Antimicrobial resistance and genetic relatedness among Salmonella from retail foods of animal origin: NARMS retail meat surveillance

Salmonella isolates were recovered from a monthly sampling of chicken breasts, ground turkey, ground beef, and pork chops purchased from selected grocery stores in six participating FoodNet sites (Connecticut, Georgia, Maryland, Minnesota, Oregon, and Tennessee) in 2002 and an additional two sites in 2003 (California and New York). In 2002 and 2003, a total of 6,046 retail meats were examined, including 1,513 chicken breasts, 1,499 ground turkey samples, 1,522 ground beef samples, and 1,502 pork chops. Retail meat samples tested increased to 3,533 in 2003 as compared to 2,513 in 2002. Overall, six percent of 6,046 retail meat samples (n = 365) were contaminated with Salmonella, the bulk recovered from either ground turkey (52%) or chicken breast (39%). Salmonella isolates were serotyped and susceptibility tested using a panel of 16 antimicrobial agents. S. Heidelberg was the predominant serotype identified (23%), followed by S. Saintpaul (12%), S. Typhimurium (11%), and S. Kentucky (10%). Overall, resistance was most often observed to tetracycline (40%), streptomycin (37%), ampicillin (26%), and sulfamethoxazole (25%). Twelve percent of isolates were resistant to cefoxitin and ceftiofur, though only one isolate was resistant to ceftriaxone. All isolates were susceptible to amikacin and ciprofloxacin; however, 3% of isolates were resistant to nalidixic acid and were almost exclusive to ground turkey samples (n = 11/12). All Salmonella isolates were analyzed for genetic relatedness using pulsed-field gel electrophoresis (PFGE) patterns generated by digestion with Xba1 or Xba1 plus Bln1. PFGE fingerprinting profiles showed that Salmonella, in general, were genetically diverse with a total of 175 Xba1 PFGE profiles generated from the 365 isolates. PFGE profiles showed good correlation with serotypes and in some instances, antimicrobial resistance profiles. Results demonstrated a varied spectrum of antimicrobial resistance and PFGE patterns, including several multidrug resistant clonal groups among Salmonella isolates, and signify the importance of sustained surveillance of foodborne pathogens in retail meats.     

Outbreak of multidrug-resistant Salmonella newport--United States,January-April 2002

During January-April 2002, Salmonella serotype Newport was isolated from 47 persons in five states: New York (34 cases), Michigan (five), Pennsylvania (four), Ohio (two), and Connecticut (two). Antimicrobial-susceptibility testing of three isolates by CDC revealed resistance to amoxicillin/clavulanate, ampicillin, cefoxitin, ceftiofur, cephalothin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline. In addition, two of three isolates were resistant to kanamycin; two had decreased susceptibility or resistance to ceftriaxone. To determine the cause of the outbreak, the New York State Department of Health (NYSDOH) and CDC conducted a case-control study. This report summarizes the results of this investigation, which implicated exposure to raw or undercooked ground beef as the vehicle of transmission. The findings also highlight the emergence of multidrug-resistant S. Newport in the United States. These strains exhibit decreased susceptibility or resistance to ceftriaxone, thereby complicating empiric therapy for serious Salmonella infections. Clinicians should be informed of the emergence of these S. Newport strains, and persons should refrain from eating undercooked ground beef and wash their hands after handling raw ground beef.     

Trends in antimicrobial resistance phenotypes in non-typhoid Salmonellae from human and poultry origins in France

A total of 1873 strains from human origin and 4283 strains from non-human origin of Salmonella enterica serotypes Typhimurium, Enteritidis, Heidelberg, Hadar and Virchow, collected over three years 1993, 1997 and 2000, were examined in order to determine the rate of antimicrobial resistance to 12 antimicrobial drugs. The objective of the study was to describe and to compare the evolution of the main resistance types in human and non-human isolates, focusing on the poultry sector. The evolution and the rates of antimicrobial resistances for the five serotypes, with the exception of Virchow, were almost comparable in strains isolated from human and non-human sources over the period studied. The most striking result concerning single resistance was the spectacular increase of the resistance frequency to nalidixic acid for the strains belonging to serotypes Hadar and Virchow, especially in the poultry food sector (14% in 1993 vs. 72% in 2000 for Salmonella Virchow, 4% in 1993 vs. 70% in 2000 for Salmonella Hadar) and also in human isolates (24% in 1997 vs. 48% in 2000 for S. Virchow, 31% in 1997 vs. 78% in 2000 for S. Hadar). In addition to the classical resistance to ampicillin, streptomycin, sulphonamide, chloramphenicol and tetracycline (ASSuCT resistance type), which stabilized between 1997 and 2000, the emergence of a new resistance type was observed.     

