Comparison of Automated System Vitek-2 with Conventional Methods, for Identification and Antibiotic Sensitivity in Gram Positive Organisms.
Abstract
Abstract
Background: Prompt identification (ID) and antimicrobial susceptibility testing (AST) of organisms causing blood stream infections has a significant impact on the morbidity and mortality associated with these infections. The need to circumvent the slow turnaround time of conventional gold standard methods has paved way for the rapid automated systems.
Aim: To Compare the results of Vitek-2 for the ID and AST of Gram positive isolates with conventional manual methods.
Methodology: A total of 215 non-duplicate isolates of Gram positive bacteria recovered from blood samples were part of this prospective study carried out in the Department of Microbiology. Organisms were processed on the Vitek-2 system and by manual methods (ID/AST) for comparison. Descriptive statistics was used for the presentation and comparison of data and appropriate statistical charts were used to present the data.
Observations: Concordant identification (ID) results of Vitek-2 were seen with all the isolates of S. aureus, S. epidermidis, S. pneumonia, E. faecalis and E. faecium. Discordant results of Vitek-2 were seen for S. hominis (5 isolates of the organism misidentified as S. epidermidis). No minor, major or very major error with 100% categorical agreement (CA) was seen for penicillin, cefoxitin, oxacillin, linezolid, ciprofloxacin, tetracycline, co-trimoxazole, clindamycin and erythromycin for various organisms tested. Enterococci gave minor error of 4.5% with an overall CA of 95.5% for ampicillin and a major error of 2.8% with an overall CA of 97.2% for vancomycin.
Conclusion: The organisms having slow metabolic rates and late lactose fermenters (S. hominis) are prone to errors by the Vitek-2 system; hence need to be reconfirmed with other possible method. Also AST results for critical antibiotics like vancomycin need to be verified manually before reporting.
Key words: Antimicrobial Susceptibility testing, Enterococci, Vitek-2
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References
2. Ling T, Liu Z, Cheng A. Evaluation of the VITEK 2 System for Rapid Direct Identification and Susceptibility Testing of Gram-Negative Bacilli from Positive Blood Cultures. Journal of Clinical Microbiology. 2003; 41(10):4705-4707.
3. Duggal S, Gaind R, Tandon N, Deb M, Chugh T. Comparison of an Automated System with Conventional Identification and Antimicrobial Susceptibility Testing. ISRN Microbiology. 2012; 2012:1-4.
4. Jossart M, Courcol R. Evaluation of an Automated System for Identification of Enterobacteriaceae and Non fermenting Bacilli. European Journal of Clinical Microbiology & Infectious Diseases. 1999; 18(12):902-907.
5. Bourbeau P, Ledeboer N. Automation in Clinical Microbiology. Journal of Clinical Microbiology. 2013; 51(6):1658-1665.
6. Doern, G. V., R. Vautour, M. Gaudet, and B. Levy. 1994. Clinical impact of rapid in vitro susceptibility and bacterial identification. J. Clin. Microbiol.32:1757–1762.
7. Clinical and Laboratory Standards Institute. Performance standards for antimi-crobial susceptibility testing; eighteenth information supplement. 2015; M100-S
8. Nadheema H., Khetam H.R., Jumaah D. H. Frequency of Extended Spectrum Beta Lactamase producing Gram negative bacteria isolated from blood cultures at children hospital in Baghdad Volume : 4 | Issue : 1 | January 2015 • ISSN No 2277 – 8179.
9. Espinar M, Rocha R, Ribeiro M, Goncalves R. A, Pina-Vaz C. Extended-spectrum -lactamases of Escherichia coli and Klebsiella pneumoniae screened by the VITEK 2 system. Journal of Medical Microbiology. 2011; 60(6):756-760.
10. De Cueto M, Ceballos E, Martinez-Martinez L, Perea E, Pascual A. Use of Positive Blood Cultures for Direct Identification and Susceptibility Testing with the Vitek 2 System. Journal of Clinical Microbiology. 2004; 42(8):3734-3738.
11. Spanu T, Sanguinetti M, Ciccaglione D, D'Inzeo T, Romano L, Leone F et al. Use of the VITEK 2 System for Rapid Identification of Clinical Isolates of Sta-phylococci from Bloodstream Infections. Journal of Clinical Microbiology. 2003; 41(9):4259-4263.
12. Fahr A, Eigner U, Armbrust M, Caganic A, Dettori G, Chezzi C et al. Two-Center Collaborative Evaluation of the Performance of the BD Phoenix Auto-mated Microbiology System for Identification and Antimicrobial Susceptibility Testing of Enterococcus spp. and Staphylococcus spp. Journal of Clinical Mi-crobiology. 2003; 41(3):1135-1142.
13. Ligozzi M, Bernini C, Bonora M, de Fatima M, Zuliani J, Fontana R. Evaluation of the VITEK 2 System for Identification and Antimicrobial Susceptibility Testing of Medically Relevant Gram-Positive Cocci. Journal of Clinical Microbiology. 2002; 40(5):1681-1686.
14. Fernando Garcia-Garrote, Emilia Cercenado, Emilio Bouza. Evaluation of a New System, VITEK 2, for Identification and Antimicrobial Susceptibility Testing of Enterococci. J. ClinMicrobiol. 2000 Jun; 38(6): 2108–2111.
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