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Citrobacter species are enteric gram-negative bacilli. They are normal human gut flora. They are mostly a nosocomial pathogen found in compromised hosts, patients over 60 years of age, and in neonates. Common infections are of the urinary tract, line infections, pneumonia, and in neonates CNS infections.

Antibiotic Sensitivities[1]

Category Antibiotic Citrobacter freundii Citrobacter diversus Other Citrobacter sp.
Penicillins Penicillin G R R R
Penicillin V R R R
Anti-Staphylocccal Penicillins Methicillin R R R
Nafcillin/Oxacillin R R R
Cloxacillin/Diclox. R R R
Amino-Penicillins AMP/Amox R R R
Amox-Clav R R R
AMP-Sulb R R R
Anti-Pseudomonal Penicillins Ticarcillin S S S
Ticar-Clav S S S
Pip-Tazo S S S
Piperacillin S S S
Carbapenems Doripenem S S S
Ertapenem S S S
Imipenem S S S
Meropenem S S S
Aztreonam S S S
Fluroquinolones Ciprofloxacin S S S
Ofloxacin S S S
Pefloxacin S S S
Levofloxacin S S S
Moxifloxacin S S S
Gemifloxacin X1 X1 X1
Gatifloxacin S S S
1st G Cephalo Cefazolin R R R
2nd G. Cephalo Cefotetan R I I
Cefoxitin R I I
Cefuroxime R I I
3rd/4th G. Cephalo Cefotaxime S S S
Cefizoxime R S S
Ceftaroline X1 S S
CefTAZidime R S S
Cefepime S S S
Oral 1st G. Cephalo Cefadroxil R R X1
Cephalexin R R R
Oral 2nd G. Cephalo Cefaclor/Loracarbef R R I
Cefproxil R R R
Cefuroxime axetil R X1 I
Oral 3rd G. Cephalo Cefixime R X1 S
Ceftibuten R S S
Cefpodox/Cefdinir/Cefditoren R X1 S
Aminoglycosides Gentamicin X1 X1 X1
Tobramycin X1 X1 X1
Amikacin X1 X1 X1
Chloramphenicol X1 X1 X1
Clindamycin X1 X1 X1
Macrolides Erythromycin X1 X1 X1
Azithromycin X1 X1 X1
Clarithromycin X1 X1 X1
Ketolide Telithromycin X1 X1 X1
Tetracyclines Doxycycline X1 X1 X1
Minocycline X1 X1 X1
Glycylcycline Tigecycline X1 X1 X1
Daptomycin X1 X1 X1
Glyco/Lipoclycopeptides Vancomycin X1 X1 X1
Teicoplanin X1 X1 X1
Telavancin X1 X1 X1
Fusidic Acid X1 X1 X1
Trimethoprim X1 X1 X1
Urinary Agents Nitrofurantoin X1 X1 X1
Fosfomycin X1 X1 X1
Other Rifampin X1 X1 X1
Metronidazole X1 X1 X1
Quinupristin dalfoppristin X1 X1 X1
Linezolid X1 X1 X1
Colistimethate X1 X1 X1


  • S susceptible/sensitive (usually)
  • I intermediate (variably susceptible/resistant)
  • R resistant (or not effective clinically)
  • S+ synergistic with cell wall antibiotics
  • U sensitive for UTI only (non systemic infection)
  • X1 no data
  • X2 active in vitro, but not used clinically
  • X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
  • X4 active in vitro, but not clinically effective for strep pneumonia

Table Overview

See Also


  1. Sanford Guide to Antimicrobial Therapy 2014