Outbreak of imipenem-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex harboring different carbapenemase gene-associated genetic structures in an intensive care unit.

To investigate the clinical and molecular epidemiology of the imipenem-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii (IRAcb) complex during an outbreak in an intensive care unit (ICU). Forty-six clinical and 11 environmental isolates of the IRAcb complex were collected from the ICU of Taipei Veterans General Hospital, Taiwan between December 2003 and March 2004. These isolates were genotyped using pulsed-field gel electrophoresis (PFGE). Carbapenemase genes and their associated genetic structures were analyzed using PCR. Clinical data obtained from the patients were also reviewed and analyzed. The isolates were identified at the genomic species level as A. baumannii (42 clinical and five environmental isolates) and Acinetobacter genomic species 13TU (four clinical and six environmental isolates). Both species were comprised of two pulsotypes, but those of A. baumannii were closely related (83% similar). IS1008-ΔISAba3-bla(OXA-58-like) and ISAba1-bla(OXA-51-like) were identified in 22 and 21 clinical isolates of A. baumannii, respectively (one isolate contained both). The ISAba3-bracketed bla(OXA-58-like) gene was detected in all isolates of Acinetobacter genomic species 13TU. Patient transfers between different sections of the ICU were important factors that contributed to the spread of the two pulsotypes of A. baumannii. However, among the A. baumannii isolates identified, only those carrying IS1008-ΔISAba3-bla(OXA-58-like) could be found in the environment, indicating an additional route of transmission. The prior use of carbapenem or cefepime was associated with the subsequent infection with A. baumannii carrying the ISAba1-bla(OXA-51-like) gene, while prior piperacillin/tazobactam use was associated with the subsequent infection with A. baumannii carrying the IS1008-ΔISAba3-bla(OXA-58-like) gene. A. baumannii isolates carrying different carbapenemase genes and their associated genetic structures might be transmitted or selected in different ways.

Lee YT ，Fung CP ，Wang FD ，Chen CP ，Chen TL ，Cho WL ... -  《-》

Clusters of imipenem-resistant Acinetobacter baumannii clones producing different carbapenemases in an intensive care unit.

Tsakris A ，Ikonomidis A ，Poulou A ，Spanakis N ，Vrizas D ，Diomidous M ，Pournaras S ，Markou F ... -  《-》

Wide spread of Tn2006 in an AbaR4-type resistance island among carbapenem-resistant Acinetobacter baumannii clinical isolates in Taiwan.

Carbapenem resistance in Acinetobacter baumannii is a global problem. The purpose of this study was to elucidate current resistance mechanisms of imipenem-resistant A. baumannii (IRAB) in Taiwan and their correlation with patient outcomes. Acinetobacter baumannii clinical isolates from two teaching hospitals in Taiwan were collected in 2009 and were examined by Etest for determination of the minimum inhibitory concentrations (MICs) of imipenem, ceftazidime and ceftriaxone. Primers specific for carbapenemase genes and upstream regions were designed for PCR amplification. Bacterial isolates were genotyped by pulsed-field gel electrophoresis (PFGE). Clinical presentations of patients were analysed retrospectively. Upstream insertion sequence ISAba1 was found in 34 isolates that carried bla(OXA-23), including 28 with transposon Tn2006 (ISAba1-bla(OXA-23)-ISAba1) in an AbaR4-type resistance island and 6 with Tn2008 (ISAba1-bla(OXA-23)), as well as in 8 isolates carrying ISAba1-bla(OXA-51-like). All of these isolates expressed full resistance to imipenem (MIC>32 mg/L). Forty-one different PFGE genotypes were found among 62 isolates. Tn2006 was found in 19 genotypes (46.3%), which is more common than ISAba1-bla(OXA-51-like) (12.2%) (P=0.001). Prior use of carbapenems or extended-spectrum cephalosporins for ≥5 days was the only independent risk factor significantly associated with IRAB infection (odds ratio=361.175). Higher mortality was significantly associated with infection caused by IRAB and ISAba1-bla(OXA-23)-carrying strains compared with infection caused by imipenem-susceptible A. baumannii and ISAba1-bla(OXA-51-like)-carrying strains (P=0.009 and 0.027, respectively). Tn2006 is currently the most common imipenem resistance determinant, which showed a higher ability to spread among A. baumannii and was associated with a higher mortality in IRAB-infected patients.

Lee HY ，Chang RC ，Su LH ，Liu SY ，Wu SR ，Chuang CH ，Chen CL ，Chiu CH ... -  《-》

Outbreak of multiple clones of imipenem-resistant Acinetobacter baumannii isolates expressing OXA-58 carbapenemase in an intensive care unit.

Pournaras S ，Markogiannakis A ，Ikonomidis A ，Kondyli L ，Bethimouti K ，Maniatis AN ，Legakis NJ ，Tsakris A ... -  《JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY》

Molecular epidemiology of an outbreak of imipenem-resistant Acinetobacter baumannii carrying the ISAba1-bla(OXA-51-like) genes in a Korean hospital.

Chaulagain BP ，Jang SJ ，Ahn GY ，Ryu SY ，Kim DM ，Park G ，Kim WY ，Shin JH ，Kook JK ，Kang SH ，Moon DS ，Park YJ ... -  《-》