Identification of natural pneumococcal isolates expressing serotype 6D by genetic, biochemical and serological characterization

1 Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA 2 Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294, USA 3 Department of Pediatrics, School of Medicine, Ewha Woman's University, Seoul, Korea 4 Department of Pediatrics, School of Medicine, The Catholic University of Korea, Seoul, Korea 5 Department of Pediatrics, School of Medicine, Jeju National University, Jeju City, Korea The recently discovered pneumococcal serotype 6C was created when the original wciN gene in the 6A capsule gene locus was naturally replaced with a new gene. Since the capsule gene loci of 6A and 6B serotypes may differ by only one base pair in the wciP gene, it was speculated that a new serotype ‘6D’ would be possible if the new wciN gene were inserted into the 6B capsule gene locus. Although pneumococci expressing serotype 6D could be produced in the laboratory, initial searches for natural pneumococcal isolates expressing serotype 6D were unsuccessful. However, we now report the discovery of two naturally occurring pneumococcal isolates from Korea that have the serological, genetic and biochemical features predicted for serotype 6D. Correspondence Moon H. Nahm nahm{at}uab.edu Abbreviations: PS, polysaccharide The GenBank/EMBL/DDBJ accession numbers for the sequences of the wciN and wciP regions determined in this study are GQ848645 for MNZ21 and GQ848646 for MNZ22.