Abstract
Cholera remains a major global public health threat and continuous emergence of new Vibrio cholerae strains is of major concern. We conducted a molecular epidemiological study to detect virulence markers and antimicrobial resistance patterns of V. cholerae isolates obtained from the 2012–2015 cholera outbreaks in Ghana. Archived clinical isolates obtained from the 2012, 2014 and 2015 cholera outbreaks in Ghana were revived by culture and subjected to microscopy, biochemical identification, serotyping, antibiotic susceptibility testing, molecular detection of distinct virulence factors and Multi-Locus Variable-Number of Tandem-Repeat Analysis (MLVA). Of 277 isolates analysed, 168 (60.6%) were confirmed to be V. cholerae and 109 (39.4%) isolates constituted other bacteria (Escherichia coli, Aeromonas sobria, Pseudomonas aeruginosa, Enterobacter cloacae and Enterococci faecalis). Serotyping the V. cholerae isolates identified 151 (89.9%) as Ogawa, 3 (1.8%) as Inaba and 14 (8.3%) as non-O1/O139 serogroup. The O1 serogroup isolates (154/168, 91.7%) carried the cholera toxin ctxB gene as detected by PCR. Additional virulence genes detected include zot, tcpA, ace, rtxC, toxR, rtxA, tcpP, hlyA and tagA. The most common and rare virulence factors detected among the isolates were rtxC (165 isolates) and tcpP (50 isolates) respectively. All isolates from 2014 and 2015 were multidrug resistant against the selected antibiotics. MLVA differentiated the isolates into 2 large unique clones A and B, with each predominating in a particular year. Spatial analysis showed clustering of most isolates at Ablekuma sub-district. Identification of several virulence genes among the two different genotypes of V. cholerae isolates and resistance to first- and second-line antibiotics, calls for scaleup of preventive strategies to reduce transmission, and strengthening of public health laboratories for rapid antimicrobial susceptibility testing to guide accurate treatment. Our findings support the current WHO licensed cholera vaccines which include both O1 Inaba and Ogawa serotypes.
Highlights
Cholera is a highly virulent, lethal diarrhoeal disease caused by ingestion of water or food contaminated with the bacterium, Vibrio cholerae (V. cholerae)
A total of 277 archived isolates were used of which 43.3% (120) were received from the National Public Health and Reference laboratory, Korle-Bu and the remaining 157 (56.7%) were isolated from human stool samples at the Bacteriology Department of Noguchi Memorial Institute for Medical Research (NMIMR)
While the isolates from the National Public Health and Reference Laboratory (NPHRL) (120) were collected across Ghana, the 157 NMIMR isolates were from selected health facilities in the Greater Accra region Ga West Municipal hospital 100 (63.7%), Achimota hospital 15 (9.6%), Korle-Bu Polyclinic 12 (7.6%), La General Hospital 9 (5.7%), University of Ghana hospital 8 (5.2%), Princess Marie Luis children’s hospital 12 (7.6%), and 37 Military hospital 1(0.6%) (Fig 1)
Summary
Cholera is a highly virulent, lethal diarrhoeal disease caused by ingestion of water or food contaminated with the bacterium, Vibrio cholerae (V. cholerae). Seven cholera pandemics have been experienced globally and it continues to cause outbreaks locally and regionally across the African continent [1, 2]. The requirements for preventing outbreaks include improvement in sanitation, provision of safe drinking water, and safe food and water practices as well as hand washing. These are difficult to achieve in developing countries including Ghana, where annual cycles of cholera outbreaks continue to occur. Over the last two decades, the country reported an average of 3,066 (range: 50– 10,628) cholera cases with case fatality rate of 1.7%, though the WHO estimates more than 40,000 cases occur annually in years of large outbreaks [3]. Recent reports indicate the emergence of antibiotic resistant V. cholerae strains from cholera-endemic African countries [7, 8]
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