Vol.59 No.2 March 2011

Scoring analysis using breakpoint-checker board plates or antibiotic combination therapy in multidrug-resistant Pseudomonas aeruginosa

Toyoko Oguri¹⁾, Yoshikazu Ishii²⁾, Shigeki Misawa³⁾, Kazuhiro Tateda²⁾, Katsuko Okuzumi⁴⁾, Atsushi Yoshida⁴⁾, Miyuki Tsukahara⁵⁾, Tsuyoshi Oishi⁵⁾, Masaru Baba⁶⁾, Akiko Yoneyama⁶⁾, Midori Sumitomo⁷⁾, Toshihiro Mitsuda⁷⁾, Shinichiro Mori⁸⁾, Akiyoshi Shibayama⁹⁾, Yoshitaka Nakamori⁹⁾, Mieko Goto¹⁰⁾, Kyoji Moriya¹⁰⁾, Tomoaki Sato¹¹⁾, Norio Omagari¹²⁾, Keizo Yamaguchi²⁾ and Antibiotic combination therapy study group (ACTs)

¹⁾Kameda General Hospital, 929 Higashi-cho, Kamogawa, Chiba, Japan
²⁾Department of Microbiology and Infectious Diseases, Toho University School of Medicine
³⁾Juntendo University Hospital
⁴⁾Dokkyo Medical University Hospital
⁵⁾Tokyo Medical University Ibaraki Medical Center
⁶⁾Toranomon Hospital
⁷⁾Yokohama City University Hospital
⁸⁾National Cancer Center Hospital
⁹⁾Mishuku Hospital
¹⁰⁾The University of Tokyo, Graduate School of Medicine and Department of Infection Control and Prevention
¹¹⁾Shizuoka Cancer Center (Current affiliations: Yamagata University, Faculty of Medicine and Yamagata University Hospital)
¹²⁾Shizuoka Cancer Center

Abstract

Scoring analysis was used from 2003 to 2006 to evaluate results breakpoint checkerboard plate in antibiotic combination therapy using 63 multidrug-resistant Pseudomonas aeruginosa(MDRP) clinical isolates from 8 hospitals in Japan. Minimum inhibitory ceftazidime and meropenem concentrations were >128 μg/mL in 90% and 73% of tested isolates. Based on Clinical and Laboratory Standards Institute criteria, 86% of isolates were resistant to aztreonam, 100% to ciprofloxacin, and 89% to amikacin. Combination effects were scored as follows: 1 for 1 well in 4 wells growth inhibition, 2 for 2 wells, 3 for 3 wells, 4 for 4 wells, and 0 if all wells of growth were observed. We calculated total score for the antibiotic combinations by multiplying each score by the number of isolates and adding all scores for each combination. Scores for the combination of colistin and other antibiotics were high at >179, but these scores did not reflect the result of combinations. Amikacin scored higher combined with piperacillin at 75 and with aztreonam at 84, suggesting overall that these 2 combinations were most effective against MDRP. The above scoring analysis thus proved useful and objective in comparing the effects of changes in antibiotic combinations in the same hospital or among different hospitals.

Key word

B·C plate, multidrug-resistant P. aeruginosa, susceptibility testing, scoring analysis

Received

November 10, 2010

Accepted

January 5, 2011

Jpn. J. Chemother. 59 (2): 172-176, 2011