Morganella Infections Treatment & Management

Updated: Nov 04, 2019
  • Author: Shirin A Mazumder, MD, FIDSA; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Medical Care

M morganii strains are naturally resistant to penicillin, ampicillin, ampicillin/sulbactam, oxacillin, first-generation and second-generation cephalosporins, erythromycin, tigecycline, colistin, and polymyxin B.

Most strains are naturally susceptible to piperacillin, ticarcillin, mezlocillin, third-generation and fourth-generation cephalosporins, carbapenems, aztreonam, fluoroquinolones, aminoglycosides, and chloramphenicol.

The widespread use of third-generation cephalosporins has been associated with the emergence of highly resistant M morganii, as follows:

  • Many hospital-acquired strains express derepressed chromosomal ampC beta-lactamases (Bush group 1) similar to those produced by Pseudomonas aeruginosa and Enterobacter species. [19]

  • These strains may be resistant to ceftazidime and other third-generation cephalosporins, but they are usually susceptible to cefepime, imipenem, meropenem, piperacillin, the aminoglycosides, and fluoroquinolones.

  • The beta-lactamase inhibitors (ie, clavulanic acid, sulbactam) are ineffective against these enzymes; however, the combination of piperacillin and tazobactam is more effective than piperacillin alone.

  • Rare isolates of M morganii produce extended-spectrum beta-lactamases (ESBLs). These enzymes hydrolyze drugs such as ceftazidime, cefotaxime, and aztreonam but have little effect on the cephamycins (ie, cefoxitin, cefotetan). ESBLs are inhibited by clavulanic acid.


Surgical Care

Drain any abscesses. Aggressive surgical drainage is required for brain abscesses caused by M morganii.

Debride any surgical wounds.



Consultations with a microbiologist, an infection control specialist, and/or an infectious diseases specialist may be warranted.



Prevent M morganii infection by observing appropriate infection control practices and judiciously using beta-lactam antibiotics.