Final answer:
C. difficile is the organism responsible for overgrowth in antibiotic-associated colitis infections. This overgrowth commonly occurs after the normal gut microbiota is disrupted by antibiotic use, especially in immunocompromised patients. Fecal transplants can effectively restore normal gut bacteria to treat these infections.
Step-by-step explanation:
In the context of antibiotic-associated colitis infections, the organism that is typically responsible for overgrowth is Clostridium difficile (C. difficile), a gram-positive, rod-shaped bacterium. When long-term antibiotic use disrupts the normal microbiota of the gut, it potentially leads to the overgrowth of C. difficile, causing antibiotic-associated diarrhea. This condition is particularly dangerous for immunocompromised patients or those in healthcare settings for prolonged periods. In addition to causing severe colitis and diarrhea, C. difficile is also notorious for forming endospores, which allows it to survive in harsh environments and contribute to hospital-acquired infections.
Patients with C. difficile infections (CDI) are often those who have recently undergone antibiotic treatments, which reduce the competitive microbial flora in the intestine, allowing C. difficile to proliferate. An innovative treatment for CDI has involved fecal transplants to restore the normal intestinal microbial community.