Distribution of capsular serotypes and virulence markers of Streptococcus suis isolated from pigs with polyserositis in Korea

The objective of this study was to determine the capsular serotypes and potential virulence factors of Streptococcus suis isolated from pigs with polyserositis. Among the 24 isolates evaluated, serotype 3 [7 (29%) of the isolates] and serotype 4 [5 (21%)] were the most common. The isolates were also studied for the presence of the genes mrp, epf, and sly, which encode muramidase-released protein (MRP), extracellular factor (EF), and suilysin (SLY), respectively. Of the 24 isolates, 8 carried mrp: 4 of serotype 3, 2 of serotype 2, and 2 of serotype 4. One mrp(+) isolate (serotype 2) also carried the epf gene. All 24 isolates carried the sly gene. The serotype and genotype distribution greatly differed from that reported for isolates from pigs with other clinical manifestations of S. suis infection in other countries.     

Serological characterization and antimicrobial susceptibility of Streptococcus suis isolates from diagnostic samples in Denmark during 1995 and 1996

At the Danish Veterinary Laboratory Streptococcus suis infections in pigs were diagnosed in 114 cases in 1995 and in 151 cases in 1996. Isolates were serotyped using specific antisera against type 1 through 28 and a total of 67 cases from 1995 and 113 cases in 1996 were tested for resistance to 11 antimicrobial agents. The majority of cases were lung diseases (57%), followed by septicaemia (16%), meningitis (15%) and endocarditis (8%). Almost 96% of the isolates could be typed using the 28 antisera. The most common serotype was serotype 2 (29%), followed by serotype 7 (17%), and serotypes 3, 4 and 8 (9–10%). The remaining serotypes were observed in frequencies of less than 5%. Serotype 7 was more commonly isolated from septicaemia than the other serotypes. Serotype 2 was more commonly isolated from pigs older than 4 weeks compared to the other serotypes. Most isolates were susceptible to amoxycillin+clavulanate, ampicillin, ceftiofur, enrofloxacin, penicillin, spectinomycin, tiamulin and trimethoprim+sulphadiazine. A high frequency (>30%) of resistance to tetracycline was observed. Among isolates of serotype 2, 9.7% were resistant to lincomycin and 12.9% to spiramycin. Among other serotypes 56.8% were resistant to lincomycin and spiramycin. The differences in susceptibility between isolates of serotype 2 and the other serotypes were statistically significant. Compared to a previous Danish study the distribution of serotypes of S. suis causing infections among pigs in Denmark has changed during the last 15 years.     

猪链球菌PCR检测技术研究进展

猪链球菌是猪的一种重要病原菌,并且也会引起人的链球菌病。有35个荚膜血清型(1/21、~34),通常自发病或死亡猪体分离获得1,2,7,9型和14型菌株,其中2型是毒力最强的血清型。根据已知猪链球菌16 SrRNA及溶血素(sly)、谷氨酸脱氢酶(gdh)、荚膜多糖(cps)、胞壁蛋白或溶菌酶释放相关蛋白(mrp)、胞外因子(epf)编码基因序列设计特异性引物,建立猪链球菌群和1(14),2(1/2),7型和9型特异性PCR或多重PCR,建立2型致病性菌株和1型高致病性菌株毒力鉴定PCR或多重PCR,用于检测和鉴别临床病料和细菌分离物中的猪链球菌,具有高敏感性和高特异性,与其他致病菌及其他血清的猪链球菌型无交叉反应,为疫病诊断及流行病学的研究提供了快速、简便和有用的工具。     

Antimicrobial susceptibility of clinical strains of Streptococcus suis isolated from pigs in Spain

The antimicrobial susceptibility of 151 clinical Streptococcus suis strains isolated from diseased pigs in Spain was determined by a microdilution method. Isolates were mostly susceptible to beta-lactam antimicrobials, aminoglycosides, enrofloxacin, novobiocin and spectinomycin. More than 87% of the S. suis isolates were resistant to tetracyclines, sulphonamides, macrolides and clindamycin. Strains of serotype 9 were significantly more resistant than strains of serotype 2 (P<0.05) to tylosin (94% versus 77%) and clindamycin (94% versus 64%). Eighty-seven percent of the S. suis isolates were resistant to at least four antimicrobials and nine isolates (6%) were resistant to at least six antimicrobials. The most frequently identified multidrug pattern involved resistance against tetracyclines, sulphonamides, macrolides and lincosamides, with 69% of the isolates exhibiting this resistotype. Fifteen out of the 22 strains of serotype 2 (68.2%), and 84 out of the 98 of the strains of serotype 9 (85.7%) exhibited this resistotype, indicating its widespread distribution among the strains of the two most frequently isolated serotypes.     

