禽、畜养殖场分离的优势血清型沙门菌耐药性和分子分型分析

目的了解玉林市禽、畜养殖场沙门菌的流行情况、耐药性及菌株间的亲源关系,为卫生风险评估及制定公共卫生措施提供基础数据。方法收集了2018年玉林市北流禽畜养殖场环境样标本、禽畜养殖场工人肛拭子标本,参照《2018年国家食品污染和有害因素风险监测工作手册》及《2018年食源性疾病监测工作手册》,进行沙门菌分离培养及血清学鉴定;并对主要血清型进行耐药性检测和脉冲场凝胶电泳(PFGE)分子分型。结果监测40个禽畜养殖场,其中人畜共用水中沙门菌检出率为5.0%(2/40),环境样检出率为29.7%(11/37),工人肛拭子中检出率为4.0%(2/50),共分离出15株非伤寒沙门菌。其中环境样沙门菌的检出率明显高于养殖场工人肛拭子的检出率,差异有统计学意义(P<0.05)。分离出来的沙门菌主要血清型为鼠伤寒沙门菌、韦太夫雷登沙门菌。与其他来源沙门比对,PFGE显示18株鼠伤寒沙门菌有18种PFGE带型;14株韦太夫雷登沙门菌有12种PFGE带型,部分韦太夫雷登沙门菌100%同源或高度同源性。所有的沙门菌菌株均对亚胺培南、头孢他啶、头孢西丁、环丙沙星、阿奇霉素敏感,对其余9种抗生素产生不同程度的耐药,环境样来源的沙门菌要比其他来源的沙门菌耐药率要低。结论禽畜养殖场沙门菌的检出率较高,且耐药状况不容乐观,特别是对四环素类、青霉素类、氯霉素类、磺胺类、抗生素严重耐药。耐药菌株与PFGE型间具有一定的相关性,且沙门菌具有遗传的多样性,可在环境、人、食品之间相互传播。因此,应加强监测,建立科学的防控策略。     

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。     

2008-2009年北京市沙门菌流行特征和分子分型

目的 分析2008-2009年北京市沙门菌流行特征及脉冲场凝胶电泳(PFGE)分子分型. 方法 对2008-2009年通过WHO全球沙门菌监测系统及北京市肠道门诊监测系统分离到的137株沙门菌进行生化鉴定、血清分型和相关流行病学分析;利用PFGE进行分子分型. 结果 北京市2008-2009年沙门菌的流行具有明显季节性,6-9月份高发,共分离菌株84株,占64.1%(84/131);患者年龄多为18～40岁,占46.1%(58/128);男性80例,女性51例,男女比例为1.57:1.137株沙门菌分属于20种血清型,其中肠炎沙门菌和鼠伤寒沙门菌为优势菌型,分别占46.7%(64/137)和17.5%(24/137).共分71种PFGE带型,其中肠炎沙门菌和鼠伤寒沙门菌都有16种PFGE型别.肠炎沙门菌的4种PFGE型别(JEGX01.CN0001、JEGX01.CN0003、JFGX01.CN0002、JEGX01.CN0019)和鼠伤寒沙门菌的JPXX01.CN0001为优势分子型别. 结论 2008-2009年北京市沙门菌的流行具有性别、年龄和季节性分布特征;PFGE分子型别较多,且存在差异明显的多个克隆系.

Abstract：

Objective To study the epidemiological characteristics and molecular phenotypes of Salmonella by pulsed-field gel electrophoresis (PFGE) in Beijing from 2008 to 2009. Methods A total of one hundred thirty-seven isolates recovered from the WHO Global Samonella Surveillance system and entero clinic surveillance system were identified by biochemical tests and serotyping.The related epidemiological informations were also analyzed.The isolates were further typed by PFGE. Results The prevalence of Salmonella from 2008 to 2009 showed obvious seasonal character.High incidence occurred from June to September,and 64.1% (84/131) isolates were recovered in this period.Patients of 18-40 year-old were 46.1% (58/128) and 80 patients were male and 40 patients were female with the ratio of 1.57:1.These 137 Salmonella isolates belonged to 20 serotypes,including Enteritidis (46.7%,64/137) and Typhimurium (17.5%,24/137) as the dominant serotype.In total,71 PFGE profiles were identified.Four PFGE patterns of S.Enteritidis isolates (JEGX01.CN0001,JEGX01.CN0003,JEGXO1.CN0002,JEGX01.CN0019) and S.Typhimurium pattern of JPXX01.CN0001 were dominant patterns. Conclusion The prevalence of Salmonella from 2008 to 2009 showed distribution characteristics of sex,age and seasons.The numerous PFGE patterns of Salmonella showed diversity of these isolates and different clones existed in Beijing.     

