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

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.

Susceptibility of Glycopeptide-Resistant Enterococci to Linezolid, Quinupristin/dalfopristin, Tigecycline and Daptomycin in a Tertiary Greek Hospital / 감염과화학요법

We investigated the antibiotic susceptibility of glycopeptide-resistant enterococci (GRE). Seventy consecutive GRE were tested. Sixty-two isolates were identified as Enterococcus faecium (88.6%), and 8 (11.4%) as Enterococcus faecalis. All strains were susceptible to linezolid and daptomycin, while 17.1% (12/70) and 11.4% (8/70) were resistant to quinupristin/dalfopristin (QD) and tigecycline, respectively. All E. faecalis isolates were resistant to QD, while 4 of 62 (6.5%) E. faecium isolates were resistant to QD. All E. faecalis isolates were susceptible to tigecycline, while 14.5% (9/62) E. faecium isolates were resistant. Continued surveillance of GRE antibiotic susceptibilities is important for combating these multi-resistant nosocomial pathogens.