JAC Advance Access originally published online on September 26, 2005
Journal of Antimicrobial Chemotherapy 2005 56(5):827-835; doi:10.1093/jac/dki347
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Molecular epidemiology of high-level aminoglycoside-resistant enterococci isolated from patients in a university hospital in southern Italy
1 Dipartimento di Scienze Mediche Preventive, Università di Napoli ‘Federico II’, Naples, Italy; 2 Medicina Interna ed Epatologia, Dipartimento di Geriatria, Gerontologia e Malattie del Metabolismo, Seconda Università di Napoli, Naples, Italy; 3 Cattedra di Chirurgia Vascolare, Dipartimento di Internistica Clinica e Sperimentale ‘F. Magrassi’, Seconda Università di Napoli, Naples, Italy; 4 Unità di Medicina Infettivologica e dei Trapianti, Dipartimento di Scienze Cardiotoraciche e Respiratorie, Seconda Università di Napoli, Naples, Italy
Received 8 June 2005; returned 10 July 2005; revised 17 August 2005; accepted 2 September 2005
* Corresponding author. Tel: +39-081-7463026; Fax: +39-081-7463352; E-mail: rafzarri{at}unina.it
Objectives: We evaluated the genetic and molecular basis of high-level resistance to gentamicin and amikacin in 91 clinical isolates of Enterococcus faecalis and Enterococcus faecium in a university hospital in southern Italy from 1987 to 2003.
Methods: Antibiotic susceptibility was evaluated by disc diffusion and microdilution methods. Genotyping was performed by PFGE and dendrogram analysis. Aminoglycoside resistance genes were analysed by multiplex PCR. Aminoglycoside resistance gene transfer was performed by filter mating.
Results: In our strain collection, 44% of E. faecalis and 52% of E. faecium were high-level-resistant to gentamicin. Fifty-two PFGE profiles were identified for E. faecalis and 15 for E. faecium. Although the majority of PFGE patterns were single isolates, four patterns (two for E. faecalis and two for E. faecium) were isolated each in 8 and 4, and 6 and 4 different patients, respectively. The aac(6')-Ie-aph(2'')-Ia gene was responsible for high-level resistance to gentamicin and amikacin in E. faecalis and E. faecium; the aph(2'')-Id gene responsible for resistance to gentamicin was also isolated in E. faecium; the aph(3')-IIIa and ant(4')-Ia genes responsible for resistance to amikacin were also isolated in E. faecalis and E. faecium. High-level resistance to gentamicin, along with the aac(6')-Ie-aph(2'')-Ia gene, was transferred at a frequency of about 10–5 to 10–8 per recipient cell in 14 of 17 E. faecalis and 3 of 4 E. faecium different genotypes.
Conclusions: The spread of the aac(6')-Ie-aph(2'')-Ia gene was responsible for high-level resistance to gentamicin and amikacin among enterococci isolated from patients in our geographical area.
Keywords: antimicrobial resistance genes , pulsed-field gel electrophoresis , multiplex-PCR , mating
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