scholarly journals Non-Destructive Luminescence-Based Screening Tool for Listeria monocytogenes Growth on Ham

Foods ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1700
Author(s):  
Shannon D. Rezac ◽  
Cristina Resendiz-Moctezuma ◽  
Dustin D. Boler ◽  
Matthew J. Stasiewicz ◽  
Michael J. Miller
Keyword(s):  
Listeria Monocytogenes ◽  
Large Scale ◽  
Screening Tool ◽  
Growth Monitoring ◽  
Food Borne ◽  
Colony Forming Units ◽  
Potassium Lactate ◽  
Plate Counts ◽  
Antimicrobial Treatments ◽  
Non Destructive

Listeria monocytogenes is a food-borne pathogen often associated with ready-to-eat (RTE) food products. Many antimicrobial compounds have been evaluated in RTE meats. However, the search for optimum antimicrobial treatments is ongoing. The present study developed a rapid, non-destructive preliminary screening tool for large-scale evaluation of antimicrobials utilizing a bioluminescent L. monocytogenes with a model meat system. Miniature hams were produced, surface treated with antimicrobials nisin (at 0–100 ppm) and potassium lactate sodium diacetate (at 0–3.5%) and inoculated with bioluminescent L. monocytogenes. A strong correlation (r = 0.91) was found between log scale relative light units (log RLU, ranging from 0.00 to 3.35) read directly from the ham surface and endpoint enumeration on selective agar (log colony forming units (CFU)/g, ranging from 4.7 to 8.3) when the hams were inoculated with 6 log CFU/g, treated with antimicrobials, and L. monocytogenes were allowed to grow over a 12 d refrigerated shelf life at 4 °C. Then, a threshold of 1 log RLU emitted from a ham surface was determined to separate antimicrobial treatments that allowed more than 2 log CFU/g growth of L. monocytogenes (from 6 log CFU/g inoculation to 8 log CFU/g after 12 d). The proposed threshold was utilized in a luminescent screening of antimicrobials with days-to-detect growth monitoring of luminescent L. monocytogenes. Significantly different (p < 0.05) plate counts were found in antimicrobial treated hams that had reached a 1 log RLU increase (8.1–8.5 log(CFU/g)) and the hams that did not reach the proposed light threshold (5.3–7.5 log(CFU/g)). This confirms the potential use of the proposed light threshold as a qualitative tool to screen antimicrobials with less than or greater than a 2 log CFU/g increase. This screening tool can be used to prioritize novel antimicrobials targeting L. monocytogenes, alone or in combination, for future validation.

scholarly journals Microplate Fluorescence Assay for Measurement of the Ability of Strains of Listeria monocytogenes from Meat and Meat-Processing Plants To Adhere to Abiotic Surfaces

2007 ◽  
Vol 73 (16) ◽  
pp. 5235-5244 ◽  
Author(s):  
Rachel Gamble ◽  
Peter M. Muriana
Keyword(s):  
Listeria Monocytogenes ◽  
Molecular Mechanisms ◽  
Meat Processing ◽  
Abiotic Surfaces ◽  
Food Borne ◽  
Environmental Surfaces ◽  
Processing Plants ◽  
Plate Counts ◽  
Microplate Fluorescence Assay ◽  
High Level

ABSTRACT Listeria monocytogenes is a significant food-borne pathogen that is capable of adhering to and producing biofilms on processing equipment, making it difficult to eliminate from meat-processing environments and allowing potential contamination of ready-to-eat (RTE) products. We devised a fluorescence-based microplate method for screening isolates of L. monocytogenes for the ability to adhere to abiotic surfaces. Strains of L. monocytogenes were incubated for 2 days at 30°C in 96-well microplates, and the plates were washed in a plate washer. The retained cells were incubated for 15 min at 25°C with 5,6-carboxyfluorescein diacetate and washed again, and then the fluorescence was read with a plate reader. Several enzymatic treatments (protease, lipase, and cellulase) were effective in releasing adherent cells from the microplates, and this process was used for quantitation on microbiological media. Strongly adherent strains of L. monocytogenes were identified that had 15,000-fold-higher levels of fluorescence and 100,000-fold-higher plate counts in attachment assays than weakly adherent strains. Strongly adherent strains of L. monocytogenes adhered equally well to four different substrates (glass, plastic, rubber, and stainless steel); showed high-level attachment on microplates at 10, 20, 30, and 40°C; and showed significant differences from weakly adherent strains when examined by scanning electron microscopy. A greater incidence of strong adherence was observed for strains isolated from RTE meats than for those isolated from environmental surfaces. Analysis of surface adherence among Listeria isolates from processing environments may provide a better understanding of the molecular mechanisms involved in attachment and suggest solutions to eliminate them from food-processing environments.