Isolation of Streptococcus suis using a selective medium.

A selective medium containing tryptic soy agar, 5% defibrinated bovine blood, crystal violet, nalidixic acid and gentamicin significantly improved the isolation rate of Streptococcus suis from tonsilar tissue of slaughtered pigs. Ninety-five percent of the S. suis isolates identified in Guelph were confirmed as S. suis in Copenhagen, but only six out of 21 isolates typed as capsular serotype 2 in Guelph were confirmed to possess serotype 2 antigen in Copenhagen. Sixty-four percent of the S. suis isolates were not typable within the current scheme of capsular serotypes from 1 to 13 and type 1/2.     

The Streptococcus suis Epidemiological Analysis of Healthy and Infected Swine in Guangdong Province

To investigate the epidemics of Streptococcus suis in Guangdong province, 228 samples from infected pigs,and 698 samples from healthy pigs including 243 samples from tonsils of slaughtered pigs and 455 nasal swabs of healthy pigs were analyzed.The results showed that the positive rate of Streptococcus suis of infected,healthy and slaughtered pigs were 82.02%(187/228),42.20%(192/455) and 32.10%(78/243),respectively.187 strains of Streptococcus suis were isolated from infected pigs and serotyped in 11 serotypes,including serotype SS1,SS2,SS3,SS4,SS7,SS8,SS9,SS16,SS19,SS29 and SS31, in which serotype SS2(16.58%),SS3(9.63%) and SS19 (7.49%) were dominant,flowed by SS7(6.95%)and SS9(5.34%),and 48.66% strains were non-typabled.Meanwhile,154 strains of Streptococcus suis from healthy swine(including farms and slaughter houses) were classified into 17 serotypes,including serotype SS2,SS3,SS4,SS5,SS7,SS8,SS9,SS10,SS12,SS15,SS16,SS17,SS19,SS21,SS23,SS29 and SS30,in which SS2(18.83%) and SS29(14.94%)were dominant,flowed by SS16(6.50%) and 31.82% strains were non-typabled.     

重庆地区表观健康猪中猪链球菌的检测

本研究旨在调查重庆地区表观健康猪的猪链球菌带菌情况,并揭示健康猪群携带猪链球菌的公共卫生学意义。随机采集重庆市17个区县(市)定点屠宰场表观健康猪的腭扁桃体1 360份,进行猪链球菌的分离鉴定,并对致病性较强的1、2、7、9、14型及1/2型进行分型与毒力因子分析。结果共分离到225株猪链球菌,分离率为16.54%;检出猪链球菌2型4株,猪链球菌7型3株,猪链球菌9型3株,猪链球菌1/2型1株;毒力因子谱分析发现多数(10/11)分离株缺失部分毒力因子,但也存在具有全部已知毒力因子的强毒株,且在国内首次检出小片段mrp型猪链球菌1/2型1株和7型2株。结果提示,重庆地区健康猪群带菌现象普遍,且流行菌株具有与国外不同的特点,对屠宰场工作人员健康造成威胁。     

广东地区健康猪群和发病猪群猪链球菌流行病学调查分析

为了解广东地区猪群中猪链球菌（Streptococcus suis,SS）的流行情况,本研究对在广东地区养殖场采集的228份发病猪群样品及698份健康猪群样品（包括455份鼻拭子样品及243份屠宰场扁桃体样品）进行了SS携带情况的统计分析。结果显示,发病猪群SS的阳性率为82.02%（187/228）,健康猪群的SS阳性率为42.20%（192/455）,其中屠宰场屠宰猪群的SS阳性率为32.10%（78/243）。将从发病猪群分离到的187株SS及健康猪群（含养猪场和屠宰场）分离得到的154株SS进行血清型定型分析,结果显示,发病猪群共检测到11个血清型,包括SS1、SS2、SS3、SS4、SS7、SS8、SS9、SS16、SS19、SS29和SS31型,主要以SS2、SS3和SS19型为主,分别占16.58%、9.63%和7.49%;其次为SS7型（6.95%）和SS9型（5.34%）,未定型菌株占48.66%;健康猪群共检测到17个血清型,包括SS2、SS3、SS4、SS5、SS7、SS8、SS9、SS10、SS12、SS15、SS16、SS17、SS19、SS21、SS23、SS29和SS30型,主要以血清型SS2和SS29型为主,分别占18.83%和14.94%,其次为SS16型（6.50%）,未定型菌株占31.82%。     

