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1.
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2.
Classical hemolytic complement (C) of calves was analyzed during a protocol designed to imitate the usual market handling of feeder calves from the southeastern United States. Serum C concentrations of the calves (n = 100 x 4 years) were evaluated on their farm of origin, on arrival at an auction market, on arrival at a feedyard, and during their first 4 weeks in the feedyard. Complement concentrations (measured in CH50 units) were typically lowest at the farm of origin and highest when the calves entered the auction market 28 to 133 days later. Serum C concentrations decreased after the calves encountered the severe stresses of being in the auction market for 7 days, 24-hour truck transport (1,932 km) to the feedyard, and the first 7 days in the feedyard. The C concentrations recovered after 21 to 28 days in the feedyard. Steers had significantly (P less than or equal to 0.05) lower C concentrations than did heifers in 3 of 4 years at the farm of origin, and in 2 of 4 years at the auction market. Morbid calves had significantly (P less than or equal to 0.05) lower C values than did healthy calves on day 7 in the feedyard in 3 of 4 years. There were significant differences in C concentrations of calves from different farms of origin in each of the 4 years. There was no significant difference in C concentrations of calves that were vaccinated vs those not vaccinated with Pasteurella haemolytica.  相似文献   

3.
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   

4.
To estimate herd prevalence of Salmonella spp, fecal specimens were obtained for culture from neonatal calves of 47 Ohio dairy herds. Of the 452 calves tested, 10 calves from 7 farms were culture-positive. Salmonella serotypes isolated were S dublin, S typhimurium, S enteritidis, S agona, S mbandaka, and S montevideo. Bulk tank milk filters from these dairies were also submitted for culture. Salmonella sp was isolated from 1 of the 50 filters, and 2 calves from this herd were found to be shedding Salmonella sp of the same serotype.  相似文献   

5.
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   

6.
OBJECTIVE To identify the common serotypes and antimicrobial resistance patterns of Salmonella spp. associated with diarrhoea in Australian dairy calves under the age of 6 weeks. DESIGN Cross-sectional study. METHODS Faecal samples were collected from outbreaks of diarrhoea in dairy and dairy beef calves less than 6 weeks old. Samples were screened for Salmonella using standard enrichment culture techniques. The antimicrobial susceptibility to 12 commonly used veterinary and human antimicrobials was assessed using the Kirby-Bauer disk diffusion method and the susceptibility profiles of dairy and dairy beef properties were compared using Fisher's exact test. RESULTS Salmonella ser. Dublin, S. ser. Typhimurium and S. ser. Bovismorbificans were the three most common salmonella serotypes isolated. The majority of properties had one serotype. Most of the Salmonella isolates were not resistant to any of the antimicrobials tested. No resistance was seen to amikacin and nalidixic acid, and only one isolate was resistant to ceftiofur or amoxicillin-clavulanic acid. The most common antimicrobial resistance was to streptomycin, ampicillin or combination sulfonamides. Multi-drug resistance was detected in S. ser. Anatum, S. ser. Bovismorbificans, S. ser. Muenster, S. ser. Newport and S. ser. Typhimurium. Isolates from dairy beef properties were more likely to be resistant to ampicillin, kanamycin, neomycin, sulfamethoxazole/trimethoprim and tetracycline (P < 0.05) and were more likely to exhibit multi-drug resistance. CONCLUSION The prevalence of antimicrobial resistance in Salmonella isolates from dairy calves in Australia is low compared with that reported overseas. From a human health perspective, resistance to antimicrobials used in the treatment of human salmonellosis was infrequent.  相似文献   

7.
In a representative study, 380 manure samples of pig farms distributed all over Bavaria (Germany) were screened for the presence of Salmonella spp. at the time of manure application to soil using methods adapted to DIN EN ISO 6579. The isolates were tested according to DIN 58940 for their susceptibility towards 26 antimicrobial substances - such substances partly administered in animals, but mainly used in human therapy. Six out of 380 manure samples and, in addition, the only separated liquid manure sample examined, contained Salmonella isolates. Serotypes represented S. Typhimurium (n = 5), S. Derby (n = 1) and S. Infantis/S. Serogroup C1-(6,7:r:-)-form (each n = 1). Within the serovar S. Typhimurium, the most common phage type was DT104 (n = 3). All Salmonella isolates originated from 'big' farms (>30/45 sows on combined/breeding farms or >220 fattening pigs). Four out of six manure samples contained resistant isolates; all resistant Salmonellae were multi-resistant. Two out of three DT104-isolates showed the typical penta-resistance pattern often found in S. Typhimurium DT104, which was, furthermore, supplemented by other resistances. One Escherichia coli isolated together with a phage type DT104 S. Typhimurium also expressed the same penta-resistance pattern.  相似文献   