Representative Salmonella serovars isolated from poultry and poultry environments in Saudi Arabia

The authors describe the source and prevalence of pathogenic Salmonella serovars among poultry farms in Saudi Arabia. A total of 1,052 (4%) Salmonella isolates were recovered from 25,759 samples of poultry (broilers, layers, broiler breeders and layer breeders) and poultry environments (box liner, litter, drag swab, droppings, mice and feed) were examined bacteriologically between 1988 and 1997 at the Poultry Disease Laboratory at the National Agriculture and Water Research Center in Riyadh. Eleven Salmonella serogroups representing 38 different Salmonella serovars were identified by means of antigenic analysis. The majority of the 276 isolates (26.2%) of Salmonella typed, were recovered from liver, heart and intestines of the broilers and layers. The most prominent Salmonella serogroups isolated were as follows: serogroup C1 (392 isolates, 37.26%), B (289 isolates, 27.47%) and D1 (269 isolates, 25.69%). However, untypable and multiple serogroups were also encountered, the most frequent isolates serotyped belonged to groups C1 (97 isolates, 24.7%), D1 (86 isolates, 31.9%), and B (71 isolates, 24.6%). Salmonella Enteritidis (85 isolates, 98.8%), Salmonella Virchow (48 isolates, 57.8%), Salmonella Paratyphi B var. Java (41 isolates, 57.7%) and Salmonella Infantis (30 isolates, 20.6%) were distributed the most widely as all were encountered in poultry and in poultry environments. S. Enteritidis phage type 4 (30 isolates, 35.3%), was the phage type most frequently detected among group D1 phage types, while 39 (45.8%) of the isolates of S. Enteritidis could not be phage typed.     

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.     

Antibiotic resistance in Salmonella enterica serotypes Typhimurium, Enteritidis and Infantis from human infections, foodstuffs and farm animals in Italy

The antimicrobial susceptibility of isolates of Salmonella enterica serotypes Typhimurium, Enteritidis, and Infantis isolated from humans, foodstuffs and farm animals in Italy between 1999 and 2001 was examined. All the isolates were susceptible to cefotaxime and ciprofloxacin, but high rates of resistance were observed for several other drugs, especially for S. Typhimurium. The rates of resistance and multiresistance were generally higher among animal and food isolates than in human strains; conversely, no significant difference was observed between animal and food isolates. Among S. Typhimurium, multiresistance was more common in bovine, poultry and rabbit strains than in swine isolates, and was rare in strains from pigeon. Resistance to trimethoprim sulphamethoxazole was mainly found in isolates of swine and human origin. This study confirms the role of livestock as a reservoir of drug-resistant Salmonella spp. and underlines the need for integrated surveillance systems of antibiotic resistance that consider isolates not only from human disease but also from the animal reservoirs and the food vehicles.     

Emergence of Salmonella enteritidis outbreaks in broiler chickens in the Lebanon: epidemiological markers and competitive exclusion control

This study investigates the first emergence of Salmonella Enteritidis outbreaks among chickens in the Lebanon and identifies the epidemiological markers of selected recovered Enteritidis strains. In addition, the authors evaluate a competitive exclusion approach to control infection in broiler chickens by Enteritidis organisms which possess the prevalent identified markers. The basic procedure in this investigation involved recording signs and lesions in eleven broiler chicken flocks on eleven farms, and culturing livers, spleens, and caeca of ten randomly selected birds per flock for Salmonella isolation and serotyping. Furthermore, culturing for Salmonella and serotyping was attempted from the livers, spleens, caeca and oviduct swabs of ten hens in four broiler breeder flocks which provided hatching eggs for the broilers under study. The identification of epidemiological markers in recovered S. Enteritidis included the determination of drug-resistance patterns and plasmid profiling. The competitive exclusion was evaluated by spraying the microflora on day-old broilers in the hatchery, followed by a controlled oral challenge at three days of age, with 2.85 x 10(5) colony-forming units of S. Enteritidis organisms per bird. Exclusion was evaluated by culturing for S. Enteritidis in anal swabs, spleens, livers, and caeca of individual challenged birds treated with the microflora and in untreated challenged birds. A total of 112 invasive S. Enteritidis strains were recovered on eleven farms from individual organs of broiler chickens with typical signs and lesions of salmonellosis. The prevalent resistance to drugs in such strains was to furaltadone and gentamycin, a marker identified in 93 strains (83%), recovered from nine out of eleven farms. The same resistance pattern was present in S. Enteritidis strains recovered from breeders on one out of four farms. The prevalent plasmid profile in nine S. Enteritidis organisms selected randomly from a pool of 93 strains (one per each of the nine broiler farms) was 14.1 kilobases (kb) and approximately 50.0 kb, a typical pattern to that identified in S. Enteritidis organisms recovered from oviducts of breeders on one out of four breeder farms. The exclusion significantly reduced cumulative mortality in birds of up to 45 days of age by 3.93%, in comparison to that observed in untreated challenged birds (P < 0.05). At 45 days of age, exclusion resulted in a 15.6% reduction in the percentage infection rate by S. Enteritidis in spleens or livers and a 34.4% reduction in the percentage infection rate of the caeca (P < 0.05).     

