The aim of this study was to develop a rapid single-tube two-color flow cytometric method to distinguish between febrile bacterial and viral infections.

In this prospective comparative study, the quantitative flow cytometric analysis of CD35 and CD64 on isolated human leukocytes was obtained from 286 hospitalized febrile patients, of which 197 patients were found to have either a bacterial (n = 136) or viral (n = 61) infection. The data from infected patients was compared to 49 healthy controls and 23 patients in an inflammatory state.

We developed a flow cytometric marker for bacterial infections, defined as the two-color bacterial infection index (TC-BI-index), by incorporating the quantitative analysis of CD35 and CD64 on isolated neutrophils, monocytes, and B-lymphocytes, which displayed 90% sensitivity and specificity in distinguishing between microbiologically confirmed bacterial (n = 77) and viral infections (n = 61) within 45 min.

We propose that TC-BI-index test will be useful in assisting physicians to ascertain whether antibiotic treatment is required, thus limiting unnecessary antimicrobial usage.