Patient description: The patient is a 60-year-old woman admitted to the stroke department with a recent history of a second course of intravenous antibiotics for aspiration pneumonia. She is febrile and complained of abdominal pain and diarrhea (bowel movements eight times in 3 hours, large volumes of greenish, liquid stool each time). The patient's abdomen is generally tender and distend with hyperactive bowel sounds. She is febrile (38.4°C), tachycardic (113/min) and hypotensive (80/40 mmHg). The stool samples must were positive for Clostridium difficile toxin.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Clostridium Difficile Infection Participant has a diagnosis of CDI defined as: a) presence of diarrhea (passage of 3 or more loose stools in 24 or fewer hours); and b) positive test for toxigenic C. difficile from a stool collected no more than 7 days before study infusion Participant is receiving SOC therapy (i.e., oral metronidazole, oral vancomycin, IV metronidazole concurrent with oral vancomycin, oral fidaxomicin, or oral fidaxomicin concurrent with IV metronidazole) for CDI Participant is highly unlikely to become pregnant or to impregnate a partner by meeting at least one of the following a) females not of reproductive potential (i.e., one who has either (1) reached natural menopause, defined as 6 months of spontaneous amenorrhea with serum follicle stimulating hormone [FSH] levels in the postmenopausal range, or 12 months of spontaneous amenorrhea not including cases with an underlying disease, such as anorexia nervosa, that causes amenorrhea; (2) 6 weeks post surgical bilateral oophorectomy with or without hysterectomy; or (3) bilateral tubal ligation); or b) participants of reproductive potential who agree to remain abstinent or use (or have their partner use) two acceptable methods of birth control (i.e., intrauterine device [IUD], diaphragm with spermicide; contraceptive sponge, condom, vasectomy and any registered and marketed hormonal contraceptives that contain an estrogen and/or progestational agent including oral, subcutaneous, intrauterine, or intramuscular agents) starting at enrollment and throughout the 12-week study  Participant with an uncontrolled chronic diarrheal illness such that their normal 24-hour bowel movement habit is 3 or more loose stools Participant with planned surgery for CDI within 24 hours Female participant with a positive pregnancy test in the 48 hours before infusion and pre-menopausal females who are not sterilized and therefore have the potential to bear a child who are unwilling to undergo pregnancy testing Female participant breast feeding or planning to breast feed before completion of the 12-week study Female participant planning to donate ova before completion of the 12-week study and male participants planning to impregnate or donate sperm before completion of the 12-week study Participant has previously participated in this study, has previously received MK-3415 or MK-6072 (either alone or in combination), has received a C. difficile vaccine, or has received another experimental monoclonal antibody against C. difficile toxin A or B Participant plans to donate blood and/or blood products within 6 months after infusion Participant has received immune globulin within 6 months before infusion or is planning to receive immune globulin before completion of the 12-week study Treatment with SOC therapy is planned for longer than 14 days Participant has received more than a 24-hour regimen of cholestyramine, colestimide, rifaximin, or nitazoxanide within 14 days before infusion or plans to receive these medication before completion of the 12-week study period