Preliminary exploration of redesigning positive blood culture specimen processing flow / 上海交通大学学报（医学版）

Objective·To directly detect the bacteria in positive blood culture specimens by the separation gel tube combined with MicroflexTM matrixassisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS),perform direct antimicrobial susceptibility test based on the results of mass spectrometry,and preliminary explore the redesign of conventional positive blood culture specimen processing flow.Methods·449 positive-alarm blood culture specimens of monobacterial infections in clinical microbiology laboratory of Xirhua Hospital affiliated to Shanghai Jiao Tong University School of Medicine from September 1,2015 to August 31,2016 were collected and prepared according to the new positive blood culture specimens processing flow.The new redesigned processing flow included smear staining and microscopy,separation gel/mass spectrometry direct identification,bacteria film/mass spectrometry identification,pure colony/mass spectrometry identification,direct antimicrobial susceptibility test,and conventional antimicrobial susceptibility test,etc.According to the results of microscopic examination,identification test,and antimicrobial susceptibility test,level Ⅰ direct microscopic examination report,positive blood culture level Ⅱ (direct identification/bacteria film identification or direct antimicrobial susceptibility) report,and level Ⅲ final report were provided sequentially.Results·With the new redesigned processing flow,bacterial specieslevel identification reports for 82.2％,95.8％,and 100％ of positive blood samples could be obtain at 10 am and 17 pm on the current day and 10 am in the next morning,respectively,and be sent to clinical departments.Initial antimicrobial susceptibility reports for the bacteria that were considered as clinical significant pathogens by preliminary assessment could be provided in the next day of blood culture positive alarm with a higher coincidence rate as compared to the results of traditional antimicrobial susceptibility tests.Conclusion·The time from blood culture positive alarm to the provision of initial identification and antimicrobial susceptibility reports is shorter by 1-2 d for the redesigned processing flow than for the traditional one,which can provide fast and accurate etiologic diagnosis evidence for bloodstream infections for clinicians and is important for improving early diagnosis and treatment of clinical bloodstream infections.

Effects of Blood Volume Monitoring on the Rate of Positive Blood Cultures from the Emergency Room / 대한임상미생물학회지

BACKGROUND: Blood cultures are essential in diagnosing and treating sepsis. There are several factors that affect the diagnostic yield of blood cultures such as the number of blood sampling episodes, the incubation period, the type and volume of culture media, and the amount of blood drawn. This study aimed to elucidate whether monitoring the volume of blood drawn with an educational intervention could affect the diagnostic quality of blood cultures. METHODS: We implemented quality monitoring for the blood volume drawn during blood culture testing for adults in an emergency room. We instructed the nurses in the emergency room to draw the optimal amount of blood and to reduce the number of blood culture sets from three to two. We analyzed and compared the amount of blood drawn, the rate of positive blood cultures, the contamination rate, and time to positivity (TTP) between 908 patients pre-intervention and 921 patients post-intervention. RESULTS: The amount of blood drawn increased from 0.7±0.3 mL per bottle (pre-intervention) to 6.5±1.7 mL per bottle (post-intervention) (P<0.0001). The rate of positive blood culture post-intervention (12.14%) was higher than that pre-intervention (6.65%) (P<0.0001). The contamination rate post-intervention (1.82%) was also significantly greater than that pre-intervention (0.60%) (P<0.0001). Except for anaerobes, there was no significant difference in the distribution of microorganisms between the pre- and post-intervention periods. The TTP for anaerobe bottles post-intervention was significantly shorter than that of pre-intervention (16.1±16.3 versus 18.6±18.3 h). CONCLUSION: This study suggests that continuing education about adequate blood volume and aseptic techniques is needed to increase the rate of positive blood cultures and reduce the contamination rate of blood cultures.

Direct Identification and Antimicrobial Susceptibility Testing of Bacteria From Positive Blood Culture Bottles by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and the Vitek 2 System

