Suis Disease Research Articles

A novel intranasal mouse model for mucosal colonization by Streptococcus suis serotype 2

Streptococcus suis causes meningitis and various other diseases in pigs and humans. Healthy piglets carrying virulent Streptococcus suis strains on their mucosal surfaces are epidemiologically very important. The objective of this study was to establish an intranasal Streptococcus suis mouse model for invasion and colonization of the respiratory tract. CD1 mice were infected intranasally with a highly virulent Streptococcus suis serotype 2 strain under different conditions. Clinical, histological and bacteriological screenings revealed that invasion of host tissue occurred in the majority of mice only after predisposition with 12.5 µl 1 % acetic acid per nostril. Severe fibrinosuppurative or purulent necrotizing pneumonia associated with Streptococcus suis was a common manifestation. Furthermore, a novel model to study nasopharyngeal colonization was established by reducing the volume of 1 % acetic acid per nostril to 5 µl prior to Streptococcus suis application. This model mimics asymptomatic carriage in swine, as all mice carried Streptococcus suis on their respiratory mucosa at 7 days post-infection (p.i.) in moderate to high numbers without the development of pneumonia or any other invasive Streptococcus suis disease. This intranasal Streptococcus suis model was applied to investigate the function of suilysin (SLY) in colonization. Although an isogenic SLY mutant was isolated from the upper respiratory tract at a lower recovery rate than its wild-type parental strain at 14 days p.i., the differences were not significant and did not indicate severe attenuation in colonization. In conclusion, this work describes to the best of our knowledge the first intranasal mouse model to study colonization of the respiratory tract by a highly virulent Streptococcus suis pathotype.

Streptococcus suis serotype 9 bacterin immunogenicity and protective efficacy

Streptococcus suis diseases in pigs, most importantly meningitis, are worldwide responsible for major economic losses in the pig industry. About one fourth of invasive S. suis diseases are caused by S. suis serotype 9 strains in Europe. However, little is known about serotype 9 since most studies were performed with serotype 2. The objective of this study was to determine the immunogenicity and protective efficacy of a serotype 9 bacterin in piglets. Challenge was conducted with a reference serotype 9 strain, belonging to the same clonal complex but to a different sequence type as the bacterin strain. The bacterin induced protection against mortality but not morbidity. Eleven days post infection, 3 of 7 vaccinated survivors were not fully convalescent and had not eliminated the challenge strain from inner organs completely. In accordance with the clinical findings, the majority of piglets showed fibrinous–suppurative lesions in at least one inner organ or tissue. In contrast to the placebo group such lesions were not detected in one third of bacterin-vaccinated piglets. Determination of specific serum IgG titers revealed that the bacterin elicited seroconversion against muramidase-released protein and basic membrane lipoprotein. Furthermore, vaccination was associated with induction of opsonizing antibodies against the serotype 9 challenge strain. However, titers of opsonizing antibodies were rather low in comparison to those found in our previous serotype 2 vaccination trial. Piglets developed substantially higher titers of opsonizing antibodies after challenge. Opsonizing antibodies were absorbable with the serotype 9 challenge strain but not with an unencapsulated isogenic mutant of a serotype 2 strain indicating their specificity. The results indicate that a serotype 9 bacterin is less protective than a serotype 2 bacterin, most likely due to inducing only low titers of opsonizing antibodies. This might contribute to emergence of serotype 9 strains, in particular strains of this clonal complex, in Europe.

Lineage and Virulence ofStreptococcus suisSerotype 2 Isolates from North America

We performed multilocus sequence typing of 64 North American Streptococcus suis serotype 2 porcine isolates. Strains were sequence type (ST) 28 (51%), ST25 (44%), and ST1 (5%). We identified nonrandom associations between STs and expression of the virulence markers suilysin (SLY), muramidase-relased protein (MRP), and extracellular factor (EF). Expression of pili encoded by the srtF and srtG pilus clusters was also nonrandomly associated with STs. ST1 strains were SLY+ EF+ MRP+ srtF pilus+ srtG pilus-. ST25 strains were SLY- EF- MRP- srtF pilus- srtG pilus+, and most ST28 strains were SLY- MRP+ EF- srtF pilus+ srtG pilus+. ST28 isolates proved essentially nonvirulent in a mouse infection model; ST25 strains showed moderate virulence and ST1 isolates were highly virulent. ST1 is responsible for a high proportion of S. suis disease in humans worldwide. Its presence in North America indicates that potential zoonotic S. suis outbreaks in this continent cannot be disregarded.

