Nasopharyngeal carriage of Streptococcus pneumoniae serotypes among healthy children in North India

Abstract

Background: Streptococcus pneumonia (SP) is a major cause of morbidity and mortality among children worldwide. India introduced 13-valent pneumococcal conjugate vaccine (PCV-13) in 2017 in national immunization program in a three dose schedule at 6 weeks, 10 weeks and 9 months. The current study was conducted to isolate SP from nasopharyngeal (NP) swabs of healthy children and assess changes in serotypes among PCV vaccinated and unvaccinated healthy children. Methods and materials: Cross-sectional study was conducted in Lucknow District, Uttar Pradesh, India from July–August 2019. Recruitment was done from vaccination clinics of four public tertiary care hospitals. Children (2–59 months) who were permanent residents and had no clear illness/hospitalization in past one month were recruited. Single NP specimen was collected. After specimen collection, bacterial culture was done using 5% sheep agar blood plate containing gentamicin. Pneumococcal isolates were identified by optochin sensitivity and bile solubility. Serotyping was done using Quellung Method. Results: Of 300 children, 56.7% (170/300) were males and 52.0%, (156/300) were 2–11 months of age. Overall SP colonization rate was 37.6% (113/300). Vaccine serotypes isolated were 18 C, 19 A, 19 F, 23F, 3, 4, 6A, 6B, 9V. Among 60% (181/300) PCV vaccinated, SP positivity was 37.5% (68/181) and vaccine serotype were 39.7% (27/68). Among 40% (119/300) non PCV vaccinated children, 37.8% (47/119) had NP colonization positive and PCV-13 serotypes were 37.7% (17/47). Non Vaccine serotypes were 10A, 15A, 15B, 15C, 21, 34, 35B, 22F and similar in vaccinated and unvaccinated children. Conclusion: About 4 in 10 health children under 5 years of age had NP colonization with SP and around 40% serotypes were covered by PCV13. Our preliminary data suggests that SP colonization rate and serotype isolates were similar in vaccinated and unvaccinated children, however, further work is needed.