The major public health issue - Presence of Mycobacterium avium paratuberculosis in drinking and unfit water of Porto geographical area detected by quantitative PCR

Mycobacterium avium subsp. paratuberculosis (MAP) has been implicated in the development of inflammatory bowel disease (IBD) and colorectal cancer. Portugal has a high prevalence of IBD and Porto is one of the Portuguese districts with higher IBD prevalence. Our goal was to assess MAP contamination in drinking and domestic untreated water sources in Porto geographical area, since water may be an important contaminating source of MAP for humans. One liter of public drinking water and/or a domestic untreated water source were collected at different locations in Porto area in early Autumn. Biofilms were also collected by swabbing tap inner surfaces with a sterile cotton swab. A second collection of domestic untreated water was performed after winter rains, in early February. Water samples were filtered and DNA was extracted from both water filters and biofilm suspensions using specific commercial kits. MAP contamination was evaluated through a IS900-based nested PCR assay. Drinking water samples showed higher MAP contamination than domestic water collected in Autumn. In February, MAP detection significantly increased in domestic water. MAP DNA was detected at a higher frequency in tap biofilms than in the corresponding water collected. Drinking and domestic water may be important sources of MAP contamination in Porto area. The increased MAP detection observed after winter rains in domestic water may reflect soil leaching. Since MAP can resist to water treatment procedures and persist in biofilms, increased microbial surveillance and development of new water treatment methods are most needed to avoid human exposure to this resilient pathobiont.