Helicobacter suis KB1 derived from pig gastric lymphoid follicles induces the formation of gastric lymphoid follicles in mice through the activation of B cells and CD4 positive cells

“ Helicobacter heilmannii” (“ H. heilmannii”), which belongs to the genus Helicobacter, is a group of bacterial species that display a long spiral-shaped morphology. Recent studies have demonstrated that “ H. heilmannii” type 1 is actually H. suis, which mainly colonizes the stomachs of various animals and humans. However, the influence of H. suis on gastric diseases remains to be fully elucidated. In this report, we revealed the relationship between natural H. suis infection and follicular gastritis in the pig stomachs. From sequence analysis of the 16S rRNA, urease A, and urease B genes, the presence of H. suis was confirmed in pig gastric lymphoid follicles, and this bacterium was named H. suis KB1. In addition, H. suis KB1 was inoculated into C57BL/6J mice, and the following mouse model of the pathogenesis of follicular gastritis by H. suis infection was established: H. suis KB1 colonizes the mouse stomach, and moreover, induces the development of lymphoid follicles and acquired immune responses characterized by the activation of B cells and CD4 positive cells. These results may lead to better understanding of the relationship between H. suis and gastric diseases, especially follicular gastritis; and furthermore, our findings emphasize the zoonotic aspects of animal-human infection by H. suis.

Streptococcus suisMeningitis, Hawaii

<i>Streptococcus suis</i>Meningitis, Hawaii

Streptococcus suis: An Emerging Human Threat

In the world of Streptococcus, S. suis has been somewhat neglected. Indeed, at this year’s Lancefield International Symposium on Streptococci and Streptococcal Diseases, only one oral presentation was devoted to this pathogen. However, this perception should change, because S. suis is emerging as an important threat to human health. S. suis is an encapsulated Grampositive coccus possessing cell-wall antigens related to Lancefield group D. There are 35 serotypes that have been described on the basis of the composition of the polysaccharide capsule [1]. S. suis infections are considered to be a major problem worldwide in the swine industry. The pathogen’s natural habitat is the upper respiratory tract of pigs, as well as the genital and alimentary tracts [1]. The pig carrier rate is near 100%, and, in the absence of treatment, mortality reaches 20% [2]. The most important clinical feature associated with S. suis infection in pigs is meningitis. In severe cases, pigs are found dead with no premonitory signs. Other manifestations are arthritis, endocarditis, pneumonia, rhinitis, abortion, and vaginitis [1]. Until recently, S. suis disease in humans has been rare [3, 4]. Since the first human case in Denmark in 1968 [5] and before 2005, only 250 S. suis infections were reported in Europe and Asia. However, S. suis recently was identified as the third most common cause of communityacquired bacterial meningitis in Hong Kong, behind S. pneumoniae and Mycobacterium tuberculosis [6], and as the leading cause of adult meningitis in Vietnam [7]. Mysteriously, only 2 cases of S. suis meningitis have been reported in Canada [8, 9], and only 1, very recently, in the United States [10]. Although the epidemiology of S. suis infections in humans remains largely undefined, nearly all cases can be ascribed to either handling or consumption of unprocessed pork meat or to close contact with pigs. Therefore, most infected people are pig farmers, abattoir workers, meat inspectors, butchers, and veterinarian practitioners [4]. In humans, S. suis usually produces a purulent or nonpurulent meningitis. Additionally, endocarditis, cellulitis, peritonitis, rhabdomyolysis, arthritis, spondylodiscitis, pneumonia, uveitis, and endopthalmitis may occur [4, 11, 12]. Both severe infections with shock and a high mortality also have been described [13, 14]. One striking feature of S. suis–related meningitis is the complication of deafness and/or vestibular dysfunction, which occurs at a rate consistently higher than that reported for other meningitis-causing bacteria and which reaches 50% and 65% in Europe and Asia, respectively [11, 12]. Most cases of S. suis infection have been attributed to serotype 2 strains; however, cases due to serotypes 4, 14, and 16 also have been reported [4]. Strains isolated from humans are phenotypically and genotypically similar to those recovered from swine within the same geographical region [15].

