Isolation and Characterization of Dominant Culturable Actinobacteria from Spare-Parts Mechanic Workshop Soils in Effurun, Delta State, Nigeria

Abstract

Mechanic workshops constitute significant sources of soil pollution, primarily owing to automotive repair activities coupled with persistent discharge spent hydrocarbons, heavy metals, etc. The frequency of exposure impose selective pressures on indigenous microbial communities, fostering the emergence of metabolically adaptable and robust taxa. This study was aimed at identification of the predominant culturable Actinobacteria residing in soils from a prominent mechanic workshop within the Spare-parts market, Effurun, Delta State, Nigeria. Composite soil samples were collected from three distinct locations and bacteria enumerated on Bennett’s agar exhibited a 1.1 × 10⁴ ± 0.11 to 1.7 × 10⁴ ± 0.32 CFU/g range. A total of thirteen morphologically unique isolates were obtained, from which three dominant pigmented strains (yellow, creamy white, and milky yellow) were selected for comprehensive analysis. 16S rRNA analysis confirmed that all three dominant strains where Brevibacterium casei with sequence similarities between 94.15% and 99.18%, exhibiting pleomorphism with Micrococcus luteus and Arthrobacter Spp based on their biochemical profiles. Antibiotic disk diffusion and EUCAST standards for interpretation. Antibiotic susceptibility profiling revealed notable trend of resistance to multiple drug classes especially β-lactam antibiotics; Cefuroxime, Augmentin, Ceftazidime, Ceporex and Ceftriaxone, in conjunction to a resistance index (RI) of 0.43, 0.50 and 0.57 for each phenotype. From the data obtained strains of B. casei are not only predominant in co-contaminated soils but also possess clinically relevant antibiotic resistance. This multi-trait feature necessitates continuous public awareness of the dangers around such anthropogenic sites especially where consumption of food is involved.