Survival of Listeria monocytogenes Attached to Stainless Steel Surfaces in the Presence or Absence of Flavobacterium spp.

2001 ◽  
Vol 64 (9) ◽  
pp. 1369-1376 ◽  
Author(s):  
PHILIP J. BREMER ◽  
IAN MONK ◽  
CAROLYN M. OSBORNE
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Mixed Culture ◽  
Cell Population ◽  
Exposure Time ◽  
Food Processing ◽  
Pure Culture ◽  
Bacterial Biofilm ◽  
Selective Agar ◽  
Steel Surfaces

Contaminated surfaces of food processing equipment are believed to be a significant source of Listeria monocytogenes to foods. However, very little is known about the survival of Listeria in processing environments. In a mixed bacterial biofilm of L. monocytogenes and Flavobacterium spp., the number of L. monocytogenes cells attaching to stainless steel increased significantly compared to when L. monocytogenes was in a pure culture. The L. monocytogenes cells in the mixed biofilms were also recoverable for significantly longer exposure periods. On colonized coupons held at 15°C and 75% humidity, decimal reduction times were 1.2 and 18.7 days for L. monocytogenes in pure and mixed biofilms, respectively. With increasing exposure time, the proportion of cells that were sublethally injured (defined as an inability to grow on selective agar) increased from 8.1% of the recoverable cell population at day 0 to 91.4% after 40 days' exposure. At 4 and −20°C, decimal reduction times for L. monocytogenes in pure culture were 2.8 and 1.4 days, respectively, and in mixed culture, 10.5 and 14.4 days, respectively. The enhanced colonization and survival of L. monocytogenes on “unclean” surfaces increase the persistence of this pathogen in food processing environments, while the increase in the percentage of sublethally injured cells in the population with time may decrease the ability of enrichment regimes to detect it.

scholarly journals Listeria monocytogenes Attachment to and Detachment from Stainless Steel Surfaces in a Simulated Dairy Processing Environment

2009 ◽  
Vol 75 (22) ◽  
pp. 7182-7188 ◽  
Author(s):  
Sofia Poimenidou ◽  
Charalambia A. Belessi ◽  
Efstathios D. Giaouris ◽  
Antonia S. Gounadaki ◽  
George-John E. Nychas ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Food Processing ◽  
Dairy Products ◽  
Pasteurized Milk ◽  
Fresh Milk ◽  
Dairy Processing ◽  
Two Temperatures ◽  
Steel Surfaces ◽  
Suspended Cells

ABSTRACT The presence of pathogens in dairy products is often associated with contamination via bacteria attached to food-processing equipment, especially from areas where cleaning/sanitation is difficult. In this study, the attachment of Listeria monocytogenes on stainless steel (SS), followed by detachment and growth in foods, was evaluated under conditions simulating a dairy processing environment. Initially, SS coupons were immersed in milk, vanilla custard, and yogurt inoculated with the pathogen (107 CFU/ml or CFU/g) and incubated at two temperatures (5 and 20�C) for 7 days. By the end of incubation, cells were mechanically detached from coupons and used to inoculate freshly pasteurized milk which was subsequently stored at 5�C for 20 days. The suspended cells in all three products in which SS coupons were immersed were also used to inoculate freshly pasteurized milk (5�C for 20 days). When SS coupons were immersed in milk, shorter lag phases were obtained for detached than for planktonically grown cells, regardless of the preincubation temperature (5 or 20�C). The opposite was observed when custard incubated at 20�C was used to prepare the two types of inocula. However, in this case, a significant increase in growth rate was also evident when the inoculum was derived from detached cells. In another parallel study, while L. monocytogenes was not detectable on SS coupons after 7 days of incubation (at 5�C) in inoculated yogurt, marked detachment and growth were observed when these coupons were subsequently transferred and incubated at 5�C in fresh milk or/and custard. Overall, the results obtained extend our knowledge on the risk related to contamination of dairy products with detached L. monocytogenes cells.

Persistent Listeria monocytogenes Strains Show Enhanced Adherence to Food Contact Surface after Short Contact Times

2000 ◽  
Vol 63 (9) ◽  
pp. 1204-1207 ◽  
Author(s):  
JANNE M. LUNDÉN ◽  
MARIA K. MIETTINEN ◽  
TIINA J. AUTIO ◽  
HANNU J. KORKEALA
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Contact Surface ◽  
Food Processing ◽  
Contact Time ◽  
Ice Cream ◽  
Short Contact ◽  
Steel Surfaces ◽  
Food Contact Surface ◽  
Epifluorescence Microscope