Postprocess Control of Listeria monocytogenes on Commercial Frankfurters Formulated with and without Antimicrobials and Stored at 10°C

2006 ◽  
Vol 69 (1) ◽  
pp. 53-61 ◽  
Author(s):  
IFIGENIA GEORNARAS ◽  
PANAGIOTIS N. SKANDAMIS ◽  
KEITH E. BELK ◽  
JOHN A. SCANGA ◽  
PATRICIA A. KENDALL ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Lag Phase ◽  
Potassium Lactate ◽  
Potassium Benzoate ◽  
Sodium Diacetate ◽  
Specific Growth Rates ◽  
Spoilage Microflora ◽  
Antimicrobial Treatments ◽  
Microbiological Analyses ◽  
Different Sources

The antilisterial effect of postprocess antimicrobial treatments on commercially manufactured frankfurters formulated with and without a 1.5% potassium lactate–0.05% sodium diacetate combination was evaluated. Frankfurters were inoculated (ca. 3 to 4 log CFU/cm2) with 10-strain composite Listeria monocytogenes cultures originating from different sources. The inocula evaluated were cells grown planktonically in tryptic soy broth plus 0.6% yeast extract (30°C, 24 h) or in a smoked sausage homogenate (15°C, 7 days) and cells that had been removed from stainless steel coupons immersed in an inoculated smoked sausage homogenate (15°C, 7 days). Inoculated frankfurters were dipped (2 min, 25 ± 2°C) in acetic acid (AA; 2.5%), lactic acid (LA; 2.5%), potassium benzoate (PB; 5%), or Nisaplin (commercial form of nisin; 0.5%, equivalent to 5,000 IU/ml of nisin) solutions, or in Nisaplin followed by AA, LA, or PB, and were subsequently vacuum packaged and stored for 48 days at 10°C. In addition to microbiological analyses, sensory evaluations were performed with uninoculated samples that had been treated with AA, LA, or PB for 2 min. Initial L. monocytogenes populations were reduced by 1.0 to 1.8 log CFU/cm2 following treatment with AA, LA, or PB solutions, and treatments that included Nisaplin reduced initial levels by 2.4 to &gt;3.8 log CFU/cm2. All postprocessing treatments resulted in some inhibition of L. monocytogenes during the initial stages of storage of frankfurters that were not formulated with potassium lactate–sodium diacetate; however, in all cases, significant (P &lt; 0.05) growth occurred by the end of storage. The dipping of products formulated with potassium lactate–sodium diacetate in AA or LA alone—or in Nisaplin followed by AA, LA, or PB—increased lag-phase durations and lowered the maximum specific growth rates of the pathogen. Moreover, depending on the origin of the inoculum, this dipping of products led to listericidal effects. In general, differences in growth kinetics were obtained for the three inocula that were used to contaminate the frankfurters. Possible reasons for these differences include the presence of stress-adapted subpopulations and the inhibition of the growth of the pathogen due to high levels of spoilage microflora. The dipping of frankfurters in AA, LA, or PB did not (P &gt; 0.05) affect the sensory attributes of the product when compared to the control samples. The data generated in this study may be useful to U.S. ready-to-eat meat processors in their efforts to comply with regulatory requirements.

scholarly journals Distribution of serotypes of Listeria monocytogenes in chicken meats in Turkey

2020 ◽  
Vol 70 (4) ◽  
pp. 1859
Author(s):  
S. SAHIN ◽  
R. KALIN ◽  
MN MOGULKOC
Keyword(s):  
Public Health ◽  
Listeria Monocytogenes ◽  
Large Scale ◽  
Meat Products ◽  
Health Problems ◽  
Chicken Meat ◽  
Serotype Distribution ◽  
Food Borne ◽  
Serotype 1 ◽  
Food Borne Infections

Listeria monocytogenes is one of the important causes of food-borne infections. This study was conducted to determine the presence of L. monocytogenes and its serotype distribution in a total of 400 packaged chicken meat products (drumstick, breast, wing, and whole chicken) from different national companies. L. monocytogenes contamination was detected in 26.5% (106 in 400) of all samples when the products considered, drumsticks, breasts, wings, and whole chickens showed 47%, 15%, 35, and 9% positivity respectively. Four important serotypes of L. monocytogenes in human listeriosis (1/2a, 1/2b, 1/2c and 4b) were identified, and serotype 1/2a (94.3%) was determined as predominant in packaged chicken meats. The present study revealed that L. monocytogenes 1/2a serotype is prevalent in chicken meats and this may cause public health problems in Turkey. Further studies in poultry meats should be conducted on a large scale such as regional or national big markets to determine the presence of the pathogen and its dominant serotypes.

