RÉSUMÉ
Objective:Based on the high-throughput detection technique of multiplex PCR combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, constructing the characteristic SNP profiles of different strains, and establishing a rapid, accurate and highly sensitive method for the diagnosis of bloodstream infection pathogens.Methods:Seven kinds of pathogens such as common Escherichia coli were selected as target. The multiple PCR reaction conditions was optimized, and the characteristic peaks of each target bacteria were detected by MALDI-TOF MS to establish the joint detect system. Common primer pairs and central homo-sequence primer pairs were designed to analyse the formation of primer dimer. Using simulated bacterial infection blood samples with detection system to determine specificity and sensitivity. One hundred and fifty blood samples from suspected bacteremia patients were collected from June to September 2020 in a hospital in Beijing, and the identification results were compared to traditional identification method of clinical application that are using χ 2 test. Results:The cycle threshold (Ct) value of the central homo-sequence primers that were designed were more than 38, with a delay of 6-10 cycles. The joint mass spectrometry detection system could detect seven kinds of bacteria divided into two groups at the same time. The target bacteria can be detected specific product of the peak, and the clinical strains other than the target strains only had primer peaks. All maps had non-specific miscellaneous peaks. The sensitivity of Escherichia coli could reach 50 CFU/ml, and the detection limit of other bacteria was 100 CFU/ml. The detection results of 150 patients showed that 46 cases were positive by traditional method. The positive rate was 30.67% (46/150), including two cases of mixed infection. Forty-eight cases were positive by mass spectrometry, and the positive rate was 32.0% (48/150), including three cases of mixed infections. The negative coincidence rate was 100% (101/101). The comparison of the two methods showed that the P=0.625>0.01, the Kappa=0.938, the sensitivity and specificity was 97.82%(45/46) and 97.11%(101/104), respectively. There was no significant difference between the two methods, and the results of nucleic acid mass spectrometry could also be used in clinic. Conclusions:The established detection system can not only quickly and accurately detect seven common pathogens causing bloodstream infection, and effectively shorten the time needed for traditional culture and identification, but also can detect multiple bacterial mixed infections at the same time to make up for the possibility of missed detection. Besides, the method can also be used to identify other bacteria.
RÉSUMÉ
Objective To shorten the turn around time of positive blood culture results by optimizing the blood culture positive specimen processing flow.Methods In January 26,2015,the microbiology department started the blood culture positive specimen processing flow optimization project,and applied the Lean Six Sigma method in the microbiological process management.The TAT data of 124 positive blood cultures containing Enterobacteriaceae were collected before and after the start of the project in about two months.We analyzed the turnaround time median,mean and standard deviation and reference Z value,process performance index,millions of error opportunities.We decompose the turnaround time into six time periods to find the key points of the process improvement and the influencing factors,and then put forward the reform measures to optimize the blood culture inspection process.MiniTab17.0 statistical software was used to process capability analysis and double sample t test.Results After the implementation of the project,the average turnaround time of the blood culture was shortened from 77.10 h to 64.03 h,improved by 13.06 h(16.94％).Process performance greatly improved in Ppk value increased from 0.49 to 0.88,the benchmark Z value increased from 1.48 to 2.63.After the improvement,except the positive alarm time of blood culture,the mean of the other decomposition time was significantly shorter than before.Conclusions The application of Six Sigma in process management can greatly improve the work efficiency and process performance.This project can save a lot of manpower,material and financial resources,reduce the waiting,shorten turnaround time,that achieve the desired results.
RÉSUMÉ
Objective To detect the main virulence genes and biofilm formation of Enterococci strains isolated from blood samples .Methods Twenty-eight strains of Enterococcus faecalis ( E.faecalis) and 54 strains of Enterococcus faecium ( E.faecium) were collected from blood samples .Five main virulence genes (asa1, esp, hyl, cylA and gelE) were detected by multiplex PCR.Biofilm formation was investigated by using microtiter dish biofilm formation assay .Results All E.faecalis strains were positive for at least one kind of virulence genes , of which 14 strains were concurrently positive for asa1, esp, cylA and gelE.asa1, cylA and gelE were only detected in E.faecalis strains, while hyl gene only existed in E.faecium strains. Twenty-seven strains of E.faecium were esp positive, of which 12 strains were both hyl and esp positive. None of the 5 virulence genes were identified in 10 strains of E.faecium.85.7% of E.faecalis strains and 63.0%of E.faecium strains could form biofilm.Conclusion Compared with E.faecium strains, more types of virulence genes were detected in E.faecalis strains with higher positive rates .Moreover , E.faecalis strains were more likely to form biofilms than E.faecium strains.