Design and evaluation of a colorimetric method for rapid determination of minimal inhibitory concentration of the bacteria belonging to enterobacteriace

Reyhaneh Aminnezhad,1,* Siavash salmanzadeh ahraby,2 Tahere falsafi,3 Mahvash seifali,4

1. faculty of biological sciences, Alzahra university
2. faculty of biological sciences, Alzahra university
3. facultyof biology science of alzahra university

Abstract

Introduction

isolation of antibiotic resistant pathogenic bacteria in clinic may pose the serious problems. so a rapid method capable at once to detect and determine its antibiotic susceptibility may help to avoid many problems. we report a colorimetric method to detect antibiotic susceptibility, based on viability-dependent resazurn dye reduction (intense blue color changing to pink and leuco). isolation of antibiotic resistant pathogenic bacteria in clinic may pose the serious problems. so a rapid method capable at once to detect and determine its antibiotic susceptibility may help to avoid many problems. we report a colorimetric method to detect antibiotic susceptibility, based on viability-dependent resazurn dye reduction (intense blue color changing to pink and leuco).

Methods

Fifty bacterial strains used in this study were clinical isolates of diarrhaeagenic strains of escherichia coli, shigella flexneri, shigella sonnei, klebsiella pneumonia, and entrobacter cloace bacterial strains were grown in nutrient agar plate and their identification was performed according to the standard methods. their resistance to five groups of antibiotics including ciprofloxacin, kanamycin, cefotaxime, piperacillin and tetracycline were tested by using muller- hinton broth by using e. coli atcc 25922 as control in a method adopted from the nccls standards. our designed antibiotic susceptibility testing method was developed in the 96-well plates. by this protocol, the minimum inhibitory concentration of 50 clinical bacterial isolates were determined against above five antibiotics.

Results

Association was observed between the results of standard protocol and our newly designed one. the advantage of our method was that after 6 hours, a color changes was recognized with the naked eye.

Conclusion

So, we could demonstrate the usefulness of a simple and rapid antibiotic-susceptibility testing method based on the resazurin-reduction. this method may present a very strong futuristic commercial potential for an essential clinical need.

Keywords

Resazurin - minimum inhibitory concentration - enterobateriaceae