Distribution and prevalence of antimicrobial resistance among Gram-negative isolates in intensive care units (ICU) in Belgian hospitals between 1996 and 1999

Objective : to assess the distribution and prevalence of resistance rates a mong Gram-negative isolates in Belgian intensive care units (ICUs) between 1996 and 1999. Methods : During 1996-1997 and 1998-1999, over a total period of 10 and 9 m onths respectively, members of the NPRS Belgian Study group collected, on c linical indications, 3029 consecutive initial isolates of Gramnegative bact eria from patients admitted to 26 Belgian hospitals and performed minimal i nhibitory concentration (MIC) determinations by means of the E-test. Breakp oints were defined according to the criteria of the NCCLS. Results : The overall distribution of bacterial species was, in decreasing order of frequency : Pseudomonas aeruginosa >E. coli >E. aerogenes >K., pne umoniae >P. mirabilis >S. marcescens >E. cloacae >K. oxytoca >M. morganii > Stenotrophomonas maltophilia >Acinetobacter spp. All together these species and genera constituted about 90% of all isolates. The frequency of resista nce for all the initial Gram-negative isolates in 1998-9 were : amoxicillin -clavulanic acid 60%, piperacillin 31%, piperacillin-tazobactam 20%, cefuro xime 58%, ceftriaxone 31%, ceftazidime 17%, aztreonam 23%, cefepime 10%, im ipenem 13%, gentamicin 12%, amikacin 12% and ciprofloxacin 21%. Apart for a n increase in multiple drug resistance among P. aeruginosa isolates, no sig nificant trends were observed neither in species distribution nor in the ov erall prevalence of antimicrobial resistance among Gramnegative isolates fr om Belgian ICUs between 1996-7 and 1998-9. Conclusions : Among Gram-negative isolates in Belgian ICUs, a very high fre quency of resistance was seen to amoxicillin-clavulanic acid and cefuroxime , and rather high frequencies of resistance to piperacillin, ceftriaxone an d,aztreonam. Taking into account the species distribution and the prevalenc e of resistance, cefepime, imipenem, amikacin and gentamicin appeared gener ally suitable for empirical therapeutic use in severe ICU-acquired Gram-neg ative infections in Belgium. However, the therapeutic strategy should be ad apted according to the local ecology of resistance.