Investigating The Virulent Genes and Antibiotic Susceptibility Patterns of V. Cholerae O1 in Environmental and Clinical Isolates in Accra

ABSTRACT

Background: Cholera has been endemic in Ghana, since it was first detected in 1970. Outbreaks have often started in slums of the city especially Accra. In spite of the overwhelming nature of cholera outbreak that has resulted in high mortality and morbidity, there is little information on the reservoir of the causative agent. It has however, been shown that long-term survival of the bacteria may be attained in watery environments or in humans with no signs of cholera. Consequently, cholera outbreaks may be triggered predominantly in large densely populated urban areas. The perennial environmental reservoir of toxigenic V. cholerae O1 has not yet been identified in West Africa due to inadequate research. With environmental cholera sources being suspected in Ghana, enhanced monitoring of aquatic reservoirs and drinking water is therefore important particularly within urban agglomerations. This project was conducted to investigated clinical and environmental isolates of V. cholerae O1 in Accra, determine their virulent genes, their antibiotic susceptibility pattern and the environmental factors maintaining their persistence in the environment. Method: Water samples from various sources (taps, dug wells, streams and storage tanks) were analyzed for contamination with V. cholerae O1 by culturing on TCBS and TSA plates using standard methods. Forty clinical isolates from a previous cholerae outbreak were included in the study. Antibiotic susceptibility patterns of the bacteria were determined by the disc diffusion method. Virulent genes were identified by analyzing for genes for ctx, tcpA (tcpAEl tcpACl), zot, ompW, rbfO1 and attRS by PCR. Physicochemical characteristics of water (pH, temperature and salinity, total dissolved solids and conductivity) were investigated using standard methods. One- iv way ANOVA and student t- test were used to analyze the relationship between physicochemical factors and the occurrence of V. cholerae O1. Differences were considered significant at P≤0.05. Results: Eleven V. cholerae O1 strains isolated from streams, storage tanks and wells during the study period were added to 40 clinical isolates for analysis. All isolates were resistant to one or more of the eight antibiotics used. Multidrug resistant was observed in over 97% of the isolates. All isolates had genes for at least one virulence factor. Vibrio cholera toxin gene was detected in 42 (82.4%) isolates. Approximately 81.8% of the isolates were positive for tcpAET gene, but also harbored the tcpAcl gene. Isolates were grouped into thirteen genotypes based on the genes analyzed. pH salinity, TDS and conductivity significantly correlated positively with isolation of V. cholerae O1. Conclusion: V. cholerae serotype Ogawa biotype El tor is the main biotype circulating in Ghana with the emergence of a hybrid strain. Multidrug resistant Vibrio cholerae O1 with different genotypes and pathogenicity as well as the non 01/0139 are present in water sources in the study area. Temperature, salinity, TDS and conductivity are among the factors maintaining the persistence of the V. cholerae. These findings indicate an urgent need for the appropriate use of antibiotics, provision of potable water supply and regular disinfection of water from contaminated sources to prevent outbreak of cholera.