pspK gene prevalence and characterization of non-typable Streptococcus pneumonia isolates from Asian countries

Recently, it has been reported that some non-typable (NT) Streptococcus pneumoniae isolates from Korea and other countries contained a novel gene pspK in the capsular polysaccharide synthesis (cps) locus. In this study, we investigated the presence of pspK in 120 NT S. pneumoniae isolates from 12 Asian countries; isolate characteristics were also examined. The presence of pspK was assayed by PCR. Clonality of NT S. pneumoniae isolates containing pspK was investigated by MLST and PFGE. Antimicrobial susceptibility testing was performed and the structure of pspK was also determined. Nineteen NT isolates (15.8 %) were identified as containing pspK: two isolates from Korea, four from Vietnam, two from Hong Kong, eight from Thailand, and one each from Taiwan, the Philippines and Saudi Arabia. Seven isolates from Korea, Vietnam and Thailand were identified as ST1106, whereas just one or two belonged to ST310, ST393, ST10137, ST2754 or ST4136. All but one of the ST1106 NT isolates showed non-susceptibility to penicillin, and all isolates were resistant to cefuroxime, erythromycin, clindamycin and trimethoprim/sulfamethoxazole. The structure of pspK was similar amongst 20 isolates, which had a R1-R2-like region and a variable number of repeats in the repetitive region. However, one isolate (P05-11) from the Philippines lacked the R1-R2 region. NT S. pneumoniae isolates containing pspK were distributed across several Asian countries. Although MLST analysis suggested that most pspK-containing NT S. pneumoniae isolates may have emerged independently, ST1106 isolates with the selective advantage of antimicrobial resistance may have disseminated clonally throughout the countries.