Adaptive hydrophobicity shifts in Listeria monocytogenes under subinhibitory exposure to benzalkonium chloride, peracetic acid and sodium hypochlorite

The phospholipid layer is central to Listeria monocytogenes tolerance to disinfectants. We profiled surface hydrophobicity by Microbial Adhesion to Solvents (MATS) in 19 strains, tested in wild type and after adaptation to ½ MIC of benzalkonium chloride (BKC), peracetic acid (PAA), or sodium hypochlorite (SHY). We first compared two hydrocarbons for MATS (i.e. xylene vs hexadecane) to optimize solvent choice. Wild strains measured with xylene clustered near zero or negative affinity, whereas hexadecane shifted distributions to positive values with lower intra-strain variability. Across three representative strains adapted to each disinfectant, hexadecane showed significantly greater affinity than xylene (P < 0.001), and overall solvent effects were significant (P < 0.05), supporting hexadecane as the analytical solvent. Using hexadecane, wild strains were weakly hydrophobic ( 0.05). BKC adaptation produced minimal change as most strains remained 50 %), with MATS means ranging from 50.58 ± 18.75 % to 73.54 ± 7.64 %. Moreover, four strains (i.e. CECT 5672, 4423, R6, S1(R)) stayed weakly hydrophobic (6.64 ± 39.49 % to 17.97 ± 23.61 %), and two (Lm4, Lm5) were moderate (20-50 %). Overall, adaptation to subinhibitory disinfectant concentrations revealed distinct, strain-dependent surface responses that may influence bacterial persistence potential. These findings contribute to understanding how routine disinfectant exposure can shape the phenotypic resilience of L. monocytogenes, providing insights relevant to food safety management and contamination control in food-processing environments.