Tigecycline resistance of Acinetobacter bloodstream isolates in a teaching hospital

Abstract number: P1710

Vamvacopoulou S., Michalacopoulou K., Bartzavali C., Spiliopoulou I., Anastassiou E.D., Christofidou M.

Objective:Acinetobacter calcoaceticus-A. baumannii complex, an opportunistic pathogen frequently involved in infection outbreaks in Intensive Care Units (ICU), constitutes a serious problem because of its virulence and multidrug resistance. Tigecycline (TIG), is a glycylcycline antibiotic with broad-spetrum activity that appears to be the only new therapeutic option for serious infections caused by multidrug resistant (MDR) Gram negative bacteria. The aim of this study was to define the susceptibility profile of bloodstream Acinetobacter isolates to antibiotics, including TIG, during the last three years in Patras University Hospital.

Methods: A total of 162 Acinetobacter bloodstream isolates were collected between September 2005 to September 2008 from inpatients hospitalised in ICU (82), in Internal Medicine units (52) and in Surgical Wards (28). Identification at species level was performed using Gram negative BD BBL Crystal ID system. Antimicrobial susceptibility was tested by disk diffusion method, according to CLSI criteria, for cefepime (FEP), ceftazidime (CAZ), imipenem (IMP), aztreonam (AZT), gentamicin (GM), netilmicin (NET), amikacin (AN) and ciprofloxacin (CIP), and by E-test strips (AB Biodisk) for MIC of colistin (CL) and TIG. MIC breakpoint of susceptibility for CL is equal or less than 1 microg/mL whereas for TIG is equal or less than 2 microg/mL. IMP-resistant isolates were examined by double E-Test strips (IMP versus IMP plus EDTA) (AB Biodisk) for detection of metallo-b-lactamases (MBL).

Results: Forty five isolates were recovered during the first year, 61 the following year, whereas 56 isolates were identified the third year, one isolate per patient. A total of 159 (98%) isolates were identified as Acinetobacter bawmannii. Resistance rate was as high as 96%, 94%, 93% and 90% to AZT, IMP, FEP and CAZ, respectively, and 87%, 86%, 85% and 68% to AN, NET, CIP and GM. Among IMP-resistant isolates, 95% were MBL (+). No isolate was resistant to CL as MIC was 0.38–1 microg/mL. All isolates were susceptible to TIG as MIC ranged between 1–2 microg/mL.

Conclusions: A total of 148 (86%) Acinetobacter isolates were MDR (resistant to four or more used antimicrobials) in our hospital. As MBL was produced by many MDR isolates, imipenem seems not to be useful in empiric therapy of critically ill, bacteraemic patients. Colistin and tigecycline remain the only active agents towards such strains, according to our results.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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