Please cite this article in press as: Fernández-Martínez M, et al. Molecular identification of aminoglycoside-modifying enzymes in clinical isolates of Escherichia coli resistant to amoxicillin/clavulanic acid isolated in Spain. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.03.008 ARTICLE IN PRESS G Model ANTAGE-4570; No. of Pages 7 International Journal of Antimicrobial Agents xxx (2015) xxx–xxx Contents lists available at ScienceDirect International Journal of Antimicrobial Agents j o ur nal ho me pag e: http://www.elsevier.com/locate/ijantimicag Molecular identification of aminoglycoside-modifying enzymes in clinical isolates of Escherichia coli resistant to amoxicillin/clavulanic acid isolated in Spain Marta Fernández-Martínez a,∗ , Elisenda Miró b , Adriana Ortega c , Germán Bou d , Juan José González-López e , Antonio Oliver f , Alvaro Pascual g , Emilia Cercenado h , Jesús Oteo c , Luis Martínez-Martínez a,i , Ferran Navarro b,j , the Spanish Network for the Research in Infectious Diseases (REIPI) a Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla (IDIVAL), 39008 Santander, Spain b Servei de Microbiologia, Hospital de la Santa Creu i Sant Pau, Institut d’Investigació Biomèdica Sant Pau, Barcelona, Spain c Laboratorio de Antibióticos, Servicio de Bacteriología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain d Servicio de Microbiología, Complejo Hospitalario Universitario A Coru˜ na-INIBIC, A Coru˜ na, Spain e Servei de Microbiología, Hospital Universitari Vall d’Hebrón, Barcelona, Spain f Servicio de Microbiología, Hospital Son Espases, Instituto de Investigación Sanitaria de Palma (IdISPa), Palma de Mallorca, Spain g Unidad de Enfermedades Infecciosas y Microbiología Clínica, Hospital Universitario Virgen Macarena, Departamento de Microbiología, Facultad de Medicina, Universidad de Sevilla, Seville, Spain h Servicio de Microbiología, Hospital General Universitario Gregorio Mara˜ nón, Madrid, Spain i Departamento de Biología Molecular, Universidad de Cantabria, Santander, Spain j Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Barcelona, Spain a r t i c l e i n f o Article history: Received 17 September 2014 Accepted 13 March 2015 Keywords: Aminoglycoside Aminoglycoside-modifying enzyme Amoxicillin/clavulanic acid Resistance Escherichia coli a b s t r a c t The activity of eight aminoglycosides (amikacin, apramycin, arbekacin, gentamicin, kanamycin, neomycin, netilmicin and tobramycin) against a collection of 257 amoxicillin/clavulanic acid (AMC)- resistant Escherichia coli isolates was determined by microdilution. Aminoglycoside resistance rates, the prevalence of aminoglycoside-modifying enzyme (AME) genes, the relationship between AME gene detection and resistance phenotype to aminoglycosides, and the association of AME genes with mecha- nisms of AMC resistance in E. coli isolates in Spain were investigated. Aminoglycoside-resistant isolates were screened for the presence of genes encoding common AMEs [aac(3)-Ia, aac(3)-IIa, aac(3)-IVa, aac(6 ′ )- Ib, ant(2 ′′ )-Ia, ant(4 ′ )-IIa and aph(3 ′ )-Ia] or 16S rRNA methylases (armA, rmtB, rmtC and npmA). In total, 105 isolates (40.9%) were resistant to at least one of the aminoglycosides tested. Amikacin, apramycin and arbekacin showed better activity, with MIC 90 values of 2 mg/L (arbekacin) and 8 mg/L (amikacin and apramycin). Kanamycin presented the highest MIC 90 (128 mg/L). The most common AME gene was aac(6 ′ )-Ib (36 strains; 34.3%), followed by aph(3 ′ )-Ia (31 strains; 29.5%), ant(2 ′′ )-Ia (29 strains; 27.6%) and aac(3)-IIa (23 strains; 21.9%). aac(3)-Ia, aac(3)-IVa, ant(4 ′ )-IIa and the four methylases were not detected. The ant(2 ′′ )-Ia gene was usually associated with OXA-1 [21/30; 70%], whilst 23/25 (92%) strains pro- ducing CTX-M-15 had the aac(6 ′ )-Ib gene. The most prevalent AME gene was aac(6 ′ )-Ib (18/41; 44%) in nosocomial isolates, whilst ant(2 ′′ )-Ia and aph(3 ′ )-Ia genes (20/64; 31%) were more frequent in strains of community origin. In 64.6% isolates the phenotypic profile correlated with the presence of commonly encountered AMEs. © 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved. ∗ Corresponding author. Tel.: +34 942 203 357; fax: +34 942 203 462. E-mail addresses: mfmtorrelavega@yahoo.es, mfmtorrelavega@gmail.com (M. Fernández-Martínez). 1. Introduction Clinical use of aminoglycosides declined following the intro- duction of expanded-spectrum -lactams and fluoroquinolones and this correlated with decreased interest in the study of microbiological aspects of these drugs, including analysis of http://dx.doi.org/10.1016/j.ijantimicag.2015.03.008 0924-8579/© 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.