Streptococcus suisMeningitis without History of Animal Contact, Italy

<i>Streptococcus suis</i>Meningitis without History of Animal Contact, Italy

Invasive Disease and Toxic Shock due to Zoonotic Streptococcus suis: An Emerging Infection in the East?

Streptococcus suis ( S. suis) is widely recognised in the veterinary world as a cause of rapidly progressive and fatal sepsis in infant pigs, associated with meningitis, polyarthritis, and, occasionally, pneumonia. A more fulminant bacteraemic infection is seen in neonatal pigs [ 1, 2]. For reasons that are unknown, adult pigs do not succumb to this infection, although they demonstrate asymptomatic nasopharyngeal carriage ( Figure 1), and infant piglets become infected after early contact with colonised adult females. In many respects, S. suis infection is the porcine version of human group B strep disease. Zoonotic disease due to S. suis does occur sporadically in Western countries, but is encountered more commonly in countries such as Thailand, China, and Hong Kong. It affects predominantly individuals with occupational exposure to pigs. In humans, meningitis is the most common presentation (about 80% of all cases), though S. suis disease can be associated with other suppurative complications such as pneumonia and arthritis. Mortalities of 5%–10% of cases are reported [ 2], and S. suis is the third most common cause of bacterial meningitis in Hong Kong [ 3]. Figure 1 Scanning Electron Microscopy of S. suis Diplococci in a Sheet of Mucus on the Surface of the Nasopharyngeal Epithelium from a Pig

Virulence-associated gene profiling of Streptococcus suis isolates by PCR

Definition of virulent Streptococcus suis strains is controversial. One successful approach for identification of virulent European strains is differentiation of capsular serotypes (or the corresponding cps types) and subsequent detection of virulence-associated factors, namely the extracellular factor (EF, epf), the muramidase-released protein (MRP, mrp) and the hemolysin suilysin (SLY, sly). In this work we present a novel multiplex PCR (MP-PCR) and an mrp variant PCR for identification and characterization of virulent S. suis strains. These new methods were used to identify association of disease with particular profiles of virulence-associated genes. The MP-PCR allowed identification of S. suis through detection of the housekeeping gene gdh, differentiation of four cps types (1, 2, 7 and 9), and detection of epf, mrp, sly and arcA (arginine deiminase from S. suis). Furthermore, this study describes the first PCR assay for differentiation of at least six mrp variants. Expression of the corresponding size variants of MRP was shown for four of the six mrp variants, but was undetectable for the two larger mrp variants in the particular strains investigated. The results of this study suggest that cps7 strains are associated with pneumonia and that variation of mrp is very pronounced among these strains. Gene profiles of invasive, pneumonia and carrier S. suis isolates by combination of PCR assays allowed differentiation of 24 different genotypes among cps1, 2, 7 and 9 strains. Forty-five percent of the invasive S. suis diseases investigated in this study were caused by only two of these genotypes, namely cps2/ mrp+/ epf+/ sly+ and cps9/ mrp * / epf−/ sly+. Thus, this study demonstrates for the first time a uniform profile of the particular virulence-associated genes for the vast majority of the investigated invasive cps9 strains.

Sorotipagem de amostras de Streptococcus suis isoladas de suínos em granjas dos Estados de São Paulo, Minas Gerais e Paraná

