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Low Efficacy of Antibiotics Against Staphylococcus aureus Airway Colonization in Ventilated Patients
Lukas Stulik1,2, Jana Hudcova3, Donald E Craven4
1Arsanis Biosciences GmbH, Vienna, Austria.
Background:
Airway-colonization by Staphylococcus aureus predisposes to the development of ventilator-associated tracheobronchitis (VAT) and ventilator-associated pneumonia (VAP). Despite extensive antibiotic treatment of intensive care unit patients, limited data are available on the efficacy of antibiotics on bacterial airway colonization and/or prevention of infections. Therefore, microbiologic responses to antibiotic treatment were evaluated in ventilated patients.
Methods:
Results of semiquantitative analyses of S. aureus burden in serial endotracheal-aspirate (ETA) samples and VAT/VAP diagnosis were correlated to antibiotic treatment. Minimum inhibitory concentrations of relevant antibiotics using serially collected isolates were evaluated.
Results:
Forty-eight mechanically ventilated patients who were S. aureus positive by ETA samples and treated with relevant antibiotics for at least 2 consecutive days were included in the study. Vancomycin failed to reduce methicillin-resistant S. aureus (MRSA) or methicillin-susceptible S. aureus (MSSA) burden in the airways. Oxacillin was ineffective for MSSA colonization in approximately 30% of the patients, and responders were typically coadministered additional antibiotics. Despite antibiotic exposure, 15 of the 39 patients (approximately 38%) colonized only by S. aureus and treated with appropriate antibiotic for at least 2 days still progressed to VAP. Importantly, no change in antibiotic susceptibility of S. aureus isolates was observed during treatment. Staphylococcus aureus colonization levels inversely correlated with the presence of normal respiratory flora.
Conclusions:
Antibiotic treatment is ineffective in reducing S. aureus colonization in the lower airways and preventing VAT or VAP. Staphylococcus aureus is in competition for colonization with the normal respiratory flora. To improve patient outcomes, alternatives to antibiotics are urgently needed.
Insights
Antibiotic treatment fails to clear Staphylococcus aureus airway colonization or prevent ventilator-associated pneumonia (VAP) in intensive care unit patients. New strategies are needed to combat these infections and improve patient outcomes.
Area of Science:
- Critical Care Medicine
- Infectious Diseases
- Microbiology
Background:
- * Staphylococcus aureus colonization in airways increases risk for ventilator-associated tracheobronchitis (VAT) and pneumonia (VAP).
- * Limited data exist on antibiotic efficacy against bacterial colonization and infection prevention in ventilated patients.
Purpose of the Study:
- * To evaluate the microbiologic responses to antibiotic treatment in ventilated patients colonized with Staphylococcus aureus.
- * To assess the effectiveness of antibiotics in reducing S. aureus burden and preventing VAT/VAP.
Main Methods:
- * Semiquantitative analysis of S. aureus in serial endotracheal aspirate (ETA) samples.
- * Correlation of S. aureus burden with VAT/VAP diagnosis and antibiotic treatment.
- * Evaluation of minimum inhibitory concentrations (MICs) of antibiotics against serially collected S. aureus isolates.
Main Results:
- * Vancomycin was ineffective against both MRSA and MSSA airway colonization.
- * Oxacillin failed in approximately 30% of MSSA cases, often requiring co-administration of other antibiotics.
- * Despite appropriate antibiotic treatment, ~38% of patients progressed to VAP.
- * No changes in S. aureus antibiotic susceptibility were observed during treatment.
- * S. aureus colonization inversely correlated with normal respiratory flora presence.
Conclusions:
- * Current antibiotic regimens are ineffective for reducing S. aureus lower airway colonization and preventing VAT/VAP.
- * Staphylococcus aureus competes with normal respiratory flora for colonization.
- * Alternative therapeutic strategies beyond antibiotics are urgently required to improve patient outcomes.
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