Biofilm formation by multidrug-resistant Salmonella enterica serotype typhimurium phage type DT104 and other pathogens

The biofilm-forming capability of Salmonella enterica serotypes Typhimurium and Heidelberg, Pseudomonas aeruginosa, Listeria monocytogenes, Escherichia coli O157:H7, Klebsiella pneumoniae, and Acinetobacter baumannii isolated from humans, animal farms, and retail meat products was evaluated by using a microplate assay. The tested bacterial species showed interstrain variation in their capabilities to form biofilms. Strong biofilm-forming strains of S. enterica serotypes, E. coli O157: H7, P. aeruginosa, K. pneumoniae, and A. baumannii were resistant to at least four of the tested antibiotics. To understand their potential in forming biofilms in food-processing environments, the strong biofilm formers grown in beef, turkey, and lettuce broths were further investigated on stainless steel and glass surfaces. Among the tested strains, Salmonella Typhimurium phage type DT104 (Salmonella Typhimurium DT104) isolated from retail beef formed the strongest biofilm on stainless steel and glass in beef and turkey broths. K. pneumoniae, L. monocytogenes, and P. aeruginosa were also able to form strong biofilms on the tested surface materials. Salmonella Typhimurium DT104 developed a biofilm on stainless steel in beef and turkey broths through (i) initial attachment to the surface, (ii) formation of microcolonies, and (iii) biofilm maturation. These findings indicated that Salmonella Typhimurium DT104 alongwith other bacterial pathogens could be a source of cross-contamination during handling and processing of food.     

Comparison of antibiotic susceptibility profiles and molecular typing patterns of clinical and environmental Salmonella enterica serotype Newport

The genus Salmonella is composed of more than 2,400 serotypes, many of which cause enteric diseases in humans and animals. Several Salmonella serotypes are multidrug resistant, and there is evidence of the clonal spread of these strains from animals to humans. Salmonella enterica serotype Newport is one of the serotypes that increasingly present a multidrug-resistant phenotype. Source tracking and antibiotic resistance testing are important considerations for identifying the outbreak strain. The first goal of this study was to examine the antibiotic susceptibility patterns of clinical and environmental Salmonella Newport isolates from various geographic locations and to compare the discriminatory ability of two DNA fingerprinting techniques. The second goal was to determine whether the antibiotic resistance profiles and typing patterns correlated. Thirty Salmonella Newport isolates, including environmental and human clinical strains, were subjected to pulsed-field gel electrophoresis (PFGE), ribotyping, and antibiotic susceptibility testing. Eighty percent of the isolates showed total or intermediate resistance to one or more drugs; 75% of the isolates were multidrug resistant. Ribotyping with the EcoRI enzyme and PFGE with the XbaI enzyme each divided the isolates into 14 groups. Cluster analysis based on antibiotic susceptibility patterns generated 23 profiles. The susceptible and resistant isolates were not differentiated on the basis of either of the molecular typing techniques. Hence, no correlation was observed between the antibiotic resistance profiles and the DNA subtyping patterns. In conclusion, ribotyping is as discriminatory as PFGE and, when used in combination with antibiotic resistance profiles, provides a powerful tool for the source tracking of Salmonella Newport.     

