Attachment of Listeria monocytogenes and Salmonella typhimurium to Stainless Steel and Buna-N in the Presence of Milk and Individual Milk Components

1993 ◽  
Vol 56 (6) ◽  
pp. 479-484 ◽  
Author(s):  
DAVID M. HELKE ◽  
EILEEN B. SOMERS ◽  
AMY C. L. WONG
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Dairy Industry ◽  
Skim Milk ◽  
Whole Milk ◽  
Milk Components ◽  
Phosphate Buffered Saline ◽  
Β Lactoglobulin

The effects of milk and individual milk components on the attachment of Listeria monocytogenes and Salmonella typhimurium to two commonly used materials in the dairy industry were studied. Attachment of both organisms to stainless steel and Buna-N was significantly inhibited by the presence of skim, 2%, whole, or chocolate 2% milk compared to the phosphate-buffered saline (PBS) control. The addition of individual milk components, casein, α-lactalbumin, and β-lactoglobulin to the attachment menstruum significantly reduced attachment. Pretreating surfaces with milk and milk components for 1 h prior to attachment in PBS gave similar results. The presence of lactose did not affect attachment of either organism; however, attachment of S. typhimurium was significantly decreased on pretreated Buna-N. Cells of either organism pretreated with skim milk or β-lactoglobulin prior to attachment in PBS showed significantly less attachment than untreated cells. Pretreating S. typhimurium cells with casein had no effect on attachment to stainless steel. Pretreatment of S. typhimurium with lactose increased attachment to both surfaces while pretreatment had no effect on L. monocytogenes. Attachment of both organisms was significantly reduced in diluted whole milk. Both organisms attached significantly less to surfaces soiled with one or more layers of whole milk.

Survival and Growth Characteristics of Listeria monocytogenes and Salmonella typhimurium on Stainless Steel and Buna-N Rubber

1994 ◽  
Vol 57 (11) ◽  
pp. 963-968 ◽  
Author(s):  
DAVID M. HELKE ◽  
AMY C. L. WONG
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Raw Milk ◽  
Viable Count ◽  
Food Contact Surfaces ◽  
Whole Milk ◽  
Complex Ecosystem ◽  
Survival And Growth ◽  
Phosphate Buffered Saline

Microorganisms harbored on food-contact surfaces are part of a complex ecosystem. The interactions of temperature, relative humidity (RH), soil and surface on the survival of Listeria monocytogenes and Salmonella typhimurium were studied. Survival and growth were monitored at 25°C and 6°C and 32.5% RH and 75.5% RH. Survival in phosphate-buffered saline and dilute pasteurized whole milk on both stainless steel and buna-n was highest at 6°C and 75.5% RH. Both organisms were recoverable on the two surfaces after 10 days storage at 6°C and 75.5% RH. Survival of L. monocytogenes and S. typhimurium at 25°C and 75.5% RH was increased in dilute pasteurized whole milk on stainless steel, but not on buna-n. Organisms grew in pasteurized whole milk on stainless steel at 25°C and 75.5% RH, but failed to grow on buna-n. At 25°C and 75.5% RH, S. typhimurium was not recoverable on buna-n after 10 days in whole milk; however, L. monocytogenes remained close to initial levels. The survival and growth of both organisms in raw milk soil was similar to that in pasteurized whole milk soil. Buna-n was not bacteriostatic towards all organisms, as the total viable count in raw milk increased by more than a factor of 10 after 1 day storage at 25°C and 75.5% RH. Unlike other soils tested, survival of S. typhimurium at in conditions and L. monocytogenes at 25°C and both RHs in whey was higher on buna-n than on stainless steel. At 6°C and both RHs, L. monocytogenes levels remained constant on both surfaces in whey. The bacteriostatic effect of buna-n was not affected significantly by exposure to 20 cycles of a simulated clean-in-place (CIP) process.

