Departmental consumption of antibiotic drugs and subsequent resistance: a quantitative link

Objective: To look for a quantitative model linking departmental consumptio n of antibiotic drugs to the subsequent isolation of resistant hospital-acq uired coliform pathogens. Materials and methods: Included in the study were all patients with hospita l-acquired bloodstream infections caused by a coliform pathogen, detected i n six departments of internal medicine of one university hospital during th e period 1991-1996, who had not been hospitalized in the month before the i nfection (n = 394). Departmental consumption of antibiotics in the year bef ore the infection [expressed as defined daily dosages (DDD)/100 patient day s], antibiotic treatment given to the individual patient before the infecti on, the day of hospital stay on which the infection occurred, and the depar tment and the calendar year were all included in a logistic model to predic t the isolation of a resistant pathogen. We looked at five drugs: gentamici n, amikacin, cefuroxime, ceftazidime and ciprofloxacin. Results: Five logistic models were fitted for the resistance to each of the antibiotic drugs. The multivariable-adjusted odds ratios for a pathogen re sistant to the specific antibiotic were 1.03 [95% confidence interval (CI) 0.70-1.50] for gentamicin, 1.80 (95% CI 1.00-3.24) for amikacin, 1.12 (95% CI 1.02-1.23) for cefuroxime, 1.45 (95% CI 1.19-1.76) for ceftazidime and 1 .06 (95% CI 0.57-1.97) for ciprofloxacin, per 1 DDD/100 patient days. Conclusions: The departmental consumption of cephalosporin drugs and amikac in in six autonomous departments of medicine in the same hospital was assoc iated with a measurable and statistically significant increase in the proba bility of infection caused by a resistant pathogen.