广东省2008－2009 年沙门菌监测

目的 了解广东省腹泻患者中沙门菌的感染及沙门菌暴发的情况以及沙门菌株的血清型别、耐药性和分子特征.方法 对纳入研究的腹泻病患者进行沙门菌的检测,对日常监测中分离到的菌株和暴发监测收集到的菌株进行血清分型、药物敏感试验和脉冲场凝胶电泳(PFGE)分型.结果 2008年共检测1922份粪便标本,分离到7l株沙门菌,阳性率为3.7%;2009年检测2110份粪便标本,分离到85株沙门菌,阳性检出率为4.0%;156株菌共分37种血清型,鼠伤寒和肠炎沙门菌居多;监测到10起由沙门菌污染引起的食物中毒事件,其中有4起由肠炎沙门菌引起,有3起由鼠伤寒沙门菌引起;发现1起疑似肠炎沙门菌暴发,并开展流行病学调查,结果提示4名病例中有2名病例是感染同一来源的肠炎沙门菌;229株沙门菌对头孢类和喹诺酮类抗菌药物敏感率达80%以上,59.3%是多重耐药沙门菌.结论 在广东省引起感染性腹泻和食物中毒的沙门菌主要为肠炎沙门菌和鼠伤寒沙门菌.

Abstract：

Objective To understand the infection of Salmonella (S.) in patients with diarrhea and outbreaks caused by Salmonella to identify the serotypes, resistance to antibiotics and PFGE types of the strains from the surveillance program in Guangdong province. Methods S. strains from patients with diarrhea were detected, and all the positive strains collected in routine and outbreak surveillance programs, were tested by serum agglutination, antibiotic susceptibility and PFGE.Results 71 S. strains were isolated from 1922 stool samples in 2008, with positive rate as 3.7%.85 S. strains were isolated from 2110 stool samples in 2009, with positive rate as 4.0%. All the 156 strains were divided into 37 serotypes, with S. serotype typhimurium and enteritidis as the most common serotypes. 10 incidents of food poisoning were detected, of which 4 were caused by enteritidis and 3 by typhimurium. A suspected outbreak by enteritidis was discovered and under epidemiological investigation. The findings indicated that 2 of the 4 patients from this outbreak were infected with identical enteritidis isolates. 80% of the 229 isolates were found susceptible to cephalosporins and quinoione and 59.3% of them were muitiresistant to the antibiotics. Conclusion S. enteritidis and S. typhimurium were the most common serotypes that caused infectious diarrhoea and food poisoning in Guangdong province.     

肠炎沙门菌可变数目串联重复序列位点用于多位点可变数目串联重复序列分型分析的评价

目的 评价不同肠炎沙门菌可变数目串联重复序列(VNTR)位点用于多位点可变数目串联重复序列(MLVA)分型的可行性.方法 选取已报道使用的肠炎沙门菌11个VNTR位点,对中国不同时间和地区分离的16株菌进行初步评价,选取具有单一扩增条带的位点进行104株肠炎沙门茵的MLVA分型分析.对这些菌株同时进行脉冲场凝胶电泳(PFGE)分析,比较MLVA分型方法与PFGE分型方法对菌株分型能力的强弱.结果 初筛得到7个VNTR位点用于扩大菌株的分析,这些位点将104株菌分为16个MLVA型别,D值为0.7222,这些菌株同时被分为22个PFGE型别,D值为0.7974.对两种方法各自所分的最大组包含的菌株进行比较,发现PFGE具有更强的分辨能力;从频数分布看,PFGE方法分型结果比较分散,MLVA分型较为集中.结论 用于国际肠炎沙门菌分型具有扩增多态性的VNTR位点在国内分离株中并不都具有多态性结果,在MLVA方法学建立中应选择更多的VNTR位点进行广泛的筛选才有利于国际实验室间的方法的统一.

