[Microbiological characteristics of patients with severe burns caused by blast and application of meta- genomics next-generation sequencing in the detection of pathogenic microorganisms].

Abstract

Objective: To analyze the microbiological characteristics of patients with severe burns caused by blast in different periods and explore the application value of metagenomics next-generation sequencing (mNGS) in detecting pathogenic microorganisms. Methods: The retrospective observational study was applied. From June 13 to September 13, 2020, twenty-three patients (21 males and 2 females) with severe burns caused by blast who met the inclusion criteria were admitted to the Second Affiliated Hospital of Zhejiang University School of Medicine, with age of (64±5) years and total burn area of (86±14) % total body surface area. Abbreviated burn severity index (ABSI) score, revised Baux score, acute physiology and chronic health status evaluation (APACHE) Ⅱscore, and sequential organ failure assessment (SOFA) score were counted on admission. Within 7, 8-20 and 21-30 d after admission, the complications, infection source and distribution of pathogenic microorganisms in patients were recorded. The detection of pathogenic microorganisms was analyzed, and the difference in detection efficiency between microbial culture method and mNGS was compared. After admission, the infection of overall source distribution of pathogenic microorganisms in patients was analyzed, and the difference in detection efficiency between microbial culture method and mNGS was compared. Data were statistically analyzed with McNemar and Fisher exact probability test. Results: On admission, ABSI score, revised Baux score, APACHE Ⅱ score and SOFA score were (12.6±2.4), (91±22), (26±4), and (10.3±2.3) respectively. Within 7 d after admission, the main complications of patients were inhalation injury, septic shock, and hypoproteinemia. Patients were mainly infected with pathogenic microorganism on wound, blood stream, and lung. Within 8-20 d after admission, the incidence of septic shock was the highest. The incidence of inhalation injury was significantly lower than that of ≤7 d after admission (P<0.01), the main source of infection were wound, lung, and blood stream, and the incidence of wound and blood stream infection were significantly lower than that of ≤7 d after admission (P<0.01). Within 21-30 d after admission, the incidences of multiple organ failure and acute respiratory distress syndrome were low, the incidence of inhalation injury was significantly lower than that of ≤7 d after admission (P<0.01), and the incidence of septic shock was significantly lower than that of ≤7 d after admission (P<0.01) and 8-20 d after admission (P<0.01). There were only low bloodstream infections, and the incidence of wound infection was significantly lower than that of ≤7 d after admission (P<0.01) and 8-20 d after admission (P<0.05), and the incidences of lung and blood stream infection were significantly lower than those of ≤7 d after admission (P<0.01). Within ≤7 d after admission, gram-positive bacteria were mainly Staphylococcus aureus. Gram-negative bacteria were mainly Klebsiella pneumoniae and Stenotrophomonas maltophilia. The fungi contained only Candida. Within 8-20 d after admission, Staphylococcus aureus was mainly the gram-positive bacteria, and the detection rate of Enterococcus was significantly lower than that of ≤7 d after admission (P<0.01). Pseudomonas aeruginosa and Acinetobacter baumannii were the main gram-negative bacteria, and their detection rates were significantly lower than those of ≤7 d after admission (P<0.01).There was a new detection of Fusarium. Within 21-30 d after admission, Staphylococcus aureus was the mainly gram-positive bacteria, and the detection rates of Enterococcus and Bacillus were significantly lower than those of ≤7 d after admission (P<0.01). Pseudomonas aeruginosa and Acinetobacter baumannii were still the main gram-negative bacteria, and increased with the extension of time after admission. The detection rate of Pseudomonas aeruginosa was significantly higher than that of ≤7 d after admission (P<0.01) and 8-20 d after admission (P<0.01), and the detection rate of Acinetobacter baumannii was significantly higher than that of ≤7 d after admission (P<0.01). The detection rate of Klebsiella pneumoniae was significantly lower than those of ≤7 d after admission (P<0.01) and 8-20 d after admission (P<0.01). All Candida, Mould, Fusarium were detected. Within ≤7 d and 8-20 d, the consistency between mNGS and bacterial culture was high (κ=0.659, 0.596). Within 21-30 d after admission, the consistency between mNGS and bacterial culture was moderate (κ=0.407). In different time periods, the positive test rate of mNGS was basically constant, while that of microbial culture showed a decline with the extension time after admission. Five hundred and six strains of pathogenic microorganisms were isolated from wound, blood, sputum, and indwelling catheter, and Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae were the main pathogenic microorganisms. Pseudomonas aeruginosa and Acinetobacter baumannii were the most common in the wound samples, Klebsiella pneumoniae was more often seen in blood samples while Pseudomonas aeruginosa and Acinetobacter baumannii in sputum samples, and Acinetobacter baumannii in indwelling catheter samples were the most common. The detection rates of Pseudomonas aeruginosa in wound and sputum were significantly higher than those of blood (P<0.05 or P<0.01) and indwelling catheter (P<0.01), respectively. The consistency between the overall results of mNGS and microbial culture were moderate (κ=0.556). The consistency between mNGS and microbial culture was high in samples of blood and indwelling catheter (κ=0.631, 0.619), but those were moderate in sputum and wound (κ=0.558, 0.528). Conclusions: The most common infections of patients with severe burn caused by blast injury were wound infection and blood stream infection. With the extension of time after admission, the main pathogenic bacterial strains of patients changed from Staphylococcus aureus, Klebsiella pneumoniae, and Stenotrophomonas maltophilia to Acinetobacter baumannii and Pseudomonas aeruginosa. mNGS showed a higher positive rate of detecting pathogenic microorganisms than conventional microbial culture.