What are the recommended antibiotic susceptibilities for Morganella morganii infections?

From the Guidelines

Morganella morganii infections should be treated with antibiotics such as carbapenems, third and fourth-generation cephalosporins, fluoroquinolones, aminoglycosides, and piperacillin-tazobactam, with first-line options including imipenem or meropenem, ceftriaxone, ciprofloxacin, or gentamicin. The choice of antibiotic should be guided by antibiotic susceptibility testing, as resistance patterns can vary 1.

Key Considerations

• Morganella morganii has intrinsic resistance to many beta-lactam antibiotics, including ampicillin, amoxicillin, first and second-generation cephalosporins, and colistin.
• The production of inducible beta-lactamases by M. morganii can lead to treatment failure with certain antibiotics despite initial susceptibility.
• Local resistance patterns should inform empiric therapy choices, as regional variations in antibiotic susceptibility profiles exist 1.
• Combination therapy may be considered initially for severe infections until susceptibility results are available.

Treatment Options

• Imipenem or meropenem (500mg-1g IV every 8 hours)
• Ceftriaxone (1-2g IV daily)
• Ciprofloxacin (400mg IV or 500-750mg oral twice daily)
• Gentamicin (5-7mg/kg IV daily)
• Treatment duration typically ranges from 7-14 days depending on infection severity and site. It is essential to note that the most recent and highest quality study 1 provides guidance on the management of treatment failure in prosthetic joint infection, which can inform the treatment of Morganella morganii infections. However, the study 1 from 2017 provides more general guidance on the management of intra-abdominal infections, which may not be directly applicable to Morganella morganii infections. Therefore, the recommendation is based on the most recent and relevant study 1.

From the FDA Drug Label

The following in vitro data are available, but their clinical significance is unknown At least 90% of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for meropenem against isolates of similar genus or organism group. ... Morganella morganii Ciprofloxacin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections ... Morganella morganii

Antibiotic Susceptibilities for Morganella morganii:

• Meropenem: susceptible (at least 90% of isolates have an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint) 2
• Ciprofloxacin: susceptible (most strains are susceptible) 3 Note: The clinical significance of these in vitro data is unknown.

From the Research

Antibiotic Susceptibilities for Morganella morganii Infections

The recommended antibiotic susceptibilities for Morganella morganii infections are as follows:

• Ceftazidime, imipenem, and amikacin are effective against M. morganii, with the majority of isolates being susceptible to these antibiotics 4
• Gentamicin is often used in combination with a third-generation cephalosporin or another antibiotic to which M. morganii is susceptible 4
• Carbapenems, such as imipenem, are commonly used to treat M. morganii bacteremia, followed by aminoglycosides, ciprofloxacin, and colistin 5
• Third-generation cephalosporins, such as ceftazidime, may be effective against M. morganii, but the production of AmpC β-lactamases should be tested for 4

Resistance Patterns

M. morganii has been shown to be resistant to multiple antibiotics, including:

• Ciprofloxacin, trimethoprim/sulfamethoxazole, gentamicin, amoxicillin, nitrofurantoin, and colistin 5
• First-generation cephalosporins and ampicillin-clavulanate 6
• Piperacillin-tazobactam and ciprofloxacin, with resistance rates of 1.8% and 10.1%, respectively 6

Treatment Outcomes

The treatment outcomes for M. morganii infections are as follows:

• The majority of patients recover completely after antibiotic treatment 4
• The in-hospital mortality rate for M. morganii bacteremia is around 41% 5
• The risk of mortality is increased in patients who are admitted to the ICU, are older than 65 years, and have Klebsiella pneumoniae co-infection 5
• The 14-day mortality rate for M. morganii bacteremia is around 14.7% 6