Differential Diagnosis And Prognosis Analysis Of NGAL And NLR In Severe Pneumonia Infected By Gram-negative Bacteria

Objective1.To explore the value of neutrophil gelatinase-associated lipocalin(NGAL)and neutrophil to lymphocyte ratio(NLR)in early differential diagnosis and prognosis of severe pneumonia caused by different gram-negative bacteria.2.To explore the difference in the expression of NGAL and lactic acid when Klebsiella pneumoniae and Acinetobacter baumannii infect lung epithelial cells,and further explore whether lactic acid affects the expression of NGAL under the stimulation of lipopolysaccharide(LPS).Methods1.A total of 98 patients with severe pneumonia infected by gram-negative bacteria who were admitted to the Second Affiliated Hospital of Anhui Medical University from August 2021 to August 2022 and 50 healthy patients who were examined in the hospital at the same time were selected as the research objects.According to the classification of bacterial culture,the patients with severe pneumonia infected by gram-negative bacteria were divided into enterobacteria group(51 cases),non-fermentative bacteria group(47cases)and healthy control group(50 cases);The patients were divided into poor prognosis group(38 cases)and good prognosis group(60 cases)according to whether they improved after 28 days of treatment.Enzyme-linked immunosorbent assay(ELISA)was used to detect the serum NGAL level of the three groups of people,and to detect the whole blood cell count level of the three groups of subjects,and to collect general data such as age and sex of the three groups of people.2.A549 cells were infected with different concentrations of k.pneumoniae standard strain ATCC43816 and A.baumannii standard strain ATCC19606 for 3h respectively,and the cell proliferation was detected by CCK-8 method to determine the optimal number of bacterial infected cells.3.K.pneumoniae and A.baumannii with multiplicity of infection value of 50 were used to infect A549 cells,and the m RNA expression level of NGAL was detected by q RT-PCR.4.K.pneumoniae and A.baumannii with multiplicity of infection value of 50 were used to infect A549 cells,and the expression level of lactic acid was detected by micromethod.5.A549 cells were stimulated with 0,1,2,4,8,16,and 32 m M lactic acid and 0,5,10,and 15 LPS,respectively.The cell proliferation was detected by CCK-8 method to determine the appropriate concentration of stimulating cells.6.A549 cells were stimulated with 5μg/ml LPS and co-cultured with 0,1,2,4,8and 16 m M lactic acid.The m RNA expression level of NGAL was detected by q RT-PCR.Results1.There was a significant difference in NGAL and NLR levels between the enterobacteria group,the non-fermentative bacteria group and the healthy control group(P<0.05).ROC curve analysis showed that the area under the curve(AUC)values of NGAL was 0.792(95%CI:0.703～0.881,P<0.05).NGAL and NLR levels in patients with poor prognosis were higher than those in patients with greater prognosis(P<0.05).The area under the ROC curve(AUC)of NGAL and NLR and the combination of the two indicators were NGAL: 0.702(95% CI: 0.590～0.814),NLR: 0.707(95% CI:0.604～0.811),respectively.When the two indicators were combined,AUC: 0.758(95% CI: 0.66～0.856),the difference was statistically significant(P<0.05).2.CCK-8 method showed that the optimal multiple MOI of A549 concentration infected by K.pneumoniae and A.baumannii was 50:1.3.The expression of NGAL m RNA in pulmonary epithelial cells infected by K.pneumoniae was higher than that in pulmonary epithelial cells infected by A.baumannii.4.The expression of lactic acid in K.pneumoniae infected lung epithelial cells was higher than that in A.baumannii infected lung epithelial cells.5.When the concentration of lactic acid was 4m M and 8m M,the expression level of NGAL m RNA in lactic acid increased in the environment of LPS-stimulated A549 cells.Conclusion NGAL can be used to early distinguish between patients with severe pneumonia infected with enterobacteria and non-fermentative bacteria.In addition,NGAL and NLR have some usefulness in assessing the prognosis of patients with severe pneumonia who are infected with gram-negative bacteria.After K.pneumoniae and A.baumannii infected lung epithelial cells,there was a difference in NGAL and lactic acid,and lactic acid affected the expression of NGAL.