Persistence of a Salmonella enterica serotype typhimurium clone in Danish pig production units and farmhouse environment studied by pulsed field gel electrophoresis (PFGE)

The clonal relationship among Salmonella enterica serotype Typhimurium isolates from selected pig production units in Denmark was investigated by the pulsed field gel electrophoresis (PFGE) typing method to determine environmental survival and spread of Salmonella in different herds. Thirty-four Typhimurium isolated during 1996-1998 from porcine faeces and environmental samples from three pig farms designated 1, 3 and 5 were characterised by PFGE using two restriction enzymes. Farm 5 supplied piglets to farm 1 and the herds were located close to each other. Results of PFGE analysis showed both intra- and inter-relationships, i.e. identical PFGE patterns among the faecal and environmental isolates from farm 1 and farm 5. All the isolates from farm 3 irrespective of the source showed identical PFGE patterns, but were different from samples from farms 1 and 5. This study indicates spread between farms and survival of a farm-specific clone. Furthermore, identical PFGE patterns of isolates from piglet supplier and finisher herds indicate that the farrow-to-grower herd of farm 5 was sub-clinically infected prior to delivery to farm 1 and thereby caused the transmission of Salmonella.     

Salmonella enterica in swine production: assessing the association between amplified fragment length polymorphism and epidemiological units of concern

The aims of this study were to determine the ability of amplified fragment length polymorphism (AFLP) to differentiate Salmonella isolates from different units of swine production and to demonstrate the relatedness of Salmonella between farms and abattoirs by AFLP. Twenty-four farms in the midwestern United States were visited four times from 2006 to 2009. At each farm or abattoir visit, 30 fecal samples or 30 mesenteric lymph nodes were collected, respectively. A total of 220 Salmonella isolates were obtained, serotyped, and genotyped by multilocus sequence typing (MLST) and AFLP. These 220 isolates clustered into 21 serotypes, 18 MLST types, and 14 predominant AFLP clusters based on a genetic similarity threshold level of 60%. To assess genetic differentiation between farms, harvest cohorts, and pigs, analysis of molecular variance was conducted using AFLP data. The results showed 65.62% of overall genetic variation was attributed to variance among pigs, 27.21% to farms, and 7.17% to harvest cohorts. Variance components at the farm (P = 0.003) and pig (P = 0.001) levels were significant, but not at the harvest cohort level (P = 0.079). A second analysis, a permutation test using AFLP data, indicated that on-farm and at-abattoir Salmonella from pigs of the same farms were more related than from different farms. Therefore, among the three subtyping methods, serotyping, MLST, and AFLP, AFLP was the method that was able to differentiate among Salmonella isolates from different farms and link contamination at the abattoir to the farm of origin.     

Detection of Salmonella spp. in retail raw food samples from Vietnam and characterization of their antibiotic resistance

A study was conducted to examine the levels of Salmonella spp. contamination in raw food samples, including chicken, beef, pork, and shellfish, from Vietnam and to determine their antibiotic resistance characteristics. A total of 180 samples were collected and examined for the presence of Salmonella spp., yielding 91 Salmonella isolates. Sixty-one percent of meat and 18% of shellfish samples were contaminated with Salmonella spp. Susceptibility of all isolates to a variety of antimicrobial agents was tested, and resistance to tetracycline, ampicillin/amoxicillin, nalidixic acid, sulfafurazole, and streptomycin was found in 40.7%, 22.0%, 18.7%, 16.5%, and 14.3% of the isolates, respectively. Resistance to enrofloxacin, trimethoprim, chloramphenicol, kanamycin, and gentamicin was also detected (8.8 to 2.2%). About half (50.5%) of the isolates were resistant to at least one antibiotic, and multiresistant Salmonella isolates, resistant to at least three different classes of antibiotics, were isolated from all food types. One isolate from chicken (serovar Albany) contained a variant of the Salmonella genomic island 1 antibiotic resistance gene cluster. The results show that antibiotic resistance in Salmonella spp. in raw food samples from Vietnam is significant.     