Evaluating the Growth of Listeria monocytogenes in Refrigerated Ready-to-Eat Frankfurters: Influence of Strain, Temperature, Packaging, Lactate and Diacetate, and Background Microflora

2008 ◽  
Vol 71 (9) ◽  
pp. 1806-1816 ◽  
Author(s):  
AMIT PAL ◽  
THEODORE P. LABUZA ◽  
FRANCISCO DIEZ-GONZALEZ
Keyword(s):  
High Pressure ◽  
Listeria Monocytogenes ◽  
Shelf Life ◽  
Growth Rates ◽  
Maximum Growth ◽  
Lag Time ◽  
Lag Phase ◽  
Potassium Lactate ◽  
Plate Counts ◽  
Data Log

This research was conducted to study the growth of Listeria monocytogenes inoculated on frankfurters stored at different conditions as a basis for a safety-based consume by shelf life date label. Three L. monocytogenes strains were separately inoculated at 10 to 20 CFU/cm2 onto frankfurters that were previously formulated with or without high pressure and with or without added 2% potassium lactate (PL) and 0.2% sodium diacetate (SD). Inoculated frankfurters were air or vacuum packaged; stored at 4, 8, or 12°C; and L. monocytogenes and psychrotrophic plate counts were determined for 90, 60, and 45 days, respectively, or until the stationary phase was reached. The data (log CFU per square centimeter versus time) were fitted using the Baranyi-Roberts model to determine maximum growth rates and lag-phase time. The maximum growth rates and the lag time under each growth condition were used to calculate the time to reach 100-fold the initial Listeria population. In frankfurters lacking PL and SD, the count of all strains increased by 2 log after 18 to 50 days at 4°C and 4 to 13 days at 8°C. The growth was inhibited at 4 and 8°C in frankfurters containing PL and SD, but one ribotype was capable of growing, with the time to reach 100-fold the initial Listeria population ranging from 19 to 35 days at 12°C. In most cases, the time to reach 100-fold the initial Listeria population of L. monocytogenes was significantly longer in vacuum-packaged frankfurters as compared with air-packaged samples. Inclusion of PL and SD also inhibited the growth of psychrotrophs, but at all temperatures the psychrotrophic plate counts were greater than 4 log CFU/cm2 at the end of the experiments. These results indicated that despite the use of antimicrobials, certain L. monocytogenes strains could be capable of growing under storage-abuse conditions. Growth kinetics data could be useful for establishing a shelf life date label protocol under different handling scenarios.

Growth Potential of Individual Strains of Listeria monocytogenes in Fresh Vacuum-Packaged Refrigerated Ground Top Rounds of Beef

1995 ◽  
Vol 58 (4) ◽  
pp. 398-403 ◽  
Author(s):  
WERNER B. BARBOSA ◽  
JOHN N. SOFOS ◽  
GLENN R. SCHMIDT ◽  
GARY C. SMITH
Keyword(s):  
Listeria Monocytogenes ◽  
Ground Beef ◽  
Growth Potential ◽  
High Ph ◽  
Ph Values ◽  
Colony Forming Units ◽  
Serotype 1 ◽  
Plate Counts ◽  
Serotype 4B