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.     

Distribution of Campylobacter jejuni Penner serotypes in broiler flocks 1998-2000 in a small Danish community with special reference to serotype 4-complex

During the period January 1998-December 2001, all Danish broiler flocks were monitored bacteriologically for thermophilic campylobacters and isolates were stored at -80 degrees C. Six neighbouring broiler farms in a small community were selected for detailed examination of all Campylobacter jejuni isolated (n = 180) from these farms during 1998-2000 using Penner serotyping and pulsed-field gel electrophoresis (PFGE). The area and the farms were selected according to their prevalence of campylobacter so that both farms with low and high frequencies of campylobacter positive flocks were included in the study. The frequency of campylobacter positive flocks on the six farms ranged from 24.5 to 72.7%. One hundred and eighty of the isolates were C. jejuni (included in this study), 14 isolates were C. coli whereas 7 isolates belonged to other species but were not further identified. By serotyping of all C. jejuni 56 isolates (31.5%) were assigned to the 4-complex, 32 isolates (18.0%) to serotype 2, 12 isolates (6.7%) to serotype 11, and 11 isolates (6.2%) were assigned to serotype 12. In three farms, 4-complex was the most prevalent serotype, in one farm it was the second most frequently isolated serotype, while serotypes 2 and 1,44, respectively, were the most frequently isolated from the two remaining farms. This serotype distribution differed from the overall country-wide distribution where serotypes 2 and 1,44 are the most prevalent. All serotype 4-complex isolates from the six selected farms were compared by PFGE to serotype 4-complex isolates from the rest of the country. The results showed that there was a high level of diversity among isolates from the whole country, whereas isolates from the six farms were very homogeneous and only displayed one or a few different PFGE patterns on each farm. It is suggested that certain campylobacter clones persist in a confined geographical area, probably at the farm, and that the broiler houses may be repeatedly infected with a few C. jejuni clones during succeeding broiler flocks. New clones may be introduced, however, the sources and vehicles are yet unknown.     

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.     

沙门菌脉冲场凝胶电泳分型与血清型的对应关系

目的分析沙门菌脉冲场凝胶电泳分型(PFGE)与血清分型之间的对应关系.方法选择中国细菌性传染病分子分型实验室监测网络PulseNet China沙门菌监测数据中鼠伤寒(Typhimurium)、肠炎(Enteritidis)、德尔卑(Derby)、阿贡纳(Agona)及山夫登堡(Senftenberg)前五位常见血清型菌株共1230株,进行PFGE聚类分析,以血清分型作为参照进行比对.确定这5种血清型PFGE优势带型的共有条带.结果1230株菌株中,1149株经PFGE预测的血清型与实际血清型一致,PFGE预测血清型的准确率为93.4%.5种血清型经PFGE预测的血清型阳性预测值多在90.0%以上、阴性预测值均在95.0%以上.结论PFGE聚类对5种常见血清型沙门菌血清分型具有较好的提示及验证作用.     

Epidemiology of Campylobacter spp. at two Dutch broiler farms.

Broiler flocks on two Dutch poultry farms were screened weekly for the presence of campylobacter in fresh caecal droppings during eight consecutive production cycles. Hatchery and fresh litter samples were taken at the start of each new cycle. Water, feed, insects, and faeces of domestic animals, present on the farms were also included in the sampling. Penner serotyping of isolates was used to identify epidemiological factors that contribute to campylobacter colonization in the broiler flocks. Generally, broiler flocks became colonized with campylobacter at about 3-4 weeks of age with isolation percentages of 100%, and stayed colonized up to slaughter. A similar pattern of serotypes was found within the various broiler houses on one farm during one production cycle. New flocks generally showed also a new pattern of serotypes. Most serotypes isolated from the laying hens, pigs, sheep and cattle were different from those isolated from the broilers at the same time. Campylobacter serotypes from darkling beetles inside the broiler houses were identical to the ones isolated from the broilers. No campylobacter was isolated from any of the hatchery, water, feed or fresh litter samples. Conclusive evidence of transmission routes was not found, but results certainly point towards horizontal transmission from the environment. Horizontal transmission from one broiler flock to the next one via a persistent contamination within the broiler house, as well as vertical transmission from breeder flocks via the hatchery to progeny, did not seem to be very likely.     

