Ventilator-associated pneumonia due to colistin susceptible-only microorganisms

Area of Science:

• Infectious Diseases
• Critical Care Medicine
• Antimicrobial Resistance

Background:

• Acinetobacter spp. and Pseudomonas aeruginosa are leading causes of ventilator-associated pneumonia (VAP).
• Treatment strategies for VAP are challenged by evolving antimicrobial resistance patterns.
• Understanding differences between carbapenem-susceptible (Carb-S) and colistin-only-susceptible (Col-S) VAP is crucial for effective management.

Purpose of the Study:

• To compare the clinical presentation and outcomes of VAP caused by Carb-S versus Col-S Acinetobacter spp. and P. aeruginosa.
• To identify predictors associated with Col-S VAP compared to Carb-S VAP.

Main Methods:

• Retrospective study involving 61 episodes of VAP in three intensive care units.
• Isolates were categorized as Carb-S (susceptible to imipenem and/or meropenem) or Col-S (susceptible to colistin only).
• Univariate and multivariate analyses were performed to compare patient demographics, clinical course, and identify VAP predictors.

Main Results:

• No significant differences were observed in demographics, renal function changes, or mortality between Carb-S and Col-S VAP groups.
• Multivariate analysis identified prior antimicrobial therapy exceeding 10 days and a previous VAP episode as significant predictors of Col-S VAP.
• Approximately 41% of Col-S VAP cases had received prior carbapenem therapy, unlike Carb-S VAP cases.

Conclusions:

• Colistin is an effective treatment for Col-S VAP, with no significant renal dysfunction observed.
• A history of previous VAP or prolonged prior antibiotic therapy (>10 days) may indicate a higher likelihood of Col-S VAP.
• These findings support targeted antibiotic selection based on VAP history and resistance patterns.