8.
OBJECTIVE: To evaluate the association between maintaining joint hospital and maternity pens and persistence of multi-drug-resistant (MDR) Salmonella enterica serovar Newport on 2 dairy farms. DESIGN: Observational study. SAMPLE POPULATION: Feces and environmental samples from 2 dairy herds. PROCEDURE: Herds were monitored for fecal shedding of S enterica Newport after outbreaks of clinical disease. Fecal and environmental samples were collected approximately monthly from pens housing sick cows and calving cows and from pens containing lactating cows. Cattle shedding the organism were tested serially on subsequent visits to determine carrier status. One farm was resampled after initiation of interventional procedures, including separation of hospital and maternity pens. Isolates were characterized via serotyping, determination of antimicrobial resistance phenotype, detection of the CMY-2 gene, and DNA fingerprinting. RESULTS: The prevalence (32.4% and 33.3% on farms A and B, respectively) of isolating Salmonella from samples from joint hospital-maternity pens was significantly higher than the prevalence in samples from pens housing preparturient cows (0.8%, both farms) and postparturient cows on Farm B (8.8%). Multi-drug-resistant Salmonella Newport was isolated in high numbers from bedding material, feed refusals, lagoon slurry, and milk filters. One cow excreted the organism for 190 days. Interventional procedures yielded significant reductions in the prevalences of isolating the organism from fecal and environmental samples. Most isolates were of the C2 serogroup and were resistant to third-generation cephalosporins. CONCLUSIONS AND CLINICAL RELEVANCE: Management practices may be effective at reducing the persistence of MDR Salmonella spp in dairy herds, thus mitigating animal and public health risk.  相似文献   

9.
OBJECTIVE: To describe antimicrobial susceptibility patterns in Campylobacter spp isolated from dairy cattle and farms managed organically and conventionally in the midwestern and northeastern United States. DESIGN: Longitudinal study. SAMPLE POPULATION: 128 farms. PROCEDURE: Samples and data were collected every 2 months from August 2000 to October 2001. Fecal samples were collected from calves and cows. Milk samples were obtained from the bulk tank and milk line filters. Environmental samples were obtained from a water source, feed bunks of lactating cows, and cattle housing areas. Campylobacter identification and antimicrobial susceptibility testing were performed at a central laboratory by use of microbroth dilution with 2 customized antimicrobial susceptibility panels. RESULTS: 460 and 1,570 Campylobacter isolates were obtained from organic and conventional dairy farms, respectively. Most isolates from both farm types were susceptible to most antimicrobial agents tested, and antimicrobial susceptibility of conventional dairy isolates was decreased, compared with organic dairy isolates. Low proportions of isolates resistant to ampicillin (< 10%) and moderate proportions resistant (30% to 60%) to kanamycin, sulfamethoxazole, and tetracycline were observed on both farm types. The proportion of isolates resistant to tetracycline was higher for conventional than organic farms. CONCLUSIONS AND CLINICAL RELEVANCE: Campylobacter isolates from dairy cattle and farms managed organically and conventionally had similar patterns of antimicrobial resistance; the proportion of resistant isolates was higher for conventional than organic farms.  相似文献   

10.
Cloacal swabs were sampled from 100 duck farms in Taiwan between March 2000 and January 2001 for isolation and standard cultivation of Salmonella spp. and thermophilic Campylobacter spp. Salmonella spp. were isolated from 4.6% (91/2000) of ducks from 20% (20/100) of duck farms. Ten serotypes of Salmonella enterica were identified: S. Potsdam (31.9% of isolates), S. Dusseldorf (18.7%), S. Indiana (14.3%), S. Typhimurium (7.7%), S. Hadar (5.5%), S. Newport (4.4%), S. Derby (4.4%), S. Montevideo (2.2%), S. Schwarzengrund (2.2%), and S. Asinnine (1.1%). Isolation of S. Asinnine or S. Indiana from poultry had not hitherto been described in Taiwan. The salmonella isolation rate in ducklings under two weeks of age was significantly higher than the other age groups (P<0.05). Campylobacter spp. were isolated from 43.5% (1045/2400) of ducks from 92% (92/100) of duck farms. Among them, 991 isolates (94.8%) were identified as C. jejuni and 54 isolates (5.2%) as C. coli. The campylobacter isolation rate in ducklings under two weeks of age was significantly lower than other age groups (P<0.05). Antimicrobial susceptibility testing was conducted by the disk diffusion and E- test methods. The results indicated that Salmonella isolates were 100% susceptible to amikacin, amoxicillin/clavulanic acid, ceftraxone, cephalothin, ciprofloxacin, norfloxacin, ofloxacin, and polymyxin B. A markedly higher antimicrobial resistance to amoxicillin, florfenicol, flumequine, josamicin/trimethoprim, nalidixic acid, nitrofurantoin, norfloxacin, ofloxacin, polymyxin B, sulfamethoxazole/trimethoprim and tetracycline was found in campylobacter isolates.  相似文献   