猪链球菌2型毒力因子研究进展

猪链球茵(SS)病是一种严重危害养猪业的人畜共患病,呈世界性分布.根据荚膜抗原特性的不同,猪链球茵被分为35个血清型(1/2型,1型～34型),其中以猪链球菌2型(SS2)流行最广,毒力最强.SS2主要的毒力因子有溶菌酶释放蛋白、胞外蛋白因子、荚膜抗原、溶血素等.然而,新近发现的一些与SS2致病性相关的基因序列和蛋白片段已经成为当前研究的重点和热点.在基因水平上的新发现主要有orf2毒力因子、89 kb毒力岛、转录调节因子、氨基酸通透酶、ABC转运子及表面锚定蛋白基因、反应调节因子RevS基因、纤连蛋白结合蛋白基因、编码噬茵体的基因序列Ssl和分泌性核酸酶SsnA基因等.蛋白水平上的新发现主要有脂磷壁酸的D-丙氨酰位点、自溶素、精氨酸脱亚氨酸酶系统、浑浊因子,38,45,39,44 ku蛋白,以及一些蛋白酶和纤维蛋白溶血酶原受体等.     

Rapid detection of Streptococcus suis serotype 2 in weaned pigs

A survey to detect Streptococcus suis serotype 2 in 1,716 weaned pigs was done in Quebec. Forty-nine sow herds were included in this survey: in 26 herds, S suis serotype 2 had been isolated during the preceding 12 months and in 23 herds (control), the organism had not been detected during a previous study. Swab specimens of the nasal cavity and tonsils of pigs were obtained for bacteriologic culture, and S suis serotype 2 was easily detected by the use of brain-heart infusion agar containing a Streptococcus-selective supplement and 5% goat antiserum raised against S suis serotype 2. After measurement of the diameter of the precipitation zone of 539 isolates, a slide agglutination test was performed to identify the S suis serotype 2 isolates. The mean precipitation zone diameter obtained for group S suis serotype 2 was larger (P less than 0.001) than that for the group designated as "others". With slide agglutination test results as reference and on the basis of discriminant analysis to stimulate detection of S suis serotype 2, 93.1% of all isolates were correctly classified, using the precipitation zone diameter as unique classification criterion. Relative specificity was 94.5% and relative sensitivity was 88.7%. Use of the precipitation zone diameter on a quantitative basis led to the proposal of a simple and reliable technique to screen swine herds for S suis serotype 2 in weaned pigs. Nasal and tonsillar swab specimens were obtained and analyzed concurrently for S suis serotype 2. The organism was found in both sites in only 20.4% of 103 carrier pigs.(ABSTRACT TRUNCATED AT 250 WORDS)     

7型猪链球菌的分离鉴定及特性

通过生化鉴定和PCR方法从湖北省部分地区高热症猪病料中分离鉴定了17株7型猪链球菌,并对所分离菌株进行药敏、毒力基因分布及致病性等生物学特性的研究。结果表明,生化鉴定显示所分离菌株为猪链球菌2型,但经PCR鉴定为7型,测序结果经分析与已发表的7型序列同源性为100%。17株7型分离株毒力基因分布情况为：0.0%为mrp＋,11.8%为epf＋,17.6%为sly＋orf2＋,29.4%fbps＋,100.0%gdh＋。通过对28种药物的敏感试验发现各分离株耐药性差别很大,但对阿莫西林和复方阿莫西林较为敏感（88.2%）,对红霉素最为敏感（100.0%）。动物试验表明,编号为HB6、HB8、HB9的分离株致病性较强。通过对病猪和感染小鼠进行病理切片观察,各器官充血出血最为明显。总之,在以高致病性蓝耳病病毒为主要病原的高热症诊断和治疗中,同样需要考虑混合或继发感染7型猪链球菌致病的可能。     

Streptococcus suis infection in swine. A sixteen month study.

A total of 349 isolates of Streptococcus suis retrieved from different tissues from diseased pigs were examined in this study. Only 48% of them could be categorized as one of serotypes 1 to 8 and 1/2. Among typable isolates, serotype 2 was the most prevalent (23%), followed by serotype 3 (10%). The majority of all isolates originated from lungs, meninges/brain, and multiple tissues. Forty-one percent of typable isolates and 33% of untypable isolates were retrieved in pure culture. Other isolates were found in conjunction with Pasteurella multocida, Escherichia coli, Actinobacillus pleuropneumoniae, Actinomyces pyogenes, and other streptococci. Typable S. suis isolates were more frequently isolated from pigs between five and ten weeks of age, while untypable isolates were mostly found in animals aged more than 24 weeks. No obvious monthly and/or seasonal variation of the prevalence of isolation of S. suis could be detected.     

