Antibiogram profiles and genetic characteristics of Streptococcus pneumoniae clinical isolates from Pakistan

Background: Streptococcus pneumoniae is a major respiratory pathogen responsible for severe infections worldwide, with rising antibiotic resistance posing a significant clinical challenge. Objectives: This study aimed to assess the phenotypic and genotypic characteristics of S. pneumoniae isolates collected from clinical respiratory samples in different cities of Pakistan between 2022 and 2024. Methods: Antibiotic susceptibility was determined using the disc diffusion method and PCR was employed to detect resistance genes and PCV10/13 serotypes. Results: High resistance rates were observed against ofloxacin (68.8%), oxacillin (66.9%) and amoxicillin (66.0%), while the lowest resistance was noted to doxycycline (8.4%), cefotaxime (7.5%) and ceftriaxone (3.7%). Genotypic analysis revealed that 68.8% of isolates were positive for the ermB gene, 55.6% for cats and 50.9% for tetM. Additionally, 18.8% of isolates carried the mefA gene and 9.4% exhibited resistance potentially linked to the pbp2b gene. Serotype analysis showed that 66% of isolates belonged to PCV10/13 vaccine-type serotypes, with serotype 19A being the most prevalent (18.9%), followed by 19F (13.2%) and 14 (9.4%). Conclusion: These findings underscore the growing prevalence of antibiotic-resistant S. pneumoniae in Pakistan and highlight the urgent need for enhanced antimicrobial stewardship, improved surveillance systems and preventive measures to address the rising threat of resistant strains and shifting serotype distribution.