11.
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   

12.
The study objective was to describe and evaluate antimicrobial resistance profiles in Salmonella isolated from Alberta swine finishing farms. Salmonella isolates (n = 322) were obtained from 192 fecal and 84 environmental samples of the 60 Salmonella-positive swine finishing farms. Isolates were classified susceptible, intermediate or resistant based on NCCLS guidelines. More than half of the isolates (53.4%) were susceptible to all of the 18 antimicrobials in the testing panel. No resistance was observed to amikacin, amoxicillin/clavulanic acid, cefoxitin, ceftiofur, ceftriaxone, cephalothin, ciprofloxacin, imipenem or nalidixic acid. Less than 1% of isolates were resistant to apramycin, gentamicin and trimethoprim/sulfamethoxazole. Higher frequencies of resistance were observed for chloramphenicol (4.7%), ampicillin (7.8%), kanamycin (11.8%), sulfamethoxazole (21.1%), streptomycin (25.5%) and tetracycline (38.8%). Eleven Salmonella serovars had isolates with resistance to > or =3 antimicrobials. The most frequently resistant serovar was Salmonella Derby, with 27 (38.0%) isolates resistant to > or =3 antimicrobials, including resistance to five and six antimicrobials. An absence of resistance to cephalosporins and fluoroquniolones and a low proportion of isolates resistant to amikacin, amoxicillin/clavulanic acid, apramycin, gentamicin and trimethoprim/sulfamethoxazole are encouraging findings from public health and animal health perspectives. Frequent resistance observed for ampicillin, kanamycin, sulfamethoxazole, streptomycin and tetracycline, antimicrobials commonly used in veterinary medicine for decades, indicates an urgent need to utilize these antimicrobials more prudently if their benefits are to be preserved.  相似文献   

13.
OBJECTIVE: To compare the efficacy of a Salmonella bacterin and a modified live Salmonella ser. Choleraesuis vaccine on a commercial dairy. ANIMALS: 450 cows in late gestation and 80 calves. PROCEDURE: Group-1 cows (n = 150) were vaccinated once with a modified live S. Choleraesuis (serogroup C1) strain 54 (SC54) vaccine, group-2 cows (150) were vaccinated on enrollment and 30 days later with a Salmonella ser. Montevideo (serogroup C1) bacterin, and group-3 cows (150) served as unvaccinated controls. One gallon of colostrum harvested from the first 80 cows to calve was fed to each calf. Outcome assessments included fecal shedding of Salmonella spp for the first 10 days after parturition (cows) or birth (calves), milk production, involuntary culling rate, mastitis incidence, antimicrobial use, and mortality rate. RESULTS: Salmonellae were isolated from 306 of 309 (99%) cows and 64 of 74 (86.5%) calves. Shedding frequency was less in SC54-vaccinated cows and calves that received colostrum from those cows, compared with the other groups, and vaccination was specifically associated with less shedding of serogroup C1 salmonellae. Production data were similar among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination of pregnant cows with an autogenous Salmonella bacterin had no effect on fecal shedding of salmonellae, whereas vaccination with a modified live S. Choleraesuis vaccine reduced the frequency of fecal shedding of serogroup C1 salmonellae during the peripartum period. A commercial S. Choleraesuis vaccine licensed for use in swine may be more efficacious than autogenous Salmonella bacterins on dairies infected with serogroup C1 salmonellae.  相似文献   

