“…Infectious diseases associated with the biofilm of dental unit waterlines (DUWLs) are RTIs due to Legionella pneumphila, Pseudomonas aeruginosa, Mycobacterium, which are not or minimally contagious and affect immune-compromised individuals with consequently high case-fatality rates. This paper reported that the microorganisms from DUWLs were qualitatively and quantitatively different from the airborne microorganisms, thus suggesting that human microorganisms are likely to be the main source of airborne bacteria in the dental offices 6 . This result does not imply that DUWLs are not a source of airborne microorganisms, as it was previously demonstrated that more than 70% of DUWLs were contaminated by oral streptococci, selective microorganisms of the upper respiratory tract 7 , but only that human microorganisms prevail to bacteria from the aquatic biofilm.…”