C1-1044. Antibiograms of Multiresistant (MDR) Acinetobacter Baumanii Clinical Isolates Sensitive and Resistant to Colistin: No Hope for Promising Therapeutic Options
Session: Poster Session: Acinetobacter baumanii
Sunday, October 26, 2008: 12:00 AM
Room: Hall C
Background: Recently Li Y et al brought hope for new treatment options against MDR A. baumanii infections, by testing in vitro paired colistin-susceptible (CS) and colistin-resistant (CR) isolates and revealing susceptibility of CR strains to a variety of antibiotics, including those active against gram positive bacteria. The objective of our study was to confirm the observation of Li et al, by testing in vitro clinical isolates of A. baumanii
Methods: Clinical infecting or colonizing isolates of MDR A. baumani from patients hospitalized in the ICU during 2006-2007 were selected. Isolates were paired CS and CR consecutive strains from patients (a result of the selection pressure of colistin used to the patients). In vitro sensitivity to colistin and 13 other antimicrobials (found by Li et al to be more active against CR strains) was tested by the E-test methodology. Clonality and the genetic identity of the paired strains was evaluated by the REP-PCR method.
Results: 16 pairs of CS and CR MDR A. baumanii isolated from 16 patients, were tested in vitro. Isolates belonged to 5 distinct clones. CS and CR strains were similarly and only sensitive to tigecycline [minimal inhibitory concentration (MIC) < 2mg/L]. CR strains did not exhibit improved sensitivity against the tested antimicrobials except from a >2 dilutions reduction in MICs observed in 4/16 strains for tetracycline and gentamicin and in 7/16 for clarithromycin. Even in these cases the reduced MICs remained unacceptably high (>12 mg/L), except from one isolate which retained sensitivity to gentamicin (MIC=1mg/L). Conclusions: Unfortunately, the results by Li et al were not confirmed in our study. It seems that laboratory observations do not always apply to real life clinical situations.
Anastasia Antoniadou, MD1, Diamantis Plachouras, MD2, Dimitra Kavatha, MD3, Elias Karaiskos3, Evangelos Papadomichelakis, MD, PHD4, Flora Kontopidou, MD5, Garyfalia Poulakou, MD6, Helen Giamarellou, MD, PhD, Prof7, Konstantinos Protopapas3 and  A. Antoniadou, None., (1)ATTIKON UNIVERSITY GENERAL HOSPITAL, Athens, Greece, (2)4th Dept of Internal Medicine, Athens, Greece, (3)UNIVERSITY GENERAL HOSPITAL ATTIKON, (4)University of Athens, Medical School, (5)4th Department of Internal Medicine Attikon University General Hospital, Athens, Greece, (6)4th Dpt of Internal Medicine, Univ of Athens Medical School, Xaidari, Greece, (7)4th Dept of Internal Medicine, Athens Medical School, Athens, Greece

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