Longitudinal study of the persistence of antimicrobial-resistant campylobacter strains in distinct Swine production systems on farms, at slaughter, and in the environment

The objectives of this study were to compare and characterize the prevalence of antimicrobial-resistant (AR) Campylobacter in conventional and antimicrobial-free (ABF) production systems on farms, at slaughter, and in the environment. Fecal and environmental samples were collected from ABF farms (pigs, 1,239; environment, 797) and conventional farms (pigs, 1,650; environment, 1,325). At slaughter, we collected samples from carcasses, including postevisceration swabs, postchill swabs, and mesenteric lymph nodes from ABF systems (postevisceration swabs, 182; postchill swabs, 199; mesenteric lymph nodes, 184) and conventional systems (postevisceration swabs, 272; postchill swabs, 271; mesenteric lymph nodes, 255) at separate processing facilities. We also sampled the processing plant environment, including truck and lairage floor swab samples (ABF, 115; conventional, 90). Overall, a total of 2,908 Campylobacter isolates, including Campylobacter coli (farm, 2,557, 99.8%; slaughter, 341, 98.3%) and Campylobacter jejuni (farm, 4, 0.2%; slaughter, 6, 1.7%), were isolated in the study. There was no significant difference in the prevalence of Campylobacter between ABF and conventionally raised pigs (farrowing, P = 0.20; nursery, P = 0.06; finishing, P = 0.24) and the environment (P = 0.37). At slaughter, Campylobacter was isolated from all of the stages, including postchill. The highest frequencies of resistance were exhibited against tetracycline (ABF, 48.2%; conventional, 88.3%). Ciprofloxacin-resistant C. coli isolates were observed in conventionally raised (17.1%) and ABF (1.2%) pigs (P = 0.11). Antimicrobial use data from conventional farms indicated significant associations between oxytetracycline use and tetracycline resistance in the nursery pigs (P = 0.01), between tiamulin exposure and azithromycin and erythromycin resistance in nursery (P < 0.01) and finishing (P < 0.01) pigs, and between enrofloxacin exposure and ciprofloxacin and nalidixic acid resistance in farrowing (P < 0.01) and nursery (P < 0.01) pigs. Identical antimicrobial resistance profiles were observed in the pigs and their environments on farms and at slaughter. In summary, our results highlight the persistence and dissemination of AR Campylobacter from farm to slaughter in ABF and conventionally raised pigs and their environments.     

National survey for Salmonella in pigs, cattle and sheep at slaughter in Great Britain (1999-2000)

AIMS: The objective of these surveys was to estimate the prevalence of faecal carriage of Salmonella in healthy pigs, cattle and sheep at slaughter, and of pig carcase contamination with Salmonella. These data can be used as a baseline against which future change in Salmonella prevalence in these species at slaughter can be monitored. METHODS AND RESULTS: In this first randomized National Survey for faecal carriage of Salmonella in slaughter pigs, cattle and sheep in Great Britain, 2509 pigs, 891 cattle and 973 sheep were sampled in 34 pig abattoirs and 117 red meat abattoirs in England, Scotland and Wales. Carriage of Salmonella in 25 g caecal contents was identified in 578 (23.0% pigs) but in only 134 (5.3%) of carcase swabs. The predominant Salmonella serovars found in both types of sample were S. Typhimurium (11.1% caeca, 2.1% carcases) and S. Derby (6.3% caeca, 1.6% carcases). The main definitive phage types (DT) of S. Typhimurium found were DT104 (21.9% of caecal S. Typhimurium isolates), DT193 (18.7%), untypable strains (17.6%), DT208 (13.3%) and U302 (13.3%). Three isolates of S. Enteritidis (PTs 13A and 4) and one enrofloxacin-resistant S. Choleraesuis were also isolated. A positive 'meat-juice ELISA' was obtained from 15.2% of pigs at 40% optical density (O.D.) cut-off level and 35.7% at 10% cut-off. There was poor correlation between positive ELISA results or carcase contamination and the caecal carriage of Salmonella. The ratio of carcase contamination to caecal carriage rates was highest in abattoirs from the midland region of England and in smaller abattoirs. In cattle and sheep 1 g samples of rectal faeces were tested. Two isolates (i.e. 0.2%) were recovered from cattle, one each of S. Typhimurium, DT193 and DT12. One sheep sample (0.1%) contained a Salmonella, S. Typhimurium DT41. In a small subsidiary validation exercise using 25 g of rectal faeces from 174 cattle samples, three (1.7%) isolates of Salmonella (S. Typhimurium DT104, S. Agama, S. Derby) were found. CONCLUSIONS: The carriage rate of Salmonella in prime slaughter cattle and sheep in Great Britain was very low compared with pigs. This suggests that future control measures should be focused on reduction of Salmonella infection on pig farms and minimizing contamination of carcases at slaughter. SIGNIFICANCE AND IMPACT OF THE STUDY: This work has set baseline figures for Salmonella carriage in these species slaughtered for human consumption in Great Britain. These figures were collected in a representative way, which enables them to be used for monitoring trends and setting control targets.     

