638. Effect of change in aminoglycoside usage on aminoglycoside resistance patterns
Session: Poster Abstract Session: Pharmacokinetics and Adverse Drug Reactions
Friday, October 21, 2011
Room: Poster Hall B1
  • kosmidis IDSA aminoglycosides.pdf (138.3 kB)
  • Background: Aminoglycosides (AG) are important bactericidal antibiotics in an era of increasing resistance. During the last decade, we observed a change in AG prescribing patterns in our hospital. We investigated the effect this change had on AG susceptibility and the prevalence of AG resistance genes.

    Methods: Enterobacteriaceae isolated from blood cultures from 1997 and 2006 were studied. Susceptibilities to streptomycin (S), spectinomycin (Sp), kanamycin (K), neomycin (Ne), gentamicin (G), tobramycin (T), netilmycin (N) and amikacin (A) were determined with the disk diffusion method. PCR was used to detect genes encoding AG modifying enzymes and methylases. Integrons were detected by PCR and variable regions were characterized by sequencing. Yearly aminoglycoside consumption was recorded from the hospital pharmacy.  

    Results: For the years 1997 and 2006, aminoglycoside consumption in Defined Daily Doses per 100 patient-days was: A, 3.2 and 3.1; G, 1.4 and 0.8; T, 1.2 and 0.6; N, 1.8 and 0.7; S, 1.1 and 0.3, respectively. AG resistance rates for 1997 and 2006, respectively, were: S, 45.5 and 56.1; Sp, 24.5 and 21.5; Ne 23.6 and 17.1; K, 26.4 and 25; G, 14.5 and 8.8; T, 16.4 and 18.4; N, 17.3 and 15.4; and A, 14.5 and 13.6. The percentage of multiresistant strains was 77.8 and 28.6, respectively. AAC(6')-I+AAC(3)-I was most common, followed by AAC(6')-I. AAC(3)-II, AAC(6')-I+ANT(2'')-I and ANT(2'')-I were less common. AAC(6')-I+AAC(3)-I was the most common in 1997, whereas AAC(6')-I was the most common in 2006. Most aminoglycoside panresistant isolates contained integron aac(6')-Ib/aac(3)-Ia/aadA1a. In 90% of isolates carrying AAC(6')-I+AAC(3)-I, APH(3')-I was also present.  ANT(3’)-I and ΑPH(3’’)-Ib-APH(6)-Id were both responsible for streptomycin resistance. Genes encoding methylases were not found.  

    Conclusion: Reduced use of G, T and N resulted in a significant increase in G, but not T and N, susceptibility rates, as well as a significant reduction in AG panresistant Enterobacteriaceae. Decreased prevalence of AAC(3)-I explained these findings. Reduction in gentamicin use may preserve the usefulness of this agent against severe infections by multiresistant bacteria such as carbapenemase-producing Enterobacteriaceae.

    Subject Category: A. Antimicrobial agents and Resistance

    Chris Kosmidis, MD, Maria Giannopoulou, MD, Konstantina Tzanetou, MD, Anastasia Flountzi, MD, Antonis Markogiannakis, PhD, Dimitris Goukos, MMSc, George Petrikkos, MD and George L Daikos, MD, Infectious Diseases, University of Athens Medical School, Athens, Greece


    C. Kosmidis, None

    M. Giannopoulou, None

    K. Tzanetou, None

    A. Flountzi, None

    A. Markogiannakis, None

    D. Goukos, None

    G. Petrikkos, None

    G. L. Daikos, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.