Antimicrobial susceptibility of Salmonella isolates recovered from calves with diarrhoea in Australia

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.     

Salmonella Typhimurium persistence in a Hunter Valley dairy herd

OBJECTIVE: An epidemiological study was undertaken at a Hunter Valley dairy with persistent Salmonella Typhimurium infection. The aim of the study was to identify cattle currently or previously infected with Salmonella, possible sources of the organism, patterns of spread, and husbandry practices that could be improved. METHODOLOGY: Faecal samples, feed, water and environmental samples were cultured for Salmonella and blood samples were tested for antibodies against Salmonella (Dublin and Typhimurium). A questionnaire was designed to identify possible risk factors associated with Salmonella excretion. RESULTS: S Typhimurium was apparently introduced from an old to a new dairy through manure spread as fertiliser. Salmonella apparently persisted in the effluent pond, and the following year clinical cases occurred after pasture, irrigated with water from the pond, was grazed by dry cows, and adult cattle became clinically ill with salmonellosis. The disease spread to other cows and calves. Poor design of calf pens assisted spread of Salmonella from sick to healthy calves. In addition, there was suspected transmission to the dairy farmer's 9-month-old daughter. Salmonellosis on a farm is a potential zoonotic risk to farm workers and their families. There is also the risk that cull cows may carry Salmonella to the abattoir and subsequently into the human food chain. Methods of waste management, and the design of calf pens, were identified as major risk factors that could be improved to minimise the spread of salmonellosis on this property.     

张家口地区鸡白痢沙门氏菌的分离鉴定及药敏试验

目的筛选对张家口地区鸡白痢沙门氏菌的敏感药物,更好地防治鸡白痢。方法对张家口地区8个养殖场35只疑似为鸡白痢沙门氏菌性腹泻病鸡的60份病料进行病原菌分离鉴定及药物敏感性试验。结果分离的18株鸡白痢沙门氏菌对庆大霉素、阿米卡星、氟苯尼考敏感,对阿莫西林、链霉素、环丙沙星、复方新诺明不敏感,对头孢曲松、恩诺沙星、痢特灵中度敏感。结论在鸡白痢的防治中,可以选用庆大霉素、阿米卡星、氟苯尼考等药物。     

An Evaluation of Microbial Health Risks to Livestock Fed with Wastewater‐Irrigated Forage Crops

This paper presents the results of five experiments in which animal health risks associated with the consumption of crops irrigated with domestic wastewater were evaluated. Forage maize and Tanner grass were irrigated with treated wastewater and used in goats and calves feeding trials. The irrigated crops presented high levels of surface contamination with E. coli (10⁴–10⁷ 25 g^?1) and salmonellae (up to 1.6 × 10⁴ 25 g^?1), but none of the animals showed signs of infection or of disease. Further, the microbiological quality of animal products always complied with the Brazilian and European Union standards for food safety. It is suggested that the WHO guideline values for restricted irrigation (≤10⁴ E. coli 100 ml^?1 and ≤1 helminth egg l^?1), which were developed to protect the health of agricultural field workers, would be equally protective of the health of both animals fed with wastewater‐irrigated crops and humans consuming products from such animals.     

鸡源沙门氏菌对β-内酰胺类抗生素耐药相关基因的筛选及鉴定

[目的]从沙门氏菌全基因组范围筛选和鉴定其与β-内酰胺类抗生素耐药性相关的基因.[方法]对临床分离的10株沙门氏菌进行药敏试验,选择耐药性最广泛的菌株作为研究对象,利用mariner转座子对其基因组进行随机突变,获得转座子突变株文库,筛选文库中对β-内酰胺类抗生素敏感的突变体,通过套式PCR、核苷酸测序及序列比对确定突变体中转座子的插入位点及其破坏的基因.[结果]从突变株文库中筛选得到15株分别对青霉素G、氨苄西林和头孢哌酮敏感的突变株,其中3株对三种抗生素都敏感.转座子破坏基因为STM4216 (inner membrane protein)和STM4150 (50S ribosomal protein L1).[结论]筛选出的基因有望成为控制或扭转沙门氏菌耐药性的作用靶点.     

高致病性猪蓝耳病、猪瘟和沙门氏菌混合感染的诊断

通过流行病学调查、病猪剖检病变观察和实验室诊断,得出贵州省某猪场发病猪为高致病性蓝耳病、猪瘟和沙门氏菌混合感染.其中,高致病性蓝耳病感染率为100%,猪瘟感染率50%,沙门氏菌感染率25%.     

