Occurrence of multiple antibiotic resistance in Azotobacter chroococcum

Of 117 strains of Azotobacter chroococcum, isolated from local soils the antibiotic resistance pattern to ten widely used antibiotics was determined by antibiotic disk and agar plate dilution method. Over 95% of the strains were resistant to 10 micrograms ml-1 concentration of ampicillin, chloramphenicol, erythromycin and tetracycline and 70% or more were resistant to kanamycin, nalidixic acid, rifampicin, streptomycin and trimethoprim. 1 to 8% of the strains showed resistance upto 400 micrograms ml-1 concentration of 5 antibiotics (ampicillin, chloramphenicol, kanamycin, streptomycin and tetracycline). The intrinsic resistance to the 10 antibiotics was generally high in Azotobacter chroococcum strains.