Thermal Resistance of Listeria monocytogenes Scott A in Ultrafiltered Milk as Related to the Effect of Different Milk Components

2010 ◽  
Vol 73 (11) ◽  
pp. 2110-2115 ◽  
Author(s):  
KINGA SZLACHTA ◽  
SUSANNE E. KELLER ◽  
ARLETTE SHAZER ◽  
STUART CHIRTEL
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Milk Fat ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Single Measure ◽  
Total Solids ◽  
Whole Milk ◽  
Milk Components

Pasteurization parameters for grade A milk are well established and set by regulation. However, as solids levels increase, an increased amount of heat is required to destroy any pathogens present. This effect is not well characterized. In this work, the effect of increased dairy solids levels on the thermal resistance of Listeria monocytogenes was examined through the use of ultrafiltered (UF) milk, reconstituted milk powder, and the milk components lactose and caseinate. From the results obtained, lactose and caseinate did not appear to affect thermal resistance. In addition, the level of milk fat, up to 10% of the total solids in UF whole milk, did not result in statistically significant changes to thermal resistance when compared with UF skim milk. Reconstituted skim milk powder at 27% total solids (D62-value = 1.16 ± 0.2 [SD] min, z = 5.7) did result in increased thermal resistance, as compared with reconstituted skim milk powder at 17.5% (D62-value = 0.86 ± 0.02 min, z = 5.57) and UF whole milk at 27% total solids (D62-value = 0.66 ± 0.07 min, z = 5.16). However, that increase appeared to be due to the increase in salt levels, not to increases in caseinate, fat, or lactose. Consequently, total solids, as a single measure, could not be used to predict increased thermal resistance of L. monocytogenes in concentrated milk.

Growth Media and Surface Conditioning Influence the Adherence of Pseudomonas fragi, Salmonella typhimurium, and Listeria monocytogenes Cells to Stainless Steel

1997 ◽  
Vol 60 (9) ◽  
pp. 1034-1037 ◽  
Author(s):  
SCOTT K. HOOD ◽  
EDMUND A. ZOTTOLA
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Skim Milk ◽  
Epifluorescence Microscopy ◽  
Growth Media ◽  
Pseudomonas Fragi ◽  
Acridine Orange Staining ◽  
Surface Conditioning ◽  
Food Contact Surfaces

Microorganisms have been shown to adhere to food-contact surfaces and may provide a route for the contamination of processed food. To better understand this phenomenon, the effects of growth media and surface conditioning on the adherence of Pseudomonas fragi, Salmonella typhimurium and Listeria monocytogenes cells to stainless steel were studied. The microorganisms were grown in tryptic soy broth (TSB), 1% reconstituted skim milk (RSM) and RSM with 1% sucrose (RSM + S). Stainless-steel surfaces were conditioned by immersion in growth media for 1 h and then were rinsed in phosphate-buffered saline (PBS) prior to the adherence assay. After growing in each medium, cells were harvested, resuspended in PBS, and then allowed to contact the stainless steel for 30 min. Adherence was quantified by acridine orange-staining the cells and viewing under epifluorescence microscopy. Growth media had little influence on adherence to stainless steel that had not been preconditioned. P. fragi and L. monocytogenes cells adhered in the highest numbers when grown in RSM plus sucrose. S. typhimurium cells showed the highest level of adherence when grown in TSB. Analysis of variance yielded P values of less than 0.01, indicating that both growth media and surface conditioning were significant in the level of adherence observed.

Spray Method for Recovery of Heat-Injured Salmonella Typhimurium and Listeria monocytogenes

2012 ◽  
Vol 75 (10) ◽  
pp. 1867-1872 ◽  
Author(s):  
KYEONG-HWAN BACK ◽  
SANG-OH KIM ◽  
KI-HWAN PARK ◽  
MYUNG-SUB CHUNG ◽  
DONG-HYUN KANG
Keyword(s):  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Recovery Rate ◽  
Skim Milk ◽  
Selective Media ◽  
Spray Method ◽  
Selective Agar ◽  
Overlay Method ◽  
Peptone Water ◽  
Pathogen Recovery

Selective agar is inadequate for supporting recovery of injured cells. During risk assessment of certain foods, both injured and noninjured cells must be enumerated. In this study, a new method (agar spray method) for recovering sublethally heat-injured microorganisms was developed and used for recovery of heat-injured Salmonella Typhimurium and Listeria monocytogenes. Molten selective agar was applied as an overlay to presolidified nonselective tryptic soy agar (TSA) by spray application. Heat-injured cells (55°C for 10 min in 0.1% peptone water or 55°C for 15 min in sterilized skim milk) were inoculated directly onto solidified TSA. After a 2-h incubation period for cell repair, selective agar was applied to the TSA surface with a sprayer, and the plates were incubated. The recovery rate for heat-injured Salmonella Typhimurium and L. monocytogenes with the spray method was compared with the corresponding rates associated with TSA alone, selective media alone, and the conventional overlay method (selective agar poured on top of resuscitated cells grown on TSA and incubated for 2 h). No significant differences (P > 0.05) were found in pathogen recovery obtained with TSA, the overlay method, and the spray method. However, a lower recovery rate (P < 0.05) was obtained for isolation of injured cells on selective media. Overall, these results indicate that the agar spray method is an acceptable alternative to the conventional overlay method and is a simpler and more convenient approach to recovery and detection of injured cells.

