Morganella morganii is typically susceptible to cefepime
Based on FDA drug labeling and recent clinical data, Morganella morganii isolates demonstrate consistent susceptibility to cefepime, making it a reliable treatment option for infections caused by this organism.
Susceptibility Profile
The FDA-approved cefepime drug label explicitly lists Morganella morganii among the Gram-negative bacteria for which "at least 90 percent of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for cefepime" 1. This indicates robust in vitro activity against this pathogen.
Recent clinical evidence strongly supports this susceptibility pattern:
- A 2025 pediatric case series from Jordan found that all M. morganii isolates causing urinary tract infections were uniformly sensitive to cefepime 2
- A 2026 multicenter study examining cefoxitin-nonsusceptible ESCPM organisms (which includes M. morganii) demonstrated that cefepime with MIC ≤1 µg/mL showed comparable efficacy to carbapenems for treating complicated urinary tract infections 3
- Historical data from 1994-1995 showed 75% susceptibility of ceftazidime-resistant M. morganii to cefpirome (a related fourth-generation cephalosporin), and complete susceptibility to cefepime among tested isolates 4, 5
Important Caveats
MIC matters significantly: When cefepime MIC reaches 2 µg/mL (still technically susceptible but at the upper limit), treatment failure rates increase. The 2025 multicenter study found that isolates with cefepime MIC = 2 µg/mL had enhanced risk of 28-day treatment failure compared to those with MIC ≤1 µg/mL (OR 2.579,95% CI 1.012-6.572) 3. In such cases, carbapenems may be preferred.
Emerging resistance trends: A 2026 Turkish surveillance study documented statistically significant increases in cefepime resistance among M. morganii isolates over a 10-year period, particularly after 2022 6. While overall susceptibility remains high, this trend warrants attention and reinforces the importance of local antibiogram review.
Clinical Recommendation
For empiric or targeted therapy of M. morganii infections, cefepime remains an appropriate choice when susceptibility testing confirms MIC ≤1 µg/mL. However, if the MIC is 2 µg/mL or if local resistance patterns show concerning trends, consider carbapenems (meropenem, imipenem) or amikacin as alternatives, which maintain >98% activity against this organism 6.
Always verify susceptibility through formal testing rather than assuming susceptibility, particularly in healthcare-associated infections or in patients with prior antibiotic exposure.