Abstract：

Objective To evaluate the feasibility of the application of variable-number tandem repeat(VNTR)loci of Salmonella Enteritidis(S. enteritidis)in subtyping mutiple-locus variable-number tandem repeat analysis(MLVA).Methods A total of 16 isolates of S.enteritidis from different place and time in China were preliminarily assessed by choosing 11 reported VNTR loci.the loci with single amplified bands were picked to subtype all 104 S.enteritidis isolates.The isolates were also analyzed by pulse field gel electrophoresis(PFGE)to compare the superiority or inferiority of MLVA method and PFGE method.Results Seven VNTR loci were selected from the preliminary screening to expand the analysis,and the 7 VNTR loci had grouped 104 of S.enteritidis isolates into either 16 MLVA subtypes or 22 PFGE subtypes.with the D value at 0.7222 and 0.7974,respectively.Comparing with the isolates in MLVA subtypes.the isolates in PFGE showed a stronger resolving power.Meanwhile the results in PFGE showed a more disperse frequency distribution than those in MLVA.Conclusion These results indicate that some VNTR locus which have shown a good polymorphism intemationaUy,may fail to show polymorphism in China.thereby.more VNTR loci should be included in MLVA and the wide screening may benefit the unity of global laboratorial methods.     

中国嗜肺军团菌分离株脉冲场凝胶电泳分型分析以及数据库的建立

目的 对分离的262株嗜肺军团菌进行脉冲场凝胶电泳(PFGE)分析,初步建立中国嗜肺军团菌的PFGE分型数据库.方法 采用PFGE技术,对2004-2009年中国11个省(市)分离的嗜肺军团菌用AscⅠ酶切,BioNumerics软件分析PFGE图谱,并建立分子分型数据库.结果 262株嗜肺军团菌的PFGE图谱共分为108种不同的PFGE带型,相似性系数在16%～100%之间,通过聚类分析,可以分为差异明显的不同簇.不同省份、年份和血清型的菌株之间有交叉带型.结论 中国环境分离的嗜肺军团菌菌株基因组变异较大,同时也具有克隆化特征,且可能有多个克隆系存在.

Abstract：

Objective To analyze the molecular types of Legionella (L.) pneumophila strains isolated in China,and to develop the PulseNet-China Database of L.pneumophila.Methods Pulsed field gel electrophoresis (PFGE) was used to analyze 262 L.pneumophila strains collected from 11 provinces between 2004 and 2009 in China.Different kinds of genomic DNA in different L.pneumophila strains were isolated and separated after digesting with Asc Ⅰ.BioNumerics software was used to analysis the PFGE fingerprints.Results L.pneumophila strains isolated in China were quite different regarding their PFGE patterns.There were 108 PFGE types among the 262 strains tested in this study.The similarity value of these strains was in the range of 16%-100% and the same types were discovered in different provinces and years.Conclusion L.pneumophila strains isolated in China were with high genetic variations.There might be different clones existed in China.The development of PulseNet China Database was thus of great significance in monitoring the L.pneumophila strains in the future.     

社区分离金黄色葡萄球菌在健康人群中的分布及其分子生物学特点

目的 调查医科大学学生鼻腔中金黄色葡萄球菌(金葡菌)的定植状况,解析鼻腔定植社区型甲氧两林耐药性金葡菌(MRSA)克隆的分子生物学特点.方法 以无菌棉签从调查对象鼻腔中收集定植菌,鉴定出甲氧西林敏感性金葡菌(MSSA)和MRSA;多重PCR法分型MRSA携带的SCCmec基因岛;PCR测定pvl、seh、tsst1等毒素基因在菌株中的分布;脉冲场凝胶电泳(PFGE)检测MRSA菌株的脉冲场型.结果 2009年977名学生488份样本中鉴定出葡萄球菌,其中凝固酶阴性葡萄球菌(CoNS)和金葡菌分别为364份和124份,MRSA在金葡菌中所占比例为3.4%.2010年调查显示,657名学生中有310份样本鉴定为葡萄球菌属,其中CoNS为195份,金葡菌115份,MRSA在金葡菌中所占比例为7.7%.金葡菌在所有葡萄球菌属中所占比例为29.9%,而MRSA在金葡菌中所占比例为5.1%.MRSA菌株中共鉴定出5种SCCmec基因岛型,其中Ⅳa型最多(10株),为优势SCCmec基因岛类型.PFGE共有11种图谱型,7种(A～G)脉冲场型.10株MRSA均为pvl阳性.结论 1株起源于社区,基因型为Ⅳa SCCmec-pulsotype A且携带pvl毒素基因的特定MRSA克隆在健康大学生中传播.

