Evaluation And Prognostic Analysis Of Different Pretreatments Combined With MALDI-TOF MS For Rapid Identification Of Pathogenic Bacteria In Blood Culture

Part 1 Application of different pretreatments in the direct identification of pathogenic bacteria in positive blood culture by MALDI-TOF MS Objective:To evaluate the feasibility of combining MALDI-TOF MS(matrix-assisted laser desorption/ionization-time of flight mass spectrometry)for direct identification of blood-culture-positive pathogens after pretreatment with different methods.To evaluate whether there are differences in the accuracy of identification of different pathogens by different methods.Methods:Randomly collect positive blood culture bottles from the Microbiology Room of the Laboratory Department of Northern Jiangsu People’s Hospital from June to October2020,and use the separation gel method and the 5% SDS(sodium dodecyl sulfate)method to pre-process the samples and combine them MALDI-TOF MS directly identifies pathogens,and compares traditional blood culture bacterial identification methods to evaluate the accuracy of the two pretreatment methods for identifying pathogens in blood culture.Results:A total of 161 blood culture positive specimens were collected.The coincidence rates of the gel separation method,5% SDS method with the traditional blood culture identification method were 83.23% and 72.67%,respectively.There was a statistically significant difference in the accuracy of the two kinds of pretreatment identification bacteria(?2=5.98,P<0.05),separating gel method of gram-positive bacteria identification accuracy is 82.54%,significantly higher than that of 5%SDS method(66.67%),difference was statistically significant(?2=4.19,P<0.05),separating gel method,5%SDS method of gram-negative bacteria identification accuracy were 83.67% and 76.53%respectively,there was no statistically significant difference(?2=1.57,P>0.05).There was no statistically significant difference between the two methods in the identification of gram-negative bacteria and gram-positive bacteria(?2=0.35,P>0.05;?2=1.87,P>0.05).Separating gel method of aerobe identification accuracy is significantly higher than 5%SDS method,statistical differences(?2= 5.98,P< 0.05).Conclusion:The two pretreatments combined with MALDI-TOF MS can quickly and accurately identify pathogenic bacteria in positive blood culture samples,and the identification time is within 3h,which can significantly shorten the identification time compared with the traditional bacterial identification process.For the identification of gram-positive bacteria and bacteria in aerobic blood culture flask,the separation gel pretreatment method is better than 5%SDS method.Part 2 Analysis of characteristics and prognosis of 132 pathogenic bacteria infected with bloodstream infection Objective:To explore the characteristics of bloodstream infection pathogens isolated clinically in our hospital,and to explore the factors affecting the outcome of bloodstream infection patients.Methods:Cultivation and identification of 132 pathogenic bacteria isolated clinically in our hospital,collect clinical data(including age,gender,department,CRP value,PCT value,invasive operation,etc.)of patients with related bloodstream infections,according to the survival of 30 d end divided the patients into survival group and death group,the characteristics of the 132 strains of clinical isolated pathogenic bacteria were retrospectively analyzed and the factors influencing prognosis of patients with outcome.Results:1.Among the 132 bloodstream infection pathogens,81 gram-negative bacteria accounted for about 61.36%,50 gram-positive bacteria accounted for about 37.88%,and 1 fungus accounted for about 0.76%.Most of the pathogenic bacteria were isolated from ICU,gastroenterology,respiratory Internal medicine,emergency department,etc.2.The median TTP(time to positivity)of gram-negative bacteria was 12.3h,the median time of TTP for gram-positive bacteria was 24.0h.The results of Mann-Whitney U test showed a statistically significant difference in TTP between them(Z=-5.434,P<0.001),the results of Kruskal-Wallis H test showed that there was a statistical difference in TTP among different genera(H=32.539,P<0.001).3.Multiple linear regression analysis showed that endotracheal intubation,PCT had statistically significant effects on TTP(P<0.05).4.The prognosis of the patients was analyzed by univariate analysis,and the secondary bloodstream infection(?2=6.188,P=0.013),CRP(?2=10.406,P=0.001), endotracheal intubation(?2=19.579,P<0.001),catheters or gastric tubes(?2=16.674, P<0.001),CVP(?2=10.110,P=0.001),arterial blood pressure monitoring(?2=5.134, P=0.023),PICCO(?2=6.125,P=0.013)the difference between the survival group and the death group was statistically significant.Further multivariate stepwise logistic regression analysis of the above variables showed the secondary bloodstream infection(OR=4.056,95%CI=1.046~15.725,P=0.043),CRP(OR=4.152,95%CI=1.327~12.988,P=0.014),endotracheal intubation(OR=3.834,95%CI=1.269~11.586,P=0.017),catheters or gastric tubes(OR=6.777,95%CI=2.124~21.618,P=0.001) was an independent risk factor for death in patients with bloodstream infection(P<0.05).5.The ROC curve of secondary BSI,CRP,endotracheal intubation and catheters or gastric tubes for predicting the death of patients with bloodstream infection showed that the AUC=0.861,95%CI=0.781~0.941,the sensitivity was 82.80%,and the specificity was 75.30%.Conclusion:There are differences in TTP among different types of bacteria.The secondary bloodstream infection,some invasive procedures and CRP are independent risk factors for death of patients with bloodstream infection.These indicators can provide early warning information for clinicians in time.