Molecular epidemiology and diversity of Salmonella serovar Typhimurium in pigs using phenotypic and genotypic approaches

For epidemiological investigations of the most common and non-host-adapted Salmonella serotypes, such as Typhimurium, highly discriminatory approaches are essential. In the present study, we evaluated three genotyping methods; amplified fragment length polymorphism (AFLP), pulsed-field gel electrophoresis (PFGE) and repetitive palindromic extragenic-PCR (Rep-PCR) using 40 isolates. AFLP showed the highest discriminatory index (0.939), resolution and throughput. To determine clonality of Salmonella Typhimurium isolates and epidemiological relatedness in different commercial pig production units, we employed AFLP in combination with antimicrobial resistance pattern and phage typing. Salmonella serovar Typhimurium isolates (n=196) obtained from a longitudinal study of 18 pig farms over a 3-year period were studied. Using this approach, 16 distinct clonal types were identified. We found two common multidrug- resistant patterns including AmCmStSuTe and AmKmStSuTe. Two commonly multidrug- resistant phage types that are of known public health importance, DT104 and DT193, were also common. AFLP differentiated distinct clones within DT104, a phage type previously reported to be clonal. Fourteen of the clonal types were unique to one of the two production systems, showing diversity between independent commercial pig production systems located in the same geographical area. Clonal types obtained from nursery farms and corresponding finishing units were, however, similar.     

Molecular epidemiology and in vitro antimicrobial susceptibility of Salmonella isolated from poultry in Kashmir

A total of 480 samples, comprising 429 faecal samples from healthy adult birds and 51 tissue samples from dead birds, were collected from four government poultry farms in the Kashmir valley from September 2007 to April 2008. In all, 33 Salmonella isolates were obtained. Of these, 28 (84.85%) isolates were Salmonella Gallinarum, 3 (9.09%) were Salmonella Enteritidis and the remaining 2 (6.06%) were Salmonella Typhimurium. All the isolates harboured the invA, sefA, stn and spvC virulence-specific genes. However, the sopB gene was found in only 90.9% of the isolates. Pulsed-field gel electrophoresis analysis of representative isolates revealed that the majority were related but a few belonged to different clones. The majority of the isolates were resistant to cefpodoxime, nalidixic acid and sulphadiazine and sensitive to chloramphenicol, cefotaxime and tetracycline. Isolation of multidrug-resistant Salmonella, including the zoonotically important serovars, revealed a potential threat not only to poultry but also to human health in Kashmir.     

河南省肉鸡养殖和屠宰加工过程中沙门菌污染监测

目的了解河南省肉鸡养殖和屠宰过程中沙门菌的污染状况,为食品安全风险评估提供数据支持。方法选择肉鸡产品销量占河南省市场60%以上的养殖场和屠宰场,于2010年6~10月份在肉鸡养殖环节采集成年鸡肛拭子、在屠宰环节采集鸡酮体按照GB4789.4-2010进行沙门菌定性或/和定量检测。结果共检测368只鸡肛拭子,沙门氏菌检出率8.7%;186份鸡酮体,检出率24.2%。鸡肛拭子检出率最高的月份是7、8月、鸡酮体检出率较高的月份分布在6、8月份;两类样本检出沙门菌血清型前3位一致,均为印第安纳、肠炎和哈达尔沙门菌。鸡酮体沙门菌污染量较低,91.1%在10MPN/g以下。检出沙门菌均具有invA基因。肉鸡胴体和活鸡肛拭子分离沙门菌均具有严重的多重耐药现象,活鸡肛拭子沙门菌较胴体沙门菌耐药严重。结论肉鸡沙门菌的污染取决于肉鸡携带沙门菌和养殖环境中沙门菌的污染状况,并通过屠宰过程使污染扩大化和复杂化。宰后酮体鸡沙门菌的含量不高,但是沙门菌的存在将对食品安全造成潜在危害。分离沙门菌菌株耐药现象严重,提示政府要加大监测力度,养殖部门要合理使用抗生素。     

