Diagnostic value of mNGS on Gram-negative bacteria in alveolar lavage fluid of patients with lower respiratory tract infections

Zhai Cuijuan; Cao Huifang

doi:10.3969/j.issn.1674-3245.2025.03.015

Abstract：Objective To explore the diagnostic value of metagenomic next-generation sequencing(mNGS)on Gram-negative bacteria in bronchoalveolar lavage fluid(BALF)of patients with lower respiratory tract infections(LRTIs).Methods The clinical data of 148 patients with nosocomial LRTIs who received alveolar lavage in the hospital were retrospectively analyzed from March 2020 to February 2022.All patients underwent mNGS detection of BALF samples,traditional pathogenic microorganism culture and drug sensitivity test.Traditional microbial culture served as the gold standard.The diagnostic performance of mNGS for Gram-negative bacteria was evaluated using Kappa consistency analysis.According to the diagnostic results of Gram-negative bacteria,the study subjects were divided into negative group and positive group.Baseline characteristics and laboratory hematological parameters were compared between the two groups.The detection rate of mNGS resistance genes and minimum inhibitory concentration(MIC)—based resistance phenotypes of the most detected strains were recorded and detected,and the consistency of mNGS and gold standard resistance results was analyzed.Results 236 strains of pathogenic bacteria were detected in traditional pathogenic microorganism culture,including 85 cases(173 strains)of positive Gram-negative bacteria,among which Gram-negative bacteria Acinetobacter baumannii were the most in 36 cases(70 strains).227 strains of pathogenic bacteria were detected by mNGS detection,including 81 cases(168 strains)of positive Gram-negative bacteria,and the most Gram-negative bacteria were detected in 34 cases(67 strains)of Acinetobacter baumannii.Kappa consistency analysis showed that the sensitivity,specificity,accuracy rate and Kappa value of mNGS detection were 95.29％,93.94％,94.92％and 0.876 in the diagnosis of Gram-negative bacteria in BALF of nosocomial LRTIs patients,and were 94.44％,97.30％,95.89％and 0.918 in diagnosing the most detected Acinetobacter baumannii respectively.The levels of C-reactive protein(CRP)and procalcitonin(PCT)with(319.38±93.84)mg/L and(11.86±3.56)ng/ml in the positive group were higher than(104.15±32.71)mg/L and(1.78±0.48)ng/ml in the negative group(tCRP=12.847,tPCT=16.167,P＜0.05).The phenotypes of drug resistance genes detected in Acinetobacter baumannii mNGS were β-lactamases,of which OXA-23 was the most prevalent phenotype(47.76％,32/67).The Kappa value of the resistance phenotypes of imipenem resistance genes OXA-23 and OXA-58 with traditional pathogenic microorganism culture was 0.914,and the Kappa value of resistance phenotypes of penicillin and cephalosporin resistance genes TEM,IMP and PER-1 was 0.805 in traditional pathogenic microorganism culture.Conclusion mNGS has high diagnostic efficiency in the diagnosis of Gram-negative bacteria in BALF of patients with nosocomial LRTIs,and has a certain correlation with the laboratory hematological detection indicators of patients.It can better predict the drug resistance phenotypes of Acinetobacter baumannii,and has important application value on guiding clinical disease diagnosis and medication guidance.