Almost always susceptible to:

•  Aminoglycosides

•  TMP-SMX

•  Fluoroquinolones

•  Carbapenems

•  Aztreonam

•  Tigecycline

•  Colistin

Intrinsically resistant to ampicillin.

More resistant to cephalosporins than K. pneumoniae.

May be resistant to third generation cephalosporins (ESBLs), and rarely to carbapenems (carbapenemase enzymes).

Use fosfomycin and nitrofurantoin for UTI only, when confirmed susceptible.