Antimicrobial-drug susceptibility of human and animal Salmonella typhimurium, Minnesota, 1997-2003

We compared antimicrobial resistance phenotypes and pulsed-field gel electrophoresis (PFGE) subtypes of 1,028 human and 716 animal Salmonella enterica serotype Typhimurium isolates from Minnesota from 1997 to 2003. Overall, 29% of human isolates were multidrug resistant. Predominant phenotypes included resistance to ampicillin, chloramphenicol or kanamycin, streptomycin, sulfisoxazole, and tetracycline (ACSSuT or AKSSuT). Most human multidrug-resistant isolates belonged to PFGE clonal group A, characterized by ACSSuT resistance (64%), or clonal group B, characterized by AKSSuT resistance (19%). Most animal isolates were from cattle (n = 358) or swine (n = 251). Eighty-one percent were multidrug resistant; of these, 54% were at least resistance phenotype ACSSuT, and 43% were at least AKSSuT. More than 80% of multidrug-resistant isolates had a clonal group A or B subtype. Resistance to ceftriaxone and nalidixic acid increased, primarily among clonal group A/ACSSuT isolates. Clonal group B/AKSSuT isolates decreased over time. These data support the hypothesis that food animals are the primary reservoir of multidrug-resistant S. Typhimurium.     

Characterization of multidrug-resistant Salmonella enterica serovar Heidelberg isolated from humans and animals

Salmonella enterica serovar Heidelberg has been recognized as one of the most common serovar associated with foodborne infections in the United States. It is also frequently isolated from nonhuman sources and has increasingly shown resistance to various antimicrobial agents. The present study was undertaken to identify the predominant antimicrobial resistance phenotypes and genotypes of Salmonella Heidelberg (n = 95) isolates of human, swine, and turkey origin. Antimicrobial susceptibility was done using Kirby-Bauer disk diffusion method with a panel of 12 antimicrobials. Pulsed-field gel electrophoresis genotyping was used to determine the diversity of the isolates. The antimicrobial resistance genes and carriage of Class 1 and 2 integrons were determined by polymerase chain reaction. All Salmonella Heidelberg isolates from swine were resistant to one or more of the antimicrobials tested and the majority (73.3%) showed multidrug resistance to streptomycin, tetracycline, and kanamycin (R-type: StTeKm). About 80% of the Salmonella Heidelberg isolates of human origin were pan-susceptible, however, one isolate showed multidrug resistance to 10 of 12 antimicrobials tested. Among the multidrug-resistant (MDR) Salmonella Heidelberg isolates, Class 1 integrons with variable sizes of 1.2 to 1.5 kb were detected in six isolates (three each) from humans and swine. DNA sequencing revealed that Class 1 integrons of both human and swine origin carried a gene encoding aminoglycoside adenyltransferase (aadA). Resistance genes identified in other loci include aphA1-Iab, strA, bla(TEM), and tetA (B). Both human and swine MDR strains of Salmonella Heidelberg carried the resistance phenotypes on self-transferable plasmids. Dendrogram analysis of pulsotypes indicated possible clonality of Salmonella Heidelberg between isolates of human and swine origin. The findings in this study indicate the increasing significance of swine as reservoirs of emerging MDR serovars, such as MDR Salmonella Heidelberg, is of public health significance.     

Salmonella in healthy pigs: prevalence, serotype diversity and antimicrobial resistance observed during 1998-1999 and 2004-2005 in Japan

