ABSTRACT
Background: The antibiotic susceptibility of bacterial interaction with soot, a by-product of incomplete combustion of fossil fuel, has not been established. Aim: The study aimed to establish the antibiotics susceptibility of Staphylococcus aureus and Escherichia coli exposed to soot. Method: The bacteria were exposed to 12.5%, 25%, and 50% concentrations of soot at different time intervals. Control bacterial cultures without exposure to soot were also carried out. These cultures were incubated for 24 hrs. The numbers of surviving bacteria were determined by analyzing 10 μL of the incubated cultures at 6 hrs and 24 hrs on tryptone soy agar. Again, the bacteria were inoculated on Mueller Hinton agar and subjected to antibiotics susceptibility testing using the disk diffusion method. Results: After 6 hrs of exposure, the number of E. coli in the absence of soot was 102.50 ± 3.54 × 103 CFU/mL while at 12.5%, 25%, and 50% of soot, the surviving E. coli were 26.00 ± 1.41 (p = 0.0012), 21.00 ± 1.41 (p = 0.0011) and 5.50 ± 2.12 (p = 0.0009) × 103 CFU/mL respectively. Similarly, the population of S. aureus without soot was 122.5 ± 3.53 × 104 CFU/mL while at 12.5%, 25.0% and 50.0% of soot, the surviving S. aureus 46.00 ± 2.83 (p = 0.0017), 23.00 ± 1.41 (p = 0.0007) and 11.50 ± 2.12 (p = 0.0007) × 104 CFU/mL respectively. Similar results were obtained after 24 hrs of exposure. The soot shows some level of potency in reducing the number of E. coli and S. aureus significantly (p < 0.05). After 24 hrs, almost all treatment conditions (except for the Gentamicin for S. aureus), there was resistance to all the antibiotics while at 0 hr there was sensitivity to these drugs. Conclusion: These results suggest that while soot has some potency on E. coli and S. aureus, their exposure to soot could induce resistance.