The use of bulk tank milk samples to monitor trends in antimicrobial resistance on dairy farms

The routine monitoring of bacteria obtained from bulk tank milk (BTM) may be an important tool for detecting farm-level trends in antimicrobial resistance on dairy farms. This study describes and compares antimicrobial susceptibility patterns of Salmonella enterica subspecies enterica (Salmonella) and Escherichia coli recovered from dairy BTM. BTM from more than 400 dairies in a dairy-intense region of California were sampled eight times at 2- to 3-month intervals over a 29-month period. From Salmonella positive and Salmonella negative herds any one Salmonella and three E. coli isolates per sample were tested for susceptibility to 12 antimicrobials. The prevalence of multiple drug resistant (MDR) E. coli was assessed in relation to Salmonella on the farm, farm size, season, MDR Salmonella, and serovar. At each sampling period, 10-21% and 54-77% of the dairy farms were positive for Salmonella and E. coli, respectively. The most commonly recovered Salmonella serovars were Montevideo (33%), Typhimurium (14%), Dublin (13%), and Give (11%). Two-thirds, respectively, of 478 Salmonella and 1577 E. coli isolates were pan-susceptible. The antimicrobial resistance patterns of MDR Salmonella tended to be serovar dependent and were different from the antimicrobial resistance patterns of MDR E. coli. MDR E. coli were more likely to be recovered from dairies with MDR Salmonella. There were no associations between MDR E. coli and season, Salmonella serovar detected in the BTM, or dairy herd size. Bulk milk E. coli and Salmonella could be valuable to monitor the dynamics of antimicrobial resistance in dairy milk production.     

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.     

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 resistance and phage types of human and non-human Salmonella enterica isolates in Ireland, 1998-2003

Between 1998 and 2003, 5,161 isolates (3,182 human) of Salmonella enterica were received by the National Salmonella Reference Laboratory of Ireland. Serotyping, antimicrobial susceptibility testing and phage typing were performed by standard methods. The number of isolates of S. enterica serovar Typhimurium decreased from 579 (80%) in 1998 to 208 (19%) in 2003, while S. enterica serovar Enteritidis increased from 59 (8%) in 1998 to 219 (20%) in 2003. Definitive (DT) phage types 104 and DT104b accounted for a declining proportion of all Salmonella Typhimurium isolates (from n = 523 [90%] in 1998 to 126 [60%] in 2003). Numbers of Salmonella Enteritidis phage type 4 declined from 50 (85%) in 1998 to 59 (27%) in 2003. Twenty-eight isolates of typhoidal Salmonella were received with a history of recent travel in 17 cases. Resistance to multiple (four or more) antimicrobial agents was related to serotype and, where applicable, phage type, and was common in Salmonella Typhimurium. Salmonella Typhimurium predominated among isolates from cattle and pigs (n = 213 [58%]), while Salmonella Livingstone (n = 327) and S. Kentucky (n = 227) were predominant in isolates from poultry (total n = 554 [43%]). This paper discusses trends, and their implications, in Irish salmonella isolates since the establishment of the Reference Laboratory.     

Laboratory-based surveillance of nontyphoidal Salmonella infections in China

Foodborne infections are an important public health problem in China. In 2008, we conducted surveillance for laboratory-confirmed nontyphoidal Salmonella to monitor trends for this infection in China and to build capacity for rapid detection and response to foodborne outbreaks. Salmonella isolates from patients with diarrhea were sent from hospitals to local public health laboratories for confirmation, serotyping, and antimicrobial susceptibility testing. A total of 126 hospitals in 44 cities and counties from 8 provinces provided isolates and epidemiologic data for analysis. Of 23,140 stool specimens submitted to clinical laboratories, 662 (3%) grew Salmonella enterica. Salmonella were most commonly detected between April and October. The median age of infected patients was 27 years; 34% of infections occurred in patients <5 years old. Of the 662 isolates, we found 73 serotypes, of which serotype Enteritidis (31%) and serotype Typhimurium (26%) were the most common. The prevalence of resistance was high for clinically important antimicrobial agents, including ampicillin (41%) and ciprofloxacin (6%). More than 60% of isolates, including 35% of all Typhimurium, were resistant to three or more antimicrobial agents. In this first multiprovince surveillance report of laboratory-confirmed Salmonella infections in China, we found that Enteritidis and Typhimurium are the most common serotypes and that efforts to reduce antimicrobial resistance among Salmonella in China are needed. Although no outbreaks were detected using this system, efforts to improve this system's capacity to do so are underway.