Direct identification and methicillin susceptibility of Staphylococcus aureus from blood-culture bottles using the Vitek 2 system

Abstract number: p1424

Flórez  C., López-Oviedo  E., Martín  C., Cabezas  J., Morilla  D., Martín-Mazuelos  E.


To asses the ability of The Vitek System in order to rapid identification of S. aureus and detection of methicillin resistance from blood-culture bottles.


Only blood cultures bottles showing Gram-positive cocci in clusters on direct Grams stain in more than one set of blood cultures were processed. The direct method was done using a suspension made by differential centrifugation of positive blood culture broth for inoculation of the Vitek ID-GPC, ID-GP and AST-536 cards (bio-Merieux). Standard identification was done using an inoculum made from and overnight culture on solid media and coagulase production (Staphaurex, Remel). The detection of methicillin resistance was evaluated with the oxacillin disk diffusion and PBP-2a latex test (Oxoid).


A total of 51 consecutive S. aureus isolates from blood cultures were evaluated. The direct method resulted in 11.8% misidentifications or non-identifications. Methicillin resistance was detected in 6 isolates (11.8%) by direct method and the PBP-2a test and in 7 by disk diffusion.


The direct Vitek method could correctly report identification and susceptibility patterns within 8 hours in 88.2% of bacteraemic episodes with S. aureus. All direct results should be considered only preliminary reports and they should be contrasted with cultures and standard methods in order to detect mixed cultures or errors the identification or susceptibility.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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