Impact of Xpert MRSA/SA blood culture PCR assay on management of positive blood cultures in obstetric patients: a retrospective audit.

Abstract

The Xpert MRSA/SA blood culture assay (Cepheid, USA) is a rapid PCR test which can be used for positive blood cultures where Gram-positive cocci in clusters are seen. It can detect Staphylococcus aureus and also the mecA gene, which encodes for β-lactam resistance. The assay was introduced into the Rotunda Hospital for positive blood cultures to allow earlier detection of MRSA and methicillin susceptible S. aureus. To assess the impact of the Xpert MRSA/SA blood culture assay on the management of obstetric patients with a positive blood culture where Gram-positive cocci in clusters were seen. The main outcome measures were duration of intravenous antimicrobials and length of admission. Pre-intervention and post-intervention groups were identified relating to whether or not the test was in use at the time. A standardised form was used to retrospectively review the medical notes and laboratory results. There were 35 obstetric patients with positive blood cultures with Gram-positive cocci in clusters in the pre-intervention group and 22 cases in the post-intervention group. All 22 positive blood cultures in the post-intervention period were correctly identified. The antimicrobial duration was reduced from a median of 55.5-43.5h and length of admission reduced from a median of 66.5-56h (Mann-Whitney U value=161, p=0.46 and U value=256, p=0.15, respectively). This study has shown a reduction in the median duration of intravenous antimicrobials and admission; however, larger multi-centre studies are needed to evaluate this potential benefit further.