Response of Bacteria Isolated from Spent Engine Oil Contaminated Soil to Hydrocarbons, Metals and Antibiotics

ABSTRACT Automobile Mechanic Workshops (AMWs) in Low- and Middle-Income Countries (LMIC) contribute to the problem of soil contamination with petroleum hydrocarbons and toxic heavy metals as a result of indiscriminate disposal of spent engine oil (SEO). Such contaminated soil ecosystems can serve as reservoirs of bacteria harboring adaptive tolerance to metals and hydrocarbons as well as resistance to antibiotics. This study investigated the growth response of bacteria isolated from spent engine oil contaminated soils collected from AMWs in South-West, Nigeria to different concentrations of petroleum hydrocarbons, heavy metals (Cu, Zn, Pb and their mixture) and clinically relevant antibiotics. Sixty percent of the bacterial isolates (n = 192) from the hydrocarbon contaminated soil samples possess the unique ability to metabolize various hydrocarbons, tolerate heavy metals and resist at least one of the tested antibiotics. The isolates were identified as members of the Genera Pseudomonas, Bacillus, Enterobacter, Burkholderia, Micrococcus, Staphylococcus, Actinomycetes, Citrobacter and Serratia. Significant correlation (p < .05) was observed between hydrocarbon utilization and antibiotic resistance. Results showed SEO contamination plays a role in the development and spread of antibiotic resistance in the soil ecosystem. Thus, it is necessary to enforce stricter regulations on the disposal of SEO and other petroleum hydrocarbons to limit their human and environment associated hazards.