Trend in Antibiotic Resistance among Vibrio Cholerae Clinical Isolates in Kenya between 2006-2015

Vibrio cholerae is a gram negative organism which causes cholera; a disease that causes severe outbreaks of dehydrating diarrhea which can lead to death if left untreated. The standard way of treatment of cholera disease is through administration of rehydration fluids and when coupled with the use of antibiotics, it reduces the duration of illness by up to 50%. Despite the advantages that have been associated with the use of antibiotics, it has been compromised by evolution and spread of strains conferring resistance to multiple antibiotics including those recommended by World Health Organization. This evolution can occur through mutations or horizontal transfer of resistant genes from one organism to another through mobile genetic elements. Due to this global threat posed by resistance to multiple antibiotics, much still needs to be done by examining trends in antibiotic resistance and genetic determinants involved among V. cholerae isolates collected over a period of time. A total of 130 V. cholerae strains collected from various regions in Kenya archived at -80 0 c were revived. Antibiotic susceptibility testing (AST) on 12 drugs; ampicillin (10μg), cefpodoxime (10 μg), ceftazidime (30 μg), cefotaxime (30 μg), amoxicillinclavulanic acid (10/ 100 μg ratio) nalidixic acid (30 μg), tetracycline (30 μg), ciprofloxacin (10 μg), SXT (sulphamethoxazole -30 μg trimethoprim -5.2 μg), streptomycin (25 μg), gentamycin (10 μg) and chloramphenicol (30 μg) was carried out using Kirby-Bauer disc diffusion method. Antimicrobial susceptibility testing results revealed susceptibility to tetracycline, which is the drug of choice in Kenya during cholera outbreaks, among all isolates. Resistance to β-lactams and ciprofloxacin emerged in latter years while a decline in resistance to SXT, Chloramphenicol and Streptomycin was noted. Emergence of V.cholerae isolates producing extended spectrum β lactamases (ESBL) in 2010 and 2012 was reported in Kenya for the very first time. Polymerase chain reaction (PCR) was performed using relevant primers to screen for genes coding for resistance against β lactamases (blaCTX-M and blaTEM), genes coding for antibiotic resistance to streptomycin (strB), sulfamethoxazole (sulll), trimethoprim (dfra1) and screening for mobile genetic elements class 2 integrons (int 2), insertion sequence IS 26 and plasmid inc A/C. BlaCTX-M , blaTEM ,int 2 and Inc A/C plasmid were present in isolates producing ESBL indicating that the bla genes were possibly harbored in class 2 integrons and transferred through Inc A/C plasmid. strB gene was present in all isolates resistant to streptomycin. All isolates resistant to SXT harbored the dfrA1 gene coding for resistance to Trimethoprim as opposed to sul 2 gene coding for resistance to Sulfamethoxazole which was present in only 79.6% of isolates. Insertion Sequence 26 was present in selected isolates over the years though it could not be directly associated with any of the resistance genes mentioned thus its role should be studied further. This study gave a clear indication that there were changes in the resistance patterns whereby genetic determinants were involved with some resistance declining and others emerging over the ten year period. Therefore, measures should be put in place to control the use of antibiotics in clinical setups.