Determination of Fractional Inhibitory Concentration (FIC) Index as A Measure of Synergy of Antibiotics in E. coli O157:H7

Abdulabbas, Sarah Sameer; Ibrahim, Zainab Khaleel; Muhammed, Hayder Ali; AL-Khazali, Noor Ali Yazi; Ahmed, Saja Talib; Ai- Tuma, Amir Fadhil; Mahdi, Fatima Mohammed Saeed

doi:10.21608/ejhm.2022.276689

Determination of Fractional Inhibitory Concentration (FIC) Index as A Measure of Synergy of Antibiotics in E. coli O157:H7

Authors

¹ College of Pharmacy, University of Al-Zahraa for Women

² College of Medical and Health Techniques, University of Alkafeel, Iraq

³ College of Veterinary Medicine, University of Kerbala. Iraq

⁴ College of Medical and Health Technologies, University of Ahlalbayt,Iraq

10.21608/ejhm.2022.276689

Abstract

Background: MIC is the lowest concentration of an antibiotic required to inhibit the growth of an organism.
Methods: MIC was done against six conventional antibiotics e.g., Amoxicillin, Ceftriaxone, Gentamycin, Tetracycline, Ciprofloxacin, and Levofloxacin. E. coli O157:H7 was collected from hospital. The antibacterial activity of six conventional antibiotics was assessed against E. coli O157:H7by using the broth microdilution method then the fractional inhibitory concentration (FIC) index was used to define the interactions between antibiotics.
Results: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of antibiotics against E. coli O157:H7 showed that the highest concentration appeared in ciprofloxacin was 62.5 µg/ml. while ceftriaxone and gentamycin were 15.62 µg/ml. amoxicillin and levofloxacin was 7.812 µg/ml. the lowest concentration appeared in Tetracycline was 0.976 µg/ml. The higher FICI was seen in Ceftriaxone + Levofloxacin combination 0.3 % followed by Levofloxacin + Ciprofloxacin (0.1). Conclusions: The antibacterial activity of both Ceftriaxone and Levofloxacin was enhanced by the combination which proved a highly synergistic effect against E. coli O157:H7.