Differentiation of Salmonella typhimurium DT204c by plasmid profile and biotyping

Seventy per cent of the United Kingdom isolates of Salmonella typhimurium from calves are phage type 204c and the study of the epidemiology of this organism requires additional methods of strain characterisation. This paper describes the applications of biotyping and plasmid-profile analysis for this purpose. One hundred and eleven isolates from 73 outbreaks of disease were examined. All belonged to the same primary biotype, although strains from 39 of the outbreaks differed in secondary tests in failing to ferment m-inositol at 25 degrees C. Four different antibiotic resistance patterns were detected among the isolates, which possessed seven distinct plasmid profiles. The spread of a distinct type through the calf marketing chain was investigated by using these techniques.     

A survey of free-living falconiform birds for Salmonella

Of 105 migrating falconiform birds of 7 species examined for Salmonella shedding in New Jersey, 2 (1.9%) were positive for Salmonella spp. Both positive birds were immature red-tailed hawks (Buteo jamaicensis). Salmonella enteritidis and S newport were the serotypes isolated. Neither serotype expressed multiple resistance when tested against a panel of 12 antimicrobial drugs.     

A decision-support system for Salmonella in broiler-chicken flocks

We built a decision-support system to assess the risk of contamination of chicken-broiler flocks by Salmonella at the end of the rearing period. This system was developed from the survey data from 85 chicken-broiler flocks located in western France. First, we estimated the probability of contamination of the house by Salmonella before placement of day-old chicks via a cleansing inspection using a visual-inspection grid, a decontamination evaluation using count-plates, and risk factors for Salmonella persistence in the barn after cleansing and disinfection. Second, we estimated (using a logistic model) the probability of prevalent contamination of the flock by Salmonella at the end of the rearing period. Validation was carried out on 60 flocks selected from seven production companies in western France. The risk estimated by the model was compared to the Salmonella status of the flock (gold standard) assessed by samples taken from the environment of the broilers and analysed with classical bacteriological methods. The sensitivity was 97.8% and the specificity 64.3%.     

A unified serotyping scheme for Moraxella bovis.

Fifty-three Australian, seven British, two American and two New Zealand isolates of Moraxella bovis were classified into seven serogroups on the basis of their variable fimbrial (pilus) antigens using whole cell slide agglutination (SA), enzyme-linked immunosorbent assays (ELISA) and tandem-crossed immunoelectrophoresis (TCIE). Although results of serogroup classification by SA and ELISA were identical in 68.7% of isolates, it was found necessary to resolve the discrepancies between the two systems using TCIE. Results suggest that world-wide variation in the potentially host-protective fimbrial antigens of M. bovis may be relatively limited. It is proposed that the previous numerical classifications of British and Australian serogroups are appropriately amalgamated as a result of this latest study and are designated as serogroups A to G inclusive. A protocol for the further serotyping of fresh, fimbriate isolates of M. bovis is suggested.     

猪场沙门氏菌控制新标准

沙门氏菌感染一直是一种令养猪生产者头痛的疾病。自2010年起,欧洲将提高养猪场沙门氏菌控制的标准。因此,欧洲养猪生产者必须意识到并在性价比和安全性上处理好他们所涉及的不断增加的食品安全法律义务。     

New findings on the biotyping of Staphylococcus aureus isolated during milk processing]

A detailed analysis of biotypes of Staphylococcus aureus, as related to their origin and enterotoxigenicity, was performed, using 432 strains isolated from bulk milk, milking machines, quarter milk samples collected from mastitic cows, and cowherds and milkers. All strains coagulated rabbit blood plasma and produced thermonuclease (Tab. I). Human strains differed from bovine ones mostly in the production of alpha-haemolysin (94%) and fibrinolysin (66%). Biotypes C1 (35%) and C2 (38%) dominated clearly among the strains isolated from quarter milk samples. The findings of 13% of biotype A and 8% of biotype D suggest that other sources of udder infections than mastitic cows were involved. Almost 19% of human strains and two strains isolated from quarter milk samples were identified as the recently defined type G. The production of enterotoxins (Tab. III) of was associated mostly with strains of human origin (69%) and with biotypes G (35%) and A (31%). Three enterotoxigenic strains belonged to the biotype B and one strain was not classifiable.     

