Impact of spent engine oil contamination on the antibiotic resistome of a tropical agricultural soil.

Profiling of hydrocarbon-contaminated soils for antibiotic resistance genes (ARGs) is becoming increasingly important due to emerging realities of their preponderance in hydrocarbon-inundated matrices. In this study, the antibiotic resistome of an agricultural soil (1S) and agricultural soil contaminated with spent engine oil (AB1) were evaluated via functional annotation of the open reading frames (ORFs) of their metagenomes using the comprehensive antibiotic database (CARD) and KEGG KofamKOALA. CARD analysis of AB1 metagenome revealed the detection of 24 AMR (antimicrobial resistance) gene families, 66 ARGs, and the preponderance (69.7%) of ARGs responsible for antibiotic efflux in AB1 metagenome. CARD analysis of 1S metagenome revealed four AMR gene families and five ARGs. Functional annotation of the two metagenomes using KofamKOALA showed 171 ARGs in AB1 and 29 ARGs in 1S, respectively. Majority of the detected ARGs in AB1 (121; 70.8%) and 1S (16; 55.2%) using KofamKOALA are responsible for antibiotic efflux while ARGs for other resistance mechanisms were also detected. All the five major antibiotic efflux pump systems were detected in AB1 metagenome, though majority of the ARGs for antibiotic efflux belong to the RND (resistance-nodulation-cell division) and MFS (major facilitator superfamily) efflux systems. Significant differences observed in the ARGs recovered from 1S and AB1 metagenomes were statistically validated (P < 0.05). SEO contamination is believed to be responsible for ARGs increase in AB1 metagenome via mechanisms of cross-resistance especially with efflux pumps. The detection of these ARGs is of great public health concern in this era of multidrug resistant isolates resurgence.