title: Bacterial colonization patterns in mechanically ventilated patients with traumatic and medical head injury. Incidence, risk factors, and association with ventilator-associated pneumonia.
abstract: We prospectively evaluated the relation of upper airway, lower airway, and gastric colonization patterns with the development of pneumonia and its etiology in 48 patients with surgical (n = 25) and medical (n = 23) head injury. Initial colonization was assessed by cultures of nasal and pharyngeal swabs, tracheobronchial aspirates, gastric juice, and bronchoscopically retrieved protected specimen brush. Follow-up colonization was determined until the end points extubation, suspected ventilator-associated pneumonia (VAP), or death. The initial colonization rate at any site at ICU admission was 39/47 (83%). It mainly accounted for Group I pathogens (Streptococcus pneumoniae, Staphylococcus aureus, Hemophilus influenzae) of the upper and lower airways. At follow-up, colonization rates with Group II pathogens (Gram-negative enteric bacilli and Pseudomonas spp.) increased significantly. The high initial bacterial load with Group I pathogens of the upper airways and trachea decreased during Days 2 to 4, whereas that of Group II pathogens increased. Upper airway colonization was an independent predictor of follow-up tracheobronchial colonization (odds ratio [OR], 9.9; 95% confidence interval [CI], 1.8 to 56.3 for initial colonization with Group I pathogens; OR, 23.9; 95% CI, 3.8 to 153.3 for follow-up colonization with Group II pathogens). Previous (short-term) antibiotics had a protective effect against colonization with Group I pathogens of the lower respiratory tract (OR, 0.2; 95% CI, 0.05 to 0.86), but they were a risk factor for colonization with Group II pathogens (OR, 6.1; 95% CI, 1.3 to 29). Initial tracheobronchial colonization with Group I pathogens was associated with a higher probability of early onset pneumonia (OR, 4. 1; 95% CI, 0.7 to 23.3), whereas prolonged antibiotic treatment (> 24 h) independently predicted late-onset pneumonia (OR, 9.2; 95% CI, 1.7 to 51.3). We conclude that patients with head injury are colonized in the airways mainly by Group I pathogens early in the evolution of illness. The upper airways represent the main reservoir for subsequent lower airway colonization with Group I pathogens. Previous (short-term) antibiotic treatment is protective against initial tracheobronchial colonization with Group I pathogens, but it represents a risk factor for subsequent lower airway colonization by Group II pathogens.
authors.affiliation: Servei de Pneumologia i Al.lergia Respiratoria, Area de Vigilancia Intensiva, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Ewig
authors.forename: A
authors.initials: A
authors.lastname: Torres
authors.forename: M
authors.initials: M
authors.lastname: El-Ebiary
authors.forename: N
authors.initials: N
authors.lastname: Fábregas
authors.forename: C
authors.initials: C
authors.lastname: Hernández
authors.forename: J
authors.initials: J
authors.lastname: González
authors.forename: J M
authors.initials: JM
authors.lastname: Nicolás
authors.forename: L
authors.initials: L
authors.lastname: Soto
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001419:Bacteria / Q000254:growth & development*; D015169:Colony Count, Microbial; D006259:Craniocerebral Trauma / Q000382:microbiology* / Q000628:therapy*; D005260:Female; D015600:Glasgow Coma Scale; D006257:Head / Q000601:surgery*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000453:epidemiology / Q000209:etiology / Q000382:microbiology; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000009:adverse effects*; D012137:Respiratory System / Q000382:microbiology; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents