What are the effective treatment options for a urinary tract infection caused by Morganella morganii and Enterococcus faecalis?

Treatment Options for UTI Caused by Morganella morganii and Enterococcus faecalis

Based on the susceptibility testing results, ciprofloxacin is the most effective treatment option for this polymicrobial urinary tract infection caused by Morganella morganii and Enterococcus faecalis.

Analysis of Susceptibility Results

• The urine culture shows two organisms with >100,000 CFU/mL each:

  • Morganella morganii - susceptible to ciprofloxacin, levofloxacin, ertapenem, meropenem, piperacillin/tazobactam, tobramycin, and trimethoprim/sulfa 1, 2
  • Enterococcus faecalis - susceptible to ciprofloxacin, levofloxacin, nitrofurantoin, and penicillin 1

• The only antibiotics effective against both organisms are:

  • Ciprofloxacin 3
  • Levofloxacin 4

Treatment Recommendation Algorithm

First-line Treatment

• Ciprofloxacin 500 mg PO twice daily for 7-14 days 1, 3
  • Ciprofloxacin is FDA-approved for UTIs caused by both Morganella morganii and Enterococcus faecalis 3
  • Fluoroquinolones should only be used when local resistance rates are <10% 1

Alternative Treatment

• Levofloxacin 750 mg PO once daily for 5-10 days 1, 4
  • Equally effective against both organisms based on susceptibility testing 4
  • May be preferred for once-daily dosing to improve adherence 1

Special Considerations for Morganella morganii

• M. morganii is an opportunistic pathogen that can cause serious infections with high mortality rates if not properly treated 2, 5
• This organism is often resistant to multiple antibiotics including:
  • First and second-generation cephalosporins 1
  • Amoxicillin/clavulanic acid (as seen in this case) 2, 6
  • Nitrofurantoin (as seen in this case) 5
• M. morganii frequently produces AmpC β-lactamases, which can develop resistance during treatment with certain β-lactams 2, 6

Special Considerations for Enterococcus faecalis

• E. faecalis is intrinsically resistant to many antibiotics including trimethoprim-sulfamethoxazole (despite this isolate testing susceptible) 1
• For vancomycin-resistant enterococci (not the case here), linezolid or tigecycline would be appropriate 1
• The isolate is resistant to tetracycline, which is a common finding for enterococci 1

Treatment Duration

• For complicated UTIs (polymicrobial infections are generally considered complicated), treatment duration should be 7-14 days 1
• A shorter course (7 days) may be considered when the patient has been afebrile for at least 48 hours and is hemodynamically stable 1
• Longer duration (14 days) is recommended if there are concerns about prostatitis in male patients 1

Common Pitfalls to Avoid

• Do not use nitrofurantoin despite E. faecalis being susceptible, as M. morganii is resistant and nitrofurantoin doesn't achieve adequate tissue concentrations for upper UTIs 7, 2
• Do not use trimethoprim-sulfamethoxazole despite susceptibility results for M. morganii, as enterococci are often clinically resistant despite in vitro susceptibility 1, 8
• Do not use amoxicillin/clavulanic acid as M. morganii is resistant 2, 6
• Monitor for resistance development during therapy, especially with M. morganii which can develop resistance through AmpC β-lactamase production 2, 5

Follow-up Recommendations

• Clinical response should be assessed within 48-72 hours of initiating treatment 1
• Consider repeat urine culture if symptoms persist beyond 72 hours of appropriate therapy 1
• For recurrent UTIs, imaging may be indicated to rule out anatomical abnormalities, especially in the presence of risk factors 1