山东地区生猪和家禽屠宰环节沙门菌血清型分布

目的了解山东地区生猪和家禽屠宰环节沙门菌血清型分布,为进一步开展动物源性产品风险评估提供数据。方法 2014年9~12月从山东省部分屠宰场采集分离的335株沙门菌,应用液态悬浮芯片技术对沙门菌菌体(O)抗原、鞭毛(H)抗原和附加靶蛋白(AT)的基因进行检测,然后运用Salmonella serotyping assay软件分析鉴定血清型。结果 335株沙门菌中299株共分为29个血清型,另有36株未分型,优势血清型主要为德尔卑沙门菌(S.Derby,24.8%,83/335、)和肠炎沙门菌(S.enteritidis,15.2%,51/335)。德尔卑沙门菌、汤卜逊沙门菌(S.Thompson)和阿贡纳沙门菌(S.Agona)在生猪和家禽屠宰场中都有分布;生猪屠宰场以德尔卑沙门菌(39.8%,64/161)为主,其次为鼠伤寒沙门菌(S.typhimurium,19.3%,31/161)和汤卜逊沙门菌(13.7%,22/161);家禽屠宰场中以肠炎沙门菌(28.7%,50/174)、印第安纳沙门菌(S.Indiana,12.1%,21/174)和德尔卑沙门菌(10.9%,19/174)为主。另外,不同地区屠宰场的沙门菌血清型呈差异分布,生猪屠宰场中除鲁中部外,其他地区主要血清型为德尔卑沙门菌;家禽屠宰场中,鲁东和鲁西地区主要是肠炎沙门菌,鲁东北地区以德尔卑沙门菌为主;鲁中部地区分离株以汤卜逊沙门菌为主。结论山东省屠宰场中的沙门菌污染比较严重,且有多种血清型,需加强屠宰环节的致病菌监控,降低动物产品在屠宰环节受沙门菌污染的风险。     

Influence of serotype on the growth kinetics and the ability to form biofilms of Salmonella isolates from poultry

The influence of the serotype on the growth behaviour and the ability to form biofilms of Salmonella enterica strains was investigated. The relationships between biofilm formation and growth kinetic parameters were also determined. A total of 69 strains (61 isolates from poultry and 8 reference strains from culture collections) belonging to 10 serotypes (S. enterica serotype Typhimurium, S. Newport, S. Paratyphi B, S. Poona, S. Derby, S. Infantis, S. Enteritidis, S. Virchow, S. Agona and S. Typhi) were tested. All Salmonella strains produced biofilms on polystyrene micro-well plates (crystal violet assay). Isolates were classified as weak (35 strains), moderate (22), or strong (12) biofilm producers. S. Agona and S. Typhi produced the most substantial (P < 0.001) biofilms. Growth curves were performed at 37 °C in tryptone soy broth by means of optical density (OD_420–580) measurements from 0 to 48 h. Growth kinetic parameters (Gompertz model) varied between serotypes. The maximum growth rate (ΔOD_420–580/h) ranged from 0.030 ± 0.002 (S. Typhi) to 0.114 ± 0.011 (S. Agona). The ability of Salmonella strains to form biofilms was not related to their growth kinetic parameters. The formation of biofilms by Salmonella on polystyrene constitutes an issue of concern because plastic materials are frequently used in food facilities. The findings suggest that special efforts must be made for the effective control of Salmonella in food-processing environments when S. Agona or S. Typhi strains are present.     

Epidemiology and antibiotic resistance of Salmonella enterica Serovar Kentucky isolates from Tunisia: The new emergent multi-drug resistant serotype

Since 2002, the emergence of multidrug resistant Salmonella enterica serovar Kentucky (S. Kentucky) and the associated salmonellosis with treatment failure were declared in different parts of the world and were in most of the case contracted during travels to Northeast and Eastern Africa. In the present work, we reported an epidemiological study of S. Kentucky isolated from different environmental and clinical origins in Tunisia, using Pulsed-field gel electrophoresis (PFGE); Enterobacterial Repetitive Intergenic Consensus (ERIC-2) fingerprinting; Plasmid profiling; and antibiotic resistance profiles. ERIC-2 fingerprinting allowed the differentiation of 14 different patterns versus only 4 pulsotypes. Besides, a high proportion of strains were found to be nontypeable by XbaI-PFGE and/or by plasmid profiling (plasmid-free strains). The antibiotic resistance was mainly detected against streptomycin (80.7%), sulfonamides (42.1%) and tetracycline (15.7%). Furthermore, two avian strains were shown to be resistant to trimethoprim–sulfamethoxazole and three clinical strains have demonstrated multidrug-resistant phenotypes (against 5 to 10 antibiotics) and all of them exhibited resistance against nalidixic acid, ciprofloxacin, ofloxacin and tetracycline.ERIC-2 PCR was found to be the most discriminative. However, combination of the three typing methods offer a better mean for differentiating S. Kentucky isolates, monitoring the multiresistant types and determination of their origin.     

