The Application Value Of Next-generation Sequencing In Pathogenic Microorganisms Of Blood Samples

Research backgroundInfection has become one of the leading causes of death in all sick populations worldwide.Metagenomic next generation sequencing(mNGS)has the advantages of rapid detection and high accuracy.Patients with hematological diseases and critically ill areas often have factors such as thrombocytopenia and abnormal coagulation.For patients with CO infection,the risk of retaining samples by invasive operation is high,and the results of oral sputum,urine and stool samples are inaccurate due to many contaminating bacteria and colonizing bacteria.However,there are few studies on the detection value of mNGS in blood samples,especially in people with organ dysfunction and immunosuppression.ObjectiveTo explore the application value of mNGS technology in blood samples from patients with severe and blood disease infection.Research methods94 patients with infection in EICU of the Third Affiliated Hospital of Southern Medical University and the Hematology Department of Panyu Central Hospital from May 2020 to November 2021 were analyzed retrospectively.The characteristics of mNGS detection and traditional detection in various clinical specimens of 94 patients were analyzed.The blood samples of 84 patients who met the screening conditions were further analyzed by mngs detection and traditional culture methods.Research resultsIn the study,there were 220 traditional samples and 116 mNGS samples,including peripheral blood,alveolar lavage fluid,urine,sputum and other samples.There was significant difference between traditional detection and mNGS positive rate(21.8%vs 72.4%,P<0.001).The rates of blood culture and mNGS were 42%and 71%respectively,and there was significant difference in the positive rate between the two groups(15.1%vs 65.9%,P<0.001).14 strains and 7 species of pathogens were detected in blood culture;99 strains and 38 species of pathogens were detected by mNGS.The time for blood culture to report positive was 72 hours,the time for negative report was 7 days,and the time for mNGS to obtain results was 24 hours.Both tests were positive in 10 cases,of which 1 case was completely consistent with the pathogen,6 cases were partially consistent,and 3 cases were completely inconsistent.According to the results of mNGS,the improvement rate of anti-infective regimen was 52.3%;the improvement rate of empirical anti-infective treatment was 12.5%,and there was a statistical difference between them(P=0.001).There was no significant difference in mNGS positive rate between immunosuppressed and non-immunosuppressed patients(62.7%vs 71.0%,P=0.446),but the fungal detection rate in immunosuppressed patients was higher than that in non-immunosuppressed patients(22.0%vs 2.1%,P=0.003).There was also no significant difference in traditional blood culture between immunosuppressive and non-immunosuppressive patients(32.8%vs 33.3%,P=0.957).Univariate analysis of the influencing factors of mNGS detection showed no positive results.Conclusion1.Among the commonly used clinical samples,the positive rate of mNGS detection is high.In patients with coagulation dysfunction and thrombocytopenia,due to the limitation of invasive operation in the process of collecting clinical samples and the influence of colonization bacteria in sputum,urine and stool samples,blood samples have become the first choice for mngs detection.2.The mNGS in blood samples has advantages in terms of the positive rate of pathogens and the breadth of species.It is more meaningful for patients with special pathogens and mixed infections.The detection efficiency of mNGS is better than that of traditional blood culture.3.For patients with negative traditional pathogen detection,using mNGS detection and adjusting the treatment plan according to their detection results can improve the efficacy.4.There was no significant difference in the positive rate of mNGS and traditional culture in blood samples of patients with different immune status,but fungal infection was easy to occur in immunosuppressed patients.5.mNGS results are not affected by multiple clinical factors.