Epidemiological analysis of Streptococcus pyogenes infections in Hong Kong

SummaryAimsThe aim of this study was to characterise clinical and microbiological features of isolates obtained from both invasive and non-invasive Streptococcus pyogenes infections in Hong Kong, between October 2005 and April 2008.MethodClinical data of invasive isolates were collected retrospectively. Altogether 281 isolates were emm sequence typed and tested for antimicrobial susceptibility using disk diffusion method. Detection of the presence of the streptococcal pyrogenic exotoxin genes was also carried out.Resultsemm1, emm4 and emm12 were the most prevalent in both the invasive and non-invasive groups with an increase in incidence of emm22 compared with a previous study. emm22 was associated with invasive cellulitis and wound infection. The overall rate of erythromycin resistance was 25.6% and was significantly higher in emm22 strains (85.7%). The phage-encoded superantigen gene speA was exclusively associated with emm1 in both invasive and non-invasive isolates.ConclusionThis study revealed a changing epidemiology of S. pyogenes infection in Hong Kong, with a unique pattern compared with other Asian countries. Invasiveness is not related to the presence of speA, speC or ssa genes and the antimicrobial resistance rate was high for macrolides. The findings have an implication on the use and efficacy of the polyvalent S. pyogenes vaccine under development.