Variation of antibiotic resistance in Salmonella Enteritidis,Escherichia coli O157:H7, and Listeria monocytogenes after exposure to acid,salt, and cold stress

Bacteria with antibiotic-resistant could seriously threaten to human health, increasing the treatment cost for infections and negatively affecting treatment outcomes. Stress adaptation is one possible mechanism for the acquisition or enhancement of antibiotic resistance in bacteria as a result of cross-protection. In this study, the effects of acid, salt, and cold stress on the antibiotic resistance of Salmonella Enteritidis, Listeria monocytogenes, and Escherichia coli O157:H7 were investigated using the disc diffusion method. For S. Enteritidis, acidic growth conditions increased resistance to ciprofloxacin and erythromycin (p < .05), and addition of 4% NaCl to growth media decreased resistance to chloramphenicol (p < .05). Irrespective of pH and the NaCl concentration of the growth medium, refrigerated E. coli O157:H7 showed increased resistance to amoxycillin, ciprofloxacin, gentamicin, streptomycin, and erythromycin (p < .05). Acid-adapted L. monocytogenes showed decreased the resistance to amoxycillin, ampicillin, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, streptomycin, and tetracycline (p < .05). In conclusion, prolonged exposure of foodborne pathogens to acid, salt, and cold stress alters their antibiotic resistance. However, the effect of acid, salt, and cold stress on bacterial antibiotic resistance depend on both the bacterial species and the specific antibiotic. Therefore, multiple factors need to be considered for a foodborne antimicrobial resistant risk assessment.     

Prevalence, antibiotic resistance, and molecular characterization of Salmonella serovars in retail meat products

The prevalence of Salmonella was determined in chicken meat (n = 26), beef (n = 49), and pork (n = 56) collected from wholesale markets, retail stores, and traditional markets in Seoul, South Korea, in 2009. Antibiotic resistance was assessed, and the molecular subtypes of Salmonella isolates were ascertained using an automated repetitive sequence-based PCR (rep-PCR) system (DiversiLab). A total of 18 Salmonella strains were isolated from 17 of 131 samples: 16 strains from each of 16 samples and 2 strains from the same pork sample. The prevalence of Salmonella from the retail meats was 2.0% in beef, 8.9% in pork, and 42.3% in chicken meat. Among 10 different serotypes, Salmonella enterica Panama was recovered from a beef sample, and Salmonella London and Salmonella Montevideo were the predominant serotypes from pork and chicken meat, respectively. The highest antibiotic resistance observed was to erythromycin (100%) followed by streptomycin (22.2%) and tetracycline and chloramphenicol (16.7%). Of the 18 isolates, 5 (27.8%) were resistant to two or more antibiotics, and 1 isolate from chicken meat was resistant to eight antibiotics, including cephalosporins. Differentiation between all of the Salmonella isolates except between Salmonella Montevideo and Salmonella London was successfully performed with the automated rep-PCR system, indicating that it can be added to the toolbox for source tracking of foodborne pathogens associated with outbreaks.     

