The agency granted the treatment priority review with a Prescription Drug User Free Act action date of 23 July 2016.
Bezlotoxumab is also under review by the European Medicines Agency (EMA) for marketing authorization.
The antitoxin is given in conjunction with standard-of-care antibiotics, and is designed to neutralize C. difficile toxin B, which is capable of damaging the gut wall and lead to diarrhea.
It met primary efficacy endpoint in two phase 3 clinical trials, which included more than 2,600 participants in several countries.
C. difficile is a bacterium that causes diarrhea and more serious intestinal conditions like colitis. The incidence of C. difficile infection has increased rapidly in the last two decades.
According to the US Centers for Disease Control and Prevention (CDC), C. difficile is expected to have caused around half a million infections in the US in 2011.
Merck Research Laboratories senior vice president of clinical development Roy Baynes said: "Currently, there are no therapies approved for the prevention of C. difficile infection recurrence.
"As part of Merck’s commitment to the fight against infectious diseases, we look forward to continuing to work with the FDA and EMA to bring forward this novel medicine for appropriate patients."
In a separate development, Merck has formed a collaboration with AbCellera to generate antibodies against an undisclosed disease target.
Under the deal, AbCellera will apply its high-throughput antibody discovery platform to find antibodies that specifically modulate target function.
The deal grants Merck the option to develop antibody candidates identified through the collaboration for specified therapeutic applications.
Image: Bezlotoxumab is given in conjunction with standard-of-care antibiotics. Photo: courtesy of Mister GC/FreeDigitalPhotos.net.