ANTIBIOTIC SUSCEPTIBILITY IN AEROBIC GRAM-NEGATIVE BACILLI ISOLATED IN INTENSIVE-CARE UNITS IN 39 FRENCH TEACHING HOSPITALS (ICU STUDY)

Objective: Evaluation of the distribution and antibiotic susceptibilit y of the aerobic gramnegative bacilli (AGNB) isolated from patients in intensive care units (ICU study). Design and setting: Microbiological study carried out in 1991 in 39 teaching hospitals. A standardized me thod was used to determine the minimum inhibitory concentrations of 12 antibiotics against 3366 strains of AGNB (close to 100 strains per ho spital) during a period of 3 months. Results: The 2773 initial strains (i.e., the first AGNB isolate for a given species and a given patient ) were mainly isolated from the respiratory tract (34.4%), urinary tra ct (23%), or blood (9.6%) and were mainly Pseudomonas aeruginosa (22.9 %), Escherichia coli (22%), Acinetobacter (9.7%), and Klebsiella pneum oniae (8.3%). E. coli was prominent in urine and blood and P. aerugino sa in the respiratory tract. Overall, the rate of susceptibility of AG NB was 58 to 65% to piperacillin, cefotaxime, and gentamicin; 69 to 75 % to aztreonam, tobramycin, and ciprofloxacin; 83% to ceftazidime; and 91% to imipenem. The overall rates of susceptibility were higher for the initial strains isolated from blood than for those from the urinar y or respiratory tracts, mostly reflecting differences in species dist ribution. Susceptibility rates were lower for the 593 repeat strains ( i.e., all the subsequent isolates for a given species and a given pati ent) than for the initial strains, mostly due to the higher proportion of resistant species (P. aeruginosa 45.9%) but also due to the differ ence in susceptibility rates for some species-antibiotic combinations. Concomitant resistance (i.e., resistance to several antibiotics due t o independent mechanisms of resistance) was marked between P-lactams a nd aminoglycosides or quinolones, particularly in P. aeruginosa and K. pneumoniae. Conclusions: Rates of resistance in AGNB as a whole and i n particular species (Fi aeruginosa, Klebsiella), as well as frequency of concomitant resistance found in the French ICU study, were higher than those found in ICU studies conducted with the same methodology in Belgium, The Netherlands, and Germany, which may reflect differences in case mix.