Infecções causadas por Streptococcus suis são muito comuns em países onde a indústria de carne suína é desenvolvida. Estas infecções estão relacionadas a casos clínicos de broncopneumonia, meningite, artrite, pericardite, miocardite, endocardite, poliserosite fibrinosa, septicemia, rinite e aborto. Esta bactéria também foi descrita como patógeno de ruminantes e humanos. No Brasil há evidências clínicas da existência de processos infecciosos causados por S. suis afetando mais de 50% das granjas em Estados como São Paulo, Minas Gerais e Paraná. No presente estudo foram isoladas 51 amostras de S. suis de granjas do Estados acima referidos, coletadas de diferentes casos clínicos como septicemia, meningite, artrite e pneumonia, tendo sido obtidas ou em cultura pura ou como patógeno de maior predominância nos tecidos de suínos. Este material foi semeado em Columbia ágar sangue adicionado de 5% de sangue bovino e incubado a 37°C por 24 horas. Para a identificação bioquímica as colônias que apresentavam a-hemólise, bem como as amostras padrão, foram submetidas a testes convencionais para a confirmação da espécie S. suis, tais como: hidrólise de arginina, teste de Voges-Proskauer, e produção de ácido a partir de vários carboidratos (inulina, salicina, trealose, lactose, sacarose, sorbitol, manitol e glicerol). As amostras também foram testadas para habilidade de crescimento em meio de TSA com 6,5% de NaCl e para a produção de amilase. Todas as amostras que fizeram parte desta pesquisa foram testadas pelo sistema Api 20 Strep para confirmação dos resultados obtidos nos testes convencionais. Para a sorotipagem foram produzidos antissoros de 1 a 8. Outras amostras não pertencentes a estes sorotipos também foram sorotipadas. O antissoro produzido em coelhos foi titulado pelo teste de aglutinação em tubo com 2-mercaptoetanol e pelo teste de reação capsular e, quando adequados, foram usados no teste de co-aglutinação, para a sorotipagem das amostras de S. suis. A sorotipagem das 51 amostras isoladas mostraram os seguintes resultados: 30 (58,8%) foram classificadas como sorotipo 2, 11 (21,6%) das amostras como sorotipo 3, sete (13,72%) como sorotipo 7, duas (3,92%) como sorotipo 1 e uma amostra como pertencente ao sorotipo14 (1,96%). Este é o primeiro relato do isolamento de um grande número de amostras de S. suis no Brasil, de casos típicos de processos infecciosos causados por esta bactéria. Também foi realizada a sorotipagem dos isolados, mostrando uma alta prevalência do sorotipo 2, quando comparada com a dos demais sorotipos encontrados.

Actinobacillus suis infection in pigs in Australia.

This is the first report of the isolation of Actinobacillus suis in association with significant disease among preweaned pigs in Australia. Sudden deaths occurred in preweaned piglets at one facility and enlarged joints, particularly the stifles and tarsi, occurred at another. Isolates with the biochemical phenotype and apx genotype profile of A suis were cultured from affected piglets. Both facilities were of high health status and one had undergone a recent depopulation, disinfection and sow repopulation process. Reviewing initial reports of A suis disease overseas, it is apparent that outbreaks occurred sporadically in various locations, with disease occurring among the herds involved for some months only, before development of immunity. A suis disease is now considered an emerging disease on high health status farms.

Effect of management practices on the Streptococcus suis carrier rate in nursery swine

Summary Management practices on swine farms were analyzed to determine factor(s) associated with high prevalence of pigs that were carriers of Streptococcus suis. Samples were obtained for bacteriologic culture via direct swabbing of palatine tonsils of healthy nursery pigs on 35 farms throughout the United States. Overall, 36.7% of the pigs were determined to be carriers. Isolates of S suis were serotyped, and antimicrobial susceptibility tests were performed by use of Kirby-Bauer techniques. Streptococcus suis types 1 and 2 were most commonly isolated. All isolates were susceptible to enrofloxacin, 97% of the isolates were susceptible to ceftiofur, and 94% were susceptible to ampicillin. However, only 80% of the isolates were susceptible to penicillin, and only 18% were susceptible to tetracycline. Environmental, managerial, nutritional, and health factors were measured on each farm. Excessive temperature fluctuation, high relative humidity, crowding, and an age spread of &gt; 2 weeks between pigs in the same room were the 4 most commonly encountered problems on farms with higher-than-average percentages of carrier pigs. Continuous flow facilities were found on 50% of these farms, and various disease problems, vitamin E/selenium deficiency, inadequate vaccination programs (attributable to the presence of atypical serotypes), and penicillin-resistant strains were found on 6 to 28% of these farms. Overall, 83% (15/18) of farms with higher-than-average percentages of carrier pigs also had a history of clinical S suis disease.