Multiple Serotypes and Strains of Streptococcus Suis in Naturally Infected Swine Herds

Abstract

Streptococcus suis is a cause of pneumonia, meningitis, and arthritis in swine. 2,5,11,16 The identification of S. suis in swine herds is increasing, and anecdotal field reports of difficulty in disease control and management, especially "vaccine failure," are common. The importance of S. suis as a primary pulmonary pathogen is controversial because of the difficulty in experimentally reproducing the disease. A retrospective study of porcine cases of S. suis submitted to the Indiana Animal Disease Diagnostic Laboratory from 1985 to 1989 was conducted to gain a better understanding of this disease in swine. Infections of 256 pigs involving a single serotype of S. suis were previously reported. 12-14 Reports of infection in pigs with multiple serotypes of S. suis are sparse. 1,9 We present a brief description of the epidemiology, clinical signs, and lesions in 21 accessions in which multiple serotypes of S. suis or multiple distinct isolates (strains) of the same capsular serotype of S. suis were identified. Isolates of the same capsular serotype that had different antibiogram profiles were considered to be distinct isolates or "strains" for the purposes of this study. Streptococcus suis isolates of the same capsular serotype and identical antibiogram profiles were considered to be identical organisms. These cases were selected to determine whether or not herds infected with multiple serotypes (or strains) of S. suis had unique features that might serve to distinguish these herds from those infected with a single serotype and strain of S. suis and to provide additional information on the development of this disease in swine. Selected cases were limited to those in which isolates were identified by capsular serotyping. Untypeable isolates of S. suis were not included in this study. Case selection criteria, data collection procedures, etc., were as previously described. 12 Of 277 accessions in which S. suis was identified, 21 accessions (7.6%) involving 37 pigs were cases in which 46 different isolates of S. suis were identified. The distribution of these isolates is shown in Tables 1 and 2. Because of the small sample size, statistical analyses were not performed. Although there was a slight increase in recovery of S. suis in the fall and winter months for all serotypes, S. suis was readily isolated throughout the year. In this study, there was a slight increase (approximately 5%) in the prevalence of serotypes 3, 7, and 8 and a decrease (approximately 10%) in the prevalence of serotype 2 from those reported previously. 12 Pigs in this study were 1-32 weeks of age. Seventy-five

Relatedness of Streptococcus suis Isolates of Various Serotypes and Clinical Backgrounds as Evaluated by Macrorestriction Analysis and Expression of Potential Virulence Traits

“…Similarly, in our study only 16 of 40 S. suis isolates from pigs with pneumonia were isolated as pure cultures. In agreement with the current knowledge of the pathogenicity of S. suis (14,18,24), we therefore assumed that the isolates from pigs with typical signs (i.e., meningitis, etc.) represented the most virulent strains, whereas isolates from pigs with pneumonia were less invasive and, thus, less virulent.…”

“…In contrast to the importance of S. suis as a primary pathogen in pigs with meningitis, septicemia, or arthritis, it's causative role in pneumonia is not as clear since in many cases S. suis is isolated together with other lung pathogens such as Pasteurella spp., B. bronchiseptica, or Mycoplasma spp. (18,24). Similarly, in our study only 16 of 40 S. suis isolates from pigs with pneumonia were isolated as pure cultures.…”

“…The capsular polysaccharides are the basis for classification into serotypes (of which 35 are currently known) and have recently been shown to prevent phagocytosis and, thus, have been proposed as an important virulence trait (25). Serotype 2 is considered the most dominant one among highly virulent strains, but disease is also frequently caused by strains of other serotypes (24,33,36), suggesting that serotype-independent virulence markers must exist. MRP and EF have previously been found to be strongly associated with highly virulent isolates in Europe (35,36) but do not appear to confer virulence directly, as recently demonstrated by the use of gene knockout technology (28).…”

Development of a Multilocus Sequence Typing Scheme for the Pig Pathogen Streptococcus suis : Identification of Virulent Clones and Potential Capsular Serotype Exchange

“…However, as S. suis is often isolated from the lungs of pigs with pneumonia along with other agents potentially involved in respiratory disease (such as Pasteurella multocida, Haemophilus parasuis, Actinobacillus pleuropneumoniae, swine influenza virus, B. bronchiseptica, and Mycoplasma spp. [22,28,38]), the role of S. suis in pneumonia remains somewhat controversial. Although S. suis is isolated in pure culture from pneumonia with reasonable frequency (1,22) further epidemiological studies are required to address the etiological role of S. suis in porcine pneumonia and the particular clones involved.…”

Multiplex PCR Assays for Simultaneous Detection of Six Major Serotypes and Two Virulence-Associated Phenotypes ofStreptococcus suisin Tonsillar Specimens from Pigs

“…Earlier, it was found that pigs can be infected with multiple serotypes of S. suis (15,17). These findings may account in part for the difficulty in disease control by vaccines.…”