Identification and characterization of a novel insertion sequence, IS1106, downstream of the porA gene in B15 Neisseria meningitidis

Summary Examination of Neisseria meningitidis strains associated with endemic meningococcal disease demonstrated differences in the number of copies of a repetitive sequence. Characterization of a copy of this repetitive sequence present in B15 strains has revealed the presence of a novel insertion sequence (S1 1106) located within a complex repetitive region downstream of the gene for the major surface antigen (porA). IS 1106 has a length of 1137 bp and is flanked by 36bp inverted repeats. Two open reading frames (0RF1 and 0RF2) are present in opposite strands in codon–codon register with 0RF2 entirely located within ORF1. The predicted protein from 0RF1 demonstrates homology with the 5A protein of IS5 (Kroger and Hobom, 1962). Strains from two independent outbreaks of B15 meningococcal disease in the UK were found to contain the same genomic deletion removing a copy of IS 1106 downstream of the porA gene.