Distribution of different carbapenem resistant clones of Acinetobacter baumannii in Tehran hospitals.

The MICs of imipenem, meropenem, piperacillin-tazobactam, cefotaxime, polymixin B and tigecycline against 80 isolates of Acintobacter baumanii from 6 hospitals were determined. A multiplex-PCR was used to detect the genes encoding carbapenemases. Field Inversion Gel Electrophoresis (FIGE) was then used to investigate the genetic relationships among the carbapenem-resistant isolates. Only 7 isolates were resistant to polymixin B and tigecycline (MIC = 16). All isolates were positive for at least 2 carbapenemase genes. At least 10 distinct clones were detected by FIGE. A dominant pattern designated as pulsotype A consisting of 23 isolates was detected from 4 hospitals. The majority of isolates in this pulsotype had a bla(OXA-51/23-like) and bla(OXA-51/24-like) carbapenemase genes and cultured from the patients at burns and ICU. The pan drug resistant isolates belonged to different FIGE patterns. Nosocomial infections with different clones of Acintobacter baumanii occur at Tehran hospitals. However, inter-hospital transmission with certain pulsotypes is likely.