Longitudinal Study of Distributions of Similar Antimicrobial-Resistant Salmonella Serovars in Pigs and Their Environment in Two Distinct Swine Production Systems

The aim of this longitudinal study was to determine and compare the prevalences and genotypic profiles of antimicrobial-resistant (AR) Salmonella isolates from pigs reared in antimicrobial-free (ABF) and conventional production systems at farm, at slaughter, and in their environment. We collected 2,889 pig fecal and 2,122 environmental (feed, water, soil, lagoon, truck, and floor swabs) samples from 10 conventional and eight ABF longitudinal cohorts at different stages of production (farrowing, nursery, finishing) and slaughter (postevisceration, postchill, and mesenteric lymph nodes [MLN]). In addition, we collected 1,363 carcass swabs and 205 lairage and truck samples at slaughter. A total of 1,090 Salmonella isolates were recovered from the samples; these were isolated with a significantly higher prevalence in conventionally reared pigs (4.0%; n = 66) and their environment (11.7%; n = 156) than in ABF pigs (0.2%; n = 2) and their environment (0.6%; n = 5) (P < 0.001). Salmonella was isolated from all stages at slaughter, including the postchill step, in the two production systems. Salmonella prevalence was significantly higher in MLN extracted from conventional carcasses than those extracted from ABF carcasses (P < 0.001). We identified a total of 24 different serotypes, with Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Anatum, Salmonella enterica serovar Infantis, and Salmonella enterica serovar Derby being predominant. The highest frequencies of antimicrobial resistance (AR) were exhibited to tetracycline (71%), sulfisoxazole (42%), and streptomycin (17%). Multidrug resistance (resistance to ≥3 antimicrobials; MDR) was detected in 27% (n = 254) of the Salmonella isolates from the conventional system. Our study reports a low prevalence of Salmonella in both production systems in pigs on farms, while a higher prevalence was detected among the carcasses at slaughter. The dynamics of Salmonella prevalence in pigs and carcasses were reciprocated in the farm and slaughter environment, clearly indicating an exchange of this pathogen between the pigs and their surroundings. Furthermore, the phenotypic and genotypic fingerprint profile results underscore the potential role played by environmental factors in dissemination of AR Salmonella to pigs.     

Evaluation of the use of pooled serum, pooled muscle tissue fluid (meat juice) and pooled faeces for monitoring pig herds for Salmonella

AIMS: Monitoring for Salmonella in slaughter pigs is important to enable targeted control measures to be applied on problem farms and at the abattoir. The aim of this study was to determine whether pooled serum and meat juice could be used to identify finishing pig herds with a high prevalence of infection. METHODS AND RESULTS: Samples of meat juice, serum, caecal contents, carcase swabs and pooled faeces from pig pens were taken from 20 commercial pig finishing farms and comparisons were made between the results of Salmonella culture, individual ELISA tests on serum and meat juice and pooled samples of serum and meat juice. Salmonella was isolated from samples from 19 of 20 farms. None of the ELISA tests showed a statistically significant correlation with caecal carriage of Salmonella or contamination of carcases. Serum mean optical density (O.D.) from pools of five, 10 or 20 sera showed a significant correlation with the Salmonella status of farm pen faeces. All pooled serum O.D. and sample/positive control ratio results correlated significantly with the results of the conventional individual sample ELISA. There was a statistically significant correlation between the incidence of Salmonella in farm pen pooled faeces and the prevalence of Salmonella in caeca of slaughter pigs. CONCLUSIONS: The results show a generally poor correlation between serological and bacteriological results but pooled serum or meat juice samples could be used as a cheaper substitute for serological screening of farms for Salmonella than individual samples. SIGNIFICANCE AND IMPACT OF THE STUDY: The availability of a cheaper test should allow the costs of Salmonella monitoring of pig farms to be reduced or allow more regular testing to enhance the designation of farm Salmonella risk status.     

