Aminoglycoside resistance in domestic sewage and clinical Escherichia coli isolates

Abstract

Introduction: Escherichia coli, a Gram-negative bacillus, is found in diverse environmentsand causes several human diseases, such as pneumonia and urinary tractinfections. Aminoglycosides are antimicrobials that present high activity againstGram-negative species, including multidrug-resistant pathogens. However, theindiscriminate use of these compounds has selected resistant microorganisms, mainlydue to the production of aminoglycoside-modifying enzymes (AME). Material andmethods: The minimal inhibitory concentration of the aminoglycosides amikacin,gentamicin, and neomycin against clinical (CI, n = 52, only urinary) and domesticsewage (DS, n = 33) E. coli isolates was determined by the microdilution method,according to the European Committee on Antimicrobial Susceptibility Testing. Thepresence of AMEs among E. coli isolates was determined based on the susceptibilityprofile to amikacin, gentamicin, kanamycin, and tobramycin, according to Manciniet al. (2019). Results: Overall, 33.3% of the DS isolates and 100% of the CIisolates presented mechanisms of resistance to amikacin, gentamicin, or neomycin.The extended-spectrum beta-lactamase enzymes-producing isolates (23/27, 85%)showed mechanisms of resistance to gentamicin and/or neomycin and resistanceto amikacin was simultaneously observed only in CI isolates. All DS isolates were considered wild-type-no AME, while APH (3’) (14/52) and AAC (3’) (10/52)enzymes were detected among CI isolates, one of which produces APH (3’) andAAC (6’)-I simultaneously. Conclusion: Resistance to aminoglycosides is presentamong E. coli isolates in Brazil, but to a lesser extent in environmental isolates.Besides, AMEs are frequent in CI isolates, and surveillance for antimicrobial resistanceshould be implemented to monitor aminoglycoside-resistant E. coli infections.