Genomic relatedness among reference strains of different Streptococcus suis serotypes.

Hybridization studies using genomic DNA and a rDNA probe revealed genetic relatedness among reference strains of different Streptococcus suis serotypes. Although most serotype 22 isolates are biochemically atypical, the reference strain of capsular type 22 is genetically related to other S. suis serotypes, but not to Streptococcus pneumoniae. Using DNA digested with BamHI and BglII for ribotyping, some S. suis reference strains had common patterns, but this analysis mainly revealed variations in patterns of S. suis strains of different serotypes.     

The presence of muramidase released protein and extracellular factor protein in various serotypes of Streptococcus suis isolated from diseased and healthy pigs in Spain

A total of 142 strains from different serotypes of Streptococcus suis isolated in Spain from diseased pigs (88 strains) and healthy carrier pigs (54 strains) were studied for the presence of a muramidase released protein (MRP) and an extracellular factor (EF). The following five phenotypes: MRP+EF+, MRP+EF-, MRP-EF+, MRP+EF* and MRP*EF- were detected. A high percentage of S. suis serotype 2 strains isolated from diseased pigs (84 per cent) belonged to phenotype MRP+EF+, but this phenotype has also been noticed in other serotypes (serotypes 1, 1/2 and 14). Both proteins were detected in S. suis serotype 2 strains (26%) isolated from healthy carrier pigs and one of both proteins in serotypes 1 and 14 (phenotype MRP+EF*). The isolation of S. suis strains from healthy pigs which have shown both proteins may support the epidemiological significance of these carriers in the maintenance, transmission and distribution of virulent strains within and between swine farms.     

Detection and molecular typing of Streptococcus suis in tonsils from live pigs in France

Streptococcus suis is an important pathogen of swine, causing meningitis, arthritis, polyserositis, septicemia, and sudden death in weaning piglets as well as fattening pigs. Recently, 3 molecular tests have been developed in our laboratory: a multiplex polymerase chain reaction (m-PCR) assay for the detection of S. suis species and serotypes 2 and 1/2, and 2 molecular typing methods, pulsed-field gel electrophoresis and an approach based on PCR amplification of a fragment of rRNA genes, including a part of the 16S and 23S genes and the 16S-23S rDNA intergenic spacer region (ISR), followed by restriction fragment length polymorphism (RFLP) analysis (ISR-RFLP). In the present study, we used these tests to analyze tonsil samples from clinically healthy pigs and to identify individual isolates of S. suis during epidemiologic investigations of 8 related herds with a history of septicemia caused by S. suis serotype 2. Capsular typing showed that 58% of the strains were nontypable. Of the 17 serotypes present, serotype 22 was the most prevalent. In the 7 farms without clinical signs on the day of sampling, we detected S. suis serotype 2 or 1/2, or both, in less than 5% of the pigs by m-PCR or by bacteriologic culture. In the 8th farm, on which 2 pigs had clinical signs of septicemia on the day of sampling, we detected S. suis serotype 2 or 1/2, or both, by m-PCR in the tonsils of 40% of fattening pigs (21 wk old) that lacked symptoms. Molecular typing of the serotype 2 strains showed a common origin of contamination in these herds, given that 1 pattern (C1) was detected in the isolates from 6 of the 8 herds. However, up to 4 patterns were associated with septicemia and sudden death. Several patterns of S. suis serotype 2 can be responsible for disease in the same herd. These molecular tools may be useful for confident studies of the transmission of S. suis, thereby contributing to the control of S. suis infection.     

Distribution of capsular types and production of muramidase-released protein (MRP) and extracellular factor (EF) of Streptococcus suis strains isolated from diseased pigs in seven European countries

Streptococcus suis strains (n=411), isolated from diseased pigs in seven European countries were serotyped using specific antisera against serotype 1 to 28, and were phenotyped on the basis of their muramidase-released-protein (MRP) and extracellular-factor protein (EF) production. Overall, S. suis serotype 2 appeared to be most prevalent (32%), followed by serotype 9 (20%) and serotype 1 (12%). Serotype 2 was most frequently isolated in France, Italy and Spain, whereas serotype 9 was most frequently isolated in Belgium, The Netherlands and Germany. In the United Kingdom serotypes 1 and 14 were most frequently isolated. High percentages of S. suis serotype 1, 2, 1/2 and 14 strains, isolated from tissues associated with S. suis infections such as brain, serosa, joint, heart and organs expressed the EF-protein, indicating that in these serotypes expression of EF is likely to be associated with virulence. In contrast, strains belonging to serotype 7 and 9, isolated from tissues associated with S. suis infections did not produce EF. These results strongly suggest that in the serotypes 7 and 9 EF expression is not related to virulence. More than 80% of the S. suis serotype 9 strains produced an MRP* protein, a high molecular variant of the 136kDa MRP. Expression of MRP* in serotype 9 strains is possibly associated with virulence.     