BACKGROUND: We evaluated the reliability and accuracy of the combined use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) bacterial identification and Vitek 2 antimicrobial susceptibility testing (AST) for bacteria from positive blood culture bottles. METHODS: Direct identification and AST were performed in parallel to the standard methods in monomicrobial positive blood culture bottles. In total, 254 isolates grown on aerobic and/or anaerobic bottles were identified with MALDI-TOF Vitek MS (bioMerieux, France), and 1,978 microorganism/antimicrobial agent combinations were assessed. For isolates from anaerobic bottles, an aliquot of the culture broth was centrifuged, washed, and filtered through a nylon mesh. For isolates from aerobic/pediatric bottles, a lysis step using 9.26% ammonium chloride solution and 2% saponin solution was included. RESULTS: The overall correct identification rate was 81.8% (208/254) and that for gram-positive/gram-negative isolates was 73.9%/92.6%, respectively, and it was 81.8%, 87.6%, and 57.9% for isolates from aerobic, anaerobic, and pediatric bottles, respectively. Identification was not possible in 45 cases, and most of these isolates were streptococci (N=14) and coagulase-negative staphylococci (N=11). Misidentification occurred only in one case. Compared with standard methods, direct AST showed 97.9% (1,936/1,978) agreement with very major error of 0.25%, major error of 0.05%, and minor error of 1.8%. CONCLUSIONS: This simple and cost-effective sample preparation method gives reliable results for the direct identification and AST of bacteria. For the identification of streptococci and coagulase-negative staphylococci, the method should be further improved.

Analysis on pathogens composition and drug resistance in 1 829 cases of positive blood culture / 国际检验医学杂志

Objective To analyze the detected pathogens composition in positive blood culture samples and drug resistance in our hospital from January 2005 to December 2012 in order to accumulate the data information of pathogenic bacteria distribution and drug resistance in bacteremia .Methods The BD9240 and BacT /Alert3D 240 blood culture systems were used to perform the blood culture .The identification of isolated bacteria and the drug susceptibility test were conducted by using Microscan walkaway 40 sys‐tem and the Vitec2 compact system .The Data were analyzed by adopting the Whonet5 .6 software .Results In 1 829 positive bacte‐rial strains by blood culture ,986 strains were Gram negative bacilli ,accounting for 53 .9% ;721 strains were Gram positive coccus , accounting for 39 .4% ;104 strains were fungi ,accounting for 5 .68% .The resistant rate of staphylococcus to vancomycin ,linezolid and teicoplanin was 0% ,which to amoxycillin/clavulanic acid ,rifampicin ,amikacin ,sulfamethoxazole compound and chloramphenicol was lower than 40% .The sensitive of enterococcus to linezolid and teicoplanin was 100% ,but enterococcus faecium was resistant to vancomycin(2 .6% ) .The penicillin resistant rate of Streptococcus was 21 .7% .The resistant rates of E .coli and K lebsiella pneumo‐nia were 0% to imipenem and meropenem ,and less than 22% to amikacin ,piperacillin/tazobactam and cefoxitin .The resistant rates of salmonella to CLSI recommended five kinds of detection drug were less than 6 .5% .The resistant rates of pseudomonas aerugino‐sa were more than 25% to imipenem and more than 25% to meropenem .Conclusion The pathogens spectrum detected by blood culture is widespread .The resistance rates of different bacteria vary widely .

Rapid identification and susceptibility testing of positive blood culture caused by gram negative bacteria / 中华微生物学和免疫学杂志

Objective To reduce the turnaround time for laboratory diagnosis of bacteremia, the feasibility of rapid identification and susceptibility testing using samples taken directly from positive blood culture bottles was evaluated. Methods The growth of microorganisms in blood culture bottles was screened by the BACTEC 9000 blood culture system. 65 positive blood culture bottles containing gram-negative bacteria were adopted to test. Culture fluid was injected into BD SST vacutainer and centrifuged to pellet blood cells. After collecting required McFarland units, they were cultured on Phoenix 100 NMIC/ID-4(identification-gram-negative bacteria and susceptibility testing) cards using 0.25 McF and 0.5 McF methods respectively. They were also evaluated by the standard method, involving subculture tests from positive blood culture bottles. Results 63 of 65 gram-negative bacteria (96. 9% ) were correctly identified with 0. 25 McF method. 59 of 65 gram-negative bacteria(90.8% ) were correctly identified with 0.5 McF method. For antimicrobial susceptibility testing, the 0.25 McF direct method had an agreement rate more than 94% , the 0.5 McF method was more than 85.7% and direct blood sample KB method was more than 93.8% compared to the standard method. But the overall minor error rate in susceptibility testing of direct blood sample KB method is higher than other methods. Conclusion Applying 0. 25 McF and 0. 5 McF rapid identification and susceptibility test was practical. During to possessing more prominent advantages, laboratory put the 0. 25 McF direct method into practice had a timely, remarkable significance.