GENETIC VARIATION IN PENICILLIN-BINDING GENES 1A, 2B, AND 2X OF STREPTOCOCCUS PNEUMONIAE CAUSING INVASIVE PNEUMOCOCCAL DISEASE IN INDIAN CHILDREN

Abstract

Intro: It is widely known that India holds a high burden of pneumococcal disease and studies related to the genetic variation in the penicillin-binding proteins (PBP), the principal target of beta-lactam drugs are sparse. Further, serotype 19F of Streptococcus pneumoniae was the predominant serotype among Indian children. The present study identifies the genetic variations and AMR patterns of PBP genes 1a, 2b, and 2x of S. pneumoniae 19F serotype in Indian children (≤5 years). Methods: A total of 97 S.pneumoniae serotype 19F clinical isolates collected across India from 2009-2018, were subjected to WGS on the Illumina platform. Multiple Sequence Alignment on MEGA-X-V10.0.3 was performed for extracted PBP sequence data, and the AMR pattern was determined. Findings: Of the 97, 19F serotype isolates, 62 belonged to the pediatric age. A total of 29 different substitution mutations in PBP 1a, 2b, and 2x genes were observed. In the conserved motifs of PBP genes, the following substitutions were observed: PBP1a-85.5% (P432T), 75.8% (T371A); PBP1b-85.5% (T446A), 83.9% (Q438E), 46.8% (A619G); PBP2x- 78.3% (T338A and L546V), respectively. Whereas in the protein, active sites 100% substitutions were detected in E388D (PBP1a), and S517A (PBP2b) regions. The genetic variations were correlated phenotypically and it was interesting to note that 53 of the 62 isolates conferred resistance to penicillin (MIC = 0.5 µg/ml to 4 µg/ml). About 9 isolates displayed sensitivity to penicillin (MIC = 0.03 µg/ml) without any mutations. Conclusion: There was a higher degree of genetic diversity detected in PBPs substitutions among the isolates, a few of which were on par with previously reported data, while the major substitution mutations observed in the study resulted in high-level resistance to beta-lactams.