Which bacterium is a known opportunistic pathogen frequently found in moist environments?

Pseudomonas aeruginosa is well-recognized as an opportunistic pathogen that thrives in moist environments, making it particularly adept at causing infections in individuals with compromised immune systems, such as those with cystic fibrosis, burn wounds, or other underlying health conditions. This bacterium is common in natural and artificial moist environments, including soil, water, and various hospital settings where it can colonize equipment or surfaces.

Pseudomonas aeruginosa's ability to survive in adverse conditions, combined with its resistance to many antibiotics, makes it a significant threat in healthcare-associated infections. It can cause a wide range of infections, including respiratory tract infections, urinary tract infections, and bloodstream infections, particularly in patients who are already vulnerable.

In contrast, the other bacteria listed are associated with different clinical scenarios or environments. Staphylococcus epidermidis is primarily a skin commensal and is more commonly associated with infections related to indwelling medical devices. Clostridium tetani, the causative agent of tetanus, is found in soil and is not typically considered an opportunistic pathogen in moist environments. Enterococcus faecalis can cause infections but is not specifically linked to moist environments like Pseudomonas aeruginosa is.