台州市食源性沙门菌耐药性、毒力因子及分子分型研究

目的 了解台州市食品中分离的沙门菌耐药性、毒力因子以及基因分型情况,建立食源性沙门菌的分子特征本底信息,为食源性疾病的防治提供技术支撑.方法 对近几年从食品中分离的22株沙门菌进行12种抗生素药敏试验、10种毒力基因PCR检测、脉冲电场凝胶电泳(PFGE)基因分型,用BioNumerics 5.0软件对分型数据进行聚类分析.结果 22株食源性沙门菌的总耐药率为59.1％,耐药率居前三位的抗生素分别是复方新诺明(36％)、四环素(27％)、萘啶酸(27％);所有菌株均检出6种以上毒力因子,1株肠炎沙门菌存在毒力岛、质粒及噬菌体等多种毒力因子;PFGE分型共得到21个条带,可分为5个基因型别,包括18种指纹图谱,各基因型别间同源性小于70％.结论 台州市食源性沙门菌存在致病风险,建立的指纹图谱数据库可为食源性疾病的防治提供技术支持.     

不同来源肠炎沙门菌毒力基因特征分析

目的研究石家庄地区不同来源的肠炎沙门菌毒力基因携带情况的差异及特点。方法收集石家庄地区早市生禽销售点、生禽屠宰场及食物中毒标本中分离出的肠炎沙门菌124株,对其中8种毒力基因(invA、sopE、agfA、spvR、hilA、stn、pefA、shdA)进行聚合酶链式反应(PCR)检测。结果肠炎沙门菌具有不同的毒力基因谱型,8种毒力基因在不同来源的肠炎沙门菌中均有检出,其中毒力基因invA、sopE、stn、hilA、spvR、pefA在食物中毒分离株中的携带率高,均在94%以上。食物中毒分离株与早市生禽销售点分离株的8种毒力基因携带率差异无统计学意义(P0.05),而生禽屠宰场分离株与食物中毒和早市生禽销售点分离株之间差异有统计学意义(P0.05)。结论石家庄地区早市生禽销售点检出的肠炎沙门菌中易致病的高风险株较多,应加强对生禽的卫生监督与防控。     

2020—2021年辽宁省食源性单核细胞增生李斯特菌毒力基因分布

目的 分析2020—2021年辽宁省食源性单核细胞增生李斯特菌（Lm）毒力基因分布特征及分子血清分型情况。方法 采用普通PCR方法对Lm的19个毒力基因包括毒力岛Ⅰ在内的6个位点（prfA、plcA、plcB、hlyA、mpl和actA）和毒力岛Ⅱ内化素家族蛋白基因的10个位点（inlA、inlB、inlC、inlD、inlE、inlF、inlG、inlH/C2、inlI、inlJ）,以及3个毒力基因相关位点（iap、fbpA、hpt）进行检测。同时应用多重PCR对所有菌株进行5种（1/2a、1/2b、1/2c、4b和3a）血清型分型检测。结果 在辽宁省食源性分离到的91株Lm中,36株Lm的19种毒力基因全部检出,其检出率高达39.6%。55株Lm菌株出现2种及2种以上毒力基因的不同缺失。inlG和inlF基因缺失率较高,分别为41.8%（38/91）和52.7%（48/91）。依据毒力基因携带情况,可分为13个基因型,其中携带19种毒力基因的Ⅰ型为辽宁省的优势基因型别。辽宁省Lm被分成4组分子血清型,1/2a（3a）血清型占比为59.3%（54/91）,1/2b（3b）占比为34.1%（31/91）,1/2c（3c）占比为3.3%（3/91）,4b（4d、4e）占比为3.3%（3/91）,3株4b血清型均分离自肉及肉制品。结论 辽宁省食源性Lm的毒力基因携带率高,毒力基因缺失具有多样性且存在样品种类上的差异。     

