Heavy metal tolerance and antibiotic resistance by enteric bacterial pathogens isolated in selected parts of Nairobi
Mathaka, Raphael Ndungi
MetadataShow full item record
Enteric bacterial pathogens associated with diarrhoea have continued to develop antibiotic resistance in Kenya in recent times. Resistant genes are known to develop in the bacteria as a result of continued exposure of these bacteria to heavy metal pollution in the environment leading to increased antibiotic resistance. The objective of the study was to determine the tolerance of heavy metals and antibiotic resistance by enteric bacterial pathogens isolated from diarrhoeagenic stool samples of patients attending Githurai clinics and Nairobi hospital. Four hundred stools samples were collected from both sites and cultured in selective media. Pathogens were identified by morphological features, biochemical tests and confirmed by API 20E tests kits. The isolates were exposed to copper, zinc and iron to determine development of metal tolerance. Antibiotic susceptibility testing was carried out on the strains to check for antibiotic resistance. Plasmid DNA fingerprinting was performed by Agarose gel electrophoresis. From the four hundred stool samples, 120 bacterial strains were isolated. The isolates from both sites were Salmonella spp, Shigella spp, Escherichia coli (EPEC) and Klebsiella spp. Of the 120 isolates, a total of 45 (37.5%) were tolerant to the heavy metals. Salmonella spp and Shigella spp were more tolerant than the other strains. The bacterial tolerance to the heavy metals differed significantly in the three metals (F=3321.108, p<0.05). Iron tolerance was significantly higher than that of zinc and copper but there was no significant difference in heavy metal tolerance in the two areas of sampling the bacteria (F=0.523, p>0.05). Amongst different strains, Shigella dysenteriae was the most metal tolerant followed by Salmonella enteritidis. In sensitivity testing, all isolates were sensitive to ciprofloxacin and ceftazidime. Amongst the isolates, highest resistance was encountered in ampicillin, tetracycline and sulfamethoxazole and the lowest in kanamycin, gentamicin and erythromycin. Githurai isolates were more resistant than those from Nairobi hospital recording a 53.3% resistance. Plasmids were extracted from the metal tolerant and antibiotic resistant strains. Plasmids carry resistant genes and this indicated a positive correlation between heavy metal tolerant strains and presence of plasmids (r =0.275, p<0.05). There was also a significant correlation on the number of antibiotic resistant bacteria to the number of bacterial plasmids (r =0.482, p<0.05). These results have shown that there was association between heavy metal pollution and antibiotic resistance, and therefore there is need to enhance laws regulating heavy metal pollution in the environment in order to minimize antibiotic resistance.