Abstract
The positive detection rate of blood metagenomic next-generation sequencing (mNGS) was still too low to meet clinical needs, while pus from the site of primary infection may be advantageous for identification of pathogens. To assess the value of mNGS using pus in patients with sepsis, thirty-five samples were collected. Pathogen identification and mixed infection diagnosis obtained by use of mNGS or cultivation methods were compared. Fifty-three aerobic or facultative anaerobes, 59 obligate anaerobes and 7 fungi were identified by the two methods. mNGS increased the accuracy rate of diagnosing aerobic or facultative anaerobic infections from 44.4% to 94.4%; mNGS also increased the sensitivity of diagnosing obligate anaerobic infections from 52.9% to 100.0%; however, mNGS did not show any advantage in terms of fungal infections. Culture and mNGS identified 1 and 24 patients with mixed infection, respectively. For obligate anaerobes, source of microorganisms was analyzed. The odontogenic bacteria all caused empyema (n = 7) or skin and soft tissue infections (n = 5), whereas the gut-derived microbes all caused intra-abdominal infections (n = 7). We also compared the clinical characteristics of non-obligate anaerobic and obligate anaerobic infection groups. The SOFA score [9.0 (7.5, 14.3) vs. 5.0 (3.0, 8.0), P = 0.005], procalcitonin value [4.7 (1.8, 39.9) vs. 2.50 (0.7, 8.0), P = 0.035], the proportion of septic shock (66.7% vs. 35.3%, P = 0.044) and acute liver injury (66.7% vs. 23.5%, P = 0.018) in the non-obligate anaerobic infection group were significantly higher than those in the obligate anaerobic infection group. In patients with sepsis caused by purulent infection, mNGS using pus from the primary lesion may yield more valuable microbiological information.