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.

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.

Behavior of Psychrotropic Pathogens Listeria monocytogenes, Yersinia enterocolitica, and Aeromonas hydrophila in Commercially Pasteurized Eggs Held at 2, 6.7 and 12.8° C.

1992 ◽  
Vol 55 (1) ◽  
pp. 8-12 ◽  
Author(s):  
JOHN P. ERICKSON ◽  
PHYLLIS JENKINS
Keyword(s):  
Listeria Monocytogenes ◽  
Yersinia Enterocolitica ◽  
Aeromonas Hydrophila ◽  
Egg Yolk ◽  
Egg White ◽  
Competitive Growth ◽  
Growth Responses ◽  
Egg Products ◽  
Spoilage Microflora ◽  
Whole Egg

Four commercially pasteurized liquid egg products were individually inoculated with Listeria monocytogenes, Yersinia enterocolitica, and Aeromonas hydrophila. They were unsalted whole egg blend, unsalted egg white, 5% NaCl whole egg blend, and 10% NaCl egg yolk. The inoculated samples and uninoculated controls were held at 2, 6.7, and 12.8°C (temperature abuse) for 14 d. Psychrotropic pathogen growth or survival risks in the unsalted and NaCl supplemented eggs were Y. enterocolitica > A. hydrophila > L. monocytogenes, and L. monocytogenes > Y. enterocolitica > A. hydrophila, respectively. Y. enterocolitica produced delayed (≥4 d) growth responses in unsalted eggs held at ≤6.7°C but was inhibited by ≥5% NaCl at all three holding temperatures. L. monocytogenes growth was prevented at ≤6.7°C in the unsalted and NaCl supplemented eggs. The organism rapidly increased in the temperature abused 5% NaCl whole egg blend. L. monocytogenes and A. hydrophila were inactivated in the unsalted egg white and NaCl supplemented eggs, respectively. Psychrotropic pathogen behavior was unaffected by the competitive growth of indigenous spoilage microflora including pseudomonads, Serratia spp., and NaCl tolerant micrococci. Properly refrigerated and hygienically handled pasteurized liquid eggs are microbiologically safe against a broad range of psychrotropic pathogen strains.

Repair and Recovery of Thermally Injured Cells of Yersinia enterocolitica in Milk

1999 ◽  
Vol 62 (10) ◽  
pp. 1203-1205 ◽  
Author(s):  
RUCHI KUSHAL ◽  
SANJEEV K. ANAND
Keyword(s):  
Yersinia Enterocolitica ◽  
Skim Milk ◽  
Brain Heart Infusion ◽  
The Other ◽  
Brain Heart Infusion Broth ◽  
Standard Strain ◽  
Other Hand ◽  
Whole Milk ◽  
Test Cultures

One standard strain of the organism MTCC-861 and the two culture isolates VRW-22 and CRW-15 were exposed to batch pasteurization (62.8°C for 30 min) in brain heart infusion broth, skim milk, and whole milk. The trials were repeated three times. None of the isolates survived pasteurization treatment. However, the studies were further directed toward the repair and recovery of thermally injured cells, if any, in peptone sorbitol bile broth, skim milk, and whole milk. The results revealed that only a low number of test cultures were recovered in peptone sorbitol bile broth after 8 days of incubation at 10°C. On the other hand, the recovery was still slower in skim and whole milk, with a detection of the test isolates only on 10 days of incubation under similar conditions.

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.

Inhibition and Inactivation of Five Species of Foodborne Pathogens by Chitosan

1992 ◽  
Vol 55 (11) ◽  
pp. 916-919 ◽  
Author(s):  
GUANG-HUA WANG
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Acetic Acid ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Yersinia Enterocolitica ◽  
Foodborne Pathogens ◽  
E Coli ◽  
No Inhibition

Inhibition and inactivation of five species of foodborne pathogens (Staphylococcus aureus, Escherichia coli, Yersinia enterocolitica, Listeria monocytogenes, and Salmonella typhimurium) by chitosan were studied. Nutrient broths were supplemented with 0, 0.5, 1.0, 1.5, 2.0, and 2.5% chitosan, adjusted to pH 6.5 or 5.5 with 2% acetic acid, and incubated at 30°C. The outgrowths of these bacteria were observed. At pH 6.5, in general, antibacterial activity of chitosan was relatively weak. The effectiveness of chitosan against S. aureus was greatest, followed by S. typhimurium, E. coli, and Y. enterocolitica. As the concentration of chitosan increased, the effectiveness of chitosan against these four species of pathogens also increased. No inhibition of L. monocytogenes by chitosan occurred. At pH 5.5, presence of chitosan inactivated these pathogens except that 0.5% chitosan did not affect the growth of S. typhimurium. Thus, the antibacterial activity of chitosan was stronger at pH 5.5 than at pH 6.5.

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.

Effect of High-Temperature Short-Time Pasteurization, Freezing and Thawing and Constant Freezing, on the Survival of Yersinia enterocolitica in Milk

1992 ◽  
Vol 55 (10) ◽  
pp. 803-805 ◽  
Author(s):  
SYED TOORA ◽  
EBO BUDU-AMOAKO ◽  
RICHARD F. ABLETT ◽  
JIM SMITH
Keyword(s):  
High Temperature ◽  
Yersinia Enterocolitica ◽  
Skim Milk ◽  
Negligible Effect ◽  
Distilled Water ◽  
Freezing And Thawing ◽  
Viable Cells ◽  
High Temperature Short Time ◽  
Whole Milk ◽  
Short Time

The clinically important serotypes of Yersinia enterocolitica were shown to be highly heat sensitive, and none of the strains of serotypes 0:3; 0:5;27; 0:6,30; 0:8 and 0:9, ATCC 23715, and ATCC 27729 used in this study could survive high-temperature short-time pasteurization at 71.8°C for 18 s at 108 cell/ml. D62.8 was found to be 10.53 and 10.35 s in skim milk and whole milk, respectively. Destruction of the viable cells of Y. enterocolitica under freezing-thawing and constant freezing conditions at −20°C was more rapid in distilled water than in milk. Constant freezing at −20°C for 30 d had a negligible effect on the survival of Y. enterocolitica in milk.

