Molecular typing of multiresistant Streptococcus pneumoniae serogroup 19 in Singapore.

The prevalence of penicillin-resistant Streptococcus pneumoniae in clinical isolates from the Pathology Department of the Singapore General Hospital, in 1995, was 25%. Most of the resistant isolates belonged to serogroup 19 and were resistant to multiple antibiotics. Field-inversion gel electrophoresis (FIGE), after chromosomal digestion with the restriction enzymes Apal and Smal, was performed on all isolates of multiresistant serogroup 19 S. pneumoniae so as to determine whether they were of clonal origin. Twenty-six isolates, including six controls, were studied. Analysis of the FIGE patterns revealed three distinct clusters of closely related strains. The predominant clone comprised ten isolates of multiresistant serogroup 19 S. pneumoniae and also included two controls of a different serogroup. The presence of multiresistant serogroup 19 S. pneumoniae in Singapore, appears to be due to the spread of a small number of clones.