Nicholas T. K. D. Dayie

Invasive disease and paediatric carriage of Streptococcus pneumoniae in Ghana

Abstract This study was carried out primarily to evaluate the public health burden related to Streptococcus pneumoniae in Ghana and to provide related preliminary molecular epidemiological data on the organism. Invasive and nasopharyngeal specimens were screened for S. pneumoniae, and isolates were subjected to serotyping, multilocus sequence typing (MLST) and antibiotic susceptibility testing. Overall, the prevalence of S. pneumoniae in cerebrospinal fluid (CSF) was 1.7%, in blood was 0.2%, and in nasopharyngeal specimens was 15.3%. The prevalence of multiple drug resistance among the isolates was 48.6%, while the percentage resistance to various drugs was in the range of 11.1–84.0%. Serotyping of the S. pneumoniae isolates showed 7 different serotypes (3, 6B, 9, 10, 14, 16 and 23F). The extent of coverage of serotypes by the 7-valent pneumococcal conjugate vaccine was 57.1%, for the 10-valent vaccine was 57.1%, and for the 13-valent vaccine was 71.4%. MLST of 7 housekeeping genes of the organism showed a high level of genetic diversity among the isolates. S. pneumoniae appears to be an important organism in invasive infections in Ghana, being the most prevalent organism in CSF in this study. The high multiple drug resistance of the organism observed heightens the public health burden, which may be controlled by pneumococcal conjugate vaccines to a large extent.

Vaccination against pneumococcus in West Africa: perspectives and prospects

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.

Bioinformatics with basic local alignment search tool (BLAST) and fast alignment (FASTA)

Following advances in DNA and protein sequencing, the application of computational approaches in analysing biological data has become a very important aspect of biology. Evaluating similarities between biological sequences is crucial to our understanding of evolutionary biology, and this can be achieved by basic local alignment search tool (BLAST) and fast alignment (FASTA). BLAST and FASTA have become fundamental tools of biology and it is essential to know how they operate, the task they can accomplish and how to accurately interpret their output. This paper provides an analysis of BLAST and FASTA in sequence analysis. Both BLAST and FASTA algorithms are appropriate for determining highly similar sequences. However, BLAST appears to be faster and also more accurate than FASTA. Both BLAST and FASTA are limited in sensitivity and may not be able to capture highly divergent sequences in some cases. Consequently, evolutionarily diverse members of a family of proteins may be missed out in a BLAST or FASTA search. Key words: Bioinformatics, basic local alignment search tool (BLAST), fast alignment (FASTA), sequence alignment, prokaryotes.

Pneumococcal carriage among HIV infected children in Accra, Ghana

BackgroundPneumococcal carriage is the precursor for development of pneumococcal disease, and is also responsible for transmission of the organism from person-to-person. In Africa, little is known about the pneumococcus in relation to people with HIV infection. The aim of the study was to investigate the epidemiology of pneumococcal carriage among HIV infected children visiting a tertiary hospital in Ghana, including the carriage prevalence, risk factors and serotype distribution.MethodThis was a cross sectional study carried out from February to May, 2015 at the HIV Paediatric Clinic of the Korle-Bu Teaching Hospital in Accra, Ghana. One hundred and eighteen HIV infected children were recruited and nasopharyngeal (NP) swabs were collected from them. Epidemiological data on demographic, household and clinical features of the study participants were also collected. The NP specimens were cultured for Streptococcus pneumoniae and the isolates were serotyped by latex agglutination. The data of the study was analysed using STATA 11 (Strata Corp, College Station, TX, USA).ResultsPrevalence of pneumococcal carriage among the HIV infected children was 27.1% (95% CI: 19.1 to 35.1) and the only factor significantly associated with pneumococcal carriage was the presence of respiratory symptoms (OR, 2.63; CI, 1.06-6.53; p = 0.034). The most prevalent pneumococcal serotype among the study participants was serotype 19F (24.4%), followed by 16F (22%). Serotype coverage of the 13-valent Pneumococcal Conjugate Vaccine in this study was 41.5%. Multiple carriage of pneumococcal serotypes among the positive carriage cases was 34.3%.ConclusionPneumococcal carriage occurred in more than a quarter of the study population and was characterized by predominance of non-vaccine serotypes as well as a high prevalence of multiple carriage. Presence of respiratory symptoms appears to be a major determinant of pneumococcal carriage among the study population.

Clonal distribution of pneumococcal serotype 19F isolates from Ghana

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. Pneumococcal strains are classified according to their capsular polysaccharide and more than 90 different serotypes are currently known. In this project, three distinct groups of pneumococcal carriage isolates from Ghana were investigated; isolates from healthy children in Tamale and isolates from both healthy and children attending the outpatient department at a hospital in Accra. The isolates were previously identified and characterized by Gram staining, serotyping and susceptibility to penicillin. In this study, isolates of the common serotype 19F were further investigated by Multi-Locus Sequence Typing (MLST). Overall, 14 different Sequence Types (STs) were identified by MLST, of which nine were novel based on the international MLST database. Two clones within serotype 19F seem to circulate in Ghana, a known ST (ST 4194) and a novel ST (ST 9090). ST 9090 was only found in healthy children in Accra, whereas ST 4194 was found equally in all children studied. In the MLST database, other isolates of ST 4194 were also associated with serotype 19F, and these isolates came from other West African countries. The majority of isolates were penicillin intermediate resistant. In conclusion, two clones within serotype 19F were found to be dominating in pneumococcal carriage in Accra and Tamale in Ghana. Furthermore, it seems as though the clonal distribution of serotype 19F may be different from what is currently known in Ghana in that many new clones were identified. This supports the importance of continued monitoring of pneumococcal carriage in Ghana and elsewhere when vaccines, e.g., PCV-13, have been introduced to monitor the possible future spread of antimicrobial resistant clones.

Urinary Tract Infections among Bladder Outlet Obstruction Patients in Accra, Ghana: Aetiology, Antibiotic Resistance, and Risk Factors

The aim of this study was to investigate urinary tract infections among patients with Bladder Outlet Obstruction (BOO) at the Korle Bu Teaching Hospital (KBTH) in Accra, Ghana, including the prevalence, risk factors, aetiological agents and their antibiogram. Urine specimens were collected from 188 male patients presenting with BOO and cultured for bacteria. The bacterial isolates were identified using standard microbiological methods and tested against a spectrum of antimicrobial agents using the Kirby Bauer method. Demographic information and the clinical history of study participants were also recorded. The prevalence of urinary tract infection among the BOO patients was 76.6% and the main risk factor identified was catheterization (p < 0.0001). A wide range of bacterial organisms was isolated from urine specimens and they were predominantly, Enterobacteriaceae; Escherichia coli was the most frequent cause of bacteriuria (33.3%), followed by Klebsiella (17.3%). Bacterial isolates were most resistant to Augmentin (97.8%) followed by tetracycline (85.8%), nalidixic acid (82.8%) and ciprofloxacin (75%) while 93.6% were multi-drug resistant. The highest susceptibility was observed with amikacin, which had a resistance prevalence of 4.4% resistance. These findings have important implications in the treatment of urinary tract infections among the BOO patients in Ghana.