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ABSTRACTTrimethoprim-sulfamethoxazole alone and combined with colistin was tested in vitroagainst six carbapenem-resistant Acinetobacter baumannii(CRAB) clinical strains. After 24 h, at achievable serum concentrations, trimethoprim-sulfamethoxazole effectively killed all strains, while colistin killed only one strain. Trimethoprim-sulfamethoxazole plus colistin rapidly killed all strains after 6 h and for up to 24 h. Trimethoprim-sulfamethoxazole, one of the few remaining antimicrobials that still has a degree of activity, particularly combined with colistin, might represent an effective therapy for severe CRAB infections.

The aim of this study was to identify risk factors for tracheobronchial acquisition with the most common resistant Gram-negative bacteria in the intensive care unit ICU during the first week after intubation and mechanical ventilation. Tracheobronchial and oropharyngeal cultures were obtained at admission, after 48 hours, and after 7 days of mechanical ventilation. Patient characteristics, interventions, and antibiotic usage were recorded. Among 71 eligible patients with two negative bronchial cultures for resistant Gram-negative bacteria at admission and within 48 hours, 41 58 acquired bronchial resistant Gram-negative bacteria by day 7. Acquisition strongly correlated with presence of the same pathogens in the oropharynx: Acinetobacter baumanniiodds ratio OR20·2, 95 confidence interval CI: 5·5–73·6, Klebsiella pneumoniaeOR8·0, 95 CI: 1·9–33·6, and Pseudomonas aeruginosaOR27, 95: CI 2·7–273. Bronchial acquisition with resistant K. pneumoniaealso was associated with chronic liver disease OR3·9, 95 CI: 1·0–15·3, treatment with aminoglycosides OR4·9, 95 CI: 1·4–18·2, tigecycline OR4·9, 95 CI: 1·4–18·2, and linezolid OR3·9, 95 CI: 1·1–15·0. In multivariate analysis, treatment with tigecycline and chronic liver disease were independently associated with bronchial resistant K. pneumoniaeacquisition. Our results show a high incidence of tracheobronchial acquisition with resistant Gram-negative microorganisms in the bronchial tree of newly intubated patients. Oropharynx colonization with the same pathogens and specific antibiotics use were independent risk factors.