苏北地区白羽肉鸡父母代种鸡及其商品鸡中沙门氏菌的分离、鉴定与生物特性

【背景】沙门氏菌是一种重要的人兽共患食源性致病菌,控制沙门氏菌在动物中的感染和在食品生产链中的污染对于畜牧生产、公共卫生和食品安全具有重要意义。【目的】调查苏北地区某白羽肉鸡父母代种鸡及其商品鸡的沙门氏菌感染和流行情况,为其沙门氏菌防治提供参考依据。【方法】于2018?2019年从江苏泰州、宿迁、盐城、徐州、连云港等地区分别采集某白羽肉鸡父母代种鸡场产蛋鸡及其商品鸡场1?2日龄弱雏和10日龄雏鸡的泄殖腔拭子样品共360份,进行沙门氏菌的分离与鉴定,用纸片法和PCR方法对菌株耐药表型及相关耐药基因进行检测,通过多位点序列分型(multilocus sequence typing,MLST)技术对分离菌株的亲缘关系进行研究。【结果】从120份父母代产蛋鸡分离到3株沙门氏菌,从120份商品代1?2日龄弱雏分离到25株沙门氏菌,从120份商品代10日龄雏鸡分离到82株沙门氏菌。分离的沙门氏菌对多粘菌素B、亚胺培南、多西环素、甲氧苄啶、替加环素、氟苯尼考、头孢噻肟、恩诺沙星表现为全部敏感,对呋喃妥因、青霉素、利福平、利奈唑胺、万古霉素均表现为全部耐药;对阿莫西林耐药的菌株有30株(占27.27%),敏感的有80株(占72.73%)。耐药基因的PCR检测结果显示：β内酰胺类耐药基因blaTEM存在于所有沙门氏菌分离株中,但其他常见耐药基因在本研究的分离株中未发现。通过对分离菌7对管家基因进行PCR扩增、测序和MLST分型,发现所有沙门氏菌分离株的ST型均为ST11,属于肠炎沙门氏菌。MLST分型结果结合药敏试验结果表明,分离的沙门氏菌属于同一进化系统,具有相同或相似的来源。【结论】被调查商品鸡群的肠炎沙门氏菌感染很可能是其同一来源的父母代种鸡场垂直传播所致,这为该地区白羽肉鸡的沙门氏菌防治提供了参考。     

The incidence of antimicrobial-resistant Salmonella spp on freshly processed poultry from US Midwestern processing plants

AIMS: To determine the incidence of antimicrobial-resistant Salmonella spp. on processed poultry (turkey) at Midwestern poultry plants. METHODS AND RESULTS: Two participating plants were visited at monthly intervals for a period of 1 year. Surface swabs were obtained from carcasses at two selected points on the production line, pre- and post-chill. In addition, samples of the chill water from chill tanks were also examined. Isolation and detection of Salmonella spp. from carcass swabs and chill water was carried out using standard enrichment techniques. Immunomagnetic separation was used to enhance the recovery of the pathogen. Salmonella isolates recovered were identified, serotyped and their antimicrobial resistance profiles determined using the National Antimicrobial Resistance Monitoring System. Results from the study indicated that the overall incidence of Salmonella was approx. 16.7%, with a greater incidence of the pathogen observed on pre-chill than post-chill carcasses. Salmonella isolates recovered displayed resistance to an average of four different antimicrobials. Approximately 15 different serotypes of Salmonella spp. were recovered, with Salmonella serotype Agona, Salmonella serotype Hadar, Salmonella serotype Heidelberg and Salmonella serotype Senftenberg being the most common. CONCLUSIONS: The incidence of Salmonella spp. was relatively low and isolates recovered showed significant degrees of antimicrobial resistance. Factors such as the processing plant examined, the season and farms that were presenting animals for processing influenced the incidence of the pathogen. SIGNIFICANCE AND IMPACT OF THE STUDY: Differences were observed in the serotypes of Salmonella recovered and the types of antimicrobial resistance found at the two plants. The study suggests that the use of antimicrobials at the farm level influences the creation of an environment that promotes the selection of antimicrobial-resistant Salmonella spp. The incidence, isolation and detection of Salmonella spp. on processed poultry are discussed.     

Screening for probiotic properties of strains isolated from feces of various human groups

The present study searched for potential probiotic strains from various human fecal samples. A total of 67 aerobic and 38 anaerobic strains were isolated from 5 different categories of human feces. Systematic procedures were used to evaluate the probiotic properties of the isolated strains. These showed about 75-97% survivability in acidic and bile salt environments. Adhesion to intestinal cell line Caco-2 was also high. The isolates exhibited hydrophobic properties in hexadecane. The culture supernatants of these strains showed antagonistic effects against pathogens. The isolates were resistant to a simulated gastrointestinal environment in vitro. Of the 4 best isolates, MAbB4 (Staphylococcus succinus) and FIdM3 (Enterococcus fecium), were promising candidates for a potential probiotic. S. succinus was found to be a probiotic strain, which is the second such species reported to date in this particular genus. A substantial zone of inhibition was found against Salmonella spp., which adds further support to the suggestion that the probiotic strain could help prevent intestinal infection. This study suggested that the human flora itself is a potential source of probiotics.     

Prevalence, seasonal occurrence and antimicrobial resistance of Salmonella in poultry retail products in Greece

Aims: To detect the prevalence, the seasonal occurrence and distribution of Salmonella serotypes in poultry products and to determine the resistance profile of Salmonella isolates. Method and Results: A total of 96 skin-on chicken carcasses and 30 liver samples were analysed between May 2007 and May 2009 from twenty-two different commercial farm brands found in retail market countrywide. Salmonella was isolated from 38 (39·5%) of 96 chicken carcasses and from 10 (33·3%) of 30 liver samples. Higher isolation rate (60·4%) was observed in carcasses detected during summer (May to October), and lower isolation rate (18·7%) was observed in carcasses detected during winter (November to April); in liver samples, the positive rates were 53·4 and 13·2%, respectively. Twelve serotypes were detected with the serotypes Hadar, Enteritidis and Blockley being the most prevalent at 29·2, 22·9 and 12·5%, respectively. Nine of 11 Salm. Enteritidis isolates occurred during summer. Of 48 isolates, 38 (79%) were resistant to one or more of the antimicrobial agents used. The highest resistance rates were found to the following antimicrobials: streptomycin (64·5%), tetracycline (56·2%), nalidixic acid (39·5%), ampicillin and rifampicin (33·3%). Conclusions: The relatively high Salmonella spp. contamination rates of raw chicken meat and liver have been detected. Salm. Enteritidis isolates peaked in summer, increasing the risk to human health. Antibiotic resistance of Salmonella still remains a threat as resistance plasmids may be extensively shared between animal and humans. Significance and Impact of the Study: The study enabled us to improve the data on the seasonal occurrence of Salmonella and to determine the antimicrobial pattern profile and trends in Salmonella strains isolated from poultry retail products in Greece.     

Biochemical identification and numerical taxonomy of Aeromonas spp. isolated from environmental and clinical samples in Spain

AIMS: To study the phenotypic characteristics of Aeromonas spp. from environmental and clinical samples in Spain and to cluster these strains by numerical taxonomy. METHODS AND RESULTS: A collection of 202 Aeromonas strains isolated from bivalve molluscs, water and clinical samples was tested for 64 phenotypic properties; 91% of these isolates were identified at species level. Aeromonas caviae was predominant in bivalve molluscs and Aerom. bestiarum in freshwater samples. Cluster analyses revealed eight different phena: three containing more than one DNA-DNA hybridization group but including strains that belong to the same phenospecies complex (Aerom. hydrophila, Aerom. sobria and Aerom. caviae), Aerom. encheleia, Aerom. trota and three containing unidentified Aeromonas strains isolated from bivalve molluscs. CONCLUSIONS:Aeromonas spp. are widely distributed in environmental and clinical sources. A selection of 16 of the phenotypical tests chosen allowed the identification of most isolates (91%), although some strains remain unidentified, mainly isolates from bivalve molluscs, suggesting the presence of new Aeromonas species. Numerical taxonomy was not in total concordance with the identification of the studied strains. SIGNIFICANCE AND IMPACT OF THE STUDY: Numerical taxonomy of Aeromonas strains isolated from different sources revealed the presence of potentially pathogenic Aeromonas spp., especially in bivalve molluscs, and phena with unidentified strains that suggest new Aeromonas species.     

基于ITS1-5.8S rRNA-ITS2序列的猪源结肠小袋纤毛虫种群特征分析

【目的】为了揭示结肠小袋纤毛虫病在环境中的分子传播机制,研究了猪源结肠小袋纤毛虫的种群特征。【方法】用粪便涂片镜检和改进型DMEM培养基从病猪结肠内容物分离结肠小袋纤毛虫滋养体,然后用显微观察、吖啶橙荧光染色法和基于ITS1-5.8S rRNA-ITS2序列的分子标记技术分析了豫西地区猪群中结肠小袋纤毛虫的种群特征。【结果】结果显示,从来自豫西地区8个县市的病猪中共分离了15株小袋纤毛虫,5.8S rRNA序列相似性高达99.4%以上,同属于结肠小袋纤毛虫,根据ITS1/2序列分析结果,MJ-2和SX-1株属于结肠小袋纤毛虫基因型A,其余13株均属于结肠小袋纤毛虫基因型B。MJ-2和SX-1株滋养体形态特征明显区别其他13株,绝大多数呈球形,运动缓慢,粪便中和体外培养的虫体密度较低;而其他13株的滋养体均呈多形性,运动快速活跃,虫体密度较大。吖啶橙荧光染色显示,2种基因型滋养体的核结构没明显差别。【结论】首次报道中国猪源结肠小袋纤毛虫存在2个基因型,其中基因型B为优势种群,为防控人和动物结肠小袋纤毛虫病提供重要参考。     

Analysis of Transmission of MRSA and ESBL-E among Pigs and Farm Personnel

Livestock-associated bacteria with resistance to two or more antibiotic drug classes have heightened our awareness for the consequences of antibiotic consumption and spread of resistant bacterial strains in the veterinary field. In this study we assessed the prevalence of concomitant colonization with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and enterobacteriaceae expressing extended-spectrum betalactamases (ESBL-E) in farms at the German-Dutch border region. Nasal colonization of pigs with MRSA (113/547 (20.7%)) was less frequent than rectal colonization with ESBL-E (163/540 (30.2%)). On the individual farm level MRSA correlated with ESBL-E recovery. The data further provide information on prevalence at different stages of pig production, including abattoirs, as well as in air samples and humans living and working on the farms. Notably, MRSA was detected in stable air samples of 34 out of 35 pig farms, highlighting air as an important MRSA transmission reservoir. The majority of MRSA isolates, including those from humans, displayed tetracycline resistance and spa types t011 and t034 characteristic for LA-MRSA, demonstrating transmission from pigs to humans. ESBL-E positive air samples were detected on 6 out of 35 farms but no pig-to-human transmission was found. Detection of ESBL-E, e.g. mostly Escherichia coli with CTX-M-type ESBL, was limited to these six farms. Molecular typing revealed transmission of ESBL-E within the pig compartments; however, related strains were also found on unrelated farms. Although our data suggest that acquisition of MRSA and ESBL-E might occur among pigs in the abattoirs, MRSA and ESBL-E were not detected on the carcasses. Altogether, our data define stable air (MRSA), pig compartments (ESBL-E) and abattoir waiting areas (MRSA and ESBL-E) as major hot spots for transmission of MRSA and/or ESBL-E along the pig production chain.     

