What is the recommended treatment for infections caused by Klebsiella aerogenes?

Treatment of Klebsiella aerogenes Infections

For infections caused by Klebsiella aerogenes, novel β-lactam agents such as ceftazidime/avibactam and meropenem/vaborbactam should be the first-line treatment options when carbapenem resistance is present. 1

Treatment Algorithm Based on Resistance Pattern

For Susceptible K. aerogenes:

• First-line options:
  • Third-generation cephalosporins (e.g., ceftriaxone)
  • Fourth-generation cephalosporins
  • Quinolones
  • Carbapenems (e.g., meropenem 1g every 8 hours) 2

For Carbapenem-Resistant K. aerogenes:

1. KPC-producing strains:

   • Ceftazidime/avibactam or meropenem/vaborbactam (strongly recommended) 1
   • Alternative options: imipenem/relebactam or cefiderocol 1

2. OXA-48-like producing strains:

   • Ceftazidime/avibactam 1

3. Metallo-β-lactamase (MBL) producing strains:

   • Ceftazidime/avibactam plus aztreonam 1

4. For critically ill patients with healthcare-associated infections:

   • Meropenem 1g every 8 hours, OR

   • Doripenem 500mg every 8 hours, OR

   • Imipenem/cilastatin 1g every 8 hours 1

   • Carbapenem-sparing regimen options:

     • Ceftolozane/tazobactam 1.5g every 8 hours + metronidazole 500mg every 6 hours, OR
     • Ceftazidime/avibactam 2.5g every 8 hours + metronidazole 500mg every 6 hours 1

Special Considerations

For Intra-abdominal Infections:

• Follow the 2017 WSES guidelines for intra-abdominal infections, which recommend carbapenems or carbapenem-sparing regimens as outlined above 1

For Urinary Tract Infections:

• K. aerogenes is a common cause of nosocomial urinary tract infections, particularly in catheterized patients 3
• Treatment should target the respiratory chain components (NDH-2 and bd-terminal oxidases) which are critical for K. aerogenes metabolism in urine 4

For Endocarditis:

• Combination therapy with a third-generation cephalosporin and an aminoglycoside (gentamicin or amikacin) is recommended 1
• Surgical intervention may be necessary, especially for left-sided endocarditis 1

Management of Multidrug-Resistant (MDR) Strains

For MDR K. aerogenes with limited treatment options:

• Consider combination therapy with more than one in vitro active antibiotic 1
• For polymyxin-susceptible strains, colistin in combination with carbapenem or rifampicin or tigecycline may be effective 5
• Avoid carbapenem-based combination therapy unless the meropenem MIC is ≤8 mg/L 1

Pitfalls and Caveats

1. Resistance development: K. aerogenes can rapidly develop resistance during treatment. Monitor susceptibility testing throughout therapy.

2. Capsular protection: The organism's thick capsule makes it difficult to treat, necessitating adequate drug concentrations at the infection site 2

3. Infection control: Hand hygiene and barrier nursing are critical to prevent nosocomial spread, as K. aerogenes can persist on skin surfaces including hands, knees, and groins 3

4. Surgical site infections: For surgical site infections (e.g., after rhinoplasty), bacterial culture and sensitivity testing are essential for targeted therapy 6

5. Emergence of ceftazidime/avibactam resistance: Monitor for resistance development, which can range from 0% to 12.8% in KPC-producing isolates 1

By following this evidence-based approach to treating K. aerogenes infections, clinicians can optimize outcomes while managing the challenges posed by antimicrobial resistance.