than in the pooled samples, and resistant phenotypes with prevalence of less than 2% were detected inconsistently across periods and single and pooled samples. Resistance to individual antimicrobials was consistent by all measures when the prevalence was at least 2%. Inconsistent results were obtained for antimicrobials to which resistance rarely occurred. The apparent inconsistencies do not appear to be related to external factors but rather to sampling intensity. Short-term stability is a plausible assumption under sampling strategies that are designed to detect specific levels of prevalence. However, when resistance levels fall below these levels, there will likely be fluctuations in the presence or absence of rare resistant phenotypes and in their prevalence and central tendency measures.  相似文献   

19.

This study investigated the occurrence of antimicrobial-resistant Escherichia coli in dairy calves in southern Vietnam. Fecal samples were taken directly from the rectum of 84 calves from 41 smallholder dairy farms, when newborn and at 14 days of age for isolation of E. coli. Escherichia coli strains were isolated from 144 of the 168 fecal samples tested. Of the 144 E. coli isolates, 40% were found to be susceptible to all 12 antimicrobial drugs tested and 53% of the E. coli isolates were resistant to at least three antimicrobials. Calves were colonized with antimicrobial-resistant E. coli already on the day of birth. Resistance to tetracycline was most common, followed by resistance to sulfamethoxazole, ampicillin, trimethoprim, and ciprofloxacin. Four isolates carried a gene encoding for extended-spectrum cephalosporinases (ESC), and these genes belonged to blaCTX-M group 1 (2 isolates), blaCTX-M group 9 (1 isolate), and blaCMY-2 (1 isolate). Thirty-three isolates had a plasmid-mediated quinolone resistance (PMQR) phenotype, and 30 of these carried the qnrS gene. These results are of importance for management routines of dairy cattle to prevent the spread of antimicrobial resistance.

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20.
为了确定肉牛屠宰线沙门菌和大肠杆菌的污染情况,选取山西省2家屠宰厂(A、B),分别在屠宰线7道不同工序和屠宰刀具上进行采样,采用传统方法进行沙门菌和大肠杆菌的分离、培养,利用生化鉴定法和16SrDNA序列分析法对分离菌株进行鉴定。结果表明:A厂所有工序均未发现沙门菌和大肠杆菌污染情况;B厂所有工序均未检测出沙门菌,但在宰前皮毛和粪便中检测到8株疑似大肠杆菌,经生化鉴定法和16SrDNA序列分析法全部确定为大肠杆菌。综上表明,选取的2个肉牛屠宰加工企业屠宰线相关工序消毒、减菌措施到位,但应注重宰前动物的规范化管理,以减少宰前污染。  相似文献   

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