Tracing of Salmonella spp. in two pork slaughter and cutting plants using serotyping and macrorestriction genotyping

AIMS: The origin of Salmonella contamination of pork products is not well established. In order to further this knowledge, the transmission of Salmonella spp. from live pigs to pork cuts was investigated in two pork slaughter and cutting plants. METHODS AND RESULTS: Salmonella spp. were isolated from both pork (pigs, carcasses, cuts) and the environment before and during slaughterhouse activities. Eight serotypes were identified. XbaI and SpeI macrorestriction distinguished 20 genotypes of Salmonella Typhimurium and 16 genotypes of Salmonella Derby. A major cluster of Salmonella Typhimurium genotypes was common to both plants and all pig-related genotypes, while a predominant pig-related Salmonella Derby genotype was common to both plants. CONCLUSION: None of the Salmonella strains persisted for long periods in the pork-processing environments. SIGNIFICANCE AND IMPACT OF THE STUDY: This work shows that contaminated live pigs, because of bacterial spread due to the process and ineffective cleaning procedures, are involved in Salmonella contamination.     

Influence of environmental factors and human activity on the presence of Salmonella serovars in a marine environment

The temporal and spatial distribution of Salmonella contamination in the coastal waters of Galicia (northwestern Spain) relative to contamination events with different environmental factors (temperature, wind, hours of sunlight, rainfall, and river flow) were investigated over a 4-year period. Salmonellae were isolated from 127 of 5,384 samples of molluscs and seawater (2.4%), and no significant differences (P < 0.05) between isolates obtained in different years were observed. The incidence of salmonellae was significantly higher in water column samples (2.9%) than in those taken from the marine benthos (0.7%). Of the 127 strains of Salmonella isolated, 20 different serovars were identified. Salmonella enterica serovar Senftenberg was the predominant serovar, being represented by 54 isolates (42.5%), followed by serovar Typhimurium (19 isolates [15%]) and serovar Agona (12 isolates [9.4%]). Serovar Senftenberg was detected at specific points on the coast and could not be related to any of the environmental parameters analyzed. All serovars except Salmonella serovar Senftenberg were found principally in the southern coastal areas close to the mouths of rivers, and their incidence was associated with high southwestern wind and rainfall. Using multiple logistic regression analysis models, the prevalence of salmonellae was best explained by environmental parameters on the day prior to sampling. Understanding this relationship may be useful for the control of molluscan shellfish harvests, with wind and rainfall serving as triggers for closure.     

Streptococcus R (Streptococcus suis type II) infection in pigs in Japan

Since the first outbreak of an epizootic disease on a pig farm in Shimane Prefecture in 1979, similar diseases have occurred continually on other 8 pig farms in the same prefecture until 1982. Main clinical symptoms of the disease were recumbency, convulsion, anorexia and paddling. The diseased pigs ranged mostly from 35 to 67 days of age. Monthly fatality on one pig farm for 1 year was 0.2 to 3.6%. Morbidities in affected litters were mostly at a level of 20 to 30% on 7 pig farms. The diseases were diagnosed as streptococcal meningitis and septicemia with each one of endocarditis and pneumonitis by pathological and bacteriological studies on 20 affected pigs. Distribution of piglets from a breeding farm to pig farms was considered as one of the causes of prevalence in the prefecture. Representative 20 strains of the isolates from diseased animals on 9 pig farms were identified as Streptococcus R (Streptococcus suis type II) by biological and serological examinations. For the latter examination, anti-Streptococcus R, S and T sera were prepared. It was also indicated that the disease had occurred in 8 prefectures in addition to Shimane, because positive results had been obtained from 41 strains submitted from those prefectures for serological diagnosis. The minimal inhibitory concentration was examined in 18 drugs to 19 isolates. It was the lowest in ampicillin and thiopeptin of all the drugs.     