Comparison of antimicrobial resistance patterns and phage types of Salmonella Typhimurium isolated from pigs,pork and humans in Belgium between 2001 and 2006

Infections with non-typhoid Salmonella represent a major problem in industrialized countries.The emergence and spread of antimicrobial-resistant pathogens, among them Salmonella, has become a serious health hazard worldwide. One of the most commonly isolated non-typhoid Salmonella serovars in pigs, pork and humans is Salmonella Typhimurium. In this study the comparison of the incidences of resistance to nine antimicrobials, resistance patterns and phage types between S. Typhimurium isolated from pigs (n = 581), pork (n = 255) and humans (n = 1870) in Belgium in the period 2001 to 2006 was performed.Resistance to the antimicrobials ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline was frequently observed and varied between 23.5% and 83.1%. Resistance ranged from 15.6% to 20.7% for the combination trimethoprim–sulfonamides and from 3.4% to 5.8% for nalidixic acid. Resistance to the critical important antimicrobials cephalosporins and fluoroquinolones was found sporadically (≤ 1.2%). Resistance to the different antimicrobials was observed to be similar in S. Typhimurium isolates from the various origins. Twenty-seven antimicrobial resistance patterns representing in total 75.2%, 89.0% and 89.6% of the isolates from pigs, pork and humans respectively were found to be common among the three groups and 73 combinations antimicrobial resistance pattern/phage type were found to be common among pork and human isolates, representing 70.1% of the pork isolates and 51.0% of the human isolates. The high percentage of isolates that have a common resistance pattern, and in a less pronounced way a common combination phage type/resistance pattern, are in agreement with the hypothesis of transfer of antimicrobial resistant Salmonella from pigs via the consumption of pork to humans as one of the possible pathways. The most prevalent combination in Belgium within both the pork isolates (7.4%) and the human isolates (13.2%) was S. Typhimurium DT104 resistant to ampicillin, chloramphenicol, streptomycine, sulfonamides and tetracycline.     

深圳市畜禽产品中沙门氏菌血清型与耐药性研究

目的了解深圳市畜禽产品检出的沙门氏菌的血清型与耐药性。方法选取2013~2015年分离出的70株沙门氏菌,进行血清型鉴定和药物敏感性试验。结果共确定了18个血清型,以伦敦沙门氏菌检出数量最多。药敏试验结果显示,70株沙门氏菌有24种多重耐药谱,全部菌株对头孢唑啉、阿米卡星和庆大霉素耐药,对厄他培南、亚胺培南和美洛培南敏感。耐药5种及5种以上菌株在猪肉中占78.0%,数量最多。结论建立食源性沙门氏菌耐药性的长期监测机制,对该病原菌的防控及指导养殖业和临床合理用药具有现实和医学意义。     

全基因组测序分析2018年江西省临床分离非伤寒沙门菌耐药性研究

目的 掌握2018年江西省食源性疾病病例的非伤寒沙门菌分离株的耐药特征、耐药表型与耐药基因之间的对应关系,评价全基因组测序(whole genome sequencing,WGS)技术在耐药监测的应用前景。方法 本研究以2018年江西省食源性疾病病例分离的58株非伤寒沙门菌为研究对象,用微量肉汤稀释法检测菌株对14种抗菌药物的耐药性,对58株非伤寒沙门菌进行WGS,拼接后的序列经过与ResFinder数据库比对,注释耐药基因。结果 58株非伤寒沙门菌对四环素耐药率最高(77.59%,45/58),其次是氨苄西林(72.41%,42/58),对亚胺培南全部敏感。耐3类及3类以上抗生素的多重耐药菌株占56.90%(33/58),最高为6重耐药菌株占3.45%(2/58)。58株非伤寒沙门菌共筛选出47种11类耐药基因,喹诺酮耐药决定区(quinolone resistance-determining region, QRDR)存在gyrA、gyrB和parC基因突变。菌株对氨基糖苷类耐药基因携带率最高为100.00%(58/58),其次是四环素类耐药基因 携带率为72.41%(42/58),大环内酯类耐药基因携带率最低为3.45%(2/58)。携带3类及3类以上耐药基因的菌株占77.59%(45/58),1.72%(1/58)菌株最高携带9类耐药基因。58株非伤寒沙门菌的药敏试验结果与检测出的已知耐药基因总体符合率达93.43%(611/654)。除喹诺酮类外,其他类别的抗生素耐药表型与耐药基因符合率均高于91%,部分种类的抗生素耐药表型与基因符合率达100%。结论 非伤寒沙门菌耐药现象较为严重,其耐药表型与耐药基因有很高的一致性,WGS可作为预测沙门菌耐药性的有效手段。     

