Epigenetic effects of ceftriaxone-resistant Neisseria gonorrhoeae FC428 mosaic-like sequences found in PenA sequences unique to Neisseria subflava and related species.

The aim of this study was to explore the origin of the PenA mosaic amino acid sequence in the ceftriaxone-resistant Neisseria gonorrhoeae FC428 clone. The penA sequences of 27 Neisseria subflava pharyngeal isolates were determined by the Sanger method and penA sequences of 52 isolates from nine Neisseria species were obtained from the NCBI database. Comparative analysis of each PenA sequence was performed by multiple sequence alignment using ClustalW. In vitro resistance acquisition experiments were conducted to investigate the possibility of selection pressure by cefixime-induced amino acid substitution mutations in PenA. All N. subflava strains, including two with low susceptibility to expanded-spectrum cephalosporins (ESCs), possessed the majority of the PenA FC428 sequence. Furthermore, a number of strains, but not all, of closely related species of N. subflava showed similar results. PenA FC428 sequences were also found in some strains of distantly related species. No new mutations in the penA sequence were observed in colonies with increased MIC in in vitro resistance acquisition experiments. This study provides strong evidence that the FC428 PenA mosaic sequence originated from N. subflava and related species among oral commensal Neisseria species. The results of in vitro resistance acquisition experiments also suggested that one of the PenA FC428-like sequence gene polymorphisms resulted in the expression of ESC resistance. Furthermore, many of the PenA FC428 mosaic sequences were thought to be involved in the so-called epistasis effect that regulates the expression of resistance, without directly contributing to the resistance level itself.

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