Correlation between antibiotic use and changes in susceptibility patterns of Pseudomonas aeruginosa in a medical-surgical intensive care unit

CONTEXT: Multiple surveillance programmes have reported a decline in antibiotic susceptibility of P. aeruginosa. AIM: Our study aimed to study the relationship between the use of antipseudomonal drugs and the development of resistance of P. aerogenosa to these drugs. SETTING AND DESIGN: Our study is retrospective. It was conducted in a medical surgical intensive care unit during a five-year period (January 1(st), 1999 to December 31, 2003), which was divided into 20 quarters. We had monitored the use of antipseudomonal agents and the resistance rates of P. aeruginosa to these drugs. STATISTICAL METHODS: The associations between use and resistance were quantified using non-partial and partial correlation coefficients according to Pearson and Spearman. RESULTS: Over the study period, the most frequently used antipseudomonal agent was Imipenem (152 ± 46 DDD/1000 patients-day) and the resistance rate of P. aeruginosa to Imipenem was 44.3 ± 9.5% (range, 30 and 60%). In addition, Imipenem use correlated significantly with development of resistance to Imipenem in the same (P < 0.05) and in the following quarter (P < 0.05); and Ciprofloxacin use correlated significantly with resistance to Ciprofloxacin in the following quarter (P < 0.05). However, use of Ceftazidime or Amikacine had no apparent association with development of resistance. CONCLUSION: We conclude that the extensive use of imipenem or ciprofloxacin in intensive care units may lead to the emergence of imipenem- and ciprofloxacin-resistant strains of P. aeruginosa and that antibiotic prescription policy has a significant impact on P. aeruginosa resistance rates in an intensive care unit.