Lessons learned from a Salmonella enteritidis phage type 4 outbreak in Austria, 2005

An outbreak of gastroenteritis due to Salmonella Enteritidis phage type 4 occurred in people who attended a traditional hunting festivity in a small village in western Austria 6 through 11 November 2005. Of approximately 250 attendees, 227 had consumed dishes offered at the festival, and of these consumers 35 persons fulfilled the outbreak case definition (attack rate of 15.4%). Sp?tzle (traditional pastalike side dish) was most likely the contaminated part of the incriminated main course (relative risk of 18.9, 95% confidence interval of 4.6 to 76.7; P < 0.001). Thirteen eggs that remained from the preparation of the sp?tzle were negative for Salmonella when tested individually without shell disinfection, as were 1200 eggs collected at the egg production plant and examined with shell disinfection. The back-traced egg production farm had been initially certified as Salmonella free by a voluntary quality control program. However, an intensified environmental investigation of the incriminated egg production farm performed in the first quarter of 2006 and based on an appropriate method of sampling revealed Salmonella Enteritidis phage type 4 in 4 of 13 flocks. Although a combination of epidemiological and microbiological investigations allowed elucidation of the mode of spread, no restrictions were placed on the incriminated flocks of laying hens. These flocks were kept in production until they were stalled out due to age in August 2006. In June 2006, a cluster of 23 cases of Salmonella Enteritidis phage type 6 infection was again associated with this egg production farm. Evidence provided by epidemiological analyses is often disregarded by decision makers. However, negative results from microbiological testing of food involved in an outbreak are often weighted as strong evidence against a causal association between that food and the outbreak.     

Combined effect of bacteriophage and antibiotic on the inhibition of the development of antibiotic resistance in Salmonella typhimurium

Food Science and Biotechnology - This study was designed to evaluate the combined effects of bacteriophage and antibiotic on the reduction of the development of antibiotic-resistance in Salmonella...     

Interventions to control Salmonella contamination during poultry,cattle and pig slaughter

The fundamental principle of controlling microbial contamination during slaughter is based on sanitary and hygienic processes. Both choosing abattoir technologies and conducting individual operations should be approached with the primary goal of minimizing microbial load on the final product. Nevertheless, even when best hygienic abattoir practices are applied, complete prevention of all microbial contamination of carcasses is unachievable under commercial conditions. Therefore, in some situations it may be considered necessary to further reduce the microbial loads on carcasses through application of additional control interventions, i.e. decontamination treatments. Treatments applied on poultry carcasses or parts include water, steam and chemical solutions (e.g., lactic or acetic acid, chlorine-based compounds, cetylpyridinium chloride, and trisodium phosphate) and result in overall microbial reductions of 0.6–3.8 log units; antimicrobial activity of some chemicals (e.g., chlorine compounds) is reduced in the presence of organic material. Decontamination treatments of hides (pre-skinning) and/or cattle carcasses reduce Salmonella by < 0.7–5.1 log units. Salmonella prevalence reductions achievable by decontamination of porcine carcasses seem to be at least two-fold. Overall Salmonella reductions on final carcasses and meat can be significantly improved when multiple decontamination treatments are applied sequentially during slaughter and dressing operations. It is important to note that decontamination interventions should be validated and considered as part of a hazard analysis critical control points (HACCP)-based food safety system which is subject to verification and auditing, and they should never be used as a substitute for good sanitation and proper hygiene practices.     

