[Use of BioRad plating agar MRSASelect for the daily detection of methicillin resistant staphylococci isolated from samples taken from blood culture bottles]. / Apport de l'utilisation de la gélose MRSASelect BioRad pour la détection de routine de la résistance à la méticilline des staphylocoques isolés de flacons d'hémoculture.

ABSTRACT

Within a medium size general biology laboratory, it is not always easy to set up rapid methods for detection of methicillin-resistant staphylococci (detection of the mecA gene or PLP2a). Since we already use BioRad chromogenic plating agar MRSASelect for the detection of carriers of methicillin resistant Staphylococcus aureus, we wanted to test its use on samples taken from blood culture bottles. Between December 2004 and October 2005, all the blood bottle cultures that detected positive by direct examination for Gram positive cocci and suspected to be staphylococci, that is 45 pairs of blood cultures and 3 joint aspirations, were inoculated on quarter plates of both MRSASelect and standard non-selective agar. After culture, they were screened by the disc method. No mismatch was observed between the cultures themselves or the highlighting of methicillin resistance in either Staphylococcus aureus isolates or for coagulase-negative staphylococci, regardless of species. Furthermore, the red colour of Staphylococcus aureus on the medium allowed visualisation of the colonies after only about ten hours incubation, thus giving the clinician rapid warning of suspected methicillin resistant Staphylococcus aureus. In addition, in polymicrobial cultures the different colour of the colonies of Staphylococcus aureus (red) and coagulase-negative staphylococci (white) is extremely useful.