A MULTICENTER SURVEY OF ANTIMICROBIAL RESISTANCE IN GRAM-NEGATIVE ISOLATES FROM BELGIAN INTENSIVE-CARE UNITS IN 1994-1995

The aim of this prospective study was to evaluate the distribution and antibiotic susceptibility of aerobic Gram-negative bacilli isolated f rom patients in intensive care units in 18 Belgian hospitals during 19 94 and 1995. A standardised method (i.e. the E-test) was used in each center to determine the minimum inhibitory concentrations of 12 major antibiotics against 1435 consecutive, non duplicate, Gram-negative iso lates (close to 100 strains per hospital) during a period of 6 months. The isolates were mainly isolated from the lower respiratory tract (5 7.4%), urinary tract (17.7%), pus (7.9%) or blood specimens (7.8%) and were mainly P. aeruginosa (20.3%), E. coli (19.9%) and Enterobacter s pp. (12.6%). Overall inducible Enterobacteriaceae (IE) accounted for 2 9.8% of all isolates, and E. aerogenes was the most frequently isolate d species in this group (27.6%). The overall susceptibility rate (all species confounded) was about 70% to piperacillin, ticarcillin-clavula nic acid and ceftriaxone, 78% to piperacillin-tazobactam; 87% both to ceftazidime and to ciprofloxacin; and 90% to imipenem. Widespread resi stance was observed in several IE species to third generation cephalos porins, broad-spectrum penicillins and to ciprofloxacin. By contrast, imipenem and the aminoglycosides still retained excellent activity aga inst most multiresistant species. Although there were wide differences between hospitals in the frequencies of resistance to most antibiotic s, these were not related to the types (general vs. university) of hos pitals or to the number of beds. Some variations were however observed in the distribution of bacterial species: the prevalence of inducible Enterobasteriaceae was significantly higher in university than in gen eral hospitals and in hospitals located in Brussels and in Wallonia th an in the Flanders. Overall few trends in resistance rates were observ ed in comparison to a similar survey performed in 1991.