Impact of ceftazidime restriction on gram-negative bacterial resistance in an intensive care unit.

The present study included three periods: (1) a 12-month pre-restriction and control period in 2001; (2) a 12-month restriction period with reduced ceftazidime prescribing in favor of piperacillin-tazobactam (2002); (3) and a 24 month post-restriction period (2003-2004). Note that, for results, P represents the difference between 2002 and 2001; P', the difference between 2003 and 2001; and P'', the difference between 2004 and 2001. No changes in hygiene practices were observed during these three periods. The purpose of this study was to assess the effect of reducing ceftazidime use in an intensive care unit (ICU) upon Gram-negative bacterial resistance, particularly as regards Pseudomonas aeruginosa. During the three periods of the study, patients were similar concerning age, Simplified Acute Physiology Score (SAPSII), the site of nosocomial infection, and the requirements for mechanical ventilation (75% in 2001, 76% in 2002, 74% in 2003, and 85% in 2004). The most commonly isolated pathogens were P. aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae. The use of ceftazidime decreased significantly from 12.6% in 2001 to 9% in 2002, to 3% in 2003 (P' = 0.0009), and 2.6% in 2004 (P'' = 0.0001) in favor of piperacillin-tazobactam (0% 2001 to 3.7% in 2003; P' = 0.002; and 5% in 2004; P'' = 0.0001). Simultaneously, we observed a significant decrease in isolates of P. aeruginosa resistant to piperacillin-tazobactam (P = 0.03; P' = 0.004; P'' = 0.009), and those resistant to imipenem in 2003 (P' = 0.008). We also noted a significant decrease in A. baumannii isolates resistant to ceftazidime (P' = 0.01; P'' = 0.0004) and those resistant to imipenem in both 2002 and 2004 (P = 0.03; P'' = 0.04), and a considerable decrease in isolates of Klebsiella pneumoniae producing expanded spectrum betalactamase (ESBL) in 2003 and 2004 (P' = 0.04; P'' = 6.10(-5)). In contrast, we noted an increase in penicillinase-producing isolates of K. pneumoniae, from 6% in 2001 to 16% in 2002 (p = 0.01), 20% in 2003 (P' = 0.001), and 32% in 2004 (P'' = 10(-6)). We concluded that restriction of ceftazidime use was demonstrated to be efficient in reducing antimicrobial resistance, especially to K. pneumoniae ESBL.