To determine prevalence, serotype diversity and antimicrobial resistance of Salmonella in healthy pigs, faecal samples from 6771 pigs on 73 farms collected during 1998-1999 and 2004-2005 were examined. Salmonella isolates were serotyped and tested for susceptibility to 22 antimicrobials: benzylpenicillin, ampicillin, amoxicillin, cefazolin, cephaloridine, gentamicin, kanamycin, streptomycin, fradiomycin, colistin, tetracycline, chlortetracycline, oxytetracycline, chloramphenicol, thiamphenicol, sulfadimethoxine, sulfamethoxazole, sulfamethoxypyridazine, trimethoprim, sulfamethoxazole/trimethoprim, norfloxacin and ofloxacin. Farm-level and pig-level Salmonella prevalences were 35.5% and 2.2% in 1998-1999, and 35.7% and 3.3% in 2004-2005. Prevalence by growth stage was 2.4% for sows, 3.3% for weaned pigs, 2.7% for fattening pigs and 3.8% for finishing pigs. The predominant serotypes identified were Agona (28.4%), Typhimurium (17.9%) and Infantis (16.4%) in 1998-1999, and Typhimurium (32.5%), Anatum (24.6%) and Infantis (13.5%) in 2004-2005. Compared with the 1998-1999 isolates, the 2004-2005 isolates showed significantly higher rates of resistance to all the antimicrobials except tetracyclines (P<0.01 to P<0.05) and resistance to 2 antimicrobials [19.4% (13/67) vs. 39.7% (50/126), P<0.01]. This study provides national estimates of Salmonella prevalence in healthy pigs of different growth stages in Japan.     

成都市未成年人群腹泻沙门氏菌血清型、耐药及分子分型研究

目的 了解成都市未成年腹泻人群中沙门氏菌感染的血清型分布及耐药性。方法 2012—2019年于成都市各区、市的哨点医院采集18岁以下腹泻患者粪便标本,按照GB4789.4进行沙门氏菌的分离鉴定和血清分型,随机选择部分样本进行微量肉汤稀释法药敏试验和脉冲场凝胶电泳（PFGE）分型。结果 共检出611份腹泻粪便来源沙门氏菌,可分为36种血清型,其中鼠伤寒和肠炎沙门氏菌占据主要优势,分别为68.2%和11.0%。耐药方面,沙门氏菌对氨苄西林的耐药率排首位（76.5%）,其次为四环素（70.5%）、甲氧氨苄嘧啶/磺胺甲噁唑（44.5%）、氯霉素（40.0%）和氨苄西林/舒巴坦（38.0%）;对一、二、三代头孢类抗生素的耐药率有较大差异（4.5%~33.0%）,对亚胺培南均敏感。多重耐药现象严重,以氨苄西林-四环素-甲氧氨苄嘧啶/磺胺甲噁唑（AMP-TET-SXT,占39.0%）,氨苄西林-氨苄西林/舒巴坦-四环素（AMP-AMS-TET,占32.0%）等为主。95株鼠伤寒沙门氏菌PFGE聚类相似度为53%,分为87种带型,其中5种带型各含2~3株相同带型。结论 成都市未成年腹泻患者沙门氏菌主要血清型是鼠伤寒沙门氏菌和肠炎沙门氏菌。多重耐药较严重,AMP-TET-SXT耐药率最高,优势沙门氏菌PFGE型别呈现多样性,存在散在沙门氏菌引起食物中毒的可能。     

广州市566株腹泻病例沙门菌的血清型分布及耐药性分析

目的 了解广州市近两年腹泻病例沙门菌分离株的血清型分布及耐药情况。方法 对广州市8家腹泻病监测医院2012年、2013年间上送的566株沙门菌进行血清分型,同时采用纸片扩散法(K- B法)对12种抗菌药物进行敏感性分析。结果 566株沙门菌分为62个血清型,前三位分别为鼠伤寒沙门菌41.52%（235/566）、肠炎沙门菌15.72%（89/566）和斯坦利沙门菌7.95%（45/566）。药敏分析显示菌株对头孢类抗菌药物敏感率达85%以上,对环丙沙星的敏感性也较高,为75.44%,而对氨苄西林、磺胺复合物、四环素、萘啶酸的耐药率达60%。耐3种及以上抗生素的菌株占71.02%（402/566）,出现ACSSuT+耐药谱（对氨苄西林、氯霉素、链霉素、磺胺复合物、四环素等5种或更多药物多重耐药）的总耐药率为27.39%（155/566）。鼠伤寒沙门菌ACSSuT+耐药率达44.68%（105/235）。结论 本地区沙门菌临床分离株以鼠伤寒沙门菌和肠炎沙门菌为主,菌株对头孢类抗菌药物的敏感性较高,但某些血清型菌株存在严重的多重耐药现象,其中鼠伤寒沙门菌是耐药最严重的血清型,应引起重视。     