鼠伤寒沙门菌婴幼儿分离株耐药基因及毒力基因研究

目的基于全基因组测序结果,分析鼠伤寒沙门菌耐药表型和耐药基因的关系,研究其耐药发生机制和毒力因子。方法利用美国临床和实验室标准委员会(CLSI)推荐的微量肉汤稀释法对5岁以下腹泻患儿粪便中分离的321株鼠伤寒沙门菌开展药物敏感性试验,从中选择不同耐药表型的3株鼠伤寒沙门菌(S1:敏感;S2:TET耐药;S3:ESBLs阳性,10重耐药)进行全基因组测序,通过与抗生素抗性基因数据库(ARDB)和病原毒力因子数据库(VFDB)比对以及美国国立生物技术信息中心(NCBI)核酸数据库人工检索,对耐药基因和毒力基因进行注释。结果 321株鼠伤寒沙门菌对IPM和MEM均敏感,对TET和AMP的耐药率最高,分别为84.4%(271/321)和83.8%(269/321),206株菌株显示为耐3类以上抗生素(64.2%,206/321),11株CIP-CTX耐药株均为ESBLs阳性(3.4%,11/321);全基因组测序结果显示,S1、S2和S3的全基因组大小依次为4 876 427、4 970 690、5 133 380 bp,预测编码基因数分别为4 825、4 936和5 082个,GC含量依次为52.18%、52.14%、51.87%;对S1、S2和S3基因组中18、20和32个耐药基因进行注释,除共有基因外,S2主要携带tet A和sul2基因,S3主要携带sul1/2/3、tetB、AAC(3)-IV、AAC(6')-I、ANT(2″)-I、ANT(3″)-I、aph A1、bla_(CTX-M-14)、bla_(OXA-1)、catB3、cml_e1和cml_e3基因。与阳性鼠伤寒沙门菌株LT2的gyr A基因进行序列比对发现,S3 gyr A基因第87位密码子由GAC突变为AAC(Asp87→Asn);分别注释S1、S2和S3基因组的130、129和120个毒力基因,发现主要以三型分泌系统和粘附因子为主。结论 5岁以下腹泻患儿粪便样品中鼠伤寒沙门菌耐药现象严重;全基因组测序分析发现耐药基因与耐药表型一致,且存在多种毒力因子;为后续开展耐药基因传播机制和菌株致病性研究,评估其对人群的健康风险,防控鼠伤寒沙门菌感染提供技术支持。     

2003-2010年山东省食源性沙门菌血清分型及药敏分析

目的了解2003—2010年山东省食源性沙门菌的血清型分布及耐药情况,为制定政策提供科学依据。方法根据GB/T 4789—2008《食品卫生微生物学检验》方法进行沙门菌菌种鉴定和血清分型;采用临床实验室标准研究所(CLSI)推荐的微量肉汤稀释法进行药物敏感性试验和结果判读,确定耐药表型。结果 120株确定血清型沙门菌分属5个群(8个亚群)24个血清型,肠炎和德比沙门菌为最常见血清型。胥瓦增格隆、维也纳、布里丹、明斯特、乌赫利等9种血清型为2010年首次检出血清型。126株沙门菌对14种抗生素均有不同程度的耐药,萘啶酮酸的耐药率最高(61.90%),其次为四环素(33.33%)、氨苄青霉素(31.75%)、磺胺嘧啶(26.19%);而敏感性以头孢吡肟最高(5.37%),其次是阿米卡星(9.52%)、环丙沙星(10.32%)。结论山东省食源性沙门菌耐药形势严峻,应加强畜牧养殖业中抗生素使用的管理,从食物链的源头和动物食品生产过程中采取合理的干预措施,保障食品安全。     

江西省食源性沙门菌血清分型及脉冲场凝胶电泳指纹图谱研究

研究江西省食源性沙门菌的血清型,用脉冲场凝胶电泳(PFGE)方法对优势血清型进行分子分型,建立江西省食源性沙门菌PFGE指纹图谱资料库,为食源性疾病溯源提供数据。方法 对136株食源性沙门菌进行血清分型,对其中优势血清型德尔卑沙门菌菌株进行PFGE分型,获得分子分型指纹图谱,运用Bionumerics v6.6软件进行聚类分析。结果 136株沙门菌分离株血清群以B群为主,优势血清型主要是德尔卑沙门菌(49.26%),67株德尔卑沙门菌可分为41个型别的PFGE指纹图谱(相似值100%的为同一PFGE型别),主要集中在3个型别中。结论 江西省食源性沙门菌血清型分布呈多样性,优势血清型是德尔卑沙门菌,生肉制品是其主要的来源,同种血清型别的PFGE指纹图谱无相关性。     

