Gram-negative nosocomial pathogens in Estonian intensive care units

Abstract number: 902_p504

Lõivukene K.


While the most important reasons of mortality and morbidity in intensive care units (ICUs) are nosocomial infections caused by Gram-negative pathogens, our objective was to evaluate susceptibility pattern of those pathogens comparatively in Estonian ICUs by similar protocol. To clear up methodological discrepancies, data of E-test and disk diffusion method were compared.


During April–November 2003, a total 105 Acinetobacter baumannii, 92 Pseudomonas aeruginosa and 96 Klebsiella pneumoniae strains were collected from clinical specimens from ICUs of North Estonian Regional Hospital, East Tallinn Central Hospital and Tartu University Clinics. For susceptibility testing, E-tests and antibiotic disks (meropenem, imipenem, ampicillin/sulbactam, cefepime, amikacin, piperacillin/tazobactam, ciprofloxacin and ceftazidime) were used accordingly to NCCLS guidelines.


Ninty-five per cent of A. baumannii strains were sensitive to meropenem, 98% to imipenem, 61% to ampicillin/sulbactam, 56% to cefepime and 72% to amikacin (MIC50/90 values, respectively, 1/3, 0.75/2, 6/32, 8/32 and 6/64); 80% of P. aeruginosa strains were meropenem, 70% imipenem, 78% piperacillin/tazobactam, 68% ciprofloxacin, 75% ceftazidime and 98% amikacin sensitive (MIC50/90 values 1/16, 3/>32, 6/>256, 0.25/12, 1.5/64 and 4/12). The susceptibility of K. pneumoniae isolates to meropenem and imipenem were 99%, to ciprofloxacin 92% and to amikacin 97% (MIC50/90 values 0.023/0.19, 0.19/0.5, 0.023/1 and 2/3). Generally, MIC50/90 for meropenem was 0.38/4, imipenem 0.75/6, ampicillin/sulbactam 6/32, cefepime 8/32, amikacin 3/8, piperacillin/tazobactam 6/256, ciprofloxacin 0.125/1.5 and ceftazidime 1.5/64. In all three ICUs, the sensitivity among A. baumannii, P. aeruginosa and K. pneumoniae strains was similar, exept higher resistance to cefepime of A. baumannii strains in Tartu University Clinics. Discordance between E-test and disk-diffusion was pathogen specific. In K. pneumoniae, one major and seven minor errors were found, whereas in A. baumannii/P. aeruginosa testing, respectively, 2/4 very major, 13/12 major and 69/33 minor errors occurred. Carbapenems test results correlated better than comparisons of other agents.


Most active agents against all pathogens were carbapenems and amikacin, whereas meropenem and ciprofloxacin had lowest MICs than others. For empirical treatment meropenem is preferred due to high activity against all Gram-negative pathogens and the lowest MIC values. In case of A. baumannii and P. aeruginosa, E-tests are needed for susceptibility testing.


Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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