This article, originally published on July 12, has been updated from a previous version to include a statement from Cepheid.

Point-of-care diagnostic firm Abaxis has sued Cepheid, alleging that its PCR-based blood test for methicillin-resistant Staphylococcus aureus infringes sample-prep patents owned by Abaxis, according to recently filed court documents.

In response, Cepheid has filed a counterclaim denying the alleged infringement and asking the court to find that Abaxis' patents are invalid.