Evaluation of Vitek MS in identification of clinical filamentous fungi isolates / 中华微生物学和免疫学杂志

Objective@#To evaluate the performance of Vitek MS, an automated mass spectrometry microbial identification system, in identification of clinical filamentous fungi isolates, which provide a new insight into filamentous fungi identification strategy.@*Methods@#Twenty-five isolates of filamentous fungi genetically confirmed by molecular sequencing method were inoculated in different culture conditions to analyze the potential influences of culture conditions on the identification of filamentous fungi with Vitek MS. Further evaluation of the performance of Vitek MS in filamentous fungi identification was carried out with 207 clinical isolates of filamentous fungi and the comparison of the results with those of morphology and sequencing analysis.@*Results@#The performance of Vitek MS in filamentous fungi identification was not significantly influenced by culture conditions. Vitek MS successfully identified 87.9% (182/207) of all tested filamentous fungi. Lacking of reference MS spectra in Vitek database was the main reason that the other isolates could not be identified. Vitek MS was superior to the traditional morphological method in identification of filamentous fungi especially non-Aspergillus molds at species level.@*Conclusion@#Vitek MS is an efficient approach for clinical filamentous fungi identification. Continuous enrichment of the species coverage in database will be of great importance for improving the performance of Vitek MS in identification of filamentous fungi.

Comparison of the Bruker Biotyper and VITEK MS Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Systems Using a Formic Acid Extraction Method to Identify Common and Uncommon Yeast Isolates

BACKGROUND: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows rapid and accurate identification of clinical yeast isolates. In-tube formic acid/acetonitrile (FA/ACN) extraction is recommended prior to the analysis with MALDI Biotyper, but the direct on-plate FA extraction is simpler. We compared the Biotyper with the VITEK MS for the identification of various clinically relevant yeast species, focusing on the use of the FA extraction method. METHODS: We analyzed 309 clinical isolates of 42 yeast species (four common Candida species, Cryptococcus neoformans, and 37 uncommon yeast species) using the Biotyper and VITEK MS systems. FA extraction was used initially for all isolates. If ‘no identification' result was obtained following the initial FA extraction, these samples were then retested by using FA (both systems, additive FA) or FA/ACN (Biotyper only, additive FA/ACN) extraction. These results were compared with those obtained by sequence-based identification. RESULTS: Both systems correctly identified all 158 isolates of the four common Candida species after the initial FA extraction. The Biotyper correctly identified 8.7%, 30.4%, and 100% of 23 C. neoformans isolates after performing initial FA, additive FA, and FA/ACN extractions, respectively, while VITEK MS identified all C. neoformans isolates after the initial FA extraction. Both systems had comparable identification rates of 37 uncommon yeast species (128 isolates), following the initial FA (Biotyper, 74.2%; VITEK MS, 73.4%) or additive FA (Biotyper, 82.0%; VITEK MS, 73.4%). CONCLUSIONS: The identification rate of most common and uncommon yeast isolates is comparable between simple FA extraction/Biotyper method and VITEK MS methods, but FA/ACN extraction is necessary for C. neoformans identification by Biotyper.

Methodological study of VITEK-MS assisted by separation gel tube for fast identification of positive blood culture bacteria / 国际检验医学杂志

Objective To investigate the method of the separation gel vacuum tube combined with matrix‐assisted laser desorp‐tion/ionization time of flight mass spectrometry system (VITEK‐MS) for fasting identifying positive blood culture bacteria .Methods Fifty cases of positive blood culture by the BacT/ALERT3D blood culture system and Gram‐negative bacteria by direct staining in the First Affiliated Hospital of Guangzhou University from March to October 2015 were collected .The bacteria were directly ex‐tracted from the blood culture bottle by the separation gel tube and performed the fast identification by adopting the VITEK‐MS system .At the same time the bacteria were performed the subcultivation and identification .then the coincidence of this method was compared .Results Among 50 cases of Gram‐negative bacteria by positive blood culture ,21 cases of bacteria were not identified ,29 cases of bacteria were identified ,the positive rate was 58 .0% .the coincidence rate with the conventional identification results was 96 .6% ;the method of separation gel combined with VITEK‐MS was nearly 24 h in advance compared with the traditional method . Conclusion Adopting the separation gel vacuum tube combined with VITEK‐MS for identifying bacteria has the higher coincidence rate of positive blood culture Gram negative bacteria ,can greatly shorten the identification time ,this method is rapid and simple .

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.

