The effect of an antimicrobial restriction program on Pseudomonas aeruginosa resistance to β-lactams in a large teaching hospital

Study Objectives. To compare the use of beta-lactams and subsequent Pseudomonas aeruginosa sensitivity patterns before and after implementation of a clinical pharmacist-facilitated antimicrobial restriction program in August 1997. Design. Retrospective consecutive data collection. Setting. Large university-affiliated medical center. Intervention. The study results are the accumulation of the daily intervention activities of the antimicrobial restriction program. Data on antimicrobial grams purchased/1000 patient-days and susceptibility patterns were collected and analyzed retrospectively. Measures and Main Results. Annual grams of ceftazidime, piperacillin, piperacillin-tazobactam, and other antipseudomonal beta-lactams purchased/1000 patient-days were compared during the 2 full calendar years before the antimicrobial restriction program (1995-1996) with the 4 full calendar years after the program was implemented (1998-2001). Pseudomonas aeruginosa resistance trends for the antipseudomonal beta-lactams, ciprofloxacin, and tobramycin also were compared for the 2 years before the program (1995-1996) with the last 2 years of the program (2000-2001). A 44% reduction in ceftazidime use was documented; ostensibly, minimal changes occurred in the overall use of piperacillin and piperacillin-tazobactam. During the same time period, ceftazidime resistance fell from 24% to 11.8% (p<0.001), whereas piperacillin resistance fell from 32.5% to 18.5% (p<0.001). Imipenem resistance declined from 20.5% to 12.3% (p<0.001) with an 18% reduction in use. Aztreonam resistance declined from 29.5% to 16.5% (p<0.001) despite a 57% increase in use. No changes in resistance to either ciprofloxacin or tobramycin were found. Conclusion. Through an antimicrobial restriction program, a dramatic reduction in ceftazidime use was achieved with judicious use of other antipseudomonal antimicrobials, which resulted in reduced resistance of P aeruginosa to other beta-lactams.