新疆零售牛肉中沙门菌毒力基因的检测

目的了解新疆库尔勒市零售牛肉沙门菌污染状况和沙门菌分离株毒力基因携带状况。方法参考食品安全国家标准GB 4789.4-2016的方法,采用培养基培养和沙门菌生化鉴定试剂盒对零售牛肉中的沙门菌进行分离鉴定,并对沙门菌分离株10种毒力基因(inv A、hil A、ssa Q、mgt C、sii D、sop B、spv B、spv C、spv D、spv R)进行PCR检测。结果 317份牛肉样品共检出沙门菌阳性样品28份,分离鉴定到阳性沙门菌28株,污染率为8.8%(28/317);除ssa Q、spv C毒力基因外,其余8种毒力基因均有检出。毒力基因inv A和spv R具有高度的稳定性,携带率均为100%(28/28);毒力基因sii D、spv B和spv D的携带率也较高,分别达78.6%(22/28)、75.0%(21/28)和75.0%(21/28)。结论新疆库尔勒市零售牛肉沙门菌污染较为严重,应采取措施加强对新疆库尔勒市牛肉生产各环节的防控与食品卫生监督。     

宁波市河水环境中沙门菌分布特征和耐药性

目的了解宁波市人工河水环境中沙门菌的血清型分布特征及耐药情况,为预防、控制相应食源性疾病发生提供科学根据。方法对河水样品进行离心浓缩、蛋白胨水增菌液增菌、亚硒酸盐胱氨酸增菌液选择性增菌和沙门菌显色平板分离沙门菌,对分离菌株采用系统生化和血清凝集进行鉴定,并采用纸片法检测菌株对8种抗生素的耐药性,对多重耐药菌株和耐β-内酰胺类抗生素菌株扩增主要相关耐药基因。结果 2014年1月至2015年12月,共采集48份河水样品,分离沙门菌株105株,主要血清型为鼠伤寒(26株)、德尔卑(14株)、里森(8株)、肠炎(4株)、阿贡纳(4株)、斯坦利(4株)、阿格玛(4株),其他及未分型沙门菌41株。70株(66.7%)耐至少一种抗生素,对抗生素的耐药率分别为氨苄西林53.3%、四环素42.9%、甲氧苄啶-磺胺甲恶唑32.4%、庆大霉素11.4%、环丙沙星4.8%、头孢噻肟4.8%和产超广谱β-内酰胺酶4.8%。β-内酰胺类抗生素相关耐药基因为TEM型(n=52)、OXA型(n=6)和CTX-M型(n=3),58.1%的菌株1类整合子基因阳性。结论人工河水环境中沙门菌检出率较高,且部分血清型为重要的食源性致病菌,检出菌也有较高的耐药性,携带多种耐药基因,提示食源性疾病防控中需关注环境细菌的危害。     

2016年广西壮族自治区食源性沙门菌的耐药性与耐药谱研究

目的 了解广西壮族自治区食源性沙门菌耐药状况,建立广西壮族自治区食源性沙门菌耐药性数据库。方法 对2016年从广西壮族自治区各市县收集的分离自食品的70株沙门菌和分离自腹泻患者的234株沙门菌采用微量肉汤法对8类14种抗生素进行耐药性试验,开展耐药谱研究。结果 所有沙门菌菌株均对亚胺培南敏感,对其余13种抗生素产生不同程度的耐药。70株食品来源的沙门菌对四环素耐药率最高(45.71%,32/70);234株腹泻患者来源的沙门菌对氨苄西林耐药率最高(70.94%,166/234),其次为四环素(70.09%,164/234)。腹泻患者来源沙门菌对氨苄西林、氨苄西林/舒巴坦、四环素、萘啶酸、头孢噻肟和头孢唑啉的耐药率均高于食品分离株,差异有统计学意义(P<0.05)。2种来源的沙门菌耐药谱广泛,共同耐药谱为ACTT/S(耐氨苄西林-氯霉素-四环素-甲氧苄啶/磺胺甲噁唑)。结论 广西壮族自治区食源性沙门菌耐药状况不容乐观,特别是对青霉素类、氯霉素类、磺胺类、四环素类抗生素严重耐药,提示应对其加强监测,建立科学的防控策略。     

