Direct detection of mecA, nuc and 16S rRNA genes in BacT/Alert blood culture bottles.

A benzyl alcohol-guanidine hydrochloride extraction method was used to remove sodium polyanetholesulfonate present in BacT/Alert blood culture bottles. Multiplex PCR using touchdown annealing was used to detect the mecA, nuc, and 16S rRNA genes in bottles growing staphylococci. This direct PCR assay demonstrated excellent sensitivity, specificity and improved accuracy compared to routine phenotypic methods for determination of methicillin resistance in coagulase negative staphylococci (CoNS). However, with this PCR assay, bottles that contained both methicillin-resistant CoNS and methicillin-susceptible Staphylococcus aureus would be misidentified as containing methicillin-resistant S. aureus.