In both the 2010 and 2016 guidelines, the recommendation for empiric Gram positive coverage included Vancomycin or a first-generation cephalosporin. While I am not aware of any literature demonstrating issues with oxacillin in particular, it is true that oxacillin was removed as an option from the table of IP drug dosing for peritonitis (perhaps related to its less frequent use and therefore less literature on its use). When treating CNS peritonitis, if it is methicillin-sensitive, patients should respond to cefazolin, and if methicillin-resistant, Vancomycin should be used. In centers with high rates of methicillin-resistant organisms, it would be preferable to use Vancomycin first-line for Gram positive coverage.