Competitive Growth of Listeria monocytogenes and Yersinia enterocolitica in Milk

1993 ◽  
Vol 56 (6) ◽  
pp. 528-532 ◽  
Author(s):  
EBO BUDU-AMOAKO ◽  
SYED TOORA ◽  
RICHARD F. ABLETT ◽  
JIM SMITH
Keyword(s):  
Listeria Monocytogenes ◽  
Yersinia Enterocolitica ◽  
Skim Milk ◽  
Competitive Growth ◽  
No Inhibition ◽  
Whole Milk ◽  
Uninoculated Control ◽  
Control Samples

Sterile whole milk and skim milk were inoculated with cultures of Yersinia enterocolitica (10 CFU/ml) and Listeria monocytogenes (15 CFU/ml) either separately or together and incubated at 4, 10, and 22°C. Unlike uninoculated control samples, growth of Y. enterocolitica with or without L. monocytogenes in whole milk or skim milk at 22°C and in whole milk at 10°C led to the development of off-odors with coagulation after heating to 80°C. Growth of Y. enterocolitica alone in whole milk and in skim milk at 4°C and in skim milk at 10°C did not result in any odor changes or coagulation. Similar or lower populations did not result in any character changes in trials with L. monocytogenes. In the presence of Y. enterocolitica, the growth of L. monocytogenes was found to be competitively inhibited in whole milk at temperatures of 10 and 22°C, but not at 4°C, whereas in skim milk no inhibition was observed at all the temperatures investigated.

Biofilm Development and Sanitizer Inactivation of Listeria monocytogenes and Salmonella typhimurium on Stainless Steel and Buna-n Rubber

1993 ◽  
Vol 56 (9) ◽  
pp. 750-758 ◽  
Author(s):  
AMY B. RONNER ◽  
AMY C. L. WONG
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Biofilm Formation ◽  
Bacterial Biofilm ◽  
Extracellular Matrices ◽  
Nutrient Level ◽  
Extracellular Materials ◽  
Biofilm Development ◽  
Nutrient Conditions

Biofilm formation by seven strains of Listeria monocytogenes and one strain of Salmonella typhimurium on stainless steel and Buna-n rubber was examined under two nutrient conditions. The type of surface, nutrient level, and organism influenced biofilm development and production of extracellular materials. Buna-n had a strong bacteriostatic effect on L. monocytogenes, and biofilm formation on Buna-n under low nutrient conditions was reduced for four of the seven strains tested. Buna-n was less bacteriostatic toward S. typhimurium. It inhibited the growth of several other pathogens to varying degrees. An ethylene propylene diamine monomer rubber was less inhibitory than Buna-n, and Viton rubber had no effect. The effectiveness of sanitizers on biofilm bacteria was examined. Biofilms were challenged with four types of detergent and nondetergent sanitizers. Resistance to sanitizers was strongly influenced by the type of surface. Bacterial biofilm populations on stainless steel were reduced 3–5 log by all the sanitizers, but those on Buna-n were resistant to these sanitizers and were reduced less than 1–2 log. In contrast, planktonic (suspended) bacteria were reduced 7–8 log by these sanitizers. Chlorine and anionic acid sanitizers generally removed extracellular materials from biofilms better than iodine and quaternary ammonium detergent sanitizers. Scanning electron microscopy demonstrated that biofilm cells and extracellular matrices could remain on sanitized biofilm cells and extracellular matrices could remain surfaces from which no viable cells were recovered.

