Abstract
BackgroundThe study objective was to determine the carriage and serotype distribution of Streptococcus pneumoniae among children in Accra, Ghana, five years after the introduction of the pneumococcal conjugate vaccine (PCV-13) in 2012.MethodsNasopharyngeal swab samples were collected from 410 children below 5 years of age in Accra, Ghana, from September to December, 2016. Pneumococcal isolates were identified by optochin sensitivity and bile solubility. Serotyping was performed using the latex agglutination kit and Quellung reaction. The isolates were furthermore tested for antimicrobial susceptibility for different antimicrobials, including penicillin (PEN). Twelve isolates including seven non-typeable (NT) isolates were characterized using whole-genome sequencing analysis (WGS).ResultsThe overall carriage prevalence was found to be 54% (95% CI, 49–59%), and 20% (95% CI, 49–59%) of the children were carrying PCV-13 included serotypes, while 37% (95% CI, 33–42%) of the children were carrying non-PCV-13 serotypes. Based on the serotype distribution, 33% of all observed serotypes were included in PCV-13 while 66% were non-PCV-13 serotypes. The dominating non-PCV-13 serotypes were 23B, 16F, and 11A followed by PCV-13 serotypes 23F and 19F. The PCV-13 covers the majority of resistant isolates in Accra. A proportion of 22.3% of the isolates showed intermediate resistance to penicillin G, while only one isolate showed full resistance. Forty-five isolates (20.5%) were defined as multidrug-resistant (MDR) as they were intermediate/resistant to three or more classes of antimicrobials. Of the seven NT isolates characterized by WGS, four showed highest match to genotype 38, while the remaining three showed highest match to genotype 14. Four MDR serotype 19A isolates were found to be MLST 320.ConclusionPCV-13 introduced in Ghana did not eliminate PCV-13 covered serotypes, and the carriage rate of 54% in this study is similar to carriage studies from pre PCV-13 period. However, the penicillin non-susceptible isolates have been reduced from 45% of carriage isolates before PCV-13 introduction to 22.3% of the isolates in this study. Continuous monitoring of serotype distribution is important, and in addition, an evaluation of an alternative vaccination schedule from 3 + 0 to 2 + 1 will be important to consider.
Highlights
The study objective was to determine the carriage and serotype distribution of Streptococcus pneumoniae among children in Accra, Ghana, five years after the introduction of the pneumococcal conjugate vaccine (PCV-13) in 2012
Pneumococcal appearance in humans can be divided into two phases, carriage and the disease phase, where the carriage of S. pneumoniae is generally described as the prerequisite for developing pneumococcal infections, and often young children are considered to act as reservoirs [2, 3]
While the PCV-13 vaccination seems to have reduced penicillin resistance in Ghana, this does not appear to be the case with tetracycline, which this study found to be about 63%, while previous pre-PCV studies have shown similar or higher tetracycline resistance of about 60–85% [16, 30]
Summary
The study objective was to determine the carriage and serotype distribution of Streptococcus pneumoniae among children in Accra, Ghana, five years after the introduction of the pneumococcal conjugate vaccine (PCV-13) in 2012. Pneumococcal infections have attracted global public health attention due to the high burden of disease and associated mortality, among children under five and adults > 64 years in resource poor countries [1, 4, 5]. Since 2000, studies have shown that the introduction of the pneumococcal conjugate vaccines (PCV7, PCV-10 and PCV-13 in selected countries) has been effective among children under 5 years [1, 7,8,9,10] Based on these results, the vaccines have been introduced in other parts of the world including Africa [5, 6, 11]
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