Isolation and characterization of Streptococcus suis capsular types 9-22

The incidence and biochemical patterns of Streptococcus suis capsular types 9-22 are presented. Of 148 untypeable (with types 1-8 antisera) isolates of S. suis recovered from diseased pigs, 10% were not capsulated. Of the remaining 134 isolates, only 53% belonged to capsular types 9-22; capsular types 22 and 9 were the most prevalent, representing 19% and 13%, respectively. Capsular type 15 (de Moor's group T Streptococcus) is reported here for the first time in North America since it was described in 1963 in Europe. Of 188 untypeable isolates recovered from clinically healthy pigs, 25% were noncapsulated. Of the remaining 141 isolates, 90% belonged to the new capsular types, and 87% were identified as 1 of 4 types: 17, 18, 19, and 21. Capsular types 12 and 20 were not detected among the Canadian isolates. Almost half of strains were arginine dihydrolase-negative, and 45% fermented mannitol, which is seldom a positive test with capsular types 1-8. Although some strains were negative with salicin or trehalose, none were negative for both sugars. Only 54% of isolates tested with 1 rapid multitest system were correctly identified as S. suis. A tentative biochemical profile that might be used with a microplate identification system is also presented. Biochemical identification using the conventional system instead of the rapid multitest system is preferable.     

Production of virulence-related proteins by Canadian strains of Streptococcus suis capsular type 2.

The production of muramidase-released protein (MRP), extracellular protein factor (EF) and hemolysin (suilysin) by 101 Canadian field strains of Streptococcus suis capsular type 2 is described. Most strains (72%) isolated from diseased pigs were MRP-EF- and only 1 strain was MRP+EF+. This strain was also the only 1 to produce the hemolysin. Thirteen strains (15%) were MRP+ EF- and only 3 strains were MRP* EF-. All the strains isolated from clinically healthy pigs as well as a bovine and 2 human isolates had a MRP-EF- phenotype. In addition, 7 strains (8%) had a MRPS phenotype, which had so far been described for S. suis capsular type 1. In conclusion, most Canadian field isolates of S. suis capsular type 2 tested in this study do not produce the virulence-related proteins described so far for this bacterial pathogen.     

Epidemiological relationship of human and swine Streptococcus suis isolates

Two cases of meningitis due to Streptococcus suis in humans are reported here. A butcher and an abattoir worker were referred to a health centre in Castellón (Spain) with fever and symptoms of meningitis. After adequate treatment, a slight hipoacusia persisted as sequelae in both cases. Colonies of S. suis group R, serotype 2 and phenotype MRP+EF+ were isolated from cerebroespinal fluid. Epidemiological studies showed that both workers had in common the handling of pork meat of slaughtered healthy pigs from three closed farms. A study of the tonsils from apparently healthy, slaughtered pigs was carried out. A total of 234 tonsillar samples were obtained and 81 strains of S. suis were isolated from them. Serotype 2 appeared to be the most frequent (50.6%), and the analysis for phenotype showed a high percentage of tonsillar strains with the phenotype MRP+EF+ (35.9%). The humans and 28 tonsillar swine strains showed a similar profile (S. suis group R, serotype 2 and phenotype MRP+EF+). A total of 26 of the swine isolates were analysed by ribotyping using EcoRI. The human strains showed the same six-band hybridization pattern that shared five bands with the pattern most frequently shown by most of the tonsillar N. suis group R, serotype 2 and phenotype MRP+EF+ strains, differing only in the lightest, faintest band which was slightly less anodical in human (> or = 1.8 kb) than in swine (approximately 1.8 kb). From these results, both groups of strains, humans and porcine, showed differences; how can these differences in the pattern of ribotyping be explained if they should have the same origin? Is it possible that they have undergone an adaptation to the new host or perhaps the modification is due to other unknown causes? Further studies in this area are required in order to answer these questions.