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Chapter 4
through laboratory based models on a diverse range of surfaces including
concrete, tiles, stainless steel, glass, silestone, granite, rubber and a
multitude of synthetic plastics [97-98]. Control of Salmonella biofilm
presents a challenge for the food industry. As discussed in chapter 3,
Salmonella species have been described as environmental persisters [89].
Long-term persistence of Salmonella on surfaces is likely to be associated
with the ability to form biofilm and withstand disinfectants [56, 134].
Microbial biofilm formation may increase resistance to disinfectants due to
failure of disinfectant to penetrate through the proteinaceous
extrapolymeric substances formed on the outer layer of the biofilm
resulting in less diffusion and interaction with viable cells. Cellular changes
such as a reduced growth rate, changes in metabolic activity and up
regulation of genes responsible for biofilm formation, lipid formation,
cellular transport, chemotaxis and resistance genes may also contribute to
resistance to disinfectants and other antimicrobial compounds [102, 105].
Over an extended period of exposure or through repeated intermittent
exposure, Salmonella can develop acquired resistance to disinfectants [132,
197]. Disinfectants and other antimicrobial products are commonly used
for cleaning surfaces and equipment in the food industry to reduce the risk
of product contamination. As a result microorganisms which are
introduced to premises on raw meat and other products may come into
contact with surface disinfectants from an early stage of processing.
Furthermore, raw carcasses are frequently sprayed with antimicrobial
agents using high pressure water jets or dipping in large water tanks in
order to reduce the microbial load on raw products [199]. After the
carcasses are sprayed, the antimicrobial products are in direct contact with
microorganism on the meat and can also be introduced to the environment
in large volumes [102]. If bacteria survive disinfectant treatment, the
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