[The clinical significance of Aspergillus isolation from airway samples in critically ill patients]

To analyze the risk factors and clinical significance of Aspergillus isolation from airway samples of critically ill patients.

The study was conducted in an ICU between January 2007 and December 2007. The data of patients receiving mechanical ventilation with suspected invasive pulmonary fungal infection were analyzed. Tracheal aspirates were collected and cultured 3 times weekly. The cases were classified into groups of Aspergillus spp, Candida spp, and non-fungus spp according to the microbiological results. Isolation of Aspergillus spp. was subgrouped to proved-IPA (invasive pulmonary aspergillosis), probable-IPA or colonization. The risk factors for airway isolation of Aspergillus and infection were assessed. Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) for Windows (version 12.0) and quantitative variables were expressed as mean +/- standard deviation. The Student' s t-test or the Mann-Whitney U-test was used for the comparison of categorical and normally distributed and non normally distributed variables, respectively. The chi2 test or the Fisher's exact test was used in the comparison of categorical variables. Logistic regression analysis was conducted to evaluate risk factors for the isolation of Aspergillus spp.

The study population included 160 patients (82 men) with a mean age of (64.5 +/- 17.2) years. Aspergillus spp was isolated in 45, Candida spp in 63, and non-fungus spp in 52. The ICU mortality in the 3 groups was 48.9% (22/45 cases), 23.8% (15/63 cases), 7.7% (4/52 cases), respectively. The ICU mortality in patients with Aspergillus spp. isolation was higher than those with Candida spp and non-fungus spp. In 28 patients isolation of Aspergillus spp. was interpreted as invasive aspergillosis (2 patients were proven, 26 patients were probable). The predictive value of isolating Aspergillus from airway samples was 62% (28/45 cases). On multivariate analysis, the following factors were independently associated with Aspergillus spp. isolation: connective tissue diseases (OR 3.3, 95% CI 1.7 - 12.2, chi2 = 4.82, P<0.01), hepatic dysfunction (OR 8.1, 95% CI 1.7 - 15.2, chi2 = 19.2, P<0.01), corticosteroid use (OR 4.6, 95% CI 2.6 - 13.7, chi2 = 8.92, P<0.01) and continuous renal replacement therapy (CRRT) (OR 5.1, 95% CI 2.6 - 11.5, chi2 = 11.4, P<0.01). Higher APACHE II score (25 +/- 6, 14 +/- 8, t = 2.75, P<0.01), septic shock (57%, 27%, chi2 = 3.56, P<0.01), and prolonged use of broad-spectrum antibiotics (15.9 d, 9.2 d, t = 2.49, P<0.01) were significantly associated with Aspergillus infection as compared to colonization.

Critically ill patients with Aspergillus from airway samples had a higher mortality. Connective tissue diseases, hepatic dysfunction, corticosteroid use and CRRT were significantly associated with Aspergillus spp. isolation in critically ill patients. In severely ill patients, the isolation of Aspergillus is highly indicative of infection rather than colonization.