Differences in phenotypic and genotypic characteristics among imipenem-non-susceptible Acinetobacter isolates belonging to different genomic species in Taiwan

Section: Discussionmentioning

confidence: 67%

Genetic Basis of Multidrug Resistance in Acinetobacter Clinical Isolates in Taiwan

Lin

Hsia

Chen

et al. 2010

“…Bacteria belonging to the family Enterobacteriaceae and Pseudomonas aeruginosa were identified using a Vitek II system (bioMéri-eux, Marcy l'Etoile, France). Genes encoding class A, B, and D carbapenemases and the upstream insertion sequence of CHDL genes were detected by a PCR method, as previously described (19,20). Phenotypic tests were used to identify class B metallo-␤-lactamases, as previously described (20).…”

Section: Methodsmentioning

confidence: 99%

“…Genes encoding class A, B, and D carbapenemases and the upstream insertion sequence of CHDL genes were detected by a PCR method, as previously described (19,20). Phenotypic tests were used to identify class B metallo-␤-lactamases, as previously described (20). Imipenem, ticarcillin, and kanamycin were purchased from Sigma-Aldrich (St. Louis, MO).…”

Section: Methodsmentioning

confidence: 99%

Sheltering Effect and Indirect Pathogenesis of Carbapenem-Resistant Acinetobacter baumannii in Polymicrobial Infection

Liao¹,

Kuo

Lee

et al. 2014

Self Cite

The role of carbapenem-resistant Acinetobacter baumannii (CRAb) in polymicrobial infection remains elusive. Having observed the ability of CRAb to shelter other susceptible bacteria from carbapenem killing, we sought to determine the factors contributing to this sheltering effect by transforming different recombinant plasmids into recipient A. baumannii cells. The sheltering effects of CRAb were reproduced in recipient A. baumannii cells that highly expressed carbapenem-hydrolyzing class D ␤-lactamases (CHDLs) through their associated strong promoter. With the use of Western blot analysis and a bioassay, the highly expressed CHDLs were found to be extracellularly released and led to hydrolysis of carbapenem. The level of extracellular CHDLs increased after challenge with a higher concentration of CHDL substrates, such as carbapenem and ticarcillin. This increased CHDL may, in part, be attributed to cell lysis, as indicated by the presence of extracellular gyrase. In the planktonic condition, the sheltering effect for the cocultured susceptible bacteria might represent an indirect and passive effect of the CRAb self-defense mechanism, because coculture with the susceptible pathogen did not augment the amount of the extracellular CHDLs. Polymicrobial infection caused by CRAb and a susceptible counterpart exerted higher pathogenicity than monomicrobial infection caused by either pathogen alone in mice receiving carbapenem therapy. This study demonstrated that CHDL-producing CRAb appears to provide a sheltering effect for carbapenem-susceptible pathogens via the extracellular release of CHDLs and, by this mechanism, can enhance the pathogenesis of polymicrobial infection in the presence of carbapenem therapy.

“…The bla OXA-24 -like, bla OXA-23 -like, bla OXA-143 -like, bla IMP -like, bla VIM -like, bla SIM -like, bla GIM -like, and bla SPM -like genes were not detected in the isolates (8,11). Two isolates of pulsotype B carried bla OXA-58 genes, which were flanked by IS1006-⌬ISAba3-like (upstream) and ISAba3 (downstream) (1).…”

mentioning

confidence: 99%

Emergence of Carbapenem-Resistant Non-baumannii Species of Acinetobacter Harboring a bla _OXA-51 -Like Gene That Is Intrinsic to A. baumannii

Lee

Kuo

Chiang

et al. 2012

Self Cite

The bla OXA-51 -like gene, originally intrinsic to Acinetobacter baumannii, had been detected in two clones of Acinetobacter nosocomialis and one clone of Acinetobacter genomic species "Close to 13TU." These bla OXA-51 -like genes, all preceded by ISAba1, were located on plasmids that might have originated with A. baumannii. The plasmid-borne ISAba1--bla OXA-51 -like confers a high level of carbapenem resistance and affects the accuracy of using bla OXA-51 -like detection as a tool for differentiating A. baumannii from other Acinetobacter species.