Detection of Efflux Pump Using Ethidium Bromide-Agar Cartwheel Method in Acinetobacter baumannii Clinical Isolates

Introduction: In the past decade, multidrug-resistant Acinetobacter baumannii has become one of the most critical challenges in treating infected patients. The AdeABC efflux pump is the most important among the various resistance mechanisms. This pump can force various antibiotics and ethidium bromide out of the bacterial cell to the surrounding environment. Methods: In this study, nine A. baumannii clinical isolates were isolated and identified using different biochemicals (catalase, oxidase, TSI, hemolysis, growth at 44°C, and indole) and molecular (blaOxa51 gene) tests. Following the antibiogram test, the antibiotic resistance changes in the isolates in the presence and absence of efflux pump inhibitor (CCCP) were determined for tetracycline, and ciprofloxacin AdeABC efflux pump genes, including adeA, adeB, and adeC, were amplified by PCR. Finally, the presence of the AdeABC efflux pump was investigated using the agar ethidium-bromide cartwheel method (AEBCM). Results: According to the antibiogram test, all isolates were MDR. In the presence of efflux pump inhibitor, a reduced resistance for tetracycline was observed, but not for ciprofloxacin. The AdeABC efflux pump genes were detected in all isolates. An increase in the AdeABC pump activity in four isolates was confirmed using AEBCM. Conclusion: AEBCM, a fast and convenient tool for assessing the ethidium bromide secretion in various bacteria, provides a quick diagnosis and treatment of multidrug-resistant bacteria.