Antimicrobial Susceptibility Patterns of Haemophilus influenzae and Streptococcus pneumoniae in Respiratory Tract Infections: A Retrospective Observational Real-world Database Study in India

Introduction: Antimicrobial Resistance (AMR) presents a major worldwide challenge to public health, leading to significant levels of illness and death in India. The rise in antibiotic prescriptions during the pandemic raised concerns over the possible increase in antibiotic resistance and the risk of AMR. Aim: To investigate the real-world antibiotic susceptibility patterns of Haemophilus influenzae and Streptococcus pneumoniae to various antibiotics using diagnostic laboratory-based Antibiotic Sensitivity Testing (AST) data from India. Materials and Methods: This was a retrospective, observational, real-world database study that included 1,351 diagnostic AST records of the most common respiratory specimens collected from all ages between January 2017 and July 2022. Diagnostic AST records were collected across four accredited diagnostic laboratories in India, selected through an exhaustive Quality Control (QC) process validated by microbiology experts. The susceptibility patterns of H. influenzae and S. pneumoniae to amoxicillin-clavulanic acid, azithromycin, levofloxacin, cefixime, cefpodoxime and cefuroxime were evaluated using quantitative analysis {mean ± standard deviation, median (range) for age, frequency and proportions; and Odds Ratios (OR) comparing the susceptibility patterns of amoxicillin-clavulanic acid with other antibiotics} and reported as per the standard AST results as % Sensitive, % Intermediate and % Resistant. Results: Of the 1,351 diagnostic AST records included in the analysis, 1,257 (93.0%) were from adults (≥18 years). Most H. influenzae {566/608 (93.1%)} and S. pneumoniae {554/743 (74.6%)} isolates were from sputum samples. Most isolates of S. pneumoniae {227 (95.8%)} and H. influenzae {86 (88.7%)} were susceptible to amoxicillin-clavulanic acid. Susceptibility to amoxicillin-clavulanic acid was higher compared to most of the antibiotics evaluated. S. pneumoniae also showed high susceptibility to second-generation {cefuroxime: 87.4% (n=111)} and third-generation cephalosporins {cefixime: 91.3% (n=115), cefpodoxime: 97.5% (n=119)}. The susceptibility patterns of both organisms remained consistent during the pre- and post Coronavirus Disease-2019 (COVID-19) pandemic periods, except for H. influenzae to cefixime {94.0% (n=252) to 63.7% (n=137)}. Conclusion: The overall susceptibility patterns of H. influenzae and S. pneumoniae to the selected antibiotics varied over the 5-year study period. The susceptibility of both organisms to amoxicillin-clavulanic acid remained high with some fluctuations. This data also guides clinicians in making evidence-based decisions for managing Respiratory Tract Infections (RTIs).