Abstract：

Objective To investigate the nasal colonization of Staphylococcus (S.) aureus strains among medical university students in Shenyang and to study the molecular epidemiological characteristics of methicillin resistant S. aureus (MRSA) strains. Methods Sterilized nasal swabs were used to collect nasal bacteria from both nares of the students. Nasal specimens were further identified as S. aureus strains, sensitive or resistant to methicillin through a series of tests. Molecular related methods including staphylococcal cassette chromosome mec (SCCmec) typing, pulsed- field gel electrophoresis (PFGE) , coagulase isotyping and minimum inhibitory concentration (MIC) determination etc. were used to characterize the isolates. Prevalence of the panton-valentine leukocidin (pvl) genes (lukS and F-PV) among the isolates was also assessed. Results Staphylococci were found in 488 specimens from 977 participants through the surveillance program, conducted in 2009. Of the 488 specimens being tested, 364 were identified as coagulase-negative staphylococci (CoNS) and 124 as S. aureus. MRSA strain among the S. aureus isolates was accounted for 3.4%. In the surveillance program conducted in 2010, staphylococci grew in 310 specimens fiom 657 participants. Of the 310 specimens tested, 195 were identified as CoNS and 115 as S. aureus. The percentage of MRSA strains among the S. aureus isolates was 7.7%. In total, 239 students carried S.aureus, and the percentage of MRSA carriers among the total specimens tested in this study was 5.1%.Most of the MRSA strains could be classified into one of the five types of SCCmec elements. Type Ⅳ a SCCmec strains were most frequent seen overall (10 isolates). A total of 11 pulsotypes were identified among the MRSA strains and were classified into 7 major groups (A to G) by the mutual correlations of their banding patterns. Ten MRSA strains were identified as pvl positive strains. Conclusion An MRSA clone (Ⅳ a SCCmec pulsotype A) carrying pvl toxin gene was found to be prevalent in the nares of the healthy university students.     

上海市16个冷却塔水中军团菌脉冲场凝胶电泳分型及基因型监测

Objective To investigate the genotypic characteristics and persistence of Legionella pulsed-field gel electrophoresis (PFGE) patterns in 16 air-conditioner cooling towers in six different public sites of Shanghai. Methods From May to October, continuous sampling was operated once per month in 2007. Legionella strains isolated from the 16 cooling towers were confirmed by serological and latex agglutination. PFGE was applied for the fingerprinting of the isolates, while the culster results of PFGE were analyzed by BioNumerics software. Results 131 strains of Legionella were isolated, including L. pneumophila, L. bozemanae, L. micdadei and L anisa.52 distinguishable PFGE patterns were differentiated among the 16 cooling towers, with 37 patterns were owned by just one cooling tower, which was not shared with other cooling towers, while 15 patterns were shared by more than 2 cooling towers. All the cooling towers had ≥2 PFGE patterns,while in 13 cooling towers the same PFGE patterns were recovered during the six months. From June to October of 2007, 18 strains of Legionella belonging to the PFGE pattern of LPAs. SH0078 were isolated continuously from 6 cooling towers. Conclusion This study demonstrated great genotypic diversity and complexity of Legionella in cooling towers. Persistence of the PFGE patterns was observed in 81.25% of the cooling towers. The PFGE pattern of LPAs. SH0078 was distributed widely,suggesting it might be the dominate strain in Shanghai.     

上海市16个冷却塔水中军团菌脉冲场凝胶电泳分型及基因型监测

Objective To investigate the genotypic characteristics and persistence of Legionella pulsed-field gel electrophoresis (PFGE) patterns in 16 air-conditioner cooling towers in six different public sites of Shanghai. Methods From May to October, continuous sampling was operated once per month in 2007. Legionella strains isolated from the 16 cooling towers were confirmed by serological and latex agglutination. PFGE was applied for the fingerprinting of the isolates, while the culster results of PFGE were analyzed by BioNumerics software. Results 131 strains of Legionella were isolated, including L. pneumophila, L. bozemanae, L. micdadei and L anisa.52 distinguishable PFGE patterns were differentiated among the 16 cooling towers, with 37 patterns were owned by just one cooling tower, which was not shared with other cooling towers, while 15 patterns were shared by more than 2 cooling towers. All the cooling towers had ≥2 PFGE patterns,while in 13 cooling towers the same PFGE patterns were recovered during the six months. From June to October of 2007, 18 strains of Legionella belonging to the PFGE pattern of LPAs. SH0078 were isolated continuously from 6 cooling towers. Conclusion This study demonstrated great genotypic diversity and complexity of Legionella in cooling towers. Persistence of the PFGE patterns was observed in 81.25% of the cooling towers. The PFGE pattern of LPAs. SH0078 was distributed widely,suggesting it might be the dominate strain in Shanghai.     