青海省部分地区牛奶中几种微生物指标的检测

为掌握我省部分地区牛奶中微生物含量,本实验对2008年10月至11月青海省重点地区的8批次70份鲜牛奶样进行了菌落总数、大肠菌群、沙门氏菌的检测。结果表明,菌落总数(Cfu/mL)是:1.4×105;大肠菌群(MPN/100mL)是:7.6×104,均低于国标GB/T 4789.1～4789.31—2003的要求(菌落总数:5.0×105,大肠菌群:1.0×105)沙门氏菌检测均为阴性。说明我省的鲜奶基本符合国标要求,无公共卫生安全隐患。     

肠炎沙门氏菌SEFA基因表达和间接ELISA检测方法的初步建立

为了给临床检测肠炎沙门氏菌的感染和血清学调查提供一种切实可行的方法,本研究根据肠炎沙门氏菌SEF14菌毛操纵子亚单位sefA基因序列设计一对引物,利用PCR技术从国内标准株CMCC(B)50336中扩增sefA基因,并按预定的阅读框插入表达载体pET22b+中,获得重组质粒pET-sefA,限制性内切酶结合琼脂糖凝胶电泳分析和序列测定结果表明,该序列大小为498bp,与已发表的sefA结构编码序列完全一致。重组质粒pETsefA转化大肠杆菌E.coli BL21(DE3)并能获得高效诱导表达,通过对菌体裂解上清液SDS-PAGE和western blot分析鉴定,该重组菌可以表达大小为15.2ku的可溶性重组蛋白rSEFA。纯化的rSEFA免疫小鼠所得高免血清以及标准株CMCC(B)50336感染小鼠后所获阳性血清,均能识别标准株肠炎沙门氏菌SEF14菌毛蛋白以及纯化的重组蛋白rSEFA,结果表明明体外表达的rSEFA蛋白有较好的免疫原性和反应原性。而基于rSEFA介导的间接ELISA有较好的特异性,对肠炎沙门氏菌特异性抗体检测有潜在的应用前景。     

蛋鸡场沙门氏菌快速检测方法应用比较

探索蛋鸡场沙门氏菌快速检测方法.经试纸条、分离培养初步确定沙门氏菌阳性菌株后,进行血清学分型和荧光PCR鉴定.在601份鸡棉拭子、粪便、饮水和饲料样品中分离出37株沙门氏菌,其中沙门氏菌D群2株、其他群35株.试纸条、分离培养和荧光PCR方法相比较,快速分离培养结合荧光PCR方法敏感、快速、准确,适合实验室检测;试纸条法快速、简便,适合蛋鸡场的快速初筛和日常监测;传统方法培养时间长,有待改进.     

Salmonella and on-farm risk factors in healthy slaughter-age cattle and sheep in eastern Australia

OBJECTIVE: To examine healthy slaughter-age cattle and sheep on-farm for the excretion of Salmonella serovars in faeces and to identify possible risk factors using a questionnaire. PROCEDURE: The study involved 215 herds and flocks in the four eastern states of Australia, 56 with prior history of salmonellosis. Production systems examined included pasture beef cattle, feedlot beef cattle, dairy cattle, prime lambs and mutton sheep and animals were all at slaughter age. From each herd or flock, 25 animals were sampled and the samples pooled for Salmonella culture. All Salmonella isolated were serotyped and any Salmonella Typhimurium isolates were phage typed. Questionnaires on each production system, prepared in Epi Info 6.04, were designed to identify risk factors associated with Salmonella spp excretion, with separate questionnaires designed for each production system. RESULTS: Salmonellae were identified in all production systems and were more commonly isolated from dairies and beef feedlots than other systems. Statistical analysis revealed that dairy cattle were significantly more likely to shed Salmonella in faeces than pasture beef cattle, mutton sheep and prime lambs (P<0.05). A wide diversity of Salmonella serovars, all of which have been isolated from humans in Australia, was identified in both cattle and sheep. Analysis of the questionnaires showed access to new arrivals was a significant risk factor for Salmonella excretion on dairy properties. For beef feedlots, the presence of large numbers of flies in the feedlot pens or around stored manure were significant risk factors for Salmonella excretion. CONCLUSION: Dairy cattle pose the highest risk of all the slaughter-age animals tested. Some of the identified risk factors can be overcome by improved management practices, especially in relation to hygiene.