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。     

Prevalence of multidrug resistant Salmonella in Coriander, mint, carrot, and radish in Bareilly and Kanpur, northern India

We examined 974 samples (304 coriander, 212 mint, 258 carrot, and 200 radish) collected from vegetable vendors in two cities, Bareilly (n = 832) and Kanpur (n = 142), in northern India during the early summer season in 2004. Salmonella was isolated from 35 samples (9 coriander, 5 mint, 10 radish, and 11 carrot) while Escherichia coli was detected in 181 samples (67 coriander, 44 mint, 36 carrot, and 34 radish). None of the E. coli belonged to the O:157 serogroup. Five Salmonella isolates from samples collected at Kanpur (3 coriander and 2 mint) belonged to 4 different serovars of S. enterica ssp. enterica-S. Mons, S. Rottenest, S. Saintpaul, and S. Weltevreden. Thirty Salmonella isolates from samples collected at Bareilly (11 carrot, 10 radish, 6 coriander, and 3 mint) belonged to 7 serovars-S. Anatum, S. Bsilla, S. Newport, S. Saintpaul, S. Teko, S. Virchow, and S. Weltevreden. The majority (82.9%) of Salmonella isolates were multidrug resistant. One quarter of the isolates were resistant to >or=10 antibiotics. Based on antibiotic resistance patterns, 35 isolates could be classified into 23 resistotypes. None of the 35 isolates was resistant to streptomycin and ceftriaxone, while >80% were resistant to sulfamethoxazole, nalidixic acid, and kanamycin. Resistance to imipenem (>20%) and amikacin (>30%) was also common. The correlation between presence of Salmonella and E. coli on raw vegetables was not significant (p = 0.13).     

Genetic diversity and antibiotic resistance in Shigella dysenteriae and Shigella boydii strains isolated from children aged <5 years in Egypt

Diversity within Shigella dysenteriae (n=40) and Shigella boydii (n=30) isolates from children living in Egypt aged <5 years was investigated. Shigella-associated diarrhoea occurred mainly in summer months and in children aged <3 years, it commonly presented with vomiting and fever. Serotypes 7 (30%), 2 (28%), and 3 (23%) accounted for most of S. dysenteriae isolates; 50% of S. boydii isolates were serotype 2. S. dysenteriae and S. boydii isolates were often resistant to ampicillin, chloramphenicol and tetracycline (42%, 17%, respectively), although resistance varied among serotypes. Pulsed-field gel electrophoresis separated the isolates into distinct clusters correlating with species and serotype. Genetic differences in trimethoprim/sulfamethoxazole and β-lactam-encoding resistance genes were also evident. S. dysenteriae and S. boydii are genetically diverse pathogens in Egypt; the high level of multidrug resistance associated with both pathogens and resistance to the most available inexpensive antibiotics underlines the importance of continuing surveillance.     

Characterization of bla(CMY)-encoding plasmids among Salmonella isolated in the United States in 2007

Salmonella enterica is one of the most common bacterial causes of foodborne illness, and nontyphoidal Salmonella is estimated to cause ～1.2 million illnesses in the United States each year. Plasmids are mobile genetic elements that play a critical role in the dissemination of antimicrobial resistance determinants. AmpC-type CMY β-lactamases (bla(CMY)) confer resistance to extended-spectrum cephalosporins and β-lactam/β-lactamase inhibitor combinations and are commonly plasmid-encoded. A variety of plasmids have been shown to encode CMY β-lactamases and certain plasmids may be associated with particular Salmonella serotypes or environmental sources. In this study, we characterized bla(CMY) β-lactamase-encoding plasmids among Salmonella isolates. Isolates of Salmonella from specimens collected from humans in 2007 were submitted to the Centers for Disease Control and Prevention National Antimicrobial Resistance Monitoring System laboratory for susceptibility testing. Three percent (65/2161) of Salmonella isolates displayed resistance to ceftriaxone (minimum inhibitory concentration [MIC] ≥4?mg/L) and amoxicillin/clavulanic acid (MIC ≥32?mg/L), a combination associated with the presence of a bla(CMY) mechanism of resistance. Sixty-four (98.5%) isolates were polymerase chain reaction-positive for bla(CMY) genes. Transformation and conjugation studies showed that 95% (61/64) of the bla(CMY) genes were plasmid-encoded. Most of the bla(CMY)-positive isolates were serotype Typhimurium, Newport, Heidelberg, and Agona. Forty-three plasmids were replicon type IncA/C, 15 IncI1, 2 contained multiple replicon loci, and 1 was untypeable. IncI1 plasmids conferred only the bla(CMY)-associated resistance phenotype, whereas IncA/C plasmids conferred additional multi-drug resistance (MDR) phenotypes to drugs such as chloramphenicol, sulfisoxazole, and tetracycline. Most of the IncI1 plasmids (12/15) were sequence type 12 by plasmid multi-locus sequence typing. CMY β-lactamase-encoding plasmids among human isolates of Salmonella in the United States tended to be large MDR IncA/C plasmids or single resistance determinant IncI1 plasmids. In general, IncI1 plasmids were identified among serotypes commonly associated with poultry, whereas IncA/C plasmids were more likely to be identified among cattle/beef-associated serotypes.     

