Mycobacterium avium is a waterborne opportunistic pathogen commonly detected in
drinking water. The resistance of M. avium to common chemical disinfectants at a wide
range of temperatures and pH levels allows this microorganism to persist in drinking
water distribution systems. The mechanisms responsible for the survival of M. avium
in drinking water are not well understood. The persistence of M. avium in distribution
systems has been associated to their presence in biofilms or suspended particles inside
which these microorganisms appear to gain protection against disinfectant attack.
Because chlorine reacts with biofilm or particulate organic matter, the embedded cells
are exposed to lower disinfectant concentrations. Previous work (Tong et al., 2002)
has shown that a relatively low concentration of monochloramine (< 1 mg/L as Cl2) at
20oC and pH 8 could trigger an adaptive response, which made the bacteria about 2.8
times more resistant than the ones treated with a relatively high concentration of
monochloramine (> 5 mg/L as Cl2). Furthermore, preliminary results in this study
suggested that once the adaptive response was triggered by exposure to a relatively low
concentration of monochloramine, the bacteria were able to present greater resistance
to inactivation during subsequent exposure to a relatively high concentration of the
disinfectant. This finding can contribute to the explanation of why M. avium can
survive in drinking water distribution systems both in planktonic form and in biofilms.
Accordingly, the objective of this study was to assess if an adaptive response occurred
during the sequential inactivation of M. avium with monochloramine. Materials and methods explained in the paper included: preparation of bacterial suspension; single-step disinfection; sequential disinfection; and, viability assessment. Includes 6 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 270 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 7 |
| Published : | 11/02/2003 |
