[The role of some individual amino acid substitutions in penicillin-binding protein (PBP2) of Neisseria gonorrhoeae in the emergence of resistance to ceftriaxone].

The goal of the study was to identify amino acid replacements in the structure of penicillin-binding protein PBP2, which may influence on the development of resistance N. gonorhoeae to the III cephalosporins generation. The gene penA of 50 strains of N. gonorrhoeae was sequenced: 20 strains with high sensitivity to ceftriaxone (MIC, Minimum Inhibitory Concentration, = 0.002 mg/L) and 30 strains with decreased sensitivity to ceftriaxone (MIC = 0.03-0.25 mg/L). The difference of MIC sensitivity between these strains was 30-250 times. Then nucleotide sequence was transformed into the amino acid sequence of PBP2 protein. Mutations in the gene penA and amino acid replacements in the protein PBP2 were found in 16 of 20 strains (80%) with high sensitivity to ceftriaxone and in all strains with decreased sensitivity to ceftriaxone. Amino acid replacements in the PBP2 protein were compared with amino acid replacements in groups, which characterize the PBP2 structure in accordance with the international classification Ito M. The amino acid replacement of PBP2 at positions 346, 505, 511, 517, 543, 567, 575, 576 are associated with V group by Ito M and have features of resistance of N. gonorrhoeae to ceftriaxone authentically (OR = 3.9 ± 2.5; χ2 = 4.9; p < 0.05). It was shown that the replacement of glycine to serine at position 543 of PBP2 in the analyzed strains induced the multiple increase of resistance to ceftriaxone. These data may be significant as showing strong influence of amino acid replacements at positions 346, 505, 511, 517, 567, 575 and, in particular, 543 for development of resistance N. gonorrhoeae strains to ceftriaxone.