Susceptibility to arbekacin of clinical strains of Pseudomonas aeruginosa isolated in the Tohoku area between 2003 and 2007

We surveyed the susceptibility to ceftazidime, arbekacin(ABK), gentamycin(GM), and amikacin(AMK) of 1,348 strains of Pseudomonas aeruginosa isolated between 2003 and 2007 from patients hospitalized in the Tohoku area, Japan. Susceptibility was tested by the broth microdilution method using frozen plates. Metallo-β-lactamase (MBL) -producing P. aeruginosa was detected by the sodium mercaptoacetate(SMA) disc method, and PCR was used to detect the MBL type. Results of yearly susceptibility testing showed that the MIC₅₀ and MIC₉₀ of aminoglycoside antibiotics against 1.266 P. aeruginosa strains except for 64 MBL-producers and 18 non-MBL multidrug-resistant P. aeruginosa(MDRP) strains, between 2003 and 2007 were 2-4 μg/mL in ABK and GM, and 4 μg/mL, respectively. On the other hand, the range of MIC₉₀ of ABK and GM were 8 to 16 μg/mL and those of AMK were 8 to 32 μg/mL. ABK was more effective than AMK, but MBL-producers and non-MBL MDRP were resistant to these 3 aminoglycoside antibiotics. P. aeruginosa and methicillin-resistant Staphylococcus aureus(MRSA) are frequently isolated as the cause of nosocomial pneumonia and wound infection. Mixed infection by these strains is also frequently encountered. ABK, which is an anti-MRSA drug, may prove effective against nosocomial infection by P. aeruginosa.