14.
为了解上海市农贸市场肉鸽群体中沙门氏菌流行血清型和耐药情况,本试验于2011-2014年间从上海市各区农贸市场采集肉鸽新鲜粪便样本92份,用XLD平板和沙门氏菌属显色培养基分离疑似沙门氏菌,革兰氏染色镜检并进行生化试验,共获得沙门氏菌24株,分离率为26.1%。采用Kauffmann-White法和K-B纸片法对24株沙门氏菌进行血清型鉴定和16种抗生素的药敏试验。血清型鉴定显示,24株沙门氏菌可分为鼠伤寒（66.7%）、阿贡纳（25.0%）和科瓦利斯（8.3%）3种血清型。药敏试验结果显示,有75.0%（18株）的分离株表现出不同程度耐药,其中分离株对四环素和磺胺异唑耐药率最高,均达到62.5%,其次为链霉素（58.3%）、萘啶酸（50.0%）、氨苄西林（20.8%）。多重耐药菌株15株（62.5%）,耐4种抗菌药物的菌株最多,占16.7%（7株）。另外,分离菌株对头孢吡肟、头孢噻肟、头孢噻甲羧肟、亚胺培南、氧氟沙星等5种药物的敏感率为100.0%,对奥格门丁和环丙沙星有12.5%的中介敏感率。本研究结果表明,上海市肉鸽中沙门氏菌的携带率较高,且菌株多重耐药现象较严重,这为食品中沙门氏菌的防控工作带来较大的挑战和风险,肉鸽沙门氏菌的流行和耐药情况应值得密切关注。  相似文献   

15.
A study of randomly selected dairy farms in England and Wales was made between October 1999 and February 2001 to estimate the prevalence and incidence of Salmonella serovars. The farms were enrolled through five milk-buying companies, which represented 63 per cent of the dairy farms in England and Wales, and they were sampled on up to four occasions (449 farms at visit 1, 272 farms at visit 2, 251 farms at visit 3 and 243 farms at visit 4). In total, 19,296 samples of pooled faecal pats and slurry were collected. The farm-specific prevalence of all serovars of Salmonella ranged from 12.1 per cent (95 per cent confidence interval [CI] 8.2 to 16.0 per cent) to 24.7 per cent (95 per cent CI 19.4 to 30.1 per cent) at each visit. The most common serovars identified were Salmonella Dublin (3.7 to 6.6 per cent farm-specific prevalence at each visit), Salmonella Agama (1.8 to 7.6 per cent) and Salmonella Typhimurium (2.6 to 4.1 per cent) The prevalence varied by region and month of sampling and increased in late summer. The incidence rate of all serovars of Salmonella was 0.43 (95 per cent CI 0.34 to 0.54) cases per farm-year at risk. There was no significant difference between the incidence rates of the common serovars S Typhimurium (0.07), S Dublin (0.06) and S Agama (0.13). A total of 29 Salmonella serovars were isolated. Few of the isolates were resistant to the 16 antimicrobial agents tested, except the isolates of S Typhimurium dt104, of which 67.9 per cent were resistant to at least five of them.  相似文献   

16.
An in vitro bactericidal assay that used bovine heparinized blood was investigated for its usefulness in detecting differences in the bactericidal immunity of calves against Pasteurella haemolytica serotype 1 (Ph1). Greater than 90% of killing occurred within 30 minutes. The substitution of fetal calf serum for autologous calf plasma caused loss of bactericidal activity of the blood. Decomplemented calf serum also was low in bactericidal activity. The blood bactericidal assay appears to be opsonin antibody-dependent and complement-dependent. The coefficient of variation (CV) that can be expected with this assay was established by use of a group of 8 calves; within-day CV maximum was 0.9, and between-day CV maximum was 2.1. The blood bactericidal assay was used to evaluate 30 calves under typical market stress from 4 farms in eastern Tennessee. All calves had decreased bactericidal activity, as they moved into a feedyard in Texas. The bactericidal activity was reduced among sick calves, based on the severity of clinical signs. Morbidity was highest during the first 14 days in the feedlot. During this period, healthy calves had a decreased bactericidal index (BI) of 4 points, and calves with clinical signs of bovine respiratory tract disease for 3 days had a decreased BI of 8 points. The average reduction in the BI of calves with clinical signs of bovine respiratory tract disease for 6 or more days was 14 points.  相似文献   