鸡白痢、鸡伤寒沙门菌分子分型方法的验证

为验证鸡白痢、鸡伤寒沙门菌分子分型方法的准确性,本研究以3株鸡白痢、鸡伤寒沙门菌国际参考菌株和306株国内分离株为研究对象,采用5种已知的分子分型方法开展验证性实验。结果发现,基于特定基因可变区的2种分型方法具有良好的特异性,其检测结果与生化分型结果一致,而3种基于特定基因单核苷酸多态性的分型方法则出现假阳性或假阴性的结果。上述结果表明,鸡白痢、鸡伤寒沙门菌分子分型方法的准确性仍需进一步验证。     

Enrichment for isolating Salmonella Choleraesuis and other Salmonella spp. from pigs

The growth of Salmonella Choleraesuis was examined in Rappaport Vassiliadis broth (RV) and Hajna-tetrathionate broth (HTT) at 37 and 42 degrees C. As the enrichment in RV at 37 degrees C was satisfactory for isolating S. Choleraesuis, we used this enrichment for isolation from the samples collected from 15 asymptomatic pigs reared on a S. Choleraesuis contaminated farm. S. Choleraesuis was frequently isolated from six pigs (40.0%) under field conditions. The isolation of other Salmonella serovars than S. Choleraesuis was attempted by using both RV enrichment at 37 degrees C and HTT enrichment at 42 degrees C. Salmonella organisms were isolated from 156 (44.8%) of 348 fecal samples and more frequently with HTT at 42 degrees C (43.4%) than with RV at 37 degrees C (20.9%). If other serovars in addition to S. Choleraesuis are to be surveyed, HTT enrichment should be used in combination with RV enrichment.     

直接ELISA检测沙门氏菌方法的建立及其应用研究

从已获得的４株沙门氏菌属特异杂交瘤单克隆抗体中，筛选出ＣＢ８和Ｄｅ７两株单抗相合成酶标检测试剂，并建立了检测沙门氏菌的直接ＥＬＩＳＡ方法，它能检出沙门氏菌属９９％的菌株，而不与其他肠道杆菌反应（包括大肠杆菌，阴沟杆菌，产气杆菌，志贺氏菌，枸椽酸杆菌，克雷伯氏菌，变形杆菌和沙雷氏菌）。应用本方法检测粪样，鱼粉，奶样，其敏感性和特异性分别高达１００％和９７．６％，仅出现２．４％的假阳性率，该法不受各要     

A multiplex real-time PCR for differential detection and quantification of Salmonella spp., Salmonella enterica serovar Typhimurium and Enteritidis in meats

Salmonella (S.) Typhimurium and S. Enteritidis are the major causative agents of food-borne illnesses worldwide. Currently, a rapid detection system using multiplex real-time polymerase chain reaction (PCR) has been applied for other food-borne pathogens such as Escherichia coli, Staphylococcus aureus and Streptococcus spp. A multiplex real-time PCR was developed for the simultaneous detection of Salmonella spp., especially S. Typhimurium and S. Enteritidis, in beef and pork. For the specific and sensitive multiplex real-time PCR, three representative primers and probes were designed based on sequence data from Genbank. Among the three DNA extraction methods (boiling, alkaline lysis, and QIAamp DNA Mini Kit), the QIAamp DNA Mini Kit was the most sensitive in this study. The optimized multiplex real-time PCR was applied to artificially inoculated beef or pork. The detection sensitivity of the multiplex real-time PCR was increased. The specificity of the multiplex real-time PCR assay, using 128 pure-cultured bacteria including 110 Salmonella isolates and 18 non-Salmonella isolates, was 100%, 100% and 99.1% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The sensitivity was 100%, 100% and 91.7% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The multiplex real-time PCR assay developed in this study could detect up to 0.54 ± 0.09 and 0.65 ± 0.07 log₁₀ CFU/ml for S. Typhimurium and S. Enteritidis for beef, 1.45 ± 0.21 and 1.65 ± 0.07 log₁₀ CFU/ml for S. Typhimurium and S. Enteritidis for pork, respectively, with all conditions optimized. Our results indicated that the multiplex real-time PCR assay developed in this study could sensitively detect Salmonella spp. and specifically differentiate S. Typhimurium from S. Enteritidis in meats.     

Salmonella Vaccination in Pigs: A Review

The control of Salmonella enterica in pig production is necessary for both public and animal health. The persistent and frequently asymptomatic nature of porcine Salmonella infection and the organism's abilities to colonize other animal species and to survive in the environment mean that effective control generally requires multiple measures. Vaccination is one such measure, and the present review considers its role and its future, drawing on studies in pigs from the 1950s to the present day. Once established in the body as an intracellular infectious agent, Salmonella can evade humoral immunity, which goes some way to explaining the often disappointing performance of inactivated Salmonella vaccines. More recent approaches, using mucosal presentation of antigens, live vaccines and adjuvants to enhance cell‐mediated immunity, have met with more success. Vaccination strategies that involve stimulating both passive immunity from the dam plus active immunity in offspring appear to be most efficacious, although either approach alone can yield significant control of Salmonella. Problems that remain include relatively poor control of Salmonella serovars that are dissimilar to the vaccine antigen mix, and difficulties in measuring and predicting the performance of candidate vaccines in ways that are highly relevant to their likely use in commercial production.