Infect Chemother.  2016 Sep;48(3):190-198. 10.3947/ic.2016.48.3.190.

A 5-year Surveillance Study on Antimicrobial Resistance of Acinetobacter baumannii Clinical Isolates from a Tertiary Greek Hospital

Affiliations
  • 1Department of Clinical Microbiology, University Hospital of Heraklion, Crete, Greece. sofiamaraki@in.gr
  • 2Department of Pediatrics, Democritus University of Thrace Faculty of Medicine and University General District Hospital of Evros, Alexandroupolis, Thrace, Greece.
  • 3University of Crete Medical School, Heraklion, Greece.
  • 4Department of Internal Medicine, Infectious Diseases Unit, University of Crete Medical School, Heraklion, Crete, Greece.

Abstract

BACKGROUND
Acinetobacter baumannii has emerged as a major cause of nosocomial outbreaks. It is particularly associated with nosocomial pneumonia and bloodstream infections in immunocompromised and debilitated patients with serious underlying pathologies. Over the last two decades, a remarkable rise in the rates of multidrug resistance to most antimicrobial agents that are active against A. baumannii has been noted worldwide. We evaluated the rates of antimicrobial resistance and changes in resistance over a 5-year period (2010-2014) in A. baumannii strains isolated from hospitalized patients in a tertiary Greek hospital.
MATERIALS AND METHODS
Identification of A. baumannii was performed by standard biochemical methods and the Vitek 2 automated system, which was also used for susceptibility testing against 18 antibiotics: ampicillin/sulbactam, ticarcillin, ticarcillin/clavulanic acid, piperacillin, piperacillin/tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, meropenem, gentamicin, amikacin, tobramycin, ciprofloxacin, tetracycline, tigecycline, trimethoprim/sulfamethoxazole, and colistin. Interpretation of susceptibility results was based on the Clinical and Laboratory Standards Institute criteria, except for tigecycline, for which the Food and Drug Administration breakpoints were applied. Multidrug resistance was defined as resistance to ≥3 classes of antimicrobial agents.
RESULTS
Overall 914 clinical isolates of A. baumannii were recovered from the intensive care unit (ICU) (n = 493), and medical (n = 252) and surgical (n = 169) wards. Only 4.9% of these isolates were fully susceptible to the antimicrobials tested, while 92.89% of them were multidrug resistant (MDR), i.e., resistant to ≥3 classes of antibiotics. ICU isolates were the most resistant followed by isolates from surgical and medical wards. The most effective antimicrobial agents were, in descending order: colistin, amikacin, trimethoprim/sulfamethoxazole, tigecycline, and tobramycin. Nevertheless, with the exception of colistin, no antibiotic was associated with a susceptibility rate >40% for the entire study period. The most common phenotype showed resistance against ampicillin/sulbactam, cephalosporins, carbapenems, aminoglycosides, ciprofloxacin, and tigecycline. An extremely concerning increase in colistin-resistant isolates (7.9%) was noted in 2014, the most recent study year.
CONCLUSION
The vast majority of A. baumannii clinical isolates in our hospital are MDR. The remaining therapeutic options for critically ill patients who suffer from MDR A. baumannii infections are severely limited, with A. baumannii beginning to develop resistance even against colistin. Scrupulous application of infection control practices should be implemented in every hospital unit. Lastly, given the lack of available therapeutic options for MDR A. baumannii infections, well-controlled clinical trials of combinations of existing antibiotics are clearly needed.

Keyword

Acinetobacter baumannii; Antimicrobial susceptibilities; Colistin; Multidrug resistance; Tigecycline

MeSH Terms

Acinetobacter baumannii*
Acinetobacter*
Amikacin
Aminoglycosides
Anti-Bacterial Agents
Anti-Infective Agents
Carbapenems
Cefotaxime
Ceftazidime
Cephalosporins
Ciprofloxacin
Colistin
Critical Illness
Disease Outbreaks
Drug Resistance, Multiple
Gentamicins
Hospital Units
Humans
Imipenem
Infection Control
Intensive Care Units
Pathology
Phenotype
Piperacillin
Pneumonia
Tetracycline
Ticarcillin
Tobramycin
United States Food and Drug Administration
Amikacin
Aminoglycosides
Anti-Bacterial Agents
Anti-Infective Agents
Carbapenems
Cefotaxime
Ceftazidime
Cephalosporins
Ciprofloxacin
Colistin
Gentamicins
Imipenem
Piperacillin
Tetracycline
Ticarcillin
Tobramycin
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