Dual-Species Model Biofilm Consisting of Listeria monocytogenes and Salmonella Typhimurium: Development and Inactivation With Cold Atmospheric Plasma (CAP)

Abstract

Most environmental biofilms contain a variety of species. These species can establish cooperative and competitive interactions, possibly resulting in an increase or a decrease in antimicrobial resistance. Therefore, results obtained following inactivation of single-species biofilms by means of different technologies (e.g., Cold Atmospheric Plasma, CAP) should be validated for multi-species biofilms. First, a strongly adherent and mature Listeria monocytogenes and S. Typhimurium dual-species biofilm was developed by altering different incubation conditions, i.e., growth medium, incubation temperature, inoculum ratio of L. monocytogenes and S. Typhimurium cells, and incubation time. Adherence and maturity were quantified by means of optical density measurements and viable plate counts, respectively. Secondly, both the (1 day old) reference biofilm and a more mature 7 days old biofilm were treated for different CAP treatment times (0–30 min). Viable plate counts were again used to determine the (remaining) cell density. For both the biofilm development and inactivation, predictive models were applied to describe the growth/inactivation kinetics. Finally, the kinetics of the [1 and 7 day(s) old] dual-species biofilms were compared with those obtained for the corresponding single-species biofilms. Results implied that a strongly adherent and mature reference dual-species biofilm was obtained following 24 h of incubation at 25°C using 20-fold diluted TSB and an inoculum ratio of 1:1. Main observations regarding CAP inactivation were: (i) the dual-species biofilm age had no influence on the CAP efficacy, although a longer treatment time was required for the oldest biofilm, (ii) for the 1 day old biofilms, CAP treatment became less efficient for S. Typhimurium inactivation when this species was part of the dual-species biofilm, while L. monocytogenes inactivation was not influenced by the biofilm type, and (iii) for the 7 days old biofilms, CAP inactivation of both species became more efficient when they were part of the dual-species biofilms. It can be concluded that the efficacy of the CAP treatment is altered when cells become part of a dual-species biofilm, which is quite important with respect to a possible application of CAP for biofilm inactivation within the food industry.

Bacteriophage-Derived Depolymerases against Bacterial Biofilm

“…Importantly, due to cooperative interactions between them, the multispecies biofilms may display greater resistance to external stressful factors, including antibiotics and disinfectants, relative to the single-species community. This property is probably related to increased biomass and/or an altered composition of the EPS matrix [ 51 , 52 , 53 ].…”

Inactivation of L. monocytogenes and S. typhimurium Biofilms by Means of an Air-Based Cold Atmospheric Plasma (CAP) System

“…Predictive models were used to determine (i) the CAP inactivation kinetics and (ii) the efficacy of the treatment for each of the different model biofilms. Finally, the results obtained within this study were compared to previous research using a helium-operated CAP system for inactivation of similar single-and dual-species model biofilms [12][13][14]. Hence, the use of a small amount of previously obtained data can help to draw more general conclusions about the influence of certain plasma characteristics (i.e., the operating gas and the electrode configuration) on the biofilm inactivation efficacy of CAP.…”

“…Cold Atmospheric Plasma (CAP) is one of these promising novel methods for biofilm inactivation as log-reductions up to 4 log 10 (CFU/cm 2 ) have been obtained for inactivation of L. monocytogenes and S. typhimurium (single/dual-species) biofilms (e.g., [10][11][12][13][14]). CAP is a specific type of plasma which can be created by the addition of energy to a gas at room temperature and at atmospheric pressure.…”

All Treatment Parameters Affect Environmental Surface Sanitation Efficacy, but Their Relative Importance Depends on the Microbial Target

“…Coculturing has been shown to have heterogeneous effects on both community formation and sanitizer tolerance, generally explained by the difference between competitive and cooperative interactions among microorganisms. Govaert et al ( 33 ) compared L. monocytogenes and Salmonella Typhimurium in both mono- and cocultured biofilms, finding that the coculture was less resistant to cold atmospheric plasma compared to monocultures, possibly due to the production of bacteriocins within the community. In contrast, Pang et al ( 35 ) observed the cooperative interactions within the cocultured community.…”