台州市食源性单核细胞增生李斯特菌分子特征研究

目的了解台州市食品中分离的单核细胞增生李斯特菌的血清型、毒力基因以及基因分型情况,建立食源性单核细胞增生李斯特菌的分子特征本底信息,为食源性疾病的防治提供技术支持。方法对近几年从食品中分离的37株单核细胞增生李斯特菌进行多重PCR血清分型、9种毒力基因(prf A、inl A、inl B、iap、fla A、hly A、plc B、mpl和act A)PCR检测、PFGE基因分型,用Bio Numerics 6.6软件对分型数据进行聚类分析。结果 37株食源性单核细胞增生李斯特菌的血清型以1/2a或3a型别为主;所有菌株均检出4种以上毒力基因,有15株菌携带所有9种毒力基因;37株菌经Apa I酶切PFGE分型后,共得到22种带型,每种带型包含1~5株不等,相似度区间为67%~100%。结论台州市食源性单核细胞增生李斯特菌存在致病流行风险,建立的指纹图谱数据库可为食源性疾病的防治提供技术支持。     

温州市食品中沙门菌污染状况及特征分析

目的了解温州市食品中沙门菌的污染状况,分析分离的沙门菌血清型分布、耐药性及脉冲场凝胶电泳(PFGE)分子分型特征。方法依据GB 4789.4—2016《食品安全国家标准食品微生物学检验沙门氏菌检验》进行菌株分离鉴定及血清学分型,采用微量肉汤稀释法进行药敏试验,PFGE法进行分子分型。结果 6类食品2 039份样品中,37份样品检出沙门菌,检出率为1.8%,其中生禽肉和生畜肉检出率较高,分别为6.9%(20/290)和3.4%(10/290)。37株沙门菌分属16种血清型,居前三位分别为鼠伤寒沙门菌、德尔卑沙门菌和肠炎沙门菌。81.1%(30/37)的菌株对17种抗生素产生不同程度的耐药,呈现24种耐药谱,多重耐药率为56.8%(21/37)。PFGE图谱分为31种PFGE带型,呈多态性。结论沙门菌在温州市食品中存在一定的污染率,耐药情况形式严峻,PFGE图谱的聚集性与沙门菌的血清型有一定的联系,与耐药谱之间的关联性并不明确。     

Psychrotrophy and foodborne Salmonella

Recent reports on the behaviour of Salmonella at chill temperatures (less than 10 degrees C) raise concerns on the purported safety of refrigerated foods. The propensity for growth of salmonellae within 10-28 days in complex broth (5.9 degrees C) and agar (4.0 degrees C) media is overshadowed by more recent evidence on their capability to proliferate in fresh meats (2.0 degrees C) and shell eggs (4.0 degrees C) within 6 and 10 days, respectively. Such findings, together with the inability of many domestic refrigerators to maintain uniformly cold temperatures, are disquieting. Gaseous mixtures of CO2, N2 and O2 are widely used to extend the shelf life of chilled foods, notably fresh meats. The high levels of CO2 used in modified atmosphere packaging or generated by endogenous microflora in vacuum-packaged foods effectively inhibit the growth of psychrotrophic spoilage bacteria. Current evidence suggests that this industrial practice also arrests the growth of Salmonella but exerts little or no effect on their survival. Enhancement of the bacteriostatic potentials of pH and NaCl as temperature deviates from the optimum for growth to lower values could further contribute to the safety of chilled foods.     

Pathogenicity of foodborne Salmonella

Salmonella remains a leading etiological agent in bacterial foodborne diseases. Although human salmonellosis generally presents as a self-limiting episode of enterocolitis, the disease can degenerate into chronic and debilitating conditions. Antibiotic treatment of uncomplicated salmonellosis is contra-indicated because it tends to prolong the carrier state. Clinical management of systemic infections with newer drugs such as third-generation cephalosporins and quinolones is most promising, particularly in light of the increasing resistance of Salmonella to the traditional ampicillin, chloramphenicol and trimethoprim sulfamethoxazole therapeutic agents. Research into the development of effective vaccines from avirulent auxotrophic or from virulence plasmid-cured strains may ultimately facilitate the control of salmonellosis in human populations and in various agricultural sectors. Human salmonellosis reflects the outcome of a confrontation between humoral and cellular immune responses of the host, and virulence determinants of the invasive pathogen. Following an adhesion-dependent attachment of salmonellae to lumenal epithelial cells, the invasive pathogen is internalized within an epithelial cell by a receptor-mediated endocytotic process. Cytotoxin localized in the bacterial cell wall suggestively may facilitate Salmonella entry into the epithelial layer. Cytoplasmic translocation of the infected endosome to the basal epithelial membrane culminates in the release of salmonellae in the lamina propria. During this invasive process, Salmonella secretes a heat-labile enterotoxin that precipitates a net efflux of water and electrolytes into the intestinal lumen. Although non-typhoid salmonellae generally precipitate a localized inflammatory response in deeper tissues via lymphatics and capillaries, and elicit a major immune response. Current research efforts have focused on the molecular characterization and role of virulence plasmids and chromosomal genes in Salmonella pathogenicity.     

