Isolation, identification, and antibiotic pattern of bacteria isolates from hydrocarbons contaminated soil samples collected from oil fields in Iraq

Abstract

Twenty seven samples of contaminated soil were collected from the three selected oil fields (nine samples of each field); the samples were collected from different three depths (10, 20, and 30 cm). Bacterial isolates from the collected samples were identified. Cultural, morphological, and physiological characteristics of each isolates were used as an identification test, in addition to VITEK2 system. VITEK2 system was used to determine the bacterial susceptibility against ten antibiotics (piperacillin/tazobactam, cefazolin, ceftazidime, cefepime, imipenem, amikacin, gentamicin, ciprofloxacin, levofloxacin, and tigecycline). The detection of biofilm producer bacterial isolates was performed by using Congo Red Agar (CRA). Fifty-seven bacterial isolates were obtained from twenty-seven soil contaminated samples, all the fifty-seven collected isolates were belong to six bacterial geneses which were Pseudomonas aeruginosa, Pseudomonas luteola, Acinetobacter radiodioresistens, Burkholderia cepacia, Klebsiella pneumoniae,  and Serratia marcescens. The results of antibiotic susceptible pattern showed that (except cefazolin and tigecycline) there were high efficiency of all the tested antibiotics and the resistances were ranging from 0 % to 6.6 %, while the resistance percent of both Cefazolin and Tigecycline were 100% and 83.3% respectively. Only three Serratia marcescens isolates (5.26%) demonstrated positive biofilm formation among the fifty-seven bacterial isolates acquired in this investigation, which is statistically significant (p value <0.05).