Abstract: Objective To investigate the amino acid patterns in penicillin-binding protein 2 （PBP2） in Neisseria gonorrhoeae isolates with reduced susceptibility to ceftriaxone, and the relationship between the amino acid patterns and reduced ceftriaxone susceptibility. Methods DNA was extracted from 13 clinical isolates of N. gonorrhoeae, including 11 strains with decreased susceptibility to ceftriaxone and 2 sensitive isolates. The full-length penA gene encoding the penicillin-binding protein 2 was amplified and sequenced. BLASTn and BLASTx programs were used to assess the insertion and substitution patterns of nucleotides in penA gene and of amino acids in PBP2, respectively. Results BLASTn analysis revealed insertion or substitution of 18-38 nucleotides in the penA gene of gonococcal isolates with reduced ceftriaxone susceptibility. As shown by BLASTx analysis, there were five patterns of amino acid substitution or insertion in PBP2 of the 11 isolates with reduced ceftriaxone susceptibility. However, mosaic structure of PBP2 was not found in any of these isolates. Conclusion Mosaic PBP2 seems not to be the major factor contributing to the decrease in susceptibility of N. gonorrhoeae to ceftriaxone.

Key words: Neisseria gonorrhoeae, ceftriaxone