Antimicrobial resistance of Escherichia coli O26, O103, O111, O128, and O145 from animals and humans

Susceptibilities to fourteen antimicrobial agents important in clinical medicine and agriculture were determined for 752 Escherichia coli isolates of serotypes O26, O103, O111, O128, and O145. Strains of these serotypes may cause urinary tract and enteric infections in humans and have been implicated in infections with Shiga toxin-producing E. coli (STEC). Approximately 50% of the 137 isolates from humans were resistant to ampicillin, sulfamethoxazole, cephalothin, tetracycline, or streptomycin, and approximately 25% were resistant to chloramphenicol, trimethoprim-sulfamethoxazole, or amoxicillin-clavulanic acid. Approximately 50% of the 534 isolates from food animals were resistant to sulfamethoxazole, tetracycline, or streptomycin. Of 195 isolates with STEC-related virulence genes, approximately 40% were resistant to sulfamethoxazole, tetracycline, or streptomycin. Findings from this study suggest antimicrobial resistance is widespread among E. coli O26, O103, O111, O128, and O145 inhabiting humans and food animals.     

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.     

四川省部分地区2010－2011年猪肉生产链中沙门菌耐药特征及分子分型研究

目的 分析2010－2011年四川省部分地区猪肉生产链中沙门菌耐药特性及分子分型特征。方法 对分离的112株沙门菌采用肉汤微量稀释法进行10种抗生素 （组合） 药敏试验,参考CLSI标准 （2010） 判定结果。选取不同菌株来源、 血清型和耐药谱的74株沙门菌,按照美国PulseNet标准进行脉冲场凝胶电泳 （PFGE） 分型。结果 猪肉生产链中沙门菌对四环素耐药率最高 （89.29%）,其次为大观霉素 （36.61%）、 甲氧苄啶/磺胺甲噁唑 （35.71%）、 萘啶酸 （33.93%） 和氨苄西林 （24.11%）,多重耐药率为33.93%,对头孢噻呋敏感,共有19种耐药谱。来自猪肉生产链的74株沙门菌可分为34个PFGE谱型,其相似性为40%～100%。结论 四川省猪肉生产链中沙门菌耐药较为严重,其血清型及耐药谱与PFGE分型有一定相关性; 生产链中沙门菌可能存在自上游生产链向下游生产链水平传播的情况。     

衡阳市生畜肉及熟肉制品中沙门菌血清型、分子分型及耐药性研究

目的 了解2021年衡阳市生畜肉及熟肉制品中沙门菌污染状况,分析沙门菌血清型分布、分子分型特征及耐药情况。 方法 采集衡阳市各县区生畜肉及熟肉制品样品,依照GB4789.4进行沙门菌分离鉴定和血清分型;采用美国临床和实验室标准化协会(Clinical and Laboratory Standards Institute,CLSI)推荐的微量肉汤稀释法进行药物敏感试验;用脉冲场凝胶电泳(pulsed field gel electrophoresis,PFGE)进行分子分型,结果用BioNumerics软件聚类分析。 结果 从52份生畜肉中检出18株沙门菌,检出率为34.62%(18/52),52份熟肉制品中检出3株沙门菌,检出率为5.77%(3/52);21株沙门菌可分为7个血清型,其中伦敦沙门菌42.86%(9/21)和罗森沙门菌19.05%(4/21)占主要优势;21株沙门菌均对亚胺培南(IPM)和多粘菌素E(CT)敏感,对萘啶酸(NAL)、头孢噻肟(CTX)、头孢西丁(CFX)、头孢他啶(CAZ)敏感度均达90.00%以上,对四环素(TET)、氨苄西林(AMP)、甲氧苄啶/磺胺甲噁唑(SXT)耐药达50.00%以上,多重耐药严重,最常见的耐药谱为四环素-氨苄西林-甲氧苄啶/磺胺甲噁唑(TET-AMP-SXT),耐药率为52.38%;21株沙门菌PFGE聚类分析相似度为48.20%,罗森、伦敦沙门菌带型最为集中,但鼠伤寒沙门菌呈现多样性;各带型与耐药谱之间未见明显相关。 结论 衡阳市生畜肉及熟肉制品沙门菌污染及耐药问题严重,血清型分布广泛,同一血清型大部分菌株PFGE型可聚集成簇。     

