Study On The Correlations Between Plasma Procalcitonin And Bloodstream Infection

Bloodstream infections include bacteremia and septicemia,had high incidence and mortality rates,are the results of releasing toxins and metabolites from pathogenic bacteria into the blood.Procalcitonin(PCT),a precursor of calcitonin,has a low concentration in the peripheral blood of healthy individuals.However,as bacterial infection occurs,the level of PCT in plasma will increase significantly.Currently,reports regarding PCT have been increased significantly,but the value of its clinical application remains controversial.The purpose of this study was to evaluate the levels of PCT in patients with bloodstream infection in different bacterial species including multidrug resistant strains and some common pathogenic bacteria.From January 2013 to December 2014,we recruited 1106 patients with bloodstream infection for this study.We measured the PCT level in plasma and then randomly selected 180 samples from patients with multiple drug resistant.The BacT/Alert3D480 blood culture system was used for blood culture,Vitek II automated microbial was applied to identify the bacteria(French bioMerieux company);whereas the unidentified bacteria was assessed by the time-of-flight mass spectrometry(German Bruker MicroFlex LT).The level of PCT in plasma was determined by the electrochemical luminescence method(ROCHE E601 German).Statistical analysis was performed using SPSS 17.0 software.Moreover,the drug resistant strains were identified by employing the WHONET 5.6 bacterial drug resistance monitoring software.Median(four quantile)[M(P25-P75)]for non-normal distribution data.Mann-Whitney U test was used to compare the difference of PCT values between the groups.The P<0.05 was considered as statistically significant.We also draw the receiver operating characteristic(ROC)curve to evaluate the diagnostic performance of plasma PCT level to identify the type of pathogenic bacteria in blood flow infection,and its diagnostic efficiency of multidrug resistant strains infection.Among these 1106 patients,there are 704 male,402 female,aged between 8 to 97 years,with an average of 57.30±16.57 years.In addition,there are 507 patients from 1106 cases with positive results of blood culture(53%from ICU).296 cases are Gram positive(G+)bacteria(58.38%),while there are 141 cases with Gram negative(G’)(27.81%).17 cases were Fungi(3.35%).The positive rate of plasma PCT in patients under G" bacterial infection was 62.41%(CUTOFF value:0.5μg/L for PCT).The positive rate of plasma PCT in patients carrying G+ bacterial and fungal infections were 36.82%and 47.06%,respectively.However,when there are two kinds of bacterial infection,the positive rate of PCT reached the highest(98.04%).Notably,the PCT levels in positive blood culture group were significantly higher when compared with blood culture negative group(U=71057.5,P =0.000).Significant difference in PCT levels were observed between the mixed infection group and the G+ bacterial infection group(U=5137.5,P=0.001).Among these 507 blood culture positive samples,PCT levels in patients with G-bacterial infection were 0.95(0.28-7.57)μg/L,PCT levels in patients with G+ bacterial infection were 0.26(0.09-1.18)μg/L.Fungal positive results were almost Candida albicans,of which 5 cases were mixed infection.Furthermore,the levels of PCT in G-bacteria infected patients were higher than those in G+ bacteria infected group(U=12817.50,P=0.000).But there was no significant difference in the levels of PCT between the either G+ or G-bacterial infection groups and the fungal infection group(P>0.05).The results of this study showed that the PCT value of the blood culture positive group was significantly higher than that of the blood culture negative group(U=94131.50,P==0.000),suggesting that PCT can be used as a biomarker for patients with bloodstream infections.Multiple drug resistance(MDR)analysis showed that the positive rate of PCT in patients with MDR bacterial infection was 66.67%,when compared with non MDR bacterial infection(U=9666.500,P=0.000).The positive rate of PCT in patients with bloodstream XDR bacterial infection was 69.74%,when compared with non-XDR bacterial infection(U= 9046.000,P = 0.000).Positive rate of PCT in 6 common pathogenic bacterium including Acinetobacter Bauman(aba),Escherichia coli(eco),Enterococcus faecium(efm),Klebsiella pneumoniae(kpn),Pseudomonas aeruginosa(pae),Staphylococcus aureus(sau)infection were 64.56%,57.14%,57.14%,71.43%,83.33%and 54.55%,respectively(χ2=31.840,P=0.000)· In the course of antimicrobial therapy,within the previous 7 days,there were significant differences in the levels of PCT in patients with MDR strains of infection and the PCT levels in the patients with non-MDR strains(U=4053.500,P=0.000).But no significant difference was observed after 7 days of antimicrobial therapy(U=10362.000,P=0.845).When the CUTOFF of PCT level was 1.52μg/L,the specificity was 41.20%,and the specificity was 93.90%,and the area under the ROC curve was 0.71.Research conclusion:The PCT level of G" bacterial infection was higher than that of G+ bacteria,and the positive rate of ’mixed infection was significantly higher than that of single type of bacterial infection.The positive results of PCT levels were not applicable to predict the types of pathogens in patients with bloodstream infection.PCT concentration less than 0.25μg/L should be careful to exclude bloodstream infections.While the PCT level more than 1.52μg/L in patients under bloodstream infection,could be useful for early prediction the infection of MDR strains after the exclusion of other causes of PCT secretion.It is positive and feasible to use PCT to guide clinical treatment of patients with MDR strains of infection.