Salmonella Biofilms Extremely Resistant to Disinfectants
Disinfectants are not able to kill after 7 days growth of Salmonella
Researchers at the National University of Ireland, Galway, have discovered that
common disinfectants face an uphill battle killing Salmonella once it has had the time to form a biofilm – a community
of cells that attach to each other and a surface, increasing the density of
bacterial growth and providing support from harsh environments. Allowed Salmonella enterica cells to grow for seven days before applying
three types of disinfectant: sodium hypochlorite, sodium hydroxide and
benzalkonium chloride.
They found that none of the disinfectants was
able to kill the cells after that amount of time. Even soaking the biofilms in
disinfectant for an hour and a half failed to kill them.
Once
Salmonella cells are allowed to become established on a surface, the
number of cells will increase over time, resulting in difficulty if not impossible to completely eliminate or kill all cells once
part of a mature biofilm.
The
strains she tested were able to form a biofilm on glass, steel, polycarbonate
plastic, glazed tile and concrete.
In terms of ‘real world’ environments, it is
estimated that most organisms are capable of this, and that a high percentage
of micro-organisms will form a biofilm to optimize growth and survival.
To head off an issue of resistance, recommended appropriate and frequent cleaning
to prevent the buildup of bacteria on surfaces and improving handling practices
such as ensuring raw food is prepared in a separate area from cooked food to
reduce the risk of cross-contamination.
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