2013年泰州市健康从业人员携带的沙门氏菌耐药状况以及分子分型研究

目的 了解泰州市健康从业人员携带的沙门氏菌血清型分布、耐药状况以及分子分型特性,为食源性沙门氏菌病的防治提供检测依据。方法 将2013年泰州市健康从业人员分离的58株沙门氏菌进行生化鉴定、血清学分型、药敏试验以及脉冲场凝胶电泳(Pulsed Field Gel Electrophoresis,PFGE)分子分型,并运用BioNumeries软件分析菌株之间的流行病学关系。结果 58株沙门氏菌分为8种血清型,主要以蒙德维的亚沙门氏菌、鼠伤寒沙门氏菌、德尔卑沙门氏菌为主。药敏试验表明,58株沙门氏菌对四环素和萘定酸耐药性最高;多重耐药谱显示耐2种抗生素及以上占39.66%,最高耐10种抗生素。PFGE结果表明,同一血清型的沙门氏菌有多个PFGE带型,相似度大于50.00%,且均有带型100.00%一致的菌株存在。结论 泰州市健康从业人员携带的沙门氏菌耐药谱广,耐药性较强;基因型呈多态分布,但具有流行相关性;各血清型都有100.00%同源菌株,应结合流行病学调查,做好预防控制工作。     

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.     

Blood invasiveness of Salmonella enterica as a function of age and serotype

We explored the dual influence of the patient's age and the infecting serotype on the blood invasiveness patterns of non-Typhi Salmonella enterica (NTS). Blood invasiveness ratio (BIR) was calculated as the ratio between the number of blood and blood + stool isolates. Analysis of 14,951 NTS isolates showed that the BIR increased drastically above the age of 60 years, reaching levels 3.5-7 times higher compared to age group < 2 years. Different patterns of age-related invasiveness were observed for the five most common NTS serotypes (Enteritidis, Typhimurium, Virchow, Hadar, Infantis). Among children < 2 years, the BIR was highest for serotype Virchow and lowest for serotype Hadar, while in persons > or = 60 years it was highest for serotypes Enteritidis and lowest for serotype Infantis. The tendency of NTS serotypes to invade the bloodstream was significantly influenced by the patient's age, however the impact of age differed for various NTS serotypes.     

上海市闵行区鼠伤寒沙门菌病原学与PFGE分型研究

目的了解2015年-2017年闵行区腹泻病监测点鼠伤寒沙门菌的病原学及脉冲场凝胶电泳(PFGE)特征。方法按照《上海市腹泻病综合监测实施方案》进行沙门菌分离鉴定;药物敏感试验采用纸片扩散法(K-B法);PFGE参照Pulse Net China沙门菌PFGE分子分型标准操作规程。结果鼠伤寒沙门菌在2015年-2017年检出率呈逐年增长趋势;鼠伤寒沙门菌对10种抗生素耐药率为四环素56.32%、萘啶酸31.03%、氯霉素20.69%、复方新诺明17.24%、头孢噻肟8.05%、头孢呋辛8.05%、庆大霉素5.75%、环丙沙星3.45%、头孢西丁1.15%、诺氟沙星1.15%,存在多重耐药。PFGE将87株鼠伤寒沙门菌分为62个带型,每个带型含1株~5株菌,分为A、B两大聚类,相似度为57.2%~100%。结论经过多种抗生素共同作用筛选得到的菌株成为鼠伤寒沙门菌扩散的主要来源,在PFGE优势克隆系中能体现。PFGE技术为聚集性病例的追踪溯源提供了分子生物学依据。