Disinfectant Susceptibility of Biofilm Formed by Listeria monocytogenes under Selected Environmental Conditions

Abstract

Listeria monocytogenes is a one of the most important food-borne pathogens. Its ability to form biofilm contributes to increased resistance to disinfectants and inefficient disinfection, posing a serious threat for the food industry, and in the end the consumer. The aim of this study was the comparison of the biofilm formation ability of L. monocytogenes strains on stainless steel, under different environmental conditions (temperature, pH, NaCl concentration, nutrients availability), and the assessment of biofilm susceptibility to disinfectants. The bactericidal activity of four disinfectants in two concentrations (100% and 50% of working solution) against biofilm was conducted on four clinical strains, four strains isolated from food and one reference strain ATCC 19111. It was found that biofilm susceptibility to disinfectants was influenced by environmental conditions. Biofilm susceptibility correlated with the decrease of temperature, pH, nutrients availability and salinity of the environment. The least sensitive to disinfectants was biofilm produced at pH = 4 (the bacterial number ranged from 0.25 log CFU × cm−2 to 1.72 log CFU × cm−2) whereas the most sensitive was biofilm produced at pH = 9 (5.16 log CFU × cm−2 to 7.84 log CFU × cm−2). Quatosept was the most effective disinfectant, regardless of the conditions. In conclusion, biofilm susceptibility to disinfectants is strain-dependent and is affected by environmental conditions.

Interference of sanitizers, NaCl and curing salts on Listeria monocytogenes adhesion and subsequent biofilm formation

“…In the present study, the four tested sanitizers were active against L. monocytogenes, although the quaternary ammonium based product (S1) presented higher efficiency when compared to the other tested compounds, based in the minimum inhibitory concentration (MIC) test and response presented by each selected isolate, as shown in Table 1. Similar results have been observed by Skowron et al (2019), comparing a quaternary ammonium-based product to products based on iodine, peracetic acid and hydrogen peroxide.…”

“…1, Table S1). In addition, results also demonstrated capacity of some isolates to grow biofilms at high salt concentrations (10% NaCl and 10% curing salts) when cultured at 37°C, considering that L. monocytogenes is relatively resistant to variations in salt concentrations, as described in previous studies (Jensen et al 2007;Caly et al 2009;Galvão et al 2012;Skowron et al 2019). NaCl can enhance the attachment of bacterial cells, depending on physicochemical properties of the surface, and it is known that polystyrene is uncharged and highly hydrophobic (Tresse et al 2007;Caly et al 2009).…”

“…As observed in the present study, several characteristics of L. monocytogenes can influence the adhesion and biofilm formation, such as their serotypes, flagella expression, exopolysaccharides (EPS) composition, adhering surface and environment conditions (pH, temperature, and culture medium) (da Silva and De Martinis 2013). Listeria can rapidly adhere in food processing utensils and equipment (about 20 min), allowing the development of mature biofilms within 24 h. Once formed and matured, the complex structure of biofilms creates a protection against adverse conditions, such as temperature and pH variations, high salinity and low nutrient availability, as well as disinfectants (Skowron et al 2019). Despite being a critical step of biofilm formation, adhesion potential of the isolates was not assessed once it should be verified after the initial time of contact and growth.…”

Prevalence and antimicrobial susceptibility of Listeria monocytogenes strains isolated from a meat processing plant

“…The biofilm structure makes the eradication of bacteria from such a community much more difficult than their planktonic forms [16,36,37,38]. It has been shown (Smith and Hunter, 2008), that bacterial cells in the biofilm structure differ phenotypically from cells in the planktonic form, especially in the degree of resistance to disinfectants.…”

“…The bacterial resistance to antimicrobials in biofilm might be even 10-1,000 times higher [39]. The biofilm formation affects bacterial resistance to stress factors, including the disinfectants used to limit microbiological contamination of the food processing environment, thereby becoming a serious problem for food safety [37,40]. Resistance of biofilm to disinfectants varies depending on its structure, maturity,…”