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Citrobacter spp (other)

C. amalonaticus
C. farmer
C. gillenii
C. sedlakii

Gram Stain

Gram negative bacilli - fermenter

Clinical Significance

These organisms are found in the environment and the gastrointestinal tract of humans and animals.

They have been associated with bacteremia, urinary tract, skin/soft tissue, and bone and joint infections.

Usual Susceptibility Pattern

These organisms (except C. sedlakii) produce an inducible chromosomal β-lactamase (CTX-M cefotaximase) resulting in intrinsic resistance to ampicillin and cephalothin. Hyperproduction of this enzyme results in resistance to cefazolin, ceftriaxone, +/- beta-lactamase inhibitor combination drugs. Ceftazidime may still test susceptible but should be avoided.

Empiric Therapy
TMP/SMX
or
Gentamicin
or
Ciprofloxacin
Severe Infections:
Meropenem