Persistent <em>Listeria monocytogenes</em> Isolates from a Poultry-Processing Facility Form more Biofilm but Do Not Have a Greater Resistance to Disinfectants Than Sporadic Strains

• Main Authors: Daniel Rodríguez-Campos, Cristina Rodríguez-Melcón, Carlos Alonso-Calleja, Rosa Capita
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: Pathogens
• Subjects: listeria monocytogenes; persistent strains; sporadic strains; biofilm formation; resistance to disinfectants
• Online Access: https://www.mdpi.com/2076-0817/8/4/250

Some strains of <i>Listeria monocytogenes</i> can persist in food-processing environments, increasing the likelihood of the contamination of foodstuffs. To identify traits that contribute to bacterial persistence, a selection of persistent and sporadic <i>L. monocytogenes</i> isolates from a poultry-processing facility was investigated for biofilm-forming ability (crystal violet assay). The susceptibility of sessile cells to treatments (five minutes) with sodium hypochlorite having 10% active chlorine (SHY: 10,000 ppm, 25,000 ppm, and 50,000 ppm) and benzalkonium chloride (BZK: 2500 ppm, 10,000 ppm, and 25,000 ppm) was also studied. All isolates exhibited biofilm formation on polystyrene. Persistent strains showed larger (<i>p</i> &lt; 0.001) biofilm formation (OD₅₈₀ = 0.301 ± 0.097) than sporadic strains (OD₅₈₀ = 0.188 ± 0.082). A greater susceptibility to disinfectants was observed for biofilms of persistent strains than for those of sporadic strains. The application of SHY reduced biofilms only for persistent strains. BZK increased OD₅₈₀ in persistent strains (2500 ppm) and in sporadic strains (all concentrations). These results indicate that the use of BZK at the concentrations tested could represent a public health risk. Findings in this work suggest a link between persistence and biofilm formation, but do not support a relationship between persistence and the resistance of sessile cells to disinfectants.