Comparative evaluation of the Vitek-2 Compact and Phoenix systems for rapid identification and antibiotic susceptibility testing directly from blood cultures of Gram-negative and Gram-positive isolates

Gherardi, Giovanni; Angeletti, Silvia; Panitti, Miriam; Pompilio, Arianna; Bonaventura, Giovanni Di; Crea, Francesca; Avola, Alessandra; Fico, Laura; Palazzo, Carlo; Sapia, Genoveffa Francesca; Visaggio, Daniela; Dicuonzo, Giordano

doi:10.1016/j.diagmicrobio.2011.09.015

Cited by 97 publications

(83 citation statements)

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“…Our data indicated that the Vitek 2 system provided inaccurate susceptibility test results for oxacillin and vancomycin, as the agreement rate with the reference method was very low, and the error rates, mainly VMEs and MEs, were higher compared to other studies 14 . Although our study has evaluated the antimicrobial susceptibility of commonly isolated strains, such as S. aureus and E. faecalis, most of the isolates were microorganisms that belong to coagulase-negative staphylococci (CoNS) and non-faecalis enterococci.…”

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confidence: 45%

Performance of the Vitek 2 system software version 5.03 in the bacterial identification and antimicrobial susceptibility test: evaluation study of clinical and reference strains of Gram-positive cocci

Paim

Cantarelli

d’Azevedo

2014

Rev. Soc. Bras. Med. Trop.

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Introduction. The genera Enterococcus, Staphylococcus and Streptococcus are recognized as important Gram-positive human pathogens. The aim of this study was to evaluate the performance of Vitek 2 in identifying Gram-positive cocci and their antimicrobial susceptibilities. Methods. One hundred four isolates were analyzed to determine the accuracy of the automated system for identifying the bacteria and their susceptibility to oxacillin and vancomycin. Results. The system correctly identifi ed 77.9% and 97.1% of the isolates at the species and genus levels, respectively. Additionally, 81.8% of the Vitek 2 results agreed with the known antimicrobial susceptibility profi les. Conclusion. Vitek 2 correctly identifi ed the commonly isolated strains; however, the limitations of the method may lead to ambiguous fi ndings.Keywords: Gram-positive cocci. Vitek 2 automated system.Gram-positive cocci are widely distributed as part of the normal fl ora in humans; however, some species are recognized as major human pathogens and cause a large variety of infections worldwide. These microorganisms are frequently isolated from bloodstream infections, skin and soft tissue infections, sepsis, urinary tract infections and lower respiratory tract infections 1 .Automated bacterial identifi cation in the clinical laboratory provides a rapid and reliable diagnosis for most pathogens involved in infectious diseases. A previous study demonstrated the satisfactory performances of the automated methodologies, resulting in their use in routine practice with a highly acceptable level of identification accuracy; additionally, automated identification enabled the interpretation of antimicrobial susceptibility tests for the correct treatment of patients 2 .The aim of the present study was to evaluate the performance of the Vitek 2 automated system in the identifi cation of bacteria and antimicrobial susceptibilities of Gram-positive cocci isolates recovered from clinical samples and reference strains.The study was performed at Laboratório de Cocos GramPositivos (LCGP) of the Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA) and Laboratório Qualità, Rio Grande do Sul, Brazil. The isolates included in the present study were selected from the strain collection belonging LCGP. A total of 104 isolates of Gram-positive cocci were analyzed, including 29 reference strains selected from the American Type Culture Collection (ATCC) and 75 clinical strains isolated from different patients; these strains included Staphylococcus coagulase-negative (n=36), Enterococcus spp. (n=33) and Staphylococcus aureus (n=6). All of these strains have been previously characterized by the LCGP with regard to their virulence factors using molecular methods and susceptibility profi les and were identifi ed at the species level using conventional reference methods 3,4 . For the identifi cation of staphylococci, the following characteristics were tested: catalase; colony morphology and pigmentation; Gram stain; hemolysis; susceptibility to novobiocin; p...

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confidence: 45%

Performance of the Vitek 2 system software version 5.03 in the bacterial identification and antimicrobial susceptibility test: evaluation study of clinical and reference strains of Gram-positive cocci

Paim

Cantarelli

d’Azevedo

2014

Rev. Soc. Bras. Med. Trop.

