Nasopharyngeal carriage, serotype pattern and antimicrobial non-susceptibilities of Streptococcus pneumoniae among healthy children in the 13-valent pneumococcal conjugate vaccine era in Barbados, one of the Caribbean countries

Abstract Background Barbados like other countries in the English-speaking Caribbean introduced the 7-valent pneumococcal conjugate vaccine (PCV7) in late 2007, replaced by the 13-valent vaccine (PCV13) in 2013, using a 3+ 0 dosing schedule. We investigated the prevalence and serotype pattern of nasopharyngeal (NP) carriage of Streptococcus pneumoniae (SP) and the Antimicrobial Non-susceptibility of SP (ANSP) among children. Materials and methods A cross sectional survey of NP carriage. NP swabs were collected from healthy children (6 months to 10 years) attending the well-child clinic at the polyclinics, after parental consent, during 2016–2017. Samples were cultured for SP and isolates were serotyped by the capsular swelling method using commercial group- and type-specific sera. Susceptibility testing was conducted by broth microdilution MIC determination, according to CLSI recommended breakpoints. Results Prevalence of NP carriage of SP among 198 healthy children, 88.9% immunized for PCV , was 12.6% (95% CI  = 8.5%, 18.3%). Prevalence of NP carriage for the VT and NVT was 7.1% (95% CI = 4.1%, 11.8%) and 5.6% (95%CI = 3.0%, 10.0%) respectively. Serotype 19F was the most common NP isolate in 7 (28%; 12.9%, 49.6%) children and this was followed by 15B/C (25%), 35B (12%) and 6B (12.5%). More than 50% of isolates exhibited Antimicrobial Non-sensitive SP (ANSP) to Penicillin (Oral), Azithromycin and Co-trimoxazole. Serotypes 19F, 19A and 23F showed high level ANSP to 10/11 commonly used antibiotics. Conclusions NP carriage of SP among healthy children immunized with PCV continues to be predominantly VT and exhibit high ANSP.