上海某医院产妇乳汁中六溴环十二烷水平及新生儿经母乳日摄入量的监测分析

Objective To explore the level of hexabromocyclododecane(HBCD)in human breast milk of delivery women in a Shanghai hospital.and estimate the daily intake of newborns from breast milk.Methods Forty-eight delivery women in a Shanghai suburb hospital(Class A,Grade 3)were surveyed by questionnaires.and their breast milk samples were collected from September 2006 to April 2007.All the delivery women were singleton pregnancies,excluding high blood pressure,diabetes,HIV infection and adverse medical history.Three diastereoisomers(α-HBCD,β-HBCD,γ-HBCD)were measured by the liquid chromatography-electrospmy ion source-tandem mass spectrometry.and then esitmated the daily intake of the newborns from the breast milk.Results The total HBCD concentration of breast milk,which was detected in 79%(38/48)of samples,ranged from 0.11 ng/g lipid weight(1w)to 37.75 ng/g 1w,with the median at 1.42 ng/g 1w.The most abundant diastereoisomer was α-HBCD which detected in 77%(37/48)of samples,with a median of 1.24,g/g 1w;followed by γ-HBCD and β-HBCD,detected in 13%(6/48)and 17%(8/48)of samples respectively,whose median were both under the limit of detection (LOD).The daily intake of the newborns from the breast milk ranged from 0.71 ng/kg to 243.46 ng/kg.Conclusion The concentrations of HBCD in breast milk of delivery women in a Shanghai hospital have been in a high level.and the influence on newborns'health need to be further studied.     

上海某医院产妇乳汁中六溴环十二烷水平及新生儿经母乳日摄入量的监测分析

Objective To explore the level of hexabromocyclododecane(HBCD)in human breast milk of delivery women in a Shanghai hospital.and estimate the daily intake of newborns from breast milk.Methods Forty-eight delivery women in a Shanghai suburb hospital(Class A,Grade 3)were surveyed by questionnaires.and their breast milk samples were collected from September 2006 to April 2007.All the delivery women were singleton pregnancies,excluding high blood pressure,diabetes,HIV infection and adverse medical history.Three diastereoisomers(α-HBCD,β-HBCD,γ-HBCD)were measured by the liquid chromatography-electrospmy ion source-tandem mass spectrometry.and then esitmated the daily intake of the newborns from the breast milk.Results The total HBCD concentration of breast milk,which was detected in 79%(38/48)of samples,ranged from 0.11 ng/g lipid weight(1w)to 37.75 ng/g 1w,with the median at 1.42 ng/g 1w.The most abundant diastereoisomer was α-HBCD which detected in 77%(37/48)of samples,with a median of 1.24,g/g 1w;followed by γ-HBCD and β-HBCD,detected in 13%(6/48)and 17%(8/48)of samples respectively,whose median were both under the limit of detection (LOD).The daily intake of the newborns from the breast milk ranged from 0.71 ng/kg to 243.46 ng/kg.Conclusion The concentrations of HBCD in breast milk of delivery women in a Shanghai hospital have been in a high level.and the influence on newborns'health need to be further studied.     

