Abstract
Background: Serotype replacement and emergence of multidrug resistant S. pneumoniae has exacerbated the need for continuous regional serotype surveillance especially in the developing world. We investigated S. pneumoniae serotypes circulating among vaccinated and unvaccinated children ≤5 years in Nairobi County post PCV10 era. Methods: A total of 206 vaccinated and unvaccinated children attending Gertrude's Children's Hospital (GCH) were recruited for this study. Nasopharyngeal swabs collected using Copan Flocked Swabs were the main study specimen. Culturing and isolation of S. pneumoniae was done on BA with gentamicin and BA plates respectively at the GCH main laboratory. Serotyping was done using the Quellung reaction at the KEMRI-Wellcome Trust, Kilifi. Results: Out of the 206 subjects sampled, 20.39% (42) were found to be carriers of S. pneumoniae. About 52% (n=22) of the S. pneumoniae carriers had received the recommended dose of PCV-10, while 48% (n=20) of the carriers had not. Almost all (n=41; 19.90% of subjects) isolates contained non-vaccine type S. pneumoniae serotypes, while n=1 of the serotypes (in 0.49% of subjects) were untypeable. Serotypes 28F, 6A, 11A, 3 and 7C were prevalent in both vaccinated and unvaccinated children, whereas serotypes 23A, 17F, 35F, 48, 13 and 35B, and 23B, 20, 19B, 21, untypeable, 15B and 39 were found among unvaccinated and vaccinated groups, respectively. Conclusions: All S. pneumoniae serotypes isolated from the subjects sampled were non PCV-10 vaccine type. These results therefore highlight the importance of monitoring and evaluation to provide epidemiological information to determine the effectiveness of PCV10 in Kenya's Public health services.
Highlights
Streptococcus pneumoniae is a friendly gram positive inhabitant of the human upper respiratory tract but can be highly invasive in some conditions (Mitchell & Mitchell, 2010)
18 different S. pneumoniae serotypes were found in this population
This study found that 20.39% of all children studied, from both the PCV-10 vaccinated and unvaccinated groups, were carriers of S. pneumoniae
Summary
Streptococcus pneumoniae is a friendly gram positive inhabitant of the human upper respiratory tract but can be highly invasive in some conditions (Mitchell & Mitchell, 2010) It is a major cause of morbidity and mortality globally as it kills more children than any other illness (Jones et al, 2010). WHO and UNICEF estimates indicate that over 800,000 children under 5 years of age die from pneumococcal disease each year in the developing world (O’Brien et al, 2009). We investigated S. pneumoniae serotypes circulating among vaccinated and unvaccinated children ≤5 years in Nairobi County post PCV10 era. It needs to be indicated that circulating SPn serotypes are being investigated after the introduction of 10-valent pneumococcal conjugate vaccine (PCV10) in 2011.
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