Psychrotrophic Growth and Thermal Inactivation of Listeria monocytogenes as a Function of Milk Composition

1986 ◽  
Vol 49 (12) ◽  
pp. 994-998 ◽  
Author(s):  
CATHERINE W. DONNELLY ◽  
ELIZABETH H. BRIGGS
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Thermal Inactivation ◽  
Skim Milk ◽  
Raw Milk ◽  
Milk Composition ◽  
Cellular Growth ◽  
Whole Milk ◽  
Serotype 1 ◽  
Serotype 4B

Listeria monocytogenes strains 19111, 19113, 19115, F5027 and F5069 were grown in 11% nonfat milk solids, skim milk and whole milk at 4, 10, 22, and 37°C to determine the influence of temperature and milk composition on growth and thermal resistance. Milk composition affected cellular growth. The psychrotrophic growth of L. monocytogenes serotype 4b strains was enhanced in whole milk when compared to skim milk or 11% NFMS. This enhancement of psychrotrophic growth was not observed for serotype 1 or 3 strains. The stimulatory effect of whole milk on serotype 4b L. monocytogenes strains was most dramatic at 10°C where cells increased from 7.9 × 10° to 5.8 × 106 CFU/ml within 48 h. Milk composition did not affect the thermal resistance of L. monocytogenes. All strains used in this study had a D62.7°C value of 1.0 min or less, therefore, pasteurization as defined by current FDA guidelines should eliminate this organism from raw milk with a large margin of safety. Post-pasteurization contamination of dairy products with L. monocytogenes must be eliminated since the psychrotrophic nature of this organism ensures survival and proliferation during refrigerated storage.

Growth of Listeria monocytogenes at 10°C in Milk Preincubated with Selected Pseudomonads1

1988 ◽  
Vol 51 (4) ◽  
pp. 277-282 ◽  
Author(s):  
DOUGLAS L. MARSHALL ◽  
RONALD H. SCHMIDT
Keyword(s):  
Listeria Monocytogenes ◽  
Skim Milk ◽  
Growth Curves ◽  
Milk Composition ◽  
Pseudomonas Fragi ◽  
Pseudomonas Spp ◽  
Generation Times ◽  
Whole Milk ◽  
Dry Milk ◽  
Stimulation Of

Preliminary studies involving co-inoculation of Listeria monocytogenes with Pseudomonas fragi into whole or skim milk demonstrated that neither inhibition nor stimulation of growth occurred for either organism. Additional investigations involved preincubation of whole milk, skim milk, and 10% reconstituted nonfat dry milk (NDM) for 3 d at 10°C with P. fragi, Pseudomonas fluorescens P26, P. fluorescens T25, or P. fluorescens B52, followed by inoculation with L. monocytogenes and further incubation at 10°C. Growth curves of L. monocytogenes were constructed for each treatment combination and generation times were statistically compared for differences. Results indicated that L. monocytogenes did not affect growth or survival of the preincubated Pseudomonas spp. However, growth rates of L. monocytogenes were significantly (P<0.05) enhanced in milks preincubated with pseudomonads. Doubling times of L. monocytogenes were reduced by up to 3 h when grown in milk preincubated with Pseudomonas spp. Three strains of P. fluorescens showed more stimulation of the growth rate of L. monocytogenes compared to P. fragi in preincubated whole or skim milk but not in preincubated NDM. Milk composition had little effect on growth of either genus when incubated alone. Results of this study indicate that L. monocytogenes can grow in the presence of Pseudomonas spp. either as a co-inoculant or following preincubation in milk at 10°C. Furthermore, data suggest that the presence of the pseudomonads may enhance growth of L. monocytogenes in milk.

Growth of Listeria monocytogenes in the Presence of Pseudomonas fluorescens at 7 or 13°C in Skim Milk

1989 ◽  
Vol 52 (12) ◽  
pp. 852-855 ◽  
Author(s):  
SEHAM A. FARRAG ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Pseudomonas Fluorescens ◽  
Incubation Period ◽  
Skim Milk

Autoclaved samples of skim milk were inoculated with Listeria monocytogenes (strain Scott A, California or V7), Pseudomonas fluorescens (strain P26 or B52), or a combination of L. monocytogenes plus P. fluorescens, and incubated at 7 or 13°C for 8 weeks. McBride Listeria Agar was used to determine populations of L. monocytogenes (at 0, 7, 14, 28, 42, or 56 d), and Pseudomonas isolation agar to enumerate P. fluorescens. Growth of L. monocytogenes was somewhat enhanced after 7 d of incubation at 7 but not at 13°C in the presence of pseudomonads. However, after 14 d and until the end of the incubation period (56 d), slight inactivation of L. monocytogenes in the presence of P. fluorescens was observed. L. monocytogenes did not affect growth or survival of P. fluorescens; also, no marked changes in pH of the milk were caused either by L. monocytogenes alone or by L. monocytogenes plus P. fluorescens.

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