Adherence of 3 persistent and 14 nonpersistent Listeria monocytogenes strains to stainless steel surfaces after short and long contact times was investigated. L. monocytogenes strains were obtained from poultry plants and an ice cream plant throughout several years. Adherence tests were performed in tryptic soy broth at 25°C for 1, 2, and 72 h. Test surfaces were rinsed after the contact time, and attached cells were stained with acridine orange and enumerated with an epifluorescence microscope. The persistent poultry plant strains showed adherence 2- to 11-fold higher than the nonpersistent strains following 1- and 2-h contact times. The adherence of the persistent ice cream plant strain after 1- and 2-h contact times was higher than most of the nonpersistent strains. Seven of 12 nonpersistent ice cream strains showed an adherence of less than half that of the persistent strain. After 72 h, the differences in adherence were not as marked, since half the nonpersistent strains had reached adherence levels comparable with the persistent strains. In fact, three nonpersistent strains showed even higher adherence than the persistent strains. Thus, results of this study reveal that persistent L. monocytogenes strains show enhanced adherence at short contact times, promoting their survival in food processing facilities and possibly having an effect on initiation of persistent plant contamination.

Inactivation of Surface-adherent Listeria monocytogenes Hypochlorite and Heat

1991 ◽  
Vol 54 (1) ◽  
pp. 4-6 ◽  
Author(s):  
SHIN-HO LEE ◽  
JOSEPH F. FRANK
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Cell Population ◽  
Incubation Time ◽  
Cell Populations ◽  
Adherent Cell ◽  
Adherent Cells ◽  
D Cells

Inactivation by hypochlorite of Listeria monocytogenes cells adherent to stainless steel was determined. Adherent cell populations were prepared by incubating stainless steel slides with a 24 h culture of L. monocytogenes for 4 h at 21°C. Adherent microcolonies were prepared by growing L. monocytogenes on stainless steel slides submerged in a 1:15 dilution of tryptic soy broth at 21°C. The slides were then rinsed and transferred to fresh sterile broth every 2 d with a total incubation time of 8 d. Although the 4 h and 8 d adherent populations were at similar levels, 8 d adherent cells were over 100 times more resistant than the 4 h adherent cell population when exposed to 200 ppm hypochlorite for 30 s. When stainless steel slides containing adherent cells were heated at 72°C both adherent cell populations were inactivated after 1 min. Detectable numbers of L. monocytogenes remained on stainless steel slides after treatment at 65°C for 3 min when adherent 8 d cells were tested but not when adherent 4 h cells were used.

Behavior of Listeria monocytogenes in a Pseudomonas putida Biofilm on a Condensate-Forming Surface

2004 ◽  
Vol 67 (2) ◽  
pp. 322-327 ◽  
Author(s):  
ASHRAF N. HASSAN ◽  
DAWN M. BIRT ◽  
JOSEPH F. FRANK
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Pseudomonas Putida ◽  
Microscopic Observation ◽  
Pure Culture ◽  
Extracellular Polymeric Substances ◽  
Plate Count ◽  
Free Surfaces ◽  
Processing Plants ◽  
Humidity Chamber

Listeria monocytogenes has been isolated from condensate-forming surfaces in food processing plants. The objective of this research was to observe the behavior of L. monocytogenes on condensate-covered stainless steel with a Pseudomonas putida biofilm. L. monocytogenes–containing biofilms, either with or without added chicken protein, were incubated in a high humidity chamber at 12°C to allow formation of condensate. Samples were analyzed for attached and unattached L. monocytogenes and total plate count periodically for 35 days. Samples were also taken for microscopic observation of Listeria and bacterial extracellular polymeric substances (EPS). L. monocytogenes attached in significantly greater numbers (>3-log difference) to surfaces with preexisting P. putida biofilms than to Pseudomonas-free surfaces. L. monocytogenes survived in the presence or absence of P. putida with no added nutrients for 35 days, with numbers of survivors in the range of 3 to 4 log CFU/cm2 in the presence of P. putida and less than 2.9 log CFU/cm2 in pure culture. Attached and unattached L. monocytogenes were at similar levels throughout the incubation under all conditions studied. The addition of protein to the biofilms allowed growth of L. monocytogenes in pure culture during the first 7 days of incubation. Numbers of L. monocytogenes were not affected by the presence of P. putida when protein was present. Unattached L. monocytogenes were at levels of 3.6 to 6.7 log CFU/cm2 on the protein-containing surfaces. Microscopic observation of the condensate-covered biofilms indicated that L. monocytogenes formed microcolonies embedded within an EPS matrix over a 28-day period. This research demonstrates that L. monocytogenes can survive on condensate-forming stainless steel in low and high nutrient conditions, with or without the presence of Pseudomonas biofilm. The Listeria can detach and, therefore, have the potential to contaminate product.

scholarly journals Comparison of three neutralizing broths for environmental sampling of low levels of Listeria monocytogenes desiccated on stainless steel surfaces and exposed to quaternary ammonium compounds

