Differential Biofilm Formation and Chemical Disinfection Resistance of Sessile Cells of Listeria monocytogenes Strains under Monospecies and Dual-Species (with Salmonella enterica) Conditions

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>This study aimed to investigate the possible influence of bacterial intra- and interspecies interactions on the ability of<jats:named-content content-type="genus-species">Listeria monocytogenes</jats:named-content>and<jats:named-content content-type="genus-species">Salmonella enterica</jats:named-content>to develop mixed-culture biofilms on an abiotic substratum, as well as on the subsequent resistance of sessile cells to chemical disinfection. Initially, three strains from each species were selected and left to attach and form biofilms on stainless steel (SS) coupons incubated at 15°C for 144 h, in periodically renewable tryptone soy broth (TSB), under either monoculture or mixed-culture (mono-/dual-species) conditions. Following biofilm formation, mixed-culture sessile communities were subjected to 6-min disinfection treatments with (i) benzalkonium chloride (50 ppm), (ii) sodium hypochlorite (10 ppm), (iii) peracetic acid (10 ppm), and (iv) a mixture of hydrogen peroxide (5 ppm) and peracetic acid (5 ppm). Results revealed that both species reached similar biofilm counts (ca. 10<jats:sup>5</jats:sup>CFU cm<jats:sup>−2</jats:sup>) and that, in general, interspecies interactions did not have any significant effect either on the biofilm-forming ability (as this was assessed by agar plating enumeration of the mechanically detached biofilm bacteria) or on the antimicrobial resistance of each individual species. Interestingly, pulsed-field gel electrophoresis (PFGE) analysis clearly showed that the three<jats:named-content content-type="genus-species">L. monocytogenes</jats:named-content>strains did not contribute at the same level either to the formation of mixed-culture sessile communities (mono-/dual species) or to their antimicrobial recalcitrance. Additionally, the simultaneous existence inside the biofilm structure of<jats:named-content content-type="genus-species">S. enterica</jats:named-content>cells seemed to influence the occurrence and resistance pattern of<jats:named-content content-type="genus-species">L. monocytogenes</jats:named-content>strains. In sum, this study highlights the impact of microbial interactions taking place inside a mixed-culture sessile community on both its population dynamics and disinfection resistance.</jats:p>

Is peracetic acid suitable for the cleaning step of reprocessing flexible endoscopes?

“…Similar results were found with an E. coli biofilm and peracetic acid/H2O2 [153] . The resistance of biofilms can often further increase when the communities are composed of more than one bacterial species [134,136,[160][161][162][163] which may include resistance against 0.35% peracetic acid, which is a concentration used in many formulations [133] . Especially "build-up" biofilms mimicking repeated endoscope reprocessing cycles exhibited a significantly higher survival rate than 'traditional' biofilms [158] .…”

“…Under natural environmental conditions, biofilms are likely to be composed of a mixture of different species [131,132] . In the laboratory, they can be grown on various materials and devices, including polystyrene microtitre plates [133][134][135][136] , haemolysis glass tubes [137,138] , stainless steel coupons [134,139] and also in Teflon tubes [140][141][142][143] , similar to endoscope channels.…”

Differential biofilm formation and chemical disinfection resistance of Escherichia coli on stainless steel and polystyrene tissue culture plate

“…Biofilm formation on SS coupons was conducted using the method described by Kostaki et al, 20 with some modifications. 200 µl aliquot of 10 8 CFU/ml suspension of E. coli strain was inoculated on each of the coupons inside petri dishes and allowed to attach for 3 hours at room temperature.…”

“…19 After 16 hours of incubation, 10 ml of the incubated strain were centrifuged at 5000 x g for 5 min at 10°C, washed twice in 10 ml of Phosphate Buffer Saline (PBS) (pH 7.3). 20 The cell pellets were re-suspended in 10 ml of TSB to an optical density of 0.5 at 600 nm (OD 600 ) which corresponds to approximately 10 8 CFU/ml.…”

Efficacy of a Sonicating Swab for Removal and Capture of Listeria monocytogenes in Biofilms on Stainless Steel

“…Examples of such surfaces are found in many industries (e.g., butcher houses, floors, and machinery in food processing plants) and within medical devices in hospital settings (8)(9)(10). Biofilms are composed of bacterial cells and extracellular polymeric substances (EPS); the formation of such matrices supports desiccation tolerance, adherence, and protection from cleansers and sanitizers (11)(12)(13). Furthermore, surface adherence, especially inside and around complex topographical features, enables colonization solidity, reducing the overall efficacy of surface sampling techniques and allowing microorganisms essentially to hide from detection.…”