Vaccination against pneumococcus in West Africa: perspectives and prospects

Eric S Donkor,1 Nicholas TKD Dayie,1,2 Ebenezer V Badoe3 1Department of Microbiology, University of Ghana Medical School, Accra, Ghana; 2Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; 3Department of Child Health, University of Ghana Medical School, Accra, Ghana Background: Pneumococcal vaccination has become obligatory due to the enormous burden of pneumococcal diseases. Quite recently, pneumococcal conjugate vaccines have been developed, and have been shown to be superior to the previous polyvalent polysaccharide vaccine of the organism. Pneumococcal conjugate vaccines (PCVs) are being introduced in many West African countries and it is important to understand the expected performance, relevance, and limitations of these vaccines in the subregion. Aim: The objective of the study presented here was to provide epidemiological insights into PCVs in West Africa based on the prevailing pneumococcal serotypes in the subregion. Methods: A systematic review was carried out on pneumococcal serotypes causing invasive and noninvasive diseases in West Africa. Studies included in the review were those that reported at least 20 serotyped pneumococcal isolates and which were conducted prior to the introduction of PCVs in the region in 2009. The proportion of pneumococcal disease associated with each serotype as well as the serotype coverage of various PCVs (PCV7, PCV10, and PCV13) were calculated. Results: The data covered 718 serotyped pneumococcal isolates from six West African countries: Burkina Faso, Ghana, Nigeria, Mali, Senegal, and The Gambia. The 718 isolates covered more than 20 serotypes. Serotype 1 was the most prevalent serotype (32%), followed by serotype 5 (15%), serotype 6 (7%), serotype 2 (6%), serotype 3 (6%), and serotype 12 (5%). The estimated serotype coverage of PCVs among the West African countries was 2%–36% for PCV7, 39%–80% for PCV10, and 65%–87% for PCV13. Conclusion: A pneumococcal capsular vaccine for use in West Africa must contain serotypes 1 and 5, the most important serotypes responsible for pneumococcal disease in the region. Consequently, while PCV10 and PCV13 are generally suitable for use in West Africa, PCV7 is unsuitable. Keywords: pneumococcus, conjugate vaccines, serotype, PVC10, PVC13, pneumococcal disease, Streptococcus pneumonia

A genomic infection control study for Staphylococcus aureus in two Ghanaian hospitals

Eric S Donkor,1 Dorota Jamrozy,2 Richael O Mills,3,4 Thomas Dankwah,3 Philip K Amoo,5 Beverly Egyir,6 Ebenezer V Badoe,7 Joana Twasam,8 Stephen D Bentley2 1Department of Medical Microbiology, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, Accra, Ghana; 2Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK; 3Central Laboratory, Korle-Bu Teaching Hospital, Accra, Ghana; 4Department of Biomedical Sciences, University of Cape Coast, Cape Coast Ghana; 5Public Health Unit, Korle-Bu Teaching Hospital, Accra, Ghana; 6Bacteriology Unit, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana; 7Department of Child Health, School of Medicine and Dentistry, University of Ghana, Accra, Ghana; 8Laboratory Unit, Lekma Hospital, Accra, Ghana Background: Whole genome sequencing analysis (WGSA) provides the best resolution for typing of bacterial isolates and has the potential for identification of transmission pathways. The aim of the study was to apply WGSA to elucidate the possible transmission events involved in two suspected Staphylococcus aureus hospital outbreaks in Ghana and describe genomic features of the S. aureus isolates sampled in the outbreaks. Methods: The study was carried out at Korle-Bu Teaching Hospital and Lekma Hospital where the suspected outbreaks occurred in 2012 and 2015, respectively. The S. aureus isolates collected from the two hospitals were from three sources including carriage, invasive disease, and the environment. Whole genome sequencing of the S. aureus isolates was performed and the sequence reads were mapped to the S. aureus reference genome of strain USA300_FPR3757. A maximum-likelihood phylogenetic tree was reconstructed. Multilocus sequence typing together with the analysis of antimicrobial resistance and virulence genes were performed by short read mapping using the SRST2. Results: The S. aureus isolates belonged to diverse sequence types (STs) with ST15 and ST152 most common. All isolates carried the blaZ gene, with low prevalence of tetK and dfrG genes also observed. All isolates were mecA negative. The pvl genes were common and observed in distinct lineages that revealed diverse Sa2int phages. At Korle-Bu Teaching Hospital, the genomics data indicated several transmission events of S. aureus ST15 involving contamination of various surfaces in the pediatric emergency ward where the outbreak occurred. Conclusion: The pattern of dissemination of the ST15 clone in the emergency ward of Korle-Bu Teaching Hospital highlights a basic problem with disinfection of environmental surfaces at the hospital. Diverse phage population rather than a single highly transmissible phage type likely mediates the high prevalence of pvl genes among the S. aureus isolates. Keywords: Staphylococcus aureus, sequencing, transmission, outbreak, Ghan