Detection of Beta-lactamase gene in the culturable bacteria isolated from agricultural, pasture and mining soils around mines in Hamedan, Iran

Introduction: Growing evidence exists that agriculture affects antibiotic resistance in human pathogens. Beta-lactam antibiotics are the most commonly used antimicrobial agents in many countries. The abundance of beta-lactamase encoding genes can be used as an indicator of antibiotic resistance in the environment. So, to determine the beta-lactamase resistance genes, the abundance of culturable bacteria having bla-TEM genesin the soils under different land uses wasexamined. Materials and methods: 44 Gram-positive and 34 Gram-negative bacteria plated on nutrient agar were isolated from agricultural, pasture and mining soils and selected to study the presence of TEM-class gene using PCR amplification. Antibiotic sensitivity test of bla-TEM+isolateswas done adopting the Kirby-Bauer disk diffusion method and antibiotic discs used were: ampicillin, amoxicillin, vancomicin, streptomycin, tetracycline and gentamicin. Finally, five multi-drug resistant and bla-TEM+ isolates were identified using universal primers. Results: The highest level of beta-lactamase genes was observed in the Gram-positive and Gram-negative isolates from the pasture soils. In the agricultural and mining soils, a high abundance of bla-TEM+ isolateswasfound which also showed resistance to beta-lactam antibiotics. The identified multi-drug resistant and bla-TEM+ isolates were from these genera: Achromobacter, Bacillus, Brevibacillus, Aminobacter and Brevundimonas. Discussion and conclusion: The high number of bla-TEM+ bacteria in all the soils may be attributed to the other important feature of bla genes which is their capability to extrude toxic compounds like heavy metals in contaminated environments. Sensitivity of some bla-TEM+ bacteria to beta-lactam antibiotics was interesting. This result shows that bla-TEM genes confer resistance to beta-lactamase inhibitors in a different degree. Some of the identified isolates were pathogen. These pathogens in soils can transfer to plants and human which induce health problems. A high abundance of bla-TEM+ bacteria in the agricultural soil indicates the inefficiency of beta-lactam antibiotics