ANTIBIOTIC RESISTANCE OF METAL TOLERANT BACTERIA ISOLATED FROM SOIL IN JUJA, KENYA
Abstract
Environmental pollution and increased levels of metal concentrations may influence the composition of bacterial
populations. This study aimed to determine the relationship between antibiotic resistance and metal tolerance of
bacteria isolated from five soils samples collected from Juja. Bacteria were isolated by culturing in metal enriched
nutrient broth and a total of 41 isolates obtained. The isolates were identified by morphology and biochemical
tests. Antimicrobial resistance patterns were determined using single disc diffusion method. Tolerance to heavy
metal was determined by culturing bacteria in nutrient broth containing varying concentrations of Zinc, Mercury
and Cadmium. The isolates showed 100% resistance to Augmentin and Cefuroxime (n=41), followed by Ampicillin
92.68% and Cotrimoxazole 68.29%. Sensitivity to Gentamicin was 95.12%, Norfloxacin 90.24%, and Nalidixic acid
68.3%. All the isolates where multi drug resistant (MDR) with 16 (39.02%) being resistant to four antibiotics. Many
of the isolates were Zinc resistant (final concentration of 7.5g/l) but sensitive to mercury (50mg/l) and Cadmium
(2.8g/l). Tolerance was highest in P. aeruginosa for Cadmium at 2.0g/l, E. coli for Zinc at 5.54g/l and E. coli and S.
aureus for Mercury at 40mg/l. A direct correlation was established with correlation co-efficient (r) for Cadmium
+0.97, and Mercury + 0.95 and Zinc + 0.91. This study demonstrated a correlation between metal tolerance and
antibiotic resistance in soil bacteria from Juja. Association of metal tolerance and antibiotic resistance is of
medical concern as resistance could be transferred to pathogenic bacteria.
Key words: Metal, metal tolerance, antibiotic resistance
populations. This study aimed to determine the relationship between antibiotic resistance and metal tolerance of
bacteria isolated from five soils samples collected from Juja. Bacteria were isolated by culturing in metal enriched
nutrient broth and a total of 41 isolates obtained. The isolates were identified by morphology and biochemical
tests. Antimicrobial resistance patterns were determined using single disc diffusion method. Tolerance to heavy
metal was determined by culturing bacteria in nutrient broth containing varying concentrations of Zinc, Mercury
and Cadmium. The isolates showed 100% resistance to Augmentin and Cefuroxime (n=41), followed by Ampicillin
92.68% and Cotrimoxazole 68.29%. Sensitivity to Gentamicin was 95.12%, Norfloxacin 90.24%, and Nalidixic acid
68.3%. All the isolates where multi drug resistant (MDR) with 16 (39.02%) being resistant to four antibiotics. Many
of the isolates were Zinc resistant (final concentration of 7.5g/l) but sensitive to mercury (50mg/l) and Cadmium
(2.8g/l). Tolerance was highest in P. aeruginosa for Cadmium at 2.0g/l, E. coli for Zinc at 5.54g/l and E. coli and S.
aureus for Mercury at 40mg/l. A direct correlation was established with correlation co-efficient (r) for Cadmium
+0.97, and Mercury + 0.95 and Zinc + 0.91. This study demonstrated a correlation between metal tolerance and
antibiotic resistance in soil bacteria from Juja. Association of metal tolerance and antibiotic resistance is of
medical concern as resistance could be transferred to pathogenic bacteria.
Key words: Metal, metal tolerance, antibiotic resistance