Evaluation of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry-Based VITEK MS System for the Identification of Acinetobacter Species from Blood Cultures: Comparison with VITEK 2 and MicroScan Systems

BACKGROUND: Acinetobacter species are the leading cause of bloodstream infection (BSI), but their correct identification is challenging. We evaluated the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)-based VITEK MS (bioMerieux, France), and two automated systems, VITEK 2 (bioMerieux) and MicroScan (Siemens, USA) for identification of Acinetobacter BSI isolates. METHODS: A total of 187 BSI isolates recovered at a university hospital in Korea between 2010 and 2012 were analyzed. The identification results obtained using VITEK MS and two automated systems were compared with those of rpoB sequencing. RESULTS: Of 187 isolates analyzed, 176 were identified to the species level by rpoB sequencing: the Acinetobacter baumannii group (ABG; 101 A. baumannii, 43 A. nosocomialis, 10 A. pittii isolates) was most commonly identified (82.4%), followed by Acinetobacter genomic species 13BJ/14TU (5.3%), A. ursingii (2.1%), A. soli (2.1%), A. bereziniae (1.1%), and A. junii (1.1%). Correct identification rates to the species group (ABG) level or the species level was comparable among the three systems (VITEK MS, 90.3%; VITEK 2, 89.2%; MicroScan, 86.9%). However, VITEK MS generated fewer misidentifications (0.6%) than VITEK 2 (10.8%) and MicroScan (13.1%) (P<0.001). In addition, VITEK MS demonstrated higher specificity (100%) for discrimination between ABG and non-ABG isolates than the other systems (both, 31.8%) (P<0.001). CONCLUSIONS: The VITEK MS system is superior to the VITEK 2 and MicroScan systems for identification of Acinetobacter BSI isolates, with fewer misidentifications and better discrimination between the ABG and non-ABG isolates.

Evaluation of VITEK Mass Spectrometry (MS), a Matrix-Assisted Laser Desorption Ionization Time-of-Flight MS System for Identification of Anaerobic Bacteria

BACKGROUND: By conventional methods, the identification of anaerobic bacteria is more time consuming and requires more expertise than the identification of aerobic bacteria. Although the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems are relatively less studied, they have been reported to be a promising method for the identification of anaerobes. We evaluated the performance of the VITEK MS in vitro diagnostic (IVD; 1.1 database; bioMerieux, France) in the identification of anaerobes. METHODS: We used 274 anaerobic bacteria isolated from various clinical specimens. The results for the identification of the bacteria by VITEK MS were compared to those obtained by phenotypic methods and 16S rRNA gene sequencing. RESULTS: Among the 249 isolates included in the IVD database, the VITEK MS correctly identified 209 (83.9%) isolates to the species level and an additional 18 (7.2%) at the genus level. In particular, the VITEK MS correctly identified clinically relevant and frequently isolated anaerobic bacteria to the species level. The remaining 22 isolates (8.8%) were either not identified or misidentified. The VITEK MS could not identify the 25 isolates absent from the IVD database to the species level. CONCLUSIONS: The VITEK MS showed reliable identifications for clinically relevant anaerobic bacteria.

Direct Identification of Urinary Tract Pathogens From Urine Samples Using the Vitek MS System Based on Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

BACKGROUND: We evaluated the coincidence rate between Vitek MS system (bioMerieux, France) and Vitek 2 in identifying uropathogens directly from urine specimens. METHODS: Urine specimens submitted to our microbiology laboratory between July and September 2013 for Gram staining and bacterial culture were analyzed. Bacterial identification was performed by using the conventional method. Urine specimens showing a single morphotype by Gram staining were processed by culturing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Of 2,370 urine specimens, 251 showed a single morphotype on Gram staining, and among them, 202 were available for MALDI-TOF MS. RESULTS: In these 202 specimens, colony growth was observed in 189 specimens, and 145 specimens had significant growth of single-colony morphotype in culture. One hundred and ten (75.9%) of them had colony counts of > or =10(5) colony-forming units (CFU)/mL and included 71 enteric gram-negative bacteria (GNB), 5 glucose-non-fermenting GNB, 9 gram-positive cocci (GPC), and 25 yeasts. Furthermore, 70 (98.6%), 3 (60.0%), 4 (44.4%), and 5 (20.0%), respectively, of these were correctly identified by Vitek MS. Thirty-one specimens (21.4%; 11 GNB, 7 GPC, 12 yeasts, and 1 gram-positive bacillus) had colony counts of 10(4)-10(5) CFU/mL. Four specimens (2.8%) yielded colony counts of 10(3)-10(4) CFU/mL. CONCLUSIONS: Vitek MS showed high rate of accuracy for the identification of GNB in urine specimens (> or =10(5) CFU/mL). This could become a rapid and accurate diagnostic method for urinary tract infection caused by GNB. However, for the identification of GPC and yeasts, further studies on appropriate pre-treatment are warranted.

Evaluation of the Performance of VITEK-2 Compact,VITEK MS and Bruker MS on the Identification of Corynebacterium / 现代检验医学杂志

Objective To evaluate the performance of VITEK-2 compact,VITEK MS and Bruker MS on the identification of Corynebacterium.Methods This was a methodological evaluation study.The 40 Corynebacterium from bioMerieux were i-dentified with the three methods respectively.16S rDNA gene sequencing was conducted as reference method.Made a de-scriptive analysis of the identification ability,time and cost.Resulets The accuracy of species level of the three methods was 95.0%,88.9% and 97.5%.The mean time was 5~6 h,2~3 min and 2~3 min.The cost of consumable was 50~70 yuan, 15~25 yuan and 10~20 yuan.Conclution Three methods with high accuracy can meet the requirement of clinical diagno-sis,and the identification ability of VITEK MS on Corynebacterium amycolatum need to be further improved.