Investigation of isolation rates of Pseudomonas aeruginosa with and without multidrug resistance in medical facilities and clinical laboratories in Japan

Objectives: To perform a large-scale investigation of Pseudomonas aeruginosa strains with and without drug resistance in Japan. Methods: We distributed questionnaires to assess isolation rates of P. aeruginosa with and without drug resistance at medical facilities and clinical laboratories throughout Japan during the period January 2003 through June 2006. Completed questionnaires were obtained from 339 medical facilities and 4 clinical laboratories. Results: The total number of P. aeruginosa strains isolated at the medical facilities was 549 746 and that at clinical laboratories was 640 232. Strains resistant to carbapenems, fluoroquinolones (ciprofloxacin or levofloxacin) and amikacin were defined as multidrug-resistant (MDR) strains, and strains resistant to two of these drugs were defined as two-drug-resistant (TDR) strains. The percentage of MDR at medical facilities and clinical laboratories was 2.4% and 1.1%, respectively, and that of TDR isolates was 6.4% and 4.2%, respectively. MDR and TDR isolates were found nationwide. No MDR isolates were found at approximately one-third of the medical facilities each year. The percentages of MDR and TDR isolates increased significantly from 2003 to 2005. P. aeruginosa strains were obtained mainly from the respiratory and urinary tracts, and the percentages of MDR and TDR isolates were particularly increased in the urinary tract during these years. Conclusions: MDR P. aeruginosa was prevalent nationwide in Japan. The incidence was low, except in a limited number of facilities, but it increased significantly.