Investigation of carbapenem heteroresistance among different sequence types of Pseudomonas aeruginosa clinical isolates reveals further diversity

Pseudomonas aeruginosa is a leading infectious agent causing difficult-to-treat nosocomial infections due to the multiresistant phenotype that it often exhibits. Expression of the intrinsic AmpC b-lactamase, overexpression of Mex–Opr-type efflux pumps as well as repression of porin OprD have been associated with b-lactam resistance in this species (Lister et al., 2009). Also, different genotypes of carbapenem-susceptible P. aeruginosa have been documented to produce carbapenem-heteroresistant subpopulations (Pournaras et al., 2007).