Effect of farm type on within-herd Salmonella prevalence, serovar distribution, and antimicrobial resistance

Salmonella represents a major challenge to the pig industry, as pork presents a risk for human salmonellosis. In this study, we have examined the effect of farm type on the prevalence of fattening pigs shedding Salmonella on 12 farms at risk for harboring Salmonella. On six open (grow-to-finish) and six closed (farrow-to-finish) farms, the prevalence of pigs shedding Salmonella was determined on two occasions approximately 2 months apart. The serovar, phage type, and antimicrobial resistance of the obtained Salmonella isolates were determined. On all farms, pigs shedding Salmonella were detected on at least one of the two sampling days. The mean within-herd prevalence was 7.8%. Closed farms were two times less likely to have pigs shedding Salmonella than open farms. On open farms, the odds of finding Salmonella shedding in pigs were 1.9 times higher when sampling was performed at slaughter age than when samples were taken halfway through the fattening period. Salmonella enterica serovar Typhimurium was the most predominant serotype, with a prevalence of 62 to 63% on both farm types. Of all the Salmonella Typhimurium isolates, 65% had the tetraresistant profile ASSuT (ampicillin, streptomycin, sulfonamide, and tetracycline) with or without additional resistance to trimethoprim-sulfonamide. Phage type DT120 seemed to be especially associated with this antimicrobial-resistant profile. The prevalence of Salmonella Typhimurium isolates showing resistance to ampicillin, streptomycin, tetracycline, sulfonamide, trimethoprim-sulfonamide, and lincomycin hydrochloride and spectinomycin sulfate tetrahydrate was significantly higher on open farms than on closed farms.     

Serotyping and antibiotic resistance profiling of Salmonella in feedlot and nonfeedlot beef cattle

As part of a larger study to assess risk factors associated with hide and carcass contamination of beef cattle during transport to slaughter, a total of 281 salmonellae were isolated from 1,050 rectal, hide, carcass, and environmental samples. For feedlot cattle, salmonellae were recovered from 4.0% of rectal samples, 37.5% of hide samples, 19.0% of carcass samples, and 47.4% of environmental samples. For nonfeedlot cattle, salmonellae were recovered from 10.9% of rectal samples, 37.5% of hide samples, 54.2% of carcass samples, and 50.0% of environmental samples. Overall, the five serotypes most commonly associated with feedlot cattle and their environment were Salmonella Anatum (18.3% of the isolates), Salmonella Kentucky (17.5%), Salmonella Montevideo (9.2%), Salmonella Senftenberg (8.3%), and Salmonella Mbandaka (7.5%). The five serotypes most commonly associated with nonfeedlot cattle and their environment were Salmonella Kentucky (35.4%), Salmonella Montevideo (21.7%). Salmonella Cerro (7.5%), Salmonella Anatum (6.8%), and Salmonella Mbandaka (5.0%). Antimicrobial susceptibility testing of all of the isolates associated with feedlot cattle revealed that 21.7% were resistant to tetracycline, compared with 11.2% of the isolates associated with nonfeedlot cattle. None of the other isolates from feedlot cattle were resistant to any of other antimicrobial agents tested, whereas 6.2% of nonfeedlot cattle isolates were resistant to more than four of the antimicrobial agents tested.     

沙门氏菌环丙沙星诱导株marR, soxR和acrR基因突变与多重耐药性的相关性研究

本文对11株动物源体外诱导的环丙沙星抗性沙门氏菌的mar操纵子基因marO, marR, marA, marB, soxR, soxS和acrR基因(包括启动子区)的点突变进行检测,结果显示在沙门氏菌诱导株中marR, soxR和acrR基因检测到新突变,而marO, marA, marB和soxS基因未发现突变.应用实时荧光定量PCR对诱导株的marA和soxS基因及外排泵基因acrA, acrB和tolC的mRNA表达水平进行检测,结果表明这些基因的表达量均显著增加,且marA, soxS和acrAB-tolC的mRNA表达水平与沙门氏菌诱导株的多重耐药表型(Mar表型)相关,环丙沙星诱导株对其它氟喹诺酮类药物和结构不相关的抗生素均产生耐药.本研究结果表明沙门氏菌诱导株的调控基因突变和mar操纵子介导的acrAB-tolC的表达上调均贡献了沙门氏菌诱导株的氟喹诺酮抗性和Mar表型,且诱导株的marR, soxR和acrR基因突变与氟喹诺酮抗性和Mar表型具有相关性.     

