Metronidazole Injection, USP is indicated in the treatment of serious infections caused by susceptible anaerobic bacteria. Indicated surgical procedures should be performed in conjunction with Metronidazole therapy. In a mixed aerobic and anaerobic infection, antibiotics appropriate for the treatment of the aerobic infection should be used in addition to Metronidazole. Metronidazole is effective in Bacteroides fragilis infections resistant to clindamycin, chloramphenicol and penicillin. Intra-abdominal Infections, including peritonitis, intra-abdominal abscess and liver abscess, caused by Bacteroides species including the B. fragilis group (B. fragilis, B. distasonis, B. ovatus,B. thetaiotaomicron, B. vulgatus).Clostridium species, Eubacterium species, Peptococcus species, and Peptostreptococcus species. Skin and Skin Structure Infections caused by Bacteroides species including B. fragilis group, Clostridium species, Peptococcus species, Peptostreptococcus species and Fusobacterium species. Gynecologic Infections, including endometritis, endomyometritis, tubo-ovarian abscess, and post-surgical vaginal cuff infection, caused by Bacteroides species including the B. fragilis group, Clostridium species, Peptococcus species and Peptostreptococcus species. Bacterial Septicemia caused by Bacteroides species including the B. fragilis group and Clostridium species. Bone and Joint Infections, as adjunctive therapy, caused by Bacteroides species including the B. fragilis group. Central Nervous System (CNS) Infections, including meningitis and brain abscess, caused by Bacteroides species including the B. fragilis group. Lower Respiratory Tract Infections, including pneumonia, empyema, and lung abscess, caused by Bacteroides species including the B. fragilis group. Endocarditis caused by Bacteroides species including the B. fragilis group. Prophylaxis: The prophylactic administration of Metronidazole Injection, USP preoperatively, intraoperatively, and postoperatively may reduce the incidence of postoperative infection in patients undergoing selective colorectal surgery which is classified as contaminated or potentially contaminated.