Molecular characterization and antimicrobial resistance patterns of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in PCV-10 vaccinated children : A study in Kampala, Uganda

Abstract

In high income countries (HIC), the evidence of beneficial effect of indirect pneumococcal conjugate vaccination (PCV) protection is decreased nasopharyngeal carriage of vaccine-serotype pneumococci among unvaccinated persons. This is because in HIC they have managed to attain high vaccine coverage and sustained those rates. Although there is a high implementation of PCV in low- and middle-income countries (LMIC), the understanding of the potential indirect protection of 10-valent PCV (PCV-10) is still limited, despite the protective effect among recipients of the vaccine. This study was set out to characterize S. pneumoniae, H. influenzae, M. catarrhalis isolates from children vaccinated against 10-valent pneumococcal vaccine (PCV-10) in Kampala, Uganda as well as to determine how it affected these bacterial species susceptibilities to antibiotics and their serotypes distribution. Using a cross sectional study employing standard microbiology methods and Triplex quantitative Real-Time PCR, the prevalence and drug resistance patterns of vaccine preventable strains of S. pneumoniae, H. influenzae, M. catarrhalis were determined and the persistent S. pneumoniae serotypes present in the S. pneumoniae positive isolates detected. The study identified the 74% (46/70), 7% (6/16) and 11% (9/11) of the isolates as S. pneumoniae, H. influenzae, and M. catarrhalis respectively, with 8% of samples having S. pneumoniae and either of the other species. There was no coexistence between H. influenzae and M. catarrhalis. Almost all the isolates showed resistance to co-trimoxazole. Pneumococcal isolates showed a significant increase in resistance to tetracycline, chloramphenicol, erythromycin and clindamycin compared to the results of similar study conducted before the vaccine. A prevalence of 74.3% of H. influenzae isolates were resistant to tetracycline and 47.2% to ampicillin, while all M. catarrhalis showed susceptibly to all antibiotics except penicillin, ampicillin and co-trimoxazole where it was 100% resistant. The most prevalent serotypes detected were serotypes 14 and 19A. There was coexistence of serotypes 3 and 7F/7A. No sample was positive for serotypes 1, 5, 23F, 4, 6A, 6B, 6C, 6D and 19F. The prevalence of S. pneumoniae carriage decreased after the introduction of pneumococcal vaccine. However, a significant increase in drug resistance is reported compared to the pre-vaccine era. The findings also indicate low prevalence of H. influenzae and M. catarrhalis among PCV10 vaccinated children in Kampala.