Comparison of Oxygen Scavengers for Their Ability to Enhance Resuscitation of Heat-injured Listeria monocytogenes

1995 ◽  
Vol 58 (3) ◽  
pp. 244-250 ◽  
Author(s):  
J. R. PATEL ◽  
C.-A. HWANG ◽  
L. R. BEUCHAT ◽  
M. P. DOYLE ◽  
R. E. BRACKETT
Keyword(s):  
Listeria Monocytogenes ◽  
Incubation Time ◽  
Skim Milk ◽  
Oxygen Scavengers ◽  
Sodium Pyruvate ◽  
Percentage Recovery ◽  
Cysteine Hydrochloride ◽  
Whole Milk ◽  
Conventional Methods ◽  
Optimal Incubation

The recovery of heat-injured Listeria monocytogenes Scott A in Fraser broth (FB) supplemented with sodium thioglycolate, sodium pyruvate, L-(+)-cysteine hydrochloride, catalase or Oxyrase? was studied. After 3 h of incubation at 30°C, recovery was enhanced by all oxygen scavengers except sodium pyruvate. Oxyrase? (0.005 U ml−1) promoted the highest recovery (34%) compared to recovery in control broth (19%). All oxygen scavengers enhanced the recovery of injured L. monocytogenes in FB within 6 h of incubation. After 6 h at 30°C, 49 and 55% of injured cells underwent resuscitation in FB containing 2.5 mg of sodium pyruvate ml−1 and 400 μg of catalase ml−1, respectively, compared to 24% resuscitation in FB not supplemented with oxygen scavengers. The percentage recovery was increased as the incubation time was extended to 6 and 24 h. Nearly all injured cells were recovered within 24 h of incubation, regardless of supplementation of FB with oxygen scavengers. Fraser broth containing 2.5 mg of sodium pyruvate ml−1, 400 μg of catalase ml−1 or 0.01 U of Oxyrase? ml−1 were tested to determine the optimal incubation time and temperature for recovering heat-injured L. monocytogenes. Percentage recovery of injured cells increased with an increase in temperature from 25 to 30°C and from 30 to 35°C. The highest percentage of injured cells recovered was observed in FB containing 400 μg of catalase ml−1 (67%) and 0.01 U of Oxyrase? ml−1 (68%) within 6 h of incubation at 35°C. Catalase (400 μg ml−1) and Oxyrase? (0.01 U ml−1) in FB resulted in significantly higher recovery of injured cells from heated whole milk; however, recovery of injured cells from heated skim milk was not significantly higher. Enrichment in FB containing catalase or Oxyrase? has potential for recovering heat-injured L. monocytogenes cells within 6 h compared to 24 h required in conventional methods.

InstantLabs®Listeria monocytogenes Food Safety Kit

2014 ◽  
Vol 97 (3) ◽  
pp. 852-861
Author(s):  
Neil Sharma ◽  
Lauren Bambusch ◽  
Thu Le ◽  
Amit Morey
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Food Safety ◽  
Reference Method ◽  
Cheddar Cheese ◽  
Ice Cream ◽  
Test Method ◽  
Listeria Species ◽  
Whole Milk ◽  
Raw Shrimp

Abstract The InstantLabs®Listeria monocytogenes Food Safety Kit was validated against the International Organization for Standardization (ISO) reference method 11290-1 for the detection of Listeria monocytogenes and other Listeria species. The matrixes (stainless steel, sealed concrete, ice cream, whole milk, cheddar cheese, raw shrimp, hot dogs, deli turkey, and lettuce) were inoculated with approximately 1 CFU/test portion of L. monocytogenes to generate fractional positives (5–15) in 20 inoculated samples. Enrichments were also fractionally inoculated with L. grayii for side-by-side testing of the Listeria Species Food Safety Kit. Stainless steel and sealed concrete samples were validated using 4 × 4″ and 1 × 1″ test areas, respectively, and enriched in Buffered Listeria Enrichment Broth (BLEB) at 35 ± 1°C for 22–28 h. All food samples were tested at 25 g and enriched in BLEB at 35 ± 1°C for 24–28 h. All samples were confirmed using the ISO reference method, regardless of initial screen result. The InstantLabs test method performed as well as or better than the reference method for the detection of L. monocytogenes on stainless steel and sealed concrete and in ice cream, whole milk, cheddar cheese, raw shrimp, hot dogs, deli turkey, and lettuce. Inclusivity and exclusivity testing revealed no false negatives and no false positives among the 50 L. monocytogenes serovars and 30 non-L. monocytogenes species examined. The method was shown to be robust when the enrichment times, volumes for DNA extraction, and heat block times were varied.

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