Emergence and widespread dissemination of OXA-23, -24/40 and -58 carbapenemases among Acinetobacter spp. in Asia-Pacific nations: report from the SENTRY Surveillance Program.

OBJECTIVES: The aim of this study was to evaluate the occurrence and dissemination of acquired carbapenem-hydrolysing class D beta-lactamase (class D carbapenemase)- and metallo-beta-lactamase (MBL)-encoding genes among Acinetobacter spp. isolates recovered from medical centres in the Asia-Pacific (APAC) region.

METHODS: During 2006-07, 41 medical centres located in 10 countries in the APAC region forwarded to a central monitoring site 544 Acinetobacter spp. isolates, which were tested for susceptibility by the reference broth microdilution method. Isolates non-susceptible to imipenem or meropenem (MIC>or=8 mg/L) were screened for OXA-23-, OXA-24/40-, OXA-58- and MBL-encoding genes and confirmed by sequencing. Clonality was assessed by ribotyping and PFGE.

RESULTS: Polymyxins (99.1% susceptible) and tigecycline (98.9% susceptible) were the most active antimicrobial agents tested. Among the isolates, 230 (42.3%) were non-susceptible to imipenem or meropenem, and class D carbapenemase- or MBL-encoding genes were detected in 162 (70.4%). blaOXA-23 was found in isolates recovered from six countries, while blaOXA-24/40 and blaOXA-58 were less common. Several isolates harboured more than one class D carbapenemase, and MBL-encoding genes were detected in one Acinetobacter johnsonii from the Philippines (blaIMP-4) and one Acinetobacter baumannii from Korea (blaVIM-2)). Overall, clonal dissemination was noted within medical centres; however, genetic relatedness was also noted among class D carbapenemase-producing A. baumannii isolates recovered from different countries.

CONCLUSIONS: This study shows a high distribution of class D carbapenemase-encoding genes, mainly blaOXA-23, in Acinetobacter spp. isolates. In addition, clonal dissemination among medical centres located in different countries in the APAC region, previously documented in many regions of Europe, emphasizes the epidemic potential of these bacteria.