Abstract
Streptococcus suis naturally inhabits the tonsils and nasal cavities of pigs. Some strains can cause systemic infection, leading to a wide range of diseases. A case-control study was conducted to (i) examine serotypes isolated from systemic sites (blood/meninges/spleen) in cases, (ii) determine whether serotypes in systemic sites were found in upper respiratory sites (tonsil/nasal cavity) of the same cases, and (iii) determine the serotypes in upper respiratory sites of case and farm and pen- matched controls. In total, 606 samples from 128 pigs were cultured for S. suis. The isolates were examined for presence of gdh and recN genes by polymerase chain reaction (PCR) and were identified as S. suis if both genes were present. The S. suis isolates were then serotyped using a two step-multiplex PCR. Serotypes 9 (n = 9), (2,1/2) (n = 7) and untypable isolates (n = 7) were most commonly found in systemic sites. Detection of serotypes 9 (p = 0.03) in upper respiratory sites were positively associated with their detection in systemic sites of cases, while a trend was seen with serotype (2,1/2) (p = 0.07). Last, no association between serotypes recovered from upper respiratory sites of cases and controls could be detected. Untypable isolates were detected in high frequency, which warrants further investigation. This study confirms that a variety of serotypes can be found in commercial swine production and shows a difference in serotypes recovered from systemic sites in pigs with clinical signs of S. suis infections.
Highlights
Streptococcus suis infections have become a major problem in the swine industry worldwide [1].This bacterium is a Gram-positive facultative anaerobe that naturally inhabits the tonsils and nasal cavities of pigs, with most pigs remaining healthy carriers
Streptococcus suis Serotypes Recovered from All Samples
Serotype 9, which, in previous studies has rarely been isolated from diseased pigs in Canada, appeared as frequently as serotype (2, 1/2) and its emergence has been shown in recent years [10]
Summary
Streptococcus suis infections have become a major problem in the swine industry worldwide [1]. This bacterium is a Gram-positive facultative anaerobe that naturally inhabits the tonsils and nasal cavities of pigs, with most pigs remaining healthy carriers. S. suis is potentially zoonotic, with people who work closely with infected pigs or pork-derived products being at greatest risk in western countries [3]. There has been over 1000 S. suis human cases and over 100 deaths since 1968, with the most cases occurring in Vietnam and Thailand through the ingestion of contaminated raw pork products [4,5]
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