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Fengmin Li ◽  
Zhihan Xian ◽  
Hee Jin Kwon ◽  
Jiyoon Yoo ◽  
Laurel Burall ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Quaternary Ammonium ◽  
Storage Conditions ◽  
Ammonium Compound ◽  
Environmental Sampling ◽  
High Concentration ◽  
Environmental Test ◽  
Steel Surfaces ◽  
Low Levels

Abstract Background An effective environmental sampling method involves the use of a transport/neutralizing broth with the ability to neutralize sanitizer residues that are collected during sampling and to maintain viability of stressed Listeria monocytogenes (Lm) cells. Results We applied Lm onto stainless steel surfaces and then subjected Lm to desiccation stress for 16–18 h at room temperature (RT, 21–24 °C). This was followed by the subsequent application of Whisper™ V, a quaternary ammonium compound (QAC)-based sanitizer, diluted to 400 ppm and 8000 ppm of active quat, for 6 h. We then sampled Lm with sponges pre-moistened in three transport broths, Dey/Engley (D/E) broth, Letheen broth and HiCap™ broth, to generate environmental samples that contained sanitizer residues and low levels of stressed Lm, which were subsequently analyzed by an enrichment-based method. This scheme conformed with validation guidelines of AOAC International by using 20 environmental test portions per broth that contained low levels of Lm such that not all test portions were positive (i.e., fractional positive). We showed that D/E broth, Letheen broth and HiCap™ broth performed similarly when no quat or 400 ppm of quat was applied to the Lm contaminating stainless steel surfaces. However, when 8000 ppm of quat was applied, Letheen broth did not effectively neutralize the QAC in the samples. These comparisons were performed on samples stored under three conditions after collection to replicate scenarios of sample transport, RT for 2 h, 4 °C for 24 h and 4 °C for 72 h. Comparisons under the three different scenarios generally reached the same conclusions. In addition, we further demonstrated that storing Letheen and HiCap™ broths at RT for two months before sampling did not reduce their capacity to neutralize sanitizers. Conclusions We developed a scheme to evaluate the ability of transport broths to neutralize QAC sanitizers. The three transport broths performed similarly with a commonly used concentration of quat, but Letheen broth could not effectively neutralize a very high concentration of QAC. The performance of transport broths was not significantly affected under the assessed pre-sampling and post-sampling storage conditions.

Nanoengineered Superhydrophobic Surfaces to Prevent Adhesion of Listeria monocytogenes for Improved Food Safety

2020 ◽  
Vol 63 (5) ◽  
pp. 1401-1407
Author(s):  
Bog Eum Lee ◽  
Youngsang You ◽  
Won Choi ◽  
Eun-mi Hong ◽  
Marisa M. Wall ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Biofilm Formation ◽  
Electrochemical Etching ◽  
Contact Angles ◽  
Bacterial Attachment ◽  
Superhydrophobic Surfaces ◽  
List Type ◽  
Ptfe Film ◽  
Steel Surfaces

HighlightsNanoporous superhydrophobic surfaces were fabricated using electrochemical etching and Teflon coating.Adhesion of Listeria monocytogenes to the nanoengineered stainless steel surfaces was reduced.Self-cleanable food-contact surfaces prevent bacterial attachment and subsequent biofilm formation.Abstract. Bacterial attachment on solid surfaces and subsequent biofilm formation is a significant problem in the food industry. Superhydrophobic surfaces have potential to prevent bacterial adhesion by minimizing the contact area between bacterial cells and the surface. In this study, stainless steel-based superhydrophobic surfaces were fabricated by manipulating nanostructures with electrochemical etching and polytetrafluoroethylene (PTFE) film. The formation of nanostructures on stainless steel surfaces was characterized by field emission scanning electron microscopy (FESEM). The stainless steel surfaces etched at 10 V for 5 min and at 10 V for 10 min with PTFE deposition resulted in average water contact angles of 154° ±4° with pore diameters of 50 nm. In addition, adhesion of Listeria monocytogenes was decreased by up to 99% compared to the bare substrate. These findings demonstrate the potential for the development of antibacterial surfaces by combining nanoporous patterns with PTFE films. Keywords: Electrochemical etching, PTFE, Nanoengineered surface, L. monocytogenes, Superhydrophobic.

scholarly journals N-Acetyl-l-Cysteine Affects Growth, Extracellular Polysaccharide Production, and Bacterial Biofilm Formation on Solid Surfaces

2003 ◽  
Vol 69 (8) ◽  
pp. 4814-4822 ◽  
Author(s):  
Ann-Cathrin Olofsson ◽  
Malte Hermansson ◽  
Hans Elwing
Keyword(s):  
Stainless Steel ◽  
Bacterial Adhesion ◽  
Biofilm Formation ◽  
Paper Mill ◽  
Bacterial Biofilm ◽  
Extracellular Polysaccharides ◽  
Positive Effects ◽  
Initial Adhesion ◽  
Interesting Candidate ◽  
Steel Surfaces

