Role of initial contamination levels, biofilm maturity and presence of salt and fat on desiccation survival of Listeria monocytogenes on stainless steel surfaces

TY - JOUR

T1 - Role of initial contamination levels, biofilm maturity and presence of salt and fat on desiccation survival of Listeria monocytogenes on stainless steel surfaces

AU - Hingston, Patricia A.

AU - Stea, Emma C.

AU - Knøchel, Susanne

AU - Hansen, Truelstrup

PY - 2013/10

Y1 - 2013/10

N2 - This study investigated the effect of initial contamination levels, biofilm maturity and presence of salt and fatty food soils on desiccation survival of Listeria monocytogenes on stainless steel (SS) coupons. L.monocytogenes cultures grown (at 15°C for 48h) in Tryptic Soy Broth with 1% glucose (TSB-glu) containing either 0.5 or 5% (w/v) NaCl were re-suspended in TSB-glu containing either 0.5 or 5% NaCl and used to contaminate SS coupons at levels of 3.5, 5.5, and 7.5logCFU/cm2. Desiccation (at 15°C for 20 days, 43% RH) commenced immediately (non-biofilm) or following biofilm formation (at 15°C for 48h, 100% RH). To study the impact of food lipids, non-biofilm L.monocytogenes cells were suspended in TSB-glu containing either canola oil (5-10%) or lard (20-60%) and desiccated as above on SS coupons. Following desiccation for 20 days, survivors decreased by 1.4-3.7logCFU/cm2 for non-biofilm L.monocytogenes cells. The contamination level had no significant (p>0.05) effect on survival kinetics. SEM micrographs showed mature biofilms on coupons initially contaminated with 5.5 and 7.5logCFU/cm2. Mature biofilm cells were significantly (p<0.05) more desiccation resistant than cells in immature biofilms formed by the lowest contamination level. Besides biofilm maturity/formation, previous osmoadaptation, exposure to lard (20-60%) or salt (5%) during desiccation significantly (p<0.05) increased the bacterium's survival. In conclusion, L.monocytogenes desiccation survival can be greatly reduced by preventing presence of mature biofilms and salty or fatty soils on food contact surfaces.

AB - This study investigated the effect of initial contamination levels, biofilm maturity and presence of salt and fatty food soils on desiccation survival of Listeria monocytogenes on stainless steel (SS) coupons. L.monocytogenes cultures grown (at 15°C for 48h) in Tryptic Soy Broth with 1% glucose (TSB-glu) containing either 0.5 or 5% (w/v) NaCl were re-suspended in TSB-glu containing either 0.5 or 5% NaCl and used to contaminate SS coupons at levels of 3.5, 5.5, and 7.5logCFU/cm2. Desiccation (at 15°C for 20 days, 43% RH) commenced immediately (non-biofilm) or following biofilm formation (at 15°C for 48h, 100% RH). To study the impact of food lipids, non-biofilm L.monocytogenes cells were suspended in TSB-glu containing either canola oil (5-10%) or lard (20-60%) and desiccated as above on SS coupons. Following desiccation for 20 days, survivors decreased by 1.4-3.7logCFU/cm2 for non-biofilm L.monocytogenes cells. The contamination level had no significant (p>0.05) effect on survival kinetics. SEM micrographs showed mature biofilms on coupons initially contaminated with 5.5 and 7.5logCFU/cm2. Mature biofilm cells were significantly (p<0.05) more desiccation resistant than cells in immature biofilms formed by the lowest contamination level. Besides biofilm maturity/formation, previous osmoadaptation, exposure to lard (20-60%) or salt (5%) during desiccation significantly (p<0.05) increased the bacterium's survival. In conclusion, L.monocytogenes desiccation survival can be greatly reduced by preventing presence of mature biofilms and salty or fatty soils on food contact surfaces.

U2 - 10.1016/j.fm.2013.04.011

DO - 10.1016/j.fm.2013.04.011

M3 - Journal article

C2 - 23764219

SN - 0740-0020

VL - 36

SP - 46

EP - 56

JO - Food Microbiology

JF - Food Microbiology

IS - 1

ER -