What is the usual causative agent of hot tub lung?

Hot tub lung is primarily caused by exposure to Mycobacterium avium complex (MAC), which is a group of bacteria commonly found in water, especially in warm, stagnant conditions like those found in hot tubs. The inhalation of aerosolized water containing these bacteria can lead to lung inflammation and a characteristic hypersensitivity pneumonitis.

While other organisms, such as Aspergillus species, can be associated with pulmonary infections, particularly in immunocompromised individuals, they do not typically result in hot tub lung. Similarly, E. coli is associated with gastrointestinal infections and not with lung-related issues in this context, and Streptococcus pneumoniae is known for causing typical pneumonia but is not linked to hot tub lung. Understanding the specific environmental conditions and the nature of the pathogens involved is crucial in identifying the correct causative agent of this unique condition.