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Resolution of infectious parameters after antimicrobial therapy in patients with ventilator-associated pneumonia
P J Dennesen1, A J van der Ven, A G Kessels
1Department of Medical Microbiology, Medical Technology Assessment and Surgery, University Hospital Maastricht, Maastricht, The Netherlands.
Abstract:
Although recommended durations of antimicrobial therapy for ventilator-associated pneumonia (VAP) range from 7 to 21 d, these are not based on prospective studies and little is known about the resolution of symptoms after start of antibiotics. Resolution of these symptoms was investigated in 27 patients. VAP was diagnosed on clinical, radiographic, and microbiological criteria, including quantitative cultures of bronchoalveolar lavage. All patients received appropriate antibiotic therapy. Highest temperatures, leukocyte counts, Pa(O(2))/FI(O(2)) ratios, and semiquantitative cultures of endotracheal aspirates were recorded from start of therapy until Day 14. Resolution was defined as the first day that these parameters fulfilled the following definition: temperature < or = 38 degrees C, leukocytes < or = 10 x 10(9)/L, Pa(O(2))/FI(O(2)) ratio > or = 25 kPa, and no or +1 of bacterial growth of etiologic pathogens in cultures of endotracheal aspirate. VAP was caused by Enterobacteriaceae (n = 14), P. aeruginosa (n = 7), S. aureus (n = 6), H. influenzae (n = 3), and S. pneumoniae (n = 1). H. influenzae and S. pneumoniae were eradicated from tracheal aspirates, whereas Enterobacteriaceae, S. aureus, and P. aeruginosa persisted, despite in vitro susceptibility to antibiotics administered. Significant improvements were observed for all clinical parameters, most apparently within the first 6 d after start of antibiotics. Newly acquired colonization, especially with P. aeruginosa and Enterobacteriaceae, occurred in the second week of therapy. Six patients developed a recurrent episode of VAP, four of them with P. aeruginosa. Clinical responses to therapy for VAP occur within the first 6 d of therapy, endotracheal colonization with Gram-negative bacteria persists despite susceptibility to therapy, and acquired colonization usually occurs in the second week of therapy and frequently precedes a recurrent episode.
Insights
Clinical improvements in ventilator-associated pneumonia (VAP) appear within six days of antibiotic treatment. However, Gram-negative bacteria often persist in the airway, leading to new colonization and recurrent VAP, particularly in the second week of therapy.
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Pulmonology
Background:
- Current ventilator-associated pneumonia (VAP) treatment durations lack prospective study basis.
- Limited data exists on VAP symptom resolution following antibiotic initiation.
Purpose of the Study:
- To investigate the timeline of clinical symptom resolution in VAP patients receiving antibiotics.
- To identify patterns of microbial persistence and acquired colonization during VAP treatment.
Main Methods:
- Prospective study of 27 VAP patients diagnosed using clinical, radiographic, and microbiological criteria.
- Monitoring of temperature, leukocyte count, oxygenation (PaO2/FiO2), and endotracheal aspirate cultures for 14 days.
- Defined resolution based on specific thresholds for clinical and microbiological parameters.
Main Results:
- Significant clinical improvements observed within the first 6 days of antibiotic therapy.
- Enterobacteriaceae, S. aureus, and P. aeruginosa persisted in endotracheal aspirates despite antibiotic susceptibility.
- Acquired colonization, particularly with P. aeruginosa and Enterobacteriaceae, occurred in the second week, preceding recurrent VAP in some cases.
Conclusions:
- Clinical response to VAP therapy is evident within 6 days.
- Endotracheal colonization with Gram-negative bacteria persists despite susceptibility, highlighting treatment challenges.
- Acquired colonization in the second week is common and can lead to recurrent VAP episodes.