Mosaic-like structure of penicillin-binding protein 2 Gene (penA) in clinical isolates of Neisseria gonorrhoeae with reduced susceptibility to cefixime

Abstract

Neisseria gonorrhoeae strains with reduced susceptibility to cefixime (MICs, 0.25 to 0.5 micro g/ml) were isolated from male urethritis patients in Tokyo, Japan, in 2000 and 2001. The resistance to cephems including cefixime and penicillin was transferred to a susceptible recipient, N. gonorrhoeae ATCC 19424, by transformation of the penicillin-binding protein 2 gene (penA) that had been amplified by PCR from a strain with reduced susceptibility to cefixime (MIC, 0.5 micro g/ml). The sequences of penA in the strains with reduced susceptibilities to cefixime were different from those of other susceptible isolates and did not correspond to the reported N. gonorrhoeae penA gene sequences. Some regions in the transpeptidase-encoding domain in this penA gene were similar to those in the penA genes of Neisseria perflava (N. sicca), Neisseria cinerea, Neisseria flavescens, and Neisseria meningitidis. These results showed that a mosaic-like structure in the penA gene conferred reductions in the levels of susceptibility of N. gonorrhoeae to cephems and penicillin in a manner similar to that found for N. meningitidis and Streptococcus pneumoniae.

FIG.1.

Nucleotide sequence of penA gene of N. gonorrhoeae. The sequences of the penA genes of penicillin-susceptible strain LM306 (GenBank accession no. M32091) (A), the strain with reduced susceptibility to cefixime (strain NG-3) (B), and cefixime-susceptible strain NG-12 (C) are shown. The insertion of an extra aspartate (Asp-345A) is shown in cefixime-susceptible strain NG-12 but is not shown in the strain with reduced susceptibility to cefixime, NG-3. Asp∗, Asp-345A. The Ser-X-X-Lys, Ser-X-Asn, and Lys-Thr-Gly conserved motifs are indicated by underlining.

FIG. 2.

Schematic representation of mosaic-like penA genes of Neisseria strains. The penA gene of N. gonorrhoeae and the coding region for PBP 2 are represented in the diagram. The penA genes of cefixime-susceptible N. gonorrhoeae strain NG-12 (A), an N. gonorrhoeae strain with reduced susceptibility to cefixime (strain NG-3) (B), N. cinerea strain LPN3173 (C), and N. perflava (N. sicca) strain 1654/1659 (D) are shown. The nucleotide sequence divergences (in percent) between regions of the N. gonorrhoeae NG-3 penA genes and the corresponding regions in the penA genes of N. cinerea LPN3173 (░⃞) and N. perflava (N. sicca) 1654/1659 (▨) are shown.