Antimicrobial resistance in generic Escherichia coli isolates from wild small mammals living in swine farm, residential, landfill, and natural environments in southern Ontario, Canada

To assess the impacts of different types of human activity on the development of resistant bacteria in the feces of wild small mammals, we compared the prevalences and patterns of antimicrobial resistance and resistance genes in generic Escherichia coli and Salmonella enterica isolates from fecal samples collected from wild small mammals living in four environments: swine farms, residential areas, landfills, and natural habitats. Resistance to antimicrobials was observed in E. coli isolates from animals in all environments: 25/52 (48%) animals trapped at swine farms, 6/69 (9%) animals trapped in residential areas, 3/20 (15%) animals trapped at landfills, and 1/22 (5%) animals trapped in natural habitats. Animals trapped on farms were significantly more likely to carry E. coli isolates with resistance to tetracycline, ampicillin, sulfisoxazole, and streptomycin than animals trapped in residential areas. The resistance genes sul2, aadA, and tet(A) were significantly more likely to be detected in E. coli isolates from animals trapped on farms than from those trapped in residential areas. Three S. enterica serotypes (Give, Typhimurium, and Newport) were recovered from the feces of 4/302 (1%) wild small mammals. All Salmonella isolates were pansusceptible. Our results show that swine farm origin is significantly associated with the presence of resistant bacteria and resistance genes in wild small mammals in southern Ontario, Canada. However, resistant fecal bacteria were found in small mammals living in all environments studied, indicating that environmental exposure to antimicrobials, antimicrobial residues, resistant bacteria, or resistance genes is widespread.     

Patterns of infection by Salmonella and Yersinia spp. in commensal house mouse (Mus musculus domesticus) populations

AIMS: This study sought to examine the risk posed by house mice transmitting pathogens to livestock on typical mixed-agriculture farms in the UK. METHODS AND RESULTS: In a 10-month longitudinal study at one farm, 222 faecal samples were taken from mice and 57 swabs from the farm environment; 3.2% and 15.8%, respectively, were positive for Yersinia. Seventy-five intestinal samples were taken from house mice from three other farms and 9.3% were positive for Yersinia. The commonest species was Y. enterocolitica (of a wide range of serotypes); all isolates were non-pathogenic, except one of Y. pseudotuberculosis. Salmonella was not isolated from any sample. CONCLUSION: This study provides additional evidence that house mice are generally not significant vectors of either pathogenic Yersinia strains or Salmonella species. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first longitudinal study of Yersinia in any small mammal population, and shows infection to be a dynamic series of generally non-pathogenic, transient infections.     

Phenotypic and molecular typing of Salmonella strains reveals different contamination sources in two commercial pig slaughterhouses

This study aimed to define the origin of Salmonella contamination on swine carcasses and the distribution of Salmonella serotypes in two commercial slaughterhouses during normal activity. Salmonellae were isolated from carcasses, from colons and mesenteric lymph nodes of individual pigs, and from the slaughterhouse environment. All strains were serotyped; Salmonella enterica serotype Typhimurium and Salmonella enterica serotype Derby isolates were additionally typed beyond the serotype level by pulsed-field gel electrophoresis (PFGE) and antibiotic resistance profiling (ARP); and a subset of 31 serotype Typhimurium strains were additionally phage typed. PFGE and ARP had the same discriminative possibility. Phage typing in combination with PFGE could give extra information for some strains. In one slaughterhouse, 21% of the carcasses were contaminated, reflecting a correlation with the delivery of infected pigs. Carcass contamination did not result only from infection of the corresponding pig; only 25% of the positive carcasses were contaminated with the same serotype or genotype found in the corresponding feces or mesenteric lymph nodes. In the other slaughterhouse, 70% of the carcasses were contaminated, and only in 4% was the same genotype or serotype detected as in the feces of the corresponding pigs. The other positive carcasses in both slaughterhouses were contaminated by genotypes present in the feces or lymph nodes of pigs slaughtered earlier that day or from dispersed sources in the environment. In slaughterhouses, complex contamination cycles may be present, resulting in the isolation of many different genotypes circulating in the environment due to the supply of positive animals and in the contamination of carcasses, probably through aerosols.