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
Highlights
Infectious diseases account for two million deaths in India each year.[1]
Clinical microbiology laboratory performs identification (ID) and antimicrobial susceptibility testing (AST) of significant bacterial isolates with the aim to guide antibiotic therapy and reduce the morbidity and mortality associated with infectious diseases.Rapid bacterial identification and susceptibility testing apart from improving patient therapy and outcome, decreases the emergence of resistance and reduces costs
With regards to AST results, it has been recommended by Clinical Laboratory Standard Institute (CLSI) that an overall category error rate of
Summary
Infectious diseases account for two million deaths in India each year.[1]. Clinical microbiology laboratory performs identification (ID) and antimicrobial susceptibility testing (AST) of significant bacterial isolates with the aim to guide antibiotic therapy and reduce the morbidity and mortality associated with infectious diseases.Rapid bacterial identification and susceptibility testing apart from improving patient therapy and outcome, decreases the emergence of resistance and reduces costs. Comparison of Automated System Vitek-2 with Conventional Methods, for Identification and Antibiotic Sensitivity in Gram Positive Organisms. 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. Discordant results of Vitek-2 were seen for S. hominis (5 isolates of the organism misidentified as S. epidermidis). Conclusion: The organisms having slow metabolic rates and late lactose fermenters (S. hominis) are prone to errors by the Vitek-2 system; need to be reconfirmed with other possible method.
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