Agricultural Significance of Antibiotic Resistance Pattern in Selected Nitrogen Fixing Bacteria Strains

Abstract

Rhizobia are biological nitrogen fixing non-pathogenic micro-organisms that make inert nitrogen available to legumes establishing symbiosis and living within their nodules and promoting their growth. Livestock farmers use antibiotics without prescriptions to prevent losses, death and economic wastes, resulting in indiscriminate release of excess, un-utilized antibiotics into the environment causing detrimental effects to soil microbes particularly rhizobia.This study evaluates the susceptibility pattern of selected rhizobia strains. The intrinsic antibiotic resistance (IAR) ability of common rhizobia strains including FA3, B574, RS15, USDA136, USDA9032, R25B, 532C, CC511, RANI22, RAUG1 were investigated. The antibiotics used included Ceftazamine , Florfenicol , Cefpodoxime, Sulphamethoxazole, Ciprofloxacin, Gentamycin , Kanamycin, Ertapenem, Tetracycline , Meropenem and Carbapenem. Results showed different resistance patterns among isolates where high resistance was shown against Carbapenem and least resistance was shown against Ciprofloxacin (40mm), Tetracycline (33mm), kanamycin (45mm) and Gentamycin (50mm). Rani 22 showed most resistant. Most strains showed no resistance to these antibiotics, but it is significant to note that those with resistance can be used for the recovery of antibiotics contaminated sites and may provide potential solutions for futuristic problems associated with AMR.This study suggests that using a consortium of symbiotic rhizobia strains is a strategy to achieve optimal yields in antibiotic contaminated fields as the strains showed differences in their susceptibility pattern. Also, the antibiotics produced or contained active compounds and substances that are detrimental for the growth of rhizobia and may therefore be a hindrance to these plant growth promoting bacteria when they are applied to aid plant growth used during agricultural practises.