Morganella Infections Treatment & Management

Updated: Feb 24, 2023
  • 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. A systematic review found gentamicin to be the most common and successfully used antibiotic alongside another susceptible antibiotic. [25]  

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. [26]

  • These strains may be resistant to ceftazidime and other third-generation cephalosporins, but they usually are 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.

Resistance by M morganii also has been proposed to harbor new multi-drug resistant genes via a novel Transposon Tn 7376 alongside mobile genetic elements (MGEs), particularly the IS26-flanked MGE carrying the extra gene dfrA24 in an isolated pathogenic variant. [27]


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.