嗜水气单胞菌TaqMan实时PCR检测方法的建立

Objective To develop a TaqMan real-time PCR for the detection of aeromonas hydrophila. Methods The conserved region of major adhesion gene of aeromonas hydrophila (aha) was used to design primers and TaqMan probe. A total of six concentration gradients for forward and reverse primers ranging from 200 -700 nmol/L were chosen, and four concentration gradients for probe ranging from I00 -400 nmol/L were chosen. And then the concentration of primers and probe were optimized by ANOVA of completely randomized design respectively. The specificity of the established method was evaluated by using bacteria as contrast, including 45 strains Vibrio cholerae,20 strains Vibrio parahemolyticus, 10 strains Vibrio fluvialis,4 strains Vibrio mimicus,5 strains Vibrio vulnificus, 1 strain Vibrio aiginoayticns, 1 strain Vibrio furnissii, 5 strains Salmonella, 10 strains Shigella and 2 strains Piesiomonas shigelloides. The sensitivity, bacterial sensitivity and DNA sensitivity included,were evaluated. The stool of healthy people was contaminated by aeromonas hydrephila artificially, and the ability of the established TaqMan real-time PCR system for detection of aeromonas hydrophila was also evaluated. Results The cycle threshold (Ct) value deserved from 6 groups of primers concentration gradient was (x±s) :20.69±0.33,20.72±0.21,20.81±0. 12,20.74±0.12,20.51±0. 16 and 20.69±0. 11, respectively, and the concentration of forward primer and reverse primer was determined to be 200 nmol/L (F=1.33, P=0. 28). The Ct value deserved from 4 groups of probe concentration gradient was (x±s) : 20.56±0. 08,20.82±0.05,20. 82±0. 11 and 20.93±0.09,respectively,and the concentration of probe was determined to be 100 nmol/L(F =5.26,P =O. 01 ). The bacterial sensitivity and DNA sensitivity were 80 CFU/ml and 100 fg/μl respectively,and the sensitivity to detect aeromonas hydrophila from stool was 8 × 103 CFU/ml, which might be 8 CFU/ml after 8 hours' enrichment. No amplification was observed in the templates of other bacterial. Conclusion The TaqMan real-time PCR method targeting the aha gene of aeromonas hydrophila had a high sensitivity and specificity and might be used to detect aeromonas hydrophila from pure bacterial and stool rapidly.     

嗜水气单胞菌TaqMan实时PCR检测方法的建立

Objective To develop a TaqMan real-time PCR for the detection of aeromonas hydrophila. Methods The conserved region of major adhesion gene of aeromonas hydrophila (aha) was used to design primers and TaqMan probe. A total of six concentration gradients for forward and reverse primers ranging from 200 -700 nmol/L were chosen, and four concentration gradients for probe ranging from I00 -400 nmol/L were chosen. And then the concentration of primers and probe were optimized by ANOVA of completely randomized design respectively. The specificity of the established method was evaluated by using bacteria as contrast, including 45 strains Vibrio cholerae,20 strains Vibrio parahemolyticus, 10 strains Vibrio fluvialis,4 strains Vibrio mimicus,5 strains Vibrio vulnificus, 1 strain Vibrio aiginoayticns, 1 strain Vibrio furnissii, 5 strains Salmonella, 10 strains Shigella and 2 strains Piesiomonas shigelloides. The sensitivity, bacterial sensitivity and DNA sensitivity included,were evaluated. The stool of healthy people was contaminated by aeromonas hydrephila artificially, and the ability of the established TaqMan real-time PCR system for detection of aeromonas hydrophila was also evaluated. Results The cycle threshold (Ct) value deserved from 6 groups of primers concentration gradient was (x±s) :20.69±0.33,20.72±0.21,20.81±0. 12,20.74±0.12,20.51±0. 16 and 20.69±0. 11, respectively, and the concentration of forward primer and reverse primer was determined to be 200 nmol/L (F=1.33, P=0. 28). The Ct value deserved from 4 groups of probe concentration gradient was (x±s) : 20.56±0. 08,20.82±0.05,20. 82±0. 11 and 20.93±0.09,respectively,and the concentration of probe was determined to be 100 nmol/L(F =5.26,P =O. 01 ). The bacterial sensitivity and DNA sensitivity were 80 CFU/ml and 100 fg/μl respectively,and the sensitivity to detect aeromonas hydrophila from stool was 8 × 103 CFU/ml, which might be 8 CFU/ml after 8 hours' enrichment. No amplification was observed in the templates of other bacterial. Conclusion The TaqMan real-time PCR method targeting the aha gene of aeromonas hydrophila had a high sensitivity and specificity and might be used to detect aeromonas hydrophila from pure bacterial and stool rapidly.     

Laboratory-based surveillance of non-typhoidal Salmonella infections in Guangdong Province, China

Salmonella is one of the most common foodborne pathogens in humans. Laboratory-based surveillance for non-typhoidal Salmonella infection was conducted in Guangdong Province, China to improve understanding about the disease burden and detection of dispersed outbreaks. Salmonella isolated from patients with diarrhea were sent from 16 sentinel hospitals to local public health laboratories for confirmation, serotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis (PFGE). PFGE patterns were analyzed to identify clusters representing potential outbreaks. Between September 2009 and October 2010, 352 (4%) Salmonella isolates were obtained from 9167 stool specimens. Salmonella enterica serotype Typhimurium (45%) and Salmonella enterica serotype Enteritidis (13%) were the most common serotypes, and multidrug resistance was high, especially in Salmonella Typhimurium isolates. PFGE patterns of obtained Salmonella isolates were found to be diverse, but a unique PFGE pattern comprising 53 Salmonella Typhimurium isolates were found to occur almost exclusively in infants. Epidemiologic studies are ongoing to determine whether a common exposure is the source of the Salmonella Typhimurium strain frequently isolated from infants.     

