Distribution and composition of pathogenic bacteria causing bloodstream infections in a hospital and analysis of the value of MALDI-TOF MS in rapid identification of pathogenic bacteria
Objective To explore the types of pathogenic bacteria causing bloodstream infections in a hospital and the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF MS)technology in the rapid identification of pathogenic bacteria.Methods A total of 234 positive blood culture specimens from patients with bloodstream infections in our hospital from 2022 to 2023 were collected.The types of pathogenic bacteria isolated were identified and drug susceptibility tests were performed.The extract was directly identified by the combined method of density gradient centrifugation with cell separation solution(Percoll solution)(referred to as Percoll separation method)and sodium dodecyl sulfate(SDS)precipitation method and MALDI-TOF MS.The identification results were compared with traditional blood culture results to compare the identification efficiency of pathogenic bacteria by two different pretreatment methods combined with MALDI-TOF MS.Results Among the 234 positive blood culture specimens,the majority were mainly isolated from the gastroenterology ward(21.37％,50/234),followed by the respiratory ward(14.10％,33/234).A total of 234 pathogenic bacteria were isolated from 234 positive blood culture specimens,including 177 Gram-negative bacteria(75.64％)and 57 Gram-positive bacteria(24.36％).Among the Gram-negative bacteria,there were 103 strains of Escherichia coli(44.02％),accounting for the highest proportion,followed by 44 strains of Klebsiella pneumoniae(18.80％).Among the Gram-positive bacteria,there were 23 strains of Staphylococcus aureus(9.83％),accounting for the highest proportion,and the number of other strains was relatively small.The resistance rate of Escherichia coli to ampicillin/sulbactam,cefuroxime,ciprofloxacin,levofloxacin,cotrimoxazole,and gentamicin exceeded 50％.The resistance rate to piperacillin/tazobactam,meropenem,imipenem,and amikacin was less than 10％.The resistance rate of K.pneumoniae to cefuroxime and ciprofloxacin exceeded 50％.The resistance rate to piperacillin/tazobactam,meropenem,imipenem,and amikacin was less than 10％.There was a significant difference in the resistance rate of the two to ampicillin/sulbactam,cotrimoxazole,and gentamicin(P＜0.05),while there was no significant difference in the resistance rate to other antibiotics(P＞0.05).The resistance rate of S.aureus to penicillin G and others exceeded 50％,and the resistance rate to moxifloxacin and others was relatively low.No resistance to linezolid and vancomycin had been found.Compared with the traditional culture method,the accuracy rate of rapid identification by Percoll separation method combined with MALDI-TOF MS was 93.59％.The accuracy rate of identification results of Gram-negative bacteria was 94.92％,and the accuracy rate of identification results of Gram-positive bacteria was 89.47％.The accuracy rate of rapid identification by SDS precipitation method combined with MALDI-TOF MS was 76.5％.The accuracy rate of identification results of Gram-negative bacteria was 80.23％,and the accuracy rate of identification results of Gram-positive bacteria was 64.91％.The accuracy rate of rapid identification of pathogenic bacteria by Percoll separation method combined with MALDI-TOF MS was significantly higher than that by SDS precipitation method combined with MALDI-TOF MS.The differences in the identification accuracy rates of Gram-negative bacteria,Gram-positive bacteria,K.pneumoniae,and S.hominis were statistically significant(P＜0.05).Conclusion The positive specimens of bloodstream infection in our hospital were mainly isolated from the gastroenterology ward.E.coli and K.pneumoniae were the main pathogenic bacteria.The drug resistance monitoring showed different degrees of resistance to common antibiotics.The accuracy of rapid identification of pathogenic bacteria by Percoll separation method combined with MALDI-TOF MS was significantly better than that by SDS precipitation method,providing strong support for rapid and accurate clinical diagnosis of bloodstream infection.
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