Streptococcus suis, an important cause of adult bacterial meningitis in northern Vietnam

Abstract

Background: Streptococcus suis can cause severe systemic infection in adults exposed to infected pigs or after consumption of undercooked pig products. S. suis is often misdiagnosed, due to lack of awareness and improper testing. Here we report the first fifty cases diagnosed with S. suis infection in northern Viet Nam.

Methodology/principal findings: In 2007, diagnostics for S. suis were set up at a national hospital in Hanoi. That year there were 43 S. suis positive cerebrospinal fluid samples, of which S. suis could be cultured in 32 cases and 11 cases were only positive by PCR. Seven patients were blood culture positive for S. suis but CSF culture and PCR negative; making a total of 50 patients with laboratory confirmed S. suis infection in 2007. The number of S. suis cases peaked during the warmer months.

Conclusions/significance: S. suis was commonly diagnosed as a cause of bacterial meningitis in adults in northern Viet Nam. In countries where there is intense and widespread exposure of humans to pigs, S. suis can be an important human pathogen.

Figure 1. Location and seasonality of S. suis infections.

(A) Location of residence of 50 human S. suis cases diagnosed in northern Viet Nam in 2007 (black dot is one case) and pig density; (B) Month of diagnosis of S. suis cases during 2007.

Figure 2. PFGE after SmaI digestion of Streptococcus suis serotype 2 strains isolated from patients in northern Vietnam.

A dendrogram was generated by Dice analysis (optimization, 0.5%; band tolerance, 1.5%) and cluster analysis with unweighted pair group method with arithmetic mean, using Bionumerics software (Applied Maths). Bars indicate 95% CIs. Four representative strains from the main clusters in southern Viet Nam (A, B, C, and D) were included. Also reference strains were included (89–151 and 31533). Strains with the annotation old are from before 2007.