2011-2012年杭州市肠道沙门菌临床分离株的分子型别分析

目的研究2011-2012年杭州市肠道沙门菌临床分离株的型别,了解本地菌株分子流行病学特征。方法对66株肠道沙门菌临床分离株进行血清分型和多位点序列分型(MLST)。对其中主要血清型:鼠伤寒、甲型副伤寒、萨雷甲尼和肠炎沙门菌菌株进行脉冲场凝胶电泳(PFGE)分型。结果分布于21个血清型的66株沙门菌分成26个ST型别。发现一株纽波特沙门菌为新型ST1690。菌株血清型与MLST型别数据库中所对应的血清型符合率为100.00%。9株甲型副伤寒沙门菌的PFGE带型完全一致(P7型),与先前杭州流行菌株有差异(P1-P6型)。6株肠炎沙门菌分成4个PFGE型,型间最小相似性为92.70%。13株鼠伤寒沙门菌分为11个PFGE型,型间最小相似性为71.70%。7株萨雷甲尼沙门菌分成4个PFGE型别,型间最小相似性为91.00%。结论近年杭州腹泻病人中流行的肠道沙门菌菌株主要血清型为鼠伤寒、甲型副伤寒、萨雷甲尼和肠炎等。甲型副伤寒沙门菌菌株在杭州出现了新PFGE型别。MLST数据可以对沙门菌血清学鉴定提供一定的帮助。     

北京市40株肠炎沙门菌多重耐药和分子分型研究

目的分析2009-2010年北京市肠炎沙门菌多重耐药和脉冲场凝胶电泳（pulsed-field gel electropho-resis,PFGE）分子分型。方法对2009-2010年北京市肠道门诊监测系统分离到的40株肠炎沙门菌进行生化鉴定、血清分型并运用纸片法进行药敏检测,并采用PFGE进行分子分型。结果发现40株肠炎沙门菌中,32株多重耐药菌株,其中4～5种抗生素耐药27株（84.38%）,10种抗生素耐药1株（3.13%）;可分为14个PFGE带型,其中4个PFGE型的菌株数超过1株。结论北京市肠炎沙门菌分离株多重耐药性比较严重,PFGE分子型别较多,且存在差异明显的多个克隆系,但同一PFGE型菌株的多重耐药谱较为接近。     

Vertical and horizontal transmission of salmonella within integrated broiler production system

Salmonella remains one of the leading causes of food-borne illness in the United States, and many key questions regarding the introduction and persistence in animal production systems still remain. In order to understand the ecology of Salmonella within an integrated commercial broiler production system, 289 Salmonella enterica were recovered from two integrated poultry farms during the production and processing of seven consecutive flocks. The variety and prevalence of Salmonella serotypes differed between farms. Overall, 15 serotypes were identified, with the most common being Typhimurium (55%), Montevideo (7.9%), Kentucky (9%), and Enteritidis (9.7%). Salmonella Typhimurium and Enteritidis isolates recovered from processed carcasses from Farm One were further characterized using pulsed-field gel electrophoresis (PFGE), and were shown to be indistinguishable from isolates recovered from the poultry house environment and mice trapped on this farm. Additionally, the same broiler S. Typhimurium and S. Enteritidis strains, identified by PFGE, were also isolated from samples taken at a company breeder farm, suggesting vertical transmission of these Salmonella serotypes in this poultry production system. Results indicate that management practices at the breeder level may have a profound effect on the transmission and persistence of salmonellae within an integrated production system, as well as on the potential contamination of poultry-derived products.     

