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

Centro Integrato di Ricerche, Laboratory of Clinical Microbiology, University Campus Bio-medico, 00128 Rome, Italy.
Diagnostic microbiology and infectious disease (Impact Factor: 2.46). 01/2012; 72(1):20-31. DOI: 10.1016/j.diagmicrobio.2011.09.015
Source: PubMed


We performed a comparative evaluation of the Vitek-2 Compact and Phoenix systems for direct identification and antimicrobial susceptibility testing (AST) from positive blood culture bottles in comparison to the standard methods. Overall, 139 monomicrobial blood cultures, comprising 91 Gram-negative and 48 Gram-positive isolates, were studied. Altogether, 100% and 92.3% of the Gram-negative isolates and 75% and 43.75% of the Gram-positive isolates showed concordant identification between the direct and the standard methods with Vitek and Phoenix, respectively. AST categorical agreements of 98.7% and 99% in Gram-negative and of 96.2% and 99.5% in Gram-positive isolates with Vitek and Phoenix, respectively, were observed. In conclusion, direct inoculation procedures for Gram-negative isolates showed an excellent performance with both automated systems, while for identification of Gram-positive isolates they proved to be less reliable, although Vitek provided acceptable results. This approach contributes to reducing the turnaround time to result of blood cultures, with a positive impact on patient care.

Download full-text


Available from: Giovanni Di Bonaventura, Aug 31, 2015
  • Source
    • "The main focus of this study is the reliable identification of all CTX-resistant E. coli isolates by MAAST. Although this cannot be achieved with the low hydrolyzing strains, the gain in time for the detection of multidrug-resistant E. coli isolates is still substantial when compared to standard culture-based procedures with incubation times ranging up to approximately 12 h (Gherardi et al., 2012 "
    [Show abstract] [Hide abstract]
    ABSTRACT: Antibiotic resistance is an unsolved healthcare problem with increasing impact on patient management in the last years. In particular, multidrug resistance among Gram-negative bacterial strains has become the most pressing challenge. In order to deliver the most efficacious antimicrobial therapy with minimum delay, rapid diagnostic tests are required in order to detect multidrug resistant pathogens early during infection. In line with these efforts, we have developed a mass spectrometry-based assay for the rapid determination of ampicillin and cefotaxime resistance. The assay quantifies beta-lactamase activities towards ampicillin and cefotaxime within a turnaround time of 150min, which is substantially faster than classical susceptibility testing.
    Full-text · Article · Sep 2015 · International journal of medical microbiology: IJMM
  • Source
    • "We demonstrated here that DAST provided, within 24 h, results comparable to those obtained with CAST. DAST is employed in many laboratories to determine antibiotic susceptibility of GNB from positive blood cultures [16] [17] [18]. However, performing DAST on positive blood cultures is easier than testing respiratory samples because the former generally involve a single pathogen and the inocula are less heterogeneous [19]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Inappropriate antibiotic therapy in ventilator-associated pneumonia (VAP) is associated with increased mortality. Using broad-spectrum antibiotics for 48 h until the results of conventional cultures and antimicrobial susceptibility testing (AST) are available, may promote the emergence of drug-resistant bacteria. Performing AST directly on clinical respiratory samples would hasten the process by at least 24 h. Here, we analysed the diagnostic performance of a rapid method combining mass spectrometry and direct AST (DAST), and compared it with the conventional method (mass spectrometry with conventional AST (CAST)). Additionally, we assessed its potential impact on antimicrobial use in patients. Over a period of 18 months, the two methods were performed on 85 bronchoalveolar lavages obtained from intensive care unit patients with suspected VAP, and in which Gram-negative bacilli were observed on direct examination. Only the CAST results were reported to the clinicians. DAST produced useable results in 85.9% of the patients. The sensitivity and negative predictive values of DAST were 100% for all antibiotics tested, except gentamicin (97.1%, (95% CI 93.3-101) and 97.4% (93.7-101), respectively) and amikacin (88.9% (81.7-96.1) and 96.4% (92.1-100.7), respectively), compared with CAST. Specificity and positive predictive values ranged from 82.9 (74.2-91.5) to 100%, and from 86.4 (78.5-94.2) to 100%, respectively. If the DAST results had been reported to the clinicians, treatment could have been optimized 24 h earlier in 35/85 (41.2%) patients, with 17 carbapenem patient-days saved. Overall, routine use of the DAST method could help optimize earlier antibiotic treatment in patients with suspected VAP. Copyright © 2014 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.
    Full-text · Article · Dec 2014 · Clinical Microbiology and Infection
  • Source
    • "The overall processing time was 6.9 min per measurement, and the mean time required for identification was 5.2 hr (data not shown). Hence, only a moderate gain in time was achieved by this method, with the added disadvantage that mixed cultures and ~20% of Gram-negative bacteria could not be identified; misidentification rates for Gram-positive bacteria were even higher [19]. Since the Kiestra TLA system used in this study was not connected to an anaerobic incubator, anaerobic bacteria were not evaluated. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Microbiological laboratories seek technologically innovative solutions to cope with large numbers of samples and limited personnel and financial resources. One platform that has recently become available is the Kiestra Total Laboratory Automation (TLA) system (BD Kiestra B.V., the Netherlands). This fully automated sample processing system, equipped with digital imaging technology, allows superior detection of microbial growth. Combining this approach with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MS) (Bruker Daltonik, Germany) is expected to enable more rapid identification of pathogens. Early growth detection by digital imaging using Kiestra TLA combined with MS was compared to conventional methods (CM) of detection. Accuracy and time taken for microbial identification were evaluated for the two methods in 219 clinical blood culture isolates. The possible clinical impact of earlier microbial identification was assessed according to antibiotic treatment prescription. Pathogen identification using Kiestra TLA combined with MS resulted in a 30.6 hr time gain per isolate compared to CM. Pathogens were successfully identified in 98.4% (249/253) of all tested isolates. Early microbial identification without susceptibility testing led to an adjustment of antibiotic regimen in 12% (24/200) of patients. The requisite 24 hr incubation time for microbial pathogens to reach sufficient growth for susceptibility testing and identification would be shortened by the implementation of Kiestra TLA in combination with MS, compared to the use of CM. Not only can this method optimize workflow and reduce costs, but it can allow potentially life-saving switches in antibiotic regimen to be initiated sooner.
    Full-text · Article · Mar 2014 · Annals of Laboratory Medicine
Show more