Genetic characterization and evaluation of antimicrobial resistance patterns of human salmonella typhi isolates in kenyatta national hospital in nairobi, kenya

Abstract

The rapid increase and subsequent management of Typhoid fever in Kenya has been complicated by the emergence and rise of antimicrobial resistance to the Salmonella Typhi pathogen. This situation is yet to be addressed due to the paucity of information regarding the circulating strains and their antimicrobial resistance profiles. This study was hence designed to genetically characterize and evaluate the antimicrobial resistance patterns of human Salmonella Typhi isolates circulating among patients in Kenyatta National Hospital the largest referral health facility in Kenya. Fifty (n=50) Salmonella Typhi archived sample isolates were obtained from stool samples of patients suffering from typhoid fever who attended the facility from 2010 to 2015. The isolates were evaluated for phylogenetic relationships targeting 16s rRNA gene sequences and antimicrobial susceptibilities against a panel of 12 drugs by disk diffusion method. Phylogenetically, the isolates clustered close to Salmonella Typhi strain CT18 and its plasmid pHCM1 and plasmid IncHI1 of Salmonella Typhi strain R27 both associated with drug resistance. Antimicrobial susceptibility tests showed that 73% of the isolates were resistant to the Aminopenicillin, Sulfonamide, Phenicol and Aminoglycoside classes of drugs. A resistance of between 7% to 19% was observed for the Beta-lactamase, Fluoroquinolone and Cephalosporin classes of drugs. Only one of the isolates was fully susceptible to all the antimicrobial drugs used. A total of 23% of the isolates were intermediately resistant to all the 12 drugs used. The high resistance patterns of Salmonella Typhi evidenced necessitates the re-evaluation of the currently used antibiotic regimen and also underscores the importance of continued drug resistance monitoring for this pathogen. Key Words Salmonella Typhi, Antimicrobial resistance, Phylogenetic, Susceptibility