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Agreement, Time and Cost Comparison for the Identification of Gram Negative Bacteria Isolates Using VITEK® 2 Compact, VITEK® 60, VITEK® Mass Spectrometry and API® 20E/NE



Objectives: We aimed to compare systems in respect of 1) the agreement between VITEK®2 Compact, VITEK®2 60, VITEK® Mass Spectrometry systems and API®20E/NE for species identification, 2) the time to identification of organisms and 3) the cost of identification and susceptibility testing of each organism.

Methods: Eighty gram-negative bacilli (GNB) isolated from swabs, blood, and urine culture specimens were submitted to the microbiology laboratory at the University Hospital of the West Indies (UHWI), Jamaica. Isolates were analyzed by the VTC, at UHWI, Jamaica then shipped to Mount Sinai Hospital, Canada for identification by VT60, VMS, and API. Resolution of reproducibly discrepant inter-method identification was performed using 16S rRNA sequencing. Time-to-identification was measured and the costs were measured in Canadian dollars (CAD). Direct and indirect costs were used in the cost analysis (at the time of this study 1 CAD = 1 USD). The Chi2 test was used to determine significant associations.

Results:  Eighty organism identifications (92.5%, 95% CI: 86.5 - 98.5) agreed by  VTC, VT60, VMS and API: E. coli , A. baumannii , K. pneumoniae , P. fluorescens , E. cloacae , P. mirabilis , P. aeruginosa , K. oxytoca , M. morganii , S. maltophilia , A. faecalis, C. freundii, E. aerogenes, and S. marcescens. There was identification disagreement between VTC, VT60, VMS, and API for 6 GNB, (7.5%; 95% CI: 1.73 - 13.27) to the species level. Three organisms were resolved by 16S rRNA sequencing. The time for identifying 41 organisms, from Jamaica was 433.25 hours for VTC. For VT60, API and VMS respectively, total time-to-identification was 425.75 hours, 2256 hours and 0.91 hours. The total cost of the 43 or 53.75% (95% CI: 42.82% - 64.68%) of Jamaican isolates was $486.37.

Conclusion: Costs for VT60, API, and VMS were $850.28, $796 and $140.36 respectively for 80 organisms. There was an agreement of 92.5%, between VT60, VMS, and API for identification of commonly identified organisms. VMS costs less than VTC, VT60, and API on a per test basis and also required less time than VTC, VT60, and API to identify organisms. 

12 Dec, 2017
e-Published: 13 Dec, 2017


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