Citrus flavonoid represses Salmonella pathogenicity island 1 and motility in S. Typhimurium LT2

Most of the current commercial probiotic strains have not been selected for specific applications, but rather on the basis of their technological potential for use in diverse applications. Therefore, by selecting them from appropriate sources, depending on the target population, it is likely that better performing strains may be identified. Few strains have been specifically selected for human neonates, where the applications of probiotics may have a great positive impact. Breast-milk constitutes an interesting source of potentially probiotic bifidobacteria for inclusion in infant formulas and foods targeted to both pre-term and full-term infants. In this study six Bifidobacterium strains isolated from breast-milk were phenotypically and genotypically characterised according to international guidelines for probiotics. In addition, different in vitro tests were used to assess the safety and probiotic potential of the strains. Although clinical data would be needed before drawing any conclusion on the probiotic properties of the strains, our results indicate that some of them may have probiotic potential for their inclusion in products targeting infants.     

The control of foodborne diseases on the island of Guam

A change of government policy on Guam eliminating annual food handler medical examinations and requiring, instead, training in hygiene has reduced the incidence of foodborne disease cases associated with eating in commercial food and drink establishments. Some specific disease problems generally attributed to foodborne transmission, including Salmonella and Vibrio infections, have not been similarly reduced.     

Evaluation of the BAX gel and fluorometric systems for the detection of foodborne Salmonella

The present study compared the sensitivity of the BAX automated fluorometric and the recently discontinued BAX gel electrophoresis systems with a standard culture method to detect Salmonella in 333 high-moisture and 171 low-moisture foods. A total of 95 naturally contaminated foods, including 63 high-moisture and 32 low-moisture foods, were detected by the standard culture method. No contaminated samples were identified exclusively by the BAX systems. By means of the analytical protocol stipulated by the manufacturer, the BAX fluorometric system detected 36 (57.1%) and 29 (90.6%) of the contaminated high- and low-moisture foods, respectively. Similar results were obtained with the BAX gel electrophoresis system, which identified 40 (63.5%) and 26 (81.3%) of the contaminated high- and low-moisture foods. The rate of false-positive reactions with the BAX systems was low. Our results indicate that the low sensitivity of the BAX systems with high-moisture foods, notably raw meats and poultry products, was serovar-independent. The high levels of background microflora that commonly occur in raw meat and on fresh fruit and vegetable products, and the high successive dilutions of test materials for PCR analysis, suggestively undermined the sensitivity of the gel and the fluorometric BAX assays. The potential benefits of immunomagnetic separation of Salmonella in preenrichment cultures, of selective broth enrichment following preenrichment to markedly reduce levels of background microflora in PCR test materials, and the use of larger portions of test materials in PCR analyses should be investigated.     

Salmonella and broiler processing in the United States: Relationship to foodborne salmonellosis

Salmonella is one of the leading causes of foodborne illness worldwide, with over 40,000 cases reported each year in the United States alone. Salmonella is often associated with foods of animal origin, with chicken and dishes containing chicken often thought to be the most likely source. The Food Safety Inspection Service of the United States Department of Agriculture keeps data on the serotypes of Salmonella isolated from Hazard Analysis Critical Control Point verification samples obtained each year. The Centers for Disease Control and Prevention (CDC) publishes the most common Salmonella serotypes isolated from human disease each year. In addition, CDC maintains records of all reported foodborne outbreaks and the vehicle of illness, when determined. This review examines the overall prevalence of Salmonella serotypes isolated from broilers, the serotypes most commonly associated with human illness, and serotypes most commonly found in foodborne salmonellosis associated with chicken or chicken containing products.     

食源性沙门菌流行趋势及耐药性研究进展

沙门菌病是主要的食源性疾病,构成了全球范围内主要的公共卫生问题,我国由沙门菌引起的食源性疾病也占首位.研究发现,肉制品可能是人类沙门菌病主要的传染源,且近年来在全球范围内,肉制品中耐药性沙门菌的检出率居高不下,这使临床医生治疗时可选择的药物受到限制.随着家禽肉类食品的日益全球化,沙门菌病的控制可能会面临更严峻的挑战,因...