Prevalence of pneumococcal serotypes in adults ≥50 years of age

Currently, majority of studies on antibiotic resistance and serotype prevalence in Streptococcus pneumoniae are in paediatric population and there is limited epidemiologic data pertaining to elderly Indian population.

This study was undertaken to assess antibiotic resistance pattern and the coverage of the polysaccharide vaccine 23 (PPV23) in the elderly population.

This was a prospective 2-year pneumococcal surveillance study in patients with community-acquired pneumococcal infections of ≥50 years' age group on fifty isolates of S. pneumoniae.

Antibiotic susceptibility by Kirby-Bauer disc diffusion method and minimum inhibitory concentration susceptibility testing by E-test method were performed for various antibiotics. All isolates were serotyped by the capsular Quellung method with commercial antisera.

All S. pneumoniae isolates were sensitive to penicillin and ceftriaxone. Non-susceptibility to levofloxacin, co-trimoxazole, erythromycin and clindamycin was noted as 16%, 74%, 10% and 6%, respectively. Prevalence of multidrug resistance in S. pneumoniae was observed as 6%. The most common serotypes observed in our study were 19A (14%), 8 (10%), 19F (8%), 3 (6%) and 9N (6%). PCV7, PCV10, PCV13 and PCV23 coverage was observed as 16%, 24%, 48% and 66%, respectively. The non-vaccine serotypes (NVTs) comprised 30% (n = 15) of the isolates.

Our study shows different antibiotic susceptibility patterns of S. pneumoniae as compared to other neighbouring regions in Asia. The modest coverage of S. pneumoniae serotypes by PPV23 vaccine and prevalence of diverse NVTs in adult population make it a challenging task to recommend further changes in the future vaccine.