Genomic diversity within phage types of Salmonella enterica ssp. enterica serotypes Enteritidis and Typhimurium

The diversity among 1354 strains of Salmonella enterica subsp. enterica, serotype Enteritidis (n = 847) and Typhimurium (n = 507) isolated in Finland in 1991-2002 (n = 608) and in 2003 (n = 746) were studied. The former strains were studied retrospectively by phage typing and pulsed-field gel electrophoresis (PFGE) harmonized in the European Salm-gene project. The latter strains were studied prospectively, and the results correlated to their antimicrobial susceptibility and association with travel to popular tourist destinations. During both periods, S. Enteritidis phage types (PTs) PT1 and PT4, and S. Typhimurium definite types (DTs) DT1 and DT104 were the major phenotypes. SENTXB.0001 was the dominating single PFGE type among S. Enteritidis strains (40% in 1991-2002; 57% in 2003), and accounted correspondingly for 23% and 63% of the PT1 strains, and 81% and 88% of the PT4 strains. No PFGE types dominated among the S. Typhimurium strains but a correlation was found between certain phage and PFGE types: among DT1 strains, STYMXB.0098 accounted for 66% (1991-2002) and 98% (2003) and among the DT104 strains STYMXB.0001 accounted for 84% and 97% in the two time periods, respectively. Of the S. Enteritidis strains isolated in 2003, 91% were associated with travel, most commonly to Spain, Greece, and Bulgaria. SENTXB.0001 was the major Salmonella PFGE type in these countries. In contrast, most (55%) S. Typhimurium strains were of domestic origin. While only 1.3% of the S. Enteritidis strains were multiresistant and 24% were resistant to nalidixic acid only, 30% of the S. Typhimurium strains were multiresistant. Among the multiresistant S. Typhimurium strains, R-type ACSSuT and PFGE type STYMXB.0001 of the DT104 complex dominated.     

Differentiation of Salmonella enteritidis isolates by fluorescent amplified fragment length polymorphism

Salmonella Enteritidis is responsible for human gastroenteritis outbreaks worldwide, and the molecular characterization of isolates is an important tool for epidemiological studies. Fluorescent amplified fragment length polymorphism (FAFLP) analysis was performed on 31 Salmonella Enteritidis strains from South Brazil isolated from human, foods, swine, broiler carcasses, and other poultry-related samples to subtype isolates in comparison to pulsed-field gel electrophoresis (PFGE) analysis. Five strains of Salmonella Enteritidis from different geographical regions, Salmonella Enteritidis ATCC 13076, and four isolates of different Salmonella serovars were also tested. Among the 41 isolates tested, 96 polymorphic AFs and 40 distinct profiles were obtained, displaying a Simpson's index of diversity of 0.99; whereas the PFGE analysis presented 13 patterns and the resulting Simpson's index was 0.55. Nine FAFLP and seven PFGE clusters could be inferred based in Dice similarity coefficient. FAFLP clustering readily identified different serotypes of Salmonella but did not distinguish isolates epidemiologically nonrelated or distinct phage types. Therefore, these results indicate that FAFLP is a rapid method for epidemiological investigations of Salmonella outbreaks, presenting a high discriminatory power for subtyping of Salmonella Enteritidis.     

Recent trends in the epidemiology of non-typhoidal Salmonella in Israel, 1999-2009

The aim of the present study was to assess the recent trends in the epidemiology of non-typhoid Salmonella in Israel using a sentinel laboratory-based surveillance network. Between 1999 and 2009, 8758 Salmonella stool isolates were reported by five sentinel laboratories. There was a significant decrease in the incidence rate of Salmonella isolates from 70·5/100,000 in 1999 to 21·6/100,000 in 2005 followed by a slight increase to 30·3/100,000 in 2009. Of all Salmonella, 64·3% were isolated from children in the 0-4 years age group. Up to 2008, S. Enteritidis was the most prevalent serotype and in 2009 S. Infantis emerged as the most common Salmonella serotype. The decrease in the incidence of S. Enteritidis and S. Typhimurium and increase in S. Infantis among humans were associated with a similar trend among breeding flocks, which followed significant preventive interventions conducted against S. Enteritidis and S. Typhimurium infections in poultry. Tight surveillance and education of food handlers and consumers should be enhanced to reduce the foodborne transmission of Salmonella in Israel.     