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“…Timely intervention in the treatment of bloodstream infection is of high significance to provide precise antimicrobial [1,2].…”

Section: Introductionmentioning

confidence: 99%

Clinical Evaluation of QMAC-dRAST for Direct and Rapid Antimicrobial Susceptibility Test with Gram-Positive Cocci from Positive Blood Culture Bottles

Kim¹,

Jeong

Han³

et al. 2018

Ann Clin Microbiol

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Background: Timely intervention in the treatment of bloodstream infection is important for prescription of appropriate antimicrobials. With prompt determination of the antimicrobial susceptibility of a causative agent, rapid antimicrobial susceptibility test (AST) can help select the appropriate antimicrobial therapy. This clinical study is for evaluation of the clinical performance of the QMAC-dRAST for rapid AST directly from positive blood culture (PBC)s with Gram-positive cocci. Methods: A total of 115 PBC samples with Grampositive organisms (76 Staphylococcus spp. and 39 Enterococcus spp.) were evaluated by the QMACdRAST system, and their pure culture isolates were evaluated by the MicroScan WalkAway (Beckman Coulter, USA) as the comparative AST system. Thirteen antimicrobial agents were included, and the agreement and discrepancy rates of the QMACdRAST system (Quantamatrix Inc., Republic of Korea) compared to the MicroScan WalkAway were calculated. To resolve discrepancies, the broth microdilution method was performed. Results:The QMAC-dRAST system exhibited a categorical agreement rate of 94.9% (1,126/1,187) and an essential agreement rate of 98.3% (1,167/1,187). The QMAC-dRAST system yielded very major (falsesusceptible) errors at 1.0% (5/485), major (false-resistant) errors at 1.3% (9/693), and minor errors at 4.0% (47/1,187) compared to the MicroScan WalkAway. The QMAC-dRAST system significantly eliminated 30 hours of total turnaround time by combination of direct inoculation of PBC and an image-based approach. Conclusion:The results of the QMAC-dRAST system were highly accurate. Thereby, the QMAC-dRAST may provide essential information to accelerate therapeutic decisions for earlier and adequate antibiotic treatment and patient management in clinical settings.

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“…Likewise, the direct inoculation of growthpositive blood culture broth into automated biochemical typing systems has been described to reduce reporting turnaround times (Chen et al, 2008;Gherardi et al, 2012). However, both of these methods appear to perform less well in the identification of Gram-positive organisms as compared with that of Gram-negative organisms (Chen et al, 2008;Prod'hom et al, 2010;Kok et al, 2011;Gherardi et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Rapid identification of Gram-positive pathogens and their resistance genes from positive blood culture broth using a multiplex tandem RT-PCR assay

Hazelton

Thomas

Unver

et al. 2013

Journal of Medical Microbiology

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The early initiation of targeted antibiotic therapy in patients with bacteraemia and septic shock impacts favourably on outcomes. Rapid methods are therefore increasingly employed for bacterial identification directly from positive blood culture bottles, but with variable success. We evaluated the performance of the Gram Positive 12 multiplex tandem PCR (MT-PCR) assay (AusDiagnostics; catalogue no. 6202, version 07) containing targets for the identification of staphylococci including Staphylococcus aureus, streptococci including Streptococcus pneumoniae, enterococci including Enterococcus faecalis and Enterococcus faecium and their common antibiotic resistance genes (mecA, vanA, vanB). A total of 673 aerobic and anaerobic blood culture broths demonstrating Gram-positive cocci on microscopy were analysed in parallel with traditional phenotypic methods. Amplification of the internal control was inhibited in 79/673 (11.7 %) samples; however, MT-PCR identification was in concordance with phenotypic identification to the genus level in 96.6 % (537/556) of the remaining monomicrobial specimens and to the species level, where applicable, in 100 % (172/172) of samples. MT-PCR identification for 94.7 % (36/38) of polymicrobial samples matched traditional phenotypic identification. Meticillin and vancomycin susceptibility results determined by MT-PCR in blood culture broths demonstrated complete agreement with those determined by phenotypic methods in all 143 Staphylococcus aureus isolates and eight E. faecium isolates, respectively. Gram-positive pathogens and their key antibiotic resistance markers were reliably identified with the MT-PCR assay within 3 h of a positive blood culture result.

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Comparative evaluation of the Vitek-2 Compact and Phoenix systems for rapid identification and antibiotic susceptibility testing directly from blood cultures of Gram-negative and Gram-positive isolates

Cited by 97 publications

References 50 publications

Performance of the Vitek 2 system software version 5.03 in the bacterial identification and antimicrobial susceptibility test: evaluation study of clinical and reference strains of Gram-positive cocci

Performance of the Vitek 2 system software version 5.03 in the bacterial identification and antimicrobial susceptibility test: evaluation study of clinical and reference strains of Gram-positive cocci

Clinical Evaluation of QMAC-dRAST for Direct and Rapid Antimicrobial Susceptibility Test with Gram-Positive Cocci from Positive Blood Culture Bottles

Rapid identification of Gram-positive pathogens and their resistance genes from positive blood culture broth using a multiplex tandem RT-PCR assay

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