ABSTRACT N-Acetyl-l-cysteine (NAC) is used in medical treatment of patients with chronic bronchitis. The positive effects of NAC treatment have primarily been attributed to the mucus-dissolving properties of NAC, as well as its ability to decrease biofilm formation, which reduces bacterial infections. Our results suggest that NAC also may be an interesting candidate for use as an agent to reduce and prevent biofilm formation on stainless steel surfaces in environments typical of paper mill plants. Using 10 different bacterial strains isolated from a paper mill, we found that the mode of action of NAC is chemical, as well as biological, in the case of bacterial adhesion to stainless steel surfaces. The initial adhesion of bacteria is dependent on the wettability of the substratum. NAC was shown to bind to stainless steel, increasing the wettability of the surface. Moreover, NAC decreased bacterial adhesion and even detached bacteria that were adhering to stainless steel surfaces. Growth of various bacteria, as monocultures or in a multispecies community, was inhibited at different concentrations of NAC. We also found that there was no detectable degradation of extracellular polysaccharides (EPS) by NAC, indicating that NAC reduced the production of EPS, in most bacteria tested, even at concentrations at which growth was not affected. Altogether, the presence of NAC changes the texture of the biofilm formed and makes NAC an interesting candidate for use as a general inhibitor of formation of bacterial biofilms on stainless steel surfaces.

scholarly journals Variable Adhesion of Listeria monocytogenes Isolates from Food-Processing Facilities and Clinical Cases to Inert Surfaces

2007 ◽  
Vol 70 (7) ◽  
pp. 1569-1578 ◽  
Author(s):  
ODILE TRESSE ◽  
KELLY SHANNON ◽  
ANTHONY PINON ◽  
PIERRE MALLE ◽  
MICHÈLE VIALETTE ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Food Processing ◽  
Microtiter Plate ◽  
Clinical Strains ◽  
Microtiter Plates ◽  
Industrial Strains ◽  
Cheese Industry ◽  
Adhesion Rate ◽  
Inert Surfaces

One hundred one strains of Listeria monocytogenes isolated from seafood and cheese industry samples and from patients with listeriosis were assessed using a microtiter plate method for adhesion to polystyrene and stainless steel surfaces. The adhesion rate for these strains ranged from 3.10 to 35.29% with an inoculum of 8 × 108 cells per well. A strong correlation was found between adhesion to polystyrene and stainless steel microtiter plates, indicating that the intrinsic ability of L. monocytogenes to adhere to inert surfaces is stronger than the influence of the surface's physicochemical properties. The clinical strains were less adherent to inert surfaces than were the industrial strains. By integrating other factors such as location of the industrial strains, contamination type of the clinical strains, serotype, and pulsotype into the analysis, some weak but significant differences were noted. For the industrial isolates, the number of cells attached to both surfaces differed significantly depending on whether they were isolated from food or food-processing environments in the seafood and cheese industry. For clinical isolates, sporadic strains exhibited greater adhesion to polystyrene than did epidemic strains. Strains belonging to the pulsed-field gel electrophoretype clusters A and M (lineages II and I, respectively) were less able to adhere to polystyrene and stainless steel than were strains in the more common clusters.

Effect of Growth Nutrients on Attachment of Listeria monocytogenes To Stainless Steel

1994 ◽  
Vol 57 (8) ◽  
pp. 720-724 ◽  
Author(s):  
KWANG Y. KIM ◽  
JOSEPH F. FRANK
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Cell Surface ◽  
Minimal Medium ◽  
Cell Attachment ◽  
Chloride Concentration ◽  
Fold Increase ◽  
Hydrolyzed Protein ◽  
Steel Surfaces ◽  
Attachment Ability

Listeria monocytogenes cells grown in chemically defined minimal medium (D10), tryptic soy broth (TSB), and modifications of these media were used to determine the effect of growth nutrients on attachment ability. Stainless steel surfaces were submerged in various cell suspensions at 21°C for 4 h, and the numbers of attached cells were compared. Cells grown in D10 showed approximately 50-fold higher attachment than those grown in TSB. Addition of components of D10 to TSB did not affect the attachment ability of cells grown in TSB. The only modifications of D10, which affected attachment ability were a 10-fold increase of ammonium chloride concentration and a 1/10 reduction in iron, both of which resulted in decreases in attachment ability to one third of the D10 control. Replacement of glucose in D10 with mannose, cellobiose, fructose or trehalose did not effect cell attachment. Replacement of nitrogen components in D10 with tryptone decreased cell attachment to the equivalent level of cells grown in TSB. The reduced attachment ability of TSB-grown cells was not the result of hydrolyzed protein absorbing to the cell surface.

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