Characterization of antibiotic resistance in environmental enteric pathogens from Kibera slum in Nairobi-Kenya

Kibera slum is characterized by poor sanitation hence the frequent outbreaks of diarrheal diseases. Emergence of antibiotic resistance by diarrhoea-causing bacteria is an inevitable challenge in the area. Diarrhea-causing bacteria were isolated from water, soil, vegetables, meat and dry foods samples and their antibiotic susceptibility was characterized. 237 samples were aseptically collected and analyzed. Morphological and biochemical characterization was done using Bergey’s manual of determinative bacteriology as a reference. 174 Escherichia coli, 8 Salmonella and 6 Shigella isolates were identified. Drug susceptibility of the isolates was done using disk diffusion method where 9 antibiotics from 5 classes of antibiotics were used. The frequencies of resistant isolates to antibiotics were as follows: ampicillin (56.79%), trimethoprim+ sulphamethoxazole (29.63%), augmentin (27.16%), tetracycline (18.52%), streptomycin (13.57%), chloramphenicol (7.41%), nalidixic acid (4.94%), gentamycin (2.47%) and ciprofloxacin (0%). Polymerase chain reaction was done to amplify the antibiotic determinants tet-A, sul 1 and dfrb1. Gel electrophoresis revealed presence of tet-A gene and sul 1 genes but absence of dfrb1 in 15 isolates that were resistant to tetracycline and SXT. Plasmid extraction and profiling was done and plasmid sizes compared to plasmids of E. coli V517 and 39R861. Large and small plasmids were present in the isolates with tet-A and sul 1 genes. Plasmid of 63 bp was present in all isolates. Conjugation experiments confirmed 100% transfer of 63 bp plasmid and 90% complete phenotype in all cases. This study showed presence of contamination of the area by antibiotic resistant diarrhea-causing pathogens, hence proper hygiene procedures and adherence to correct drug prescriptions need to be reinforced.