2019 Volume 72 Issue 3 Pages 253-262
A target for the carbapenem-resistance rate of Pseudomonas aeruginosa was included in Japan’s “National Action Plan on Antimicrobial Resistance 2016–2020” In order to achieve this target, we need to make efforts to reduce the frequency of carbapenem-resistant P. aeruginosa and to ensure the appropriate use of antimicrobial agents that have the potential to induce bacterial resistance. The effectiveness of the combined use of injectable anti-P. aeruginosa agents other than carbapenems against carbapenem-resistant P. aeruginosa was evaluated using antimicrobial susceptibility data for 286 P. aeruginosa strains that were isolated in 2012.
Based on the interpretation criteria outlined in the Clinical and Laboratory Standards Institute M100-S28 standards, 84 out of 286 P. aeruginosa strains showed resistance or intermediate susceptibility to imipenem or meropenem and were classified as carbapenemresistant. The susceptibility rates of these strains for piperacillin (PIPC), tazobactam/piperacillin (TAZ/PIPC), ceftazidime (CAZ) and cefepime (CFPM) ranged from 58.3–70.2%, and those for ciprofloxacin (CPFX) and levofloxacin (LVFX) were 67.9% and 64.3%, respectively. High susceptibility rates of 88.1% and 92.9% were obtained for gentamicin (GM) and amikacin (AMK), respectively.
PIPC, TAZ/PIPC, CAZ or CFPM, which are β-lactams, were used in combination with CPFX, LVFX, GM, or AMK, and percentage of strains that were susceptible to one or both antimicrobial agents was calculated for each combination. As a result, it was found that combining β-lactams with CPFX or LVFX resulted in susceptibility rates of 64.3–86.9%, and combining β-lactams with GM or AMK produced susceptibility rates of 88.1–96.4%.
In this study, we demonstrated that the susceptibility rates of carbapenem-resistant P. aeruginosa were increased by combining β-lactams with new quinolones or aminoglycosides; i.e., non-carbapenem drugs. It is expected that the promotion of combination therapy involving these antimicrobial agents would lead to a reduction in the frequency of carbapenem resistance among P. aeruginosa.
