[Colimycin: an old antibiotic which has to be learnt to know]

Area of Science:

• Microbiology
• Pharmacology
• Infectious Diseases

Context:

• Increasing prevalence of multidrug-resistant (MDR) Gram-negative bacteria, including Pseudomonas aeruginosa, Acinetobacter baumanii, and Enterobacteriaceae.
• Resistance to last-resort antibiotics like carbapenems, quinolones, and aminoglycosides necessitates alternative treatment strategies.
• Historical challenges with colimycin, including poor clinical efficacy and significant toxicity (nephrotoxicity, neurotoxicity), led to its previous abandonment.

Purpose:

• To re-evaluate the clinical utility of colimycin in treating infections caused by MDR Gram-negative pathogens.
• To outline appropriate usage guidelines for colimycin, emphasizing susceptibility testing and combination therapy.
• To address the complexities surrounding colimycin's administration and dosing in light of its pharmacokinetic profile.

Summary:

• Colimycin, an older antibiotic, is being reconsidered due to the rise of pan-resistant bacteria.
• Its use is restricted to infections where pathogens are resistant to other agents but susceptible to colimycin, confirmed by in vitro testing.
• Combination therapy is crucial to prevent rapid resistance development; monotherapy is strongly discouraged.
• High dosages are required due to low serum concentrations relative to minimum inhibitory concentrations (MICs).

Impact:

• Provides critical guidance for clinicians managing difficult-to-treat MDR Gram-negative bacterial infections.
• Highlights the importance of susceptibility testing and strategic antibiotic selection in the era of antimicrobial resistance.
• Contributes to the understanding and optimized use of colimycin as a potential last-line therapeutic option.