Modeling the inactivation of Salmonella Typhimurium, Listeria monocytogenes, and Salmonella Enteritidis on poultry products exposed to pulsed UV light

Pulsed UV light inactivation of Salmonella Typhimurium on unpackaged and vacuum-packaged chicken breast, Listeria monocytogenes on unpackaged and vacuum-packaged chicken frankfurters, and Salmonella Enteritidis on shell eggs was explained by log-linear and Weibull models using inactivation data from previous studies. This study demonstrated that the survival curves of Salmonella Typhimurium and L. monocytogenes were nonlinear exhibiting concavity. The Weibull model was more successful than the log-linear model in estimating the inactivations for all poultry products evaluated, except for Salmonella Enteritidis on shell eggs, for which the survival curve was sigmoidal rather than concave, and the use of the Weibull model resulted in slightly better fit than the log-linear model. The analyses for the goodness of fit and performance of the Weibull model produced root mean square errors of 0.059 to 0.824, percent root mean square errors of 3.105 to 21.182, determination coefficients of 0.747 to 0.989, slopes of 0.842 to 1.042, bias factor values of 0.505 to 1.309, and accuracy factor values of 1.263 to 6.874. Overall, this study suggests that the survival curves of pathogens on poultry products exposed to pulsed UV light are nonlinear and that the Weibull model may generally be a useful tool to describe the inactivation patterns for pathogenic microorganisms affiliated with poultry products.     

Prevalence and antibiotic resistance of Salmonella serovars in ducks,duck rearing and processing environments in Penang,Malaysia

An investigation was carried out to determine the prevalence and antibiotic resistance of Salmonella serovars in ducks, their rearing and processing environments in Penang, Malaysia. A total of 531 samples collected from wet markets and duck farms, were examined from August 2009 to October 2010. The overall prevalence of Salmonella serovars was 23.5% (125/531). The 125 Salmonella isolates belong to 10 different serovars namely Typhimirium (29.6%), Enteritidis (12.0%), Gallinarum (2.4%), Braenderup (12.0%), Albany (11.2%), Hadar (20.8%), Derby (6.4%), Weltevreden (1.6%), Newbrunswick (3.4%) and London (0.8%). Salmonella serovars also showed various resistance patterns against 13 different antibiotics. All the serovars were resistant to erythromycin but susceptible to cephalothin, gentamicin and ceftriaxone. Plasmids were detected in 91 (72.8%) of the isolates with sizes ranging from 1.4 to 23.1 Kbp. Our findings provide baseline information on the distribution of Salmonella serovars in ducks, their rearing and processing environments, and indicate that ducks should be considered as an important source of food-borne pathogens.     

北京市食源性非伤寒沙门菌的分子分型和耐药性研究

目的了解北京市食源性非伤寒沙门菌的分子特征及耐药情况。方法对2004—2010年北京市食源性致病菌监测网收集的100株沙门菌进行脉冲场凝胶电泳(PFGE)分型和抗生素敏感性检测。结果 100株非伤寒沙门菌通过PFGE分型分为62个不同的带型,每个带型包含1~11株菌。抗生素敏感性结果显示,100株菌中有55株菌表现为对至少1种抗生素耐药,其中多重耐药菌株15株。菌株对各抗生素的耐药率为萘啶酸40%、四环素30%、氯霉素15%、庆大霉素10%、甲氧苄啶/磺胺甲恶唑10%、环丙沙星9%、头孢西丁1%、头孢噻肟0%。结论沙门菌PFGE带型和耐药谱均与血清型存在很高的一致性。提示北京市食源性非伤寒沙门菌的耐药情况比较严重,开展对该菌分子分型与耐药特征分析的联合监测意义重大。