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Determination of imipenem efflux-mediated resistance in Acinetobacter spp., using an efflux pump inhibitor
Ghazale Amiri1, Maryam Abbasi Shaye1, Masoumeh Bahreini1
1Deparment of Biology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
Background And Objectives:
In recent years, reports of Acinetobacter strains resistant to all known antibiotics have caused a great concern in medical communities. Overexpression of efflux pumps is one of the major causes of resistance in bacteria. The aim of this study was to investigate the role of efflux pumps in conferring resistance to imipenem in clinically important Acinetobacter spp; Acinetobacter baumannii and Acinetobacter lwoffii.
Materials And Methods:
A total number of 46 clinical Acinetobacter isolates, including 33 A. baumannii and 13 A. lwoffii isolates, previously collected from Shahid Kamyab and Ghaem hospitals of Mashhad, Iran were used in this study. Imipenem susceptibility testing was carried out by the disc diffusion method. Imipenem minimum inhibitory concentration (MIC) for resistant Acinetobacter isolates were determined both in the presence and absence of the efflux pumps inhibitor, carbonyl cyanide 3-chlorophenylhydrazone (CCCP).
Results:
Resistance to imipenem was observed in 38 isolates including 30 A. baumannii and 8 A. lwoffii isolates. Experiments in the presence of CCCP showed a 2 to 16384 fold reduction in imipenem MICs in 14 A. baumannii and 2 A. lwoffii isolates.
Conclusion:
The results obtained showed high levels of resistance to imipenem and contribution of efflux pumps in conferring resistance in both Acinetobacter species in this study. Moreover, imipenem efflux mediated resistance highlights the importance of this mechanism not only in A. baumannii but also in non-baumannii Acinetobacter Spp. which have been neglected in antibiotic resistance studies.
Insights
Efflux pumps significantly contribute to imipenem resistance in Acinetobacter species, including Acinetobacter baumannii and Acinetobacter lwoffii. Inhibiting these pumps substantially reduced imipenem resistance, highlighting their role in antibiotic resistance.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Rising concern over multidrug-resistant Acinetobacter strains.
- Efflux pump overexpression is a primary mechanism of bacterial antibiotic resistance.
- Need to understand resistance mechanisms in clinically significant Acinetobacter species.
Purpose of the Study:
- Investigate the role of efflux pumps in imipenem resistance.
- Focus on clinically important Acinetobacter baumannii and Acinetobacter lwoffii.
Main Methods:
- Tested 46 clinical Acinetobacter isolates (33 A. baumannii, 13 A. lwoffii).
- Determined imipenem susceptibility using disc diffusion.
- Measured imipenem Minimum Inhibitory Concentration (MIC) with and without CCCP (efflux pump inhibitor).
Main Results:
- 38 isolates (30 A. baumannii, 8 A. lwoffii) showed imipenem resistance.
- CCCP reduced imipenem MICs by 2 to 16384-fold in 16 resistant isolates (14 A. baumannii, 2 A. lwoffii).
Conclusions:
- Efflux pumps significantly contribute to imipenem resistance in both Acinetobacter species.
- Imipenem efflux-mediated resistance is crucial in Acinetobacter baumannii and often-neglected non-baumannii Acinetobacter.
