Distribution of epidemic antibiotic-resistant pneumococcal clones in Scottish pneumococcal isolates analysed by multilocus sequence typing

Abstract

Sequence types of pneumococci isolated in Scotland between 1996 and 2003 were compared with those of globally prevalent antibiotic-resistant clones. Multilocus sequence typing was performed on 252 invasive pneumococcal isolates referred to the Scottish Meningococcus and Pneumococcus Reference Laboratory. Isolates were not preselected for antimicrobial resistance, patient age or disease caused. Sequence types were compared with globally significant antimicrobial-resistant clones identified by the Pneumococcal Molecular Epidemiology Network (PMEN). Sequence types identical with three of the 26 PMEN clones were present in the Scottish collection; the clones were the Spain(9V)-3 clone (sequence type 156, seven isolates), the England(14)-9 clone (sequence type 9, eight isolates) and the Utah(35B)-24 clone (sequence type 377, one isolate). Many Scottish isolates related to PMEN clones had lower antimicrobial MICs than those described for the corresponding PMEN type strain. A number of single- (SLVs) and double-locus variants (DLVs) were present. Fifteen SLVs related to PMEN sequence types 37, 67, 90, 81, 156, 236 and 377 were detected. The collection contained 10 DLVs related to PMEN sequence types 37, 156, 173 and 338. The majority of SLVs and DLVs were penicillin- or erythromycin-sensitive variants of the resistant PMEN type strains. Capsule switching in isolates related to the PMEN clones was also detected. The highest levels of penicillin resistance were detected in sequence type 320 (serotype 19F), which is not a PMEN clone. These data suggest that PMEN clones are not widely distributed in disease-causing isolates in Scotland.