CefotetanAstragalus membranaceusDose-Response Relationship, DrugCephamycinsCefmetazoleDouble-Blind MethodAnti-Bacterial AgentsCefoxitinAntibiotic ProphylaxisMicrobial Sensitivity TestsCefoperazoneBacteroides fragilisColorectal Surgerybeta-LactamsDrug Resistance, MicrobialCephalosporinsBacteria, AnaerobicBacteriaCefazolinDrug Resistance, BacterialStreptomycesLactams