Serotypes, antibiotic resistance, and class 1 integrons in Salmonella isolates from pediatric cases of enteritis in Tehran, Iran

The present study was conducted to investigate serotype distribution, antimicrobial resistance patterns, carriage of class 1 integron, and clonality of Salmonella strains isolated from patients aged 0-12 years in Tehran, Iran, during 2007-2008. A total of 139 Salmonella isolates were studied. Salmonella serotypes Enteritidis, Infantis, and Typhimurium included 84.9% of isolates, Enteritidis accounting for 41.7%. The most prevalent resistances were to doxycycline (64.7%), nalidixic acid (61.2%), tetracycline (51.8%), and streptomycin (42.8%). Fifty-three (38.1%) isolates contained class 1 integron. Eight different gene cassettes were identified, aadA1 being the most frequently encountered. Pulsed-field gel electrophoresis showed that integron-positive Salmonella strains belonging to serotypes Infantis, Enteritidis, and Typhimurium were attributed to two, three, and five different pulsotypes, respectively. The findings indicated that the distribution and drug resistance pattern of most prevalent Salmonella serotypes were broadly similar to that reported globally from human isolates. Presence of class 1 integrons was common among Salmonella serotypes in Tehran, Iran. Concurrent clonal expansion and horizontal transmission events seem to contribute to increase in drug resistance prevalence among Salmonella serotypes.     

Tentative colistin epidemiological cut-off value for Salmonella spp

The objective of this research was to determine minimal inhibitory concentration (MIC) population distributions for colistin for Salmonella on subtype level. Furthermore, we wanted to determine if differences in MIC for colistin could be explained by mutations in pmrA or pmrB encoding proteins involved in processes that influence the binding of colistin to the cell membrane. During 2008-2011, 6,583 Salmonella enterica subsp. enterica isolates of human origin and 1931 isolates of animal/meat origin were collected. The isolates were serotyped, and susceptibility was tested towards colistin (range 1-16?mg/L). Moreover, 37 isolates were tested for mutations in pmrA and pmrB by polymerase chain reaction (PCR) and DNA sequencing. MIC distribution for colistin at serotype level showed that Salmonella Dublin (n=198) followed by Salmonella Enteritidis (n=1247) were less susceptible than "other" Salmonella serotypes originating from humans (n=5,274) and Salmonella Typhimurium of animal/meat origin (n=1794). MIC was ≤1?mg/L for 98.9% of "other" Salmonella serotypes originating from humans, 99.4% of Salmonella Typhimurium, 61.3% of Salmonella Enteritidis, and 12.1% of Salmonella Dublin isolates. Interestingly, Salmonella Dublin and Salmonella Enteritidis belong to the same O-group (O:1, 9,12), suggesting that surface lipopolysaccharides (LPS) of the cell (O-antigen) play a role in colistin susceptibility. The epidemiological cut-off value of >2?mg/L for colistin suggested by European Committee on Antimicrobial Susceptibility Testing (EUCAST) is placed inside the distribution for both Salmonella Dublin and Salmonella Enteritidis. All tested Salmonella Dublin isolates, regardless of MIC colistin value, had identical pmrA and pmrB sequences. Missense mutations were found only in pmrA in one Salmonella Reading and in pmrB in one Salmonella Concord isolate, both with MIC of ≤1 for colistin. In conclusion, our study indicates that missense mutations are not necessarily involved in increased MICs for colistin. Increased MICs for colistin seemed to be linked to specific serotypes (Salmonella Dublin and Salmonella Enteritidis). We recommend that Salmonella with MIC of >2?mg/L for colistin be evaluated on the serovar level.     

Molecular typing of Salmonella enterica serovars Enteritidis, Corvallis, Anatum and Typhimurium from food and human stool samples in Tunisia, 2001-2004

During the period from 2001 to 2004, a total of 72 isolates of Salmonella enterica serovars: Anatum (n=40), Enteritidis (n=18), Corvallis (n=8), and Typhimurium (n=6), of various origins (mainly food and diarrhoeagenic stool samples), were collected and further characterized by antibiotic resistance, plasmid analysis, and pulsed-field gel electrophoresis (PFGE). Forty-five isolates presented multidrug resistance to antibiotics. Among which one S. enterica serovar Anatum isolate was resistant to 11 antibiotics, and one S. enterica serovar Typhimurium DT104 isolate was resistant to eight antibiotics. Plasmid profiling identified eight plasmid profiles (with 1-5 plasmids) among the isolates, of which one plasmid profile (P01) was predominant. XbaI PFGE analysis revealed the presence of a predominant clone of the four studied Salmonella serovars circulating in Tunisia throughout the years 2001-2004.