Aminoglycoside-modifying Enzymes in Carbapenem-resistant Pseudomonas aeruginosa Clinical Isolates

Introduction: Aminoglycosides are the drug of choice for the treatment of Pseudomonas aeruginosa infections. Aminoglycoside resistance in P. aeruginosa often occurred via acquired aminoglycoside-modifying enzymes (AMEs). In this study, we aimed to investigate the presence of AME in P. aeruginosa in carbapenem-resistant and carbapenem-susceptible isolates. Materials and Methods: A total of 98 isolates of P. aeruginosa from various clinical samples presenting resistance to amikacin and/or gentamicin were included in this study. Fifty-four were carbapenem-resistant isolates. Polymerase chain reaction amplification of six genes for AMEs (aac(6')-Ib,aac(6')-IIa, aac(3')-IIa, aph(3')-Ia,aph(3')-VIa, ant(2'')-Ia) was performed. Results: The most frequent AME gene was aac(6')-Ib (n=13, 13.2%), followed by ant(2'')-Ia (n=7, 7.1%). aac(6')-Ib was the most common AME in carbapenem-resistant isolates (11/54, 20.3%); however ant(2'')-Ia was the most common AMEs in carbapenem-susceptible isolates (4/44, 9%). In 74 of the isolates, none of the AME genes was detected. aac(6')-Ib positivity in carbapenem-resistant isolates was significantly higher than that in carbapenem-susceptible isolates. Conclusion: Aminoglycosides are one of the drug of choice in carbapenem-resistant P. aeruginosa isolates. However, given the transfer of multidrug resistance determinants, the presence of AME was significantly higher in carbapenem-resistant isolates, and monitoring resistance determinants among Gram-negative bacteria is crucial.