High Disinfectant Tolerance in Pseudomonas spp. Biofilm Aids the Survival of Listeria monocytogenes

Abstract

Pseudomonas spp. are the most commonly found bacteria in food-processing environments due to properties such as a high growth rate at low temperatures, a high tolerance of antimicrobial agents, and biofilm formation. In this study, a set of Pseudomonas isolates originating from cleaned and disinfected surfaces in a salmon processing facility were screened for biofilm formation at 12 °C. A high variation in biofilm formation between the isolates was observed. Selected isolates, in both planktonic and biofilm states, were tested for resistance/tolerance to a commonly used disinfectant (peracetic acid-based) and antibiotic florfenicol. Most isolates showed a much higher tolerance in the biofilm state than in the planktonic state. In a multi-species biofilm experiment with five Pseudomonas strains with and without a Listeria monocytogenes strain, the Pseudomonas biofilm appeared to aid the survival of L. monocytogenes cells after disinfection, underscoring the importance of controlling the bacterial load in food-processing environments.

Multi-species biofilms of environmental microbiota isolated from fruit packing facilities promoted tolerance of Listeria monocytogenes to benzalkonium chloride

“…Similar to our results, previous work has shown that biofilms composed of strains of L. monocytogenes and Pseudomonas aeruginosa were dominated by Pseudomonas , which represented 99 % of the biofilm composition [ 9 ]. Similarly, Thomassen et al (2023) [ 70 ] grew multi-species biofilms composed of one strain of L. monocytogenes and five strains of Pseudomonas spp. for three days and determined that L. monocytogenes concentration represented 0.9 % of the total biofilm biomass [ 70 ].…”

“…Similarly, Thomassen et al (2023) [ 70 ] grew multi-species biofilms composed of one strain of L. monocytogenes and five strains of Pseudomonas spp. for three days and determined that L. monocytogenes concentration represented 0.9 % of the total biofilm biomass [ 70 ]. Nonetheless, it should be noted that in these two studies [ 9 , 70 ], culture-based techniques were used to quantify bacteria and likely did not account for potential persister cells within the biofilms.…”

“…for three days and determined that L. monocytogenes concentration represented 0.9 % of the total biofilm biomass [ 70 ]. Nonetheless, it should be noted that in these two studies [ 9 , 70 ], culture-based techniques were used to quantify bacteria and likely did not account for potential persister cells within the biofilms. To the best of our knowledge, no previous study has included strains of Xanthomonadaceae, Microbacteriaceae , or Flavobacteriaceae when studying multi-species biofilms and persistence of L. monocytogenes .…”

Microbial composition and dynamics in environmental samples from a ready-to-eat food production facility with a long-term colonisation of Listeria monocytogenes

“…The interactions between L. monocytogenes and Pseudomonas spp. within biofilms have been studied in laboratory models [11,12,79,80], highlighting the protective effect of Pseudomonas spp., particularly P. fluorescens, towards L. monocytogenes. The effect of other members of the resident microbiota of FPE can either enhance or inhibit the survival of L. monocytogenes [81,82].…”

“…The resident microbiota that coexists with L. monocytogenes in environmental settings may have a role in the survival of this pathogen. For example, a protective effect of Pseudomonas biofilms on L. monocytogenes has been observed, which suggested that control of Pseudomonas in the FPE could reduce contamination of L. monocytogenes [11,12]. Studies using amplicon sequencing or metagenomics alongside culture enrichments have explored the resident microbiota coexisting with L. monocytogenes in various FPE [2], including fish and meat processing settings, dairy factories [13] and fruit packing facilities [14].…”