Dissemination in Japan of multidrug-resistant Pseudomonas aeruginosa isolates producing IMP-type metallo-β-lactamases and AAC(6′)-Iae/AAC(6′)-Ib

Abstract The spread throughout Japan of antibiotic-resistance factors in multidrug-resistant (MDR) Pseudomonas aeruginosa isolates was investigated epidemiologically, using immunochromatographic assays specific for IMP-type metallo-β-lactamases (IMPs) and aminoglycoside 6′-N-acetyltransferase [AAC(6′)]-Iae and -Ib. Three hundred MDR P. aeruginosa isolates were obtained during each of two years, 2011 and 2012, from 190 hospitals in 39 prefectures in Japan. The percentage of P. aeruginosa isolates producing IMPs, AAC(6′)-Iae or AAC(6′)-Ib increased significantly from 170/300 (56.7%) in 2011 to 230/300 (76.7%) in 2012, with 134/170 (78.8%) in 2011 and 179/230 (77.8%) in 2012 producing both IMP and either AAC(6′)-Iae or AAC(6′)-Ib. The MICs of antibiotics, including cephalosporins and carbapenems, were markedly higher for isolates that did than did not produce these resistance factors. These results indicated that MDR P. aeruginosa producing IMPs, AAC(6′)-Iae or AAC(6′)-Ib have spread throughout Japan and that these antibiotic-resistance factors are useful markers for monitoring MDR P. aeruginosa in Japan.