Value of E-test in the Determination of Synergistic Antimicrobial Combinations Active Against Multi-Drug Resistant Enterobacteriacae

Abstract Background A number of methods have been used to study the in-vitro synergy between antibiotics with the checker board titration and E-test being the most widely described. Aim of the Study The aim of the present study is to determine the prevelence of Multi-Drug Resistance (MDR) among Enterobacteriacae and to compare between the E-test and the checkerboard titration method as rapid in-vitro diagnostic tests that can help to determine the synergy between selected antimicrobial combinations thought to be active against multi-drug resistant Enterobacteriacae. Materials and Methods The present study was conducted during the period between May 2017 and December 2017. A total number of 34 MDR Enterobacteriacae isolates were recovered from different clinical specimens submitted to the Main Microbiology Laboratory, Ain Shams University Hospitals. The isolates were tested using checkerboard titration method and E-test to determine the synergistic activity of selected antimicrobial combinations thought to be active against the MDR organisms. Results Out of 46 Enterobacteriacae isolates 34(74%) were MDR. According to antibiotic combination the combinations of Amikacin/Ceftazidime, Amikacin/Meropenem and Amikacin/Ampicillin+Sulbactam have synergistic effect against MDR Enterobacteriacae by E-test and checkerboard method. A statistically poor agreement was observed between the checkerboard BMD method and the E-test method regarding the results of the studied antibiotic combinations Conclusion The Checkerboard method, being the reference method for assessing antimicrobial synery, showed that the highest synergic activity belongs to Meropenem and Amikacin (40%).