Most likely pathogens
Penicillin G 2 million units IV q4h
AND
Metronidazole 500mg IV q12h
Vancomycin 25mg/kg IV loading dose x 1 dose followed by 15mg/kg IV with interval to be determined by vancomycin nomogram
Oral should only be used after adequate source control
Amoxicillin-clavulanate 875-125mg PO BID
Cotrimoxazole DS 2 tablets PO BID
Metronidazole 500mg PO BID
OR
Doxycycline 100mg PO BID