17.
OBJECTIVE: To determine whether depopulation-repopulation could be used to eradicate Salmonella serotype Typhimurium DT104 from a commercial swine farm in the midwestern United States. DESIGN: Observational study SAMPLE POPULATION: A commercial swine farm undergoing depopulation-repopulation to eliminate porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae. PROCEDURE: Pooled fecal samples, tissue samples, and serum samples were collected from pigs on the farm before and after depopulation-repopulation. When there were no pigs on the farm, environmental swab specimens were collected for bacterial culture. Serum was analyzed for anti-Salmonella antibodies with an indirect ELISA. Salmonella isolates obtained by bacterial culture of fecal, tissue, and environmental samples were characterized by means of serotyping, phage typing, pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing. RESULTS: 167 Salmonella isolates representing 9 serotypes were recovered from the farm. Results of PFGE and antimicrobial susceptibility testing suggested that S. Typhimurium DT104 strain was not eradicated from the farm. However, seroprevalence of anti-Salmonella antibodies and the percentage of pooled fecal samples positive for Salmonella spp were significantly decreased following repopulation. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that depopulation-repopulation in conjunction with stringent cleaning and disinfection, attention to biosecurity procedures, control of other diseases, and changes in feed management may reduce the occurrence of, but likely will not eliminate, Salmonella spp in commercial swine herds.  相似文献   

18.
The purpose of this study was to investigate the molecular types and antimicrobial resistance of Salmonella isolated from pigeon in Shanghai from 2011 to 2014. A total of 92 fecal samples were collected from markets. XLD plate and Salmonella chromogenic medium were used to isolate suspected Salmonella colonies, and then determined the number of Salmonella through gram staining and biochemical tests. Among them, 24(26.1%) were positive for Salmonella. Kauffmann-White method and the K-B method were used respectively for serotype identification and susceptibility testing. In result, serological identification showed that 24 isolates from pigeon could be divided into 3 serotypes including S.typhimurium (66.7%), S.agona (25.0%) and S.corvallis (8.3%). Drug susceptibility test showed that 75.0% of the isolates were resistant to one antibiotic at least. The highest level resistance were found for tetracycline as well as sulfisoxazole (62.5%), followed by streptomycin (58.3%), nalidixic acid (50.0%) and ampicillin (20.8%). Multi-drug resistant strains accounted for 62.5% (15), in which the largest number of strains (7, 16.7%) were resistant to four drugs. In addition, isolates were 100.0% susceptible to cefepime, cefotaxime, ceftazidime, imipenem and ofloxacin, but 12.5% were moderately sensitive to the amoxicillin/clavulanic acid and ciprofloxacin. The study showed that Salmonella had a high separation rate of pigeon in Shanghai farmers market and performed serious multidrug resistance, which would bring great challenges and risks to the prevention and control of Salmonella in food, so that the prevalence and drug resistance of Salmonella in pigeon deserved close attention.  相似文献   

19.
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   

20.
OBJECTIVE: To describe the occurrence of fecal shedding, persistence of shedding over time, and serogroup classification of Salmonella spp on a large number of dairy farms of various sizes. DESIGN: Longitudinal study. SAMPLE POPULATION: 22,417 fecal samples from cattle and 4,570 samples from the farm environment on 110 organic and conventional dairy farms in Minnesota, Wisconsin, Michigan, and NewYork. PROCEDURE: 5 visits were made to each farm at 2-month intervals from August 2000 to October 2001. Fecal samples from healthy cows, calves, and other targeted cattle groups and samples from bulk tank milk, milk line filters, water, feed sources, and pen floors were collected at each visit. Bacterial culture was performed at 1 laboratory. RESULTS: Salmonella spp were isolated from 4.8% of fecal samples and 5.9% of environmental samples; 92.7% of farms had at least 1 Salmonella-positive sample. The 75th percentile for median within-herd prevalence of Salmonella spp in cattle for 5 sampling visits to a given farm was 2.0% and for maximum within-herd prevalence of Salmonella spp was 13.6%. Farms with a median within-herd prevalence of Salmonella spp of > or = 2.0% accounted for 76.3% of Salmonella-positive samples. There was no significant difference in the prevalence of Salmonella spp between conventional and organic farms. Seasonal differences in Salmonella shedding were observed. More farms had at least 1 serogroup B isolate than any other serogroup, whereas serogroup E1 was the most common among all Salmonella-positive samples. More than 1 serogroup was isolated on 76.4% of Salmonella-positive farms. CONCLUSIONS AND CLINICAL RELEVANCE: Salmonella spp were isolated from > 90% of dairy farms; however, 25% of farms accounted for > 75% of Salmonella-positive samples. This information is critical for the direction of intervention strategies to decrease the prevalence of Salmonella spp on dairy farms.  相似文献   

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