Most carbapenem non-susceptible hospital UTIs are caused by P aeruginosa, A baumannii, and S maltophilia1

UTIs due to Gram-negative pathogens (210,427) in hospitalized patients

Pie graph Enterobacteriaceae 89%, P aeruginosa 10%, A baumannii 0.5%, S maltophilia 0.4%

UTIs due to carbapenem non-susceptible Gram-negative pathogens (n=7035) in hospitalized patients

Pie graph P aeruginosa 54%, S maltophilia 13%, A baumannii 7% = 74% total non-fermenters vs 26% total Enterobacteriaceae
a Enterobacteriaceae=E coli and K pneumoniae.
From a study identifying laboratory-confirmed infections in the Premier Healthcare Database between 2010 and 2015.

Carbapenem resistance can be caused by a mix of mechanisms

P aeruginosa:

  • Primary mechanism is loss of OprD porin2
  • 100% of imipenem-resistant strains have both extended-spectrum cephalosporinase (ESAC) overexpression and loss of porin channels3

A baumannii:

  • Primary mechanism is OXA carbapenemase production (OXA-23)4
  • All isolates contain chromosomally encoded OXA-515


  • Use all carbapenem-resistance mechanisms (eg, production of AmpC/ESBL, carbapenemases, and porin mutations)

Although Enterobacteriaceae cause most UTIs in hospitalized patients, they are not the most common pathogens causing carbapenem-non-susceptible UTIs1