UTILITY OF STREM-1 BIOMARKER AND HCP GENE FOR IDENTIFICATION OF ACINETOBACTER BAUMANNII COLONIZATION AND INFECTION IN LUNG

Objective: Respiratory infections or colonization of Acinetobacter baumannii (Ab) are common in clinical practice but are treated differently. Early identification of Ab infection and colonization reduces the risk of antibiotic mismatch but objective laboratory indicators to distinguish between bacterial infections and colonization are lacking. To distinguish infection and colonization of Ab, we tested the role of two biomarkers, triggering receptor expressed on myeloid cells-1 (TREM-1) and hemolysin coregulated protein. Methods: A total of 96 inpatients with Ab were divided into infection and colonization groups. Blood samples were collected on days 1, 2, 3, 5, 8, and 10 and daily maximum body temperature was recorded. Polymerase Chain Reaction and Reverse Transcription Polymerase Chain Reaction were used to detect the presence and expression levels of the hcp gene in Ab clinical isolates. Results: sTREM-1 and procalcitonin (PCT) levels on days 1 to 10 and neutrophil classification (N%) on days 1 to 3 were different (P < 0.05) in the infection group and colonization group. Receiver operating characteristic (ROC) curves showed significant differences in N% and sTREM-1 on days 2 and 3 (P < 0.01). sTREM-1 had the highest AUC(ROC) on days 1, 2, and 3 of all the markers. On day 1, the ROC curve of “WBC&N%&PCT&sTREM-1” was statistically different from individual indices (white blood cell count, N%, and PCT; P < 0.05) and was equal to the ROC curve of sTREM-1 (P > 0.05). Thirty five of 96 patients were classified as infection group and 61 as colonization group with hcp gene detection rates of 71.43% (25/35) and 31.15% (19/61), respectively. No differences in hcp gene presence and transcript levels were found between two groups (P > 0.05). Conclusions: Dynamic monitoring of sTREM-1 and PCT is valuable in identifying Ab infection and colonization. sTREM-1 can be improved by combination with multiple biomarkers in the early stage for identification of infection and colonization. The hcp gene was more likely to be present in the infection cohort.