Analysis of Amino Acid Sequences of Penicillin-Binding Proteins 1a, 2b, and 2x in InvasiveStreptococcus pneumoniaeNonsusceptible to Penicillin Isolated from Children in India

Penicillin-binding proteins are the primary targets for beta lactam drugs, which are main stay of treatment forStreptococcus pneumoniae. The emergence of increased penicillin resistance in meningeal isolates ofS. pneumoniaein India is alarming. With this background, we aimed to analyze thepbpgene mutations of penicillin nonsusceptible pneumococcal (PNSP) isolates from within India and their association with international clones. A total of 32 PNSP invasive isolates with a penicillin minimal inhibitory concentrations (MIC) of >= 0.12 mu g/mL were subjected to PCR and sequencing for multilocus sequence typing and thepbpgenes (pbp2b,pbp2x, andpbp1a). TheS. pneumoniaeR6 susceptible strain was used as the reference for the comparison analyses. In the majority of the present study isolates, amino acid substitutions were only seen in one of the three active sites of one of the threepbpgenes. Thus,pbpgenes in the absence of the major substitutions usually associated with penicillin resistance combined with mosaicism inpbp1aresulted in a slight increase in the penicillin MIC to between 0.06 and 2.0 mu g/mL, which according to meningeal break point denote resistance. Clonal analyses revealed that the emergence of PNSP in India is due to the gradual expansion of the resistant clones CC320, CC230, and CC63.