A Multicenter Study on the Prevalence of Antibiotic Resistance and Serotypes in Invasive and Nasopharyngeal Streptococcus Pneumoniae Isolates

Introduction and Aims: Streptococcus pneumoniae is a leading cause of morbidity and mortality worldwide. As epidemiological data regarding incidence of pneumococcal disease and antimicrobial susceptibility of pneumococci is scarce from developing countries, aim was to determine antimicrobial resistance patterns of pneumococcal isolates and correlate with the type of pneumococcal disease and serotypes. Methods: Retrospective study, S. pneumoniae isolates were recovered from clinical and nasopharyngeal (NP) specimens from two tertiary care hospitals during January 2022-June 2024. Identification was done by standard microbiological procedures. Antimicrobial susceptibility, using disk diffusion was performed for chloramphenicol, trimethoprim-sulphamethoxazole (TMP-SMX) and vancomycin. MICs for penicillin, azithromycin, levofloxacin, and ceftriaxone were determined by E-test. Selected isolates were serotyped using type/group-specific antisera. Results: A total of 153 non-duplicate pneumococcal isolates (51, 63, 10, 7 and 22 from pneumonia, pneumonia with concomitant sepsis, meningitis, other clinical isolates and NP carriage respectively) were collected. All meningeal and NP isolates were susceptible to penicillin and ceftriaxone (MIC 0.006-0.125 mcg/ml). Among non-meningeal isolates, penicillin and ceftriaxone susceptibility was 97.5% and 96.6% respectively (CLSI), 70.2% and 90.8% respectively (EUCAST). High level of resistance was observed to levofloxacin and TMP-SMX among both clinical (13%) and NP (38.9%) isolates. MDR was observed in 7.6% clinical isolates, 2 were pan-resistant. Mortality rate was 10%; all had at least one underlying disease. Most prevalent serotypes were 19F, 1, 7F, 12F, 18 (clinical samples) and 19F (NP carriage). Conclusion: S. pneumoniae remains susceptible to penicillin. Emergence of non-beta-lactams and multidrug resistance among S. pneumoniae requires continuous monitoring of resistance, restricted use of antibiotics and to focus attention on pneumococcal vaccination.