Separate inocula of four strains of Listeria monocytogenes were prepared at 4°C and inoculated (3.58 to 4.67 log10 colony forming units [CFU]/g) in top round ground beef (&lt; 4.0% fat) patties (78.8 ± 6.7 g) of normal (5.47 ± 0.03) or high (6.14 ± 0.08) pH, which were stored (4°C) vacuum-packaged for 56 days and analyzed for L. monocytogenes, total aerobic plate counts (APC) and pH. In normal-pH ground beef, strain N-7143 (serotype 3a), multiplied from 4.25 ± 0.71 log10 CFU/g at day of inoculation to 6.53 ± 0.34 log10 CFU/g at 35 days of storage (P &lt; 0.05); a 2.3 log10 CFU/g increase. Populations of strain Na-19 (serotype 3b) increased 1.8 log10 CFU/g in 35 days of storage, while numbers of strain Na-16 (serotype 1/2a) did not change (P &gt; 0.05) during the 56 days of storage. Strain Scott A (serotype 4b) decreased in numbers from 4.00 ± 1.21 log10 CFU/g at day-0 to 2.72 ± 0.98 log10 CFU/g at 56 days. Populations of strain Scott A were lower (P &lt; 0.05) than other strains after 21 days of storage. In high-pH ground beef, populations of strains Na-19, N-7143 and Na-16 increased (P &lt; 0.05) by 2.87, 2.64 and 2.24 log10 CFU/g, respectively, in 28 days. Populations of strain Scott A did not change significantly (P &gt; 0.05), and they were lower (P&lt; 0.05) than populations of other strains at 28 days. The results indicated that although growth of L. monocytogenes in vacuum-packaged, refrigerated ground beef was slow, it proceeded more rapidly in product of pH values above 6.0, and depended on strain of the pathogen tested.

Protective effect by Bacillus smithii TBMI12 spores of Salmonella serotype Enteritidis in mice

2010 ◽  
Vol 1 (1) ◽  
pp. 37-42 ◽  
Author(s):  
I. Suitso ◽  
E. Jõgi ◽  
E. Talpsep ◽  
P. Naaber ◽  
K. Lõivukene ◽  
...  
Keyword(s):  
Protective Effect ◽  
Competitive Exclusion ◽  
Current Paper ◽  
Control Group ◽  
Wild Type ◽  
Food Borne ◽  
Colony Forming Units ◽  
Plate Counts ◽  
Bacillus Smithii ◽  
Salmonella Serotype

Avoiding food-borne diseases by competitive exclusion agents is a proactive strategy. In the current paper, we report the use of Bacillus smithii TBMI12 spores as potential competitive exclusion agents. One group of mice was predosed for three successive days with 108 colony forming units of B. smithii TBMI12 spores followed by inoculation with 106 colony forming units of wild-type Salmonella enterica serotype Enteritidis cells. Microbial plate counts of the animals' livers and spleens showed that only 40% of the mice were infected with S. enterica serotype Enteritidis, while the control group was 100% infected. These results suggest that B. smithii TBMI12 spores may protect against infection by S. enterica serotype Enteritidis.

Effectiveness of Acidic Calcium Sulfate with Propionic and Lactic Acid and Lactates as Postprocessing Dipping Solutions To Control Listeria monocytogenes on Frankfurters with or without Potassium Lactate and Stored Vacuum Packaged at 4.5°C

2004 ◽  
Vol 67 (5) ◽  
pp. 915-921 ◽  
Author(s):  
MARYURI T. NUÑEZ de GONZALEZ ◽  
JIMMY T. KEETON ◽  
GARY R. ACUFF ◽  
LARRY J. RINGER ◽  
LISA M. LUCIA
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Calcium Sulfate ◽  
Limit Of Detection ◽  
Meat Products ◽  
Bactericidal Effect ◽  
Antimicrobial Substances ◽  
Potassium Lactate ◽  
Residual Nitrite ◽  
Plate Counts

The safety of ready-to-eat meat products such as frankfurters can be enhanced by treating with approved antimicrobial substances to control the growth of Listeria monocytogenes. We evaluated the effectiveness of acidic calcium sulfate with propionic and lactic acid, potassium lactate, or lactic acid postprocessing dipping solutions to control L. monocytogenes inoculated (ca. 108 CFU/ml) onto the surface of frankfurters with or without potassium lactate and stored in vacuum packages at 4.5° C for up to 12 weeks. Two frankfurter formulations were manufactured without (control) or with potassium lactate (KL, 3.3% of a 60% [wt/wt] commercially available syrup). After cooking, chilling, and peeling, each batch was divided into inoculated (four strains of L. monocytogenes mixture) and noninoculated groups. Each group was treated with four different dips: (i) control (saline solution), (ii) acidic calcium sulfate with propionic and lactic acid (ACS, 1:2 water), (iii) KL, or (iv) lactic acid (LA, 3.4% of a 88% [wt/wt] commercially available syrup) for 30 s. Noninoculated frankfurters were periodically analyzed for pH, water activity, residual nitrite, and aerobic plate counts (APCs), and L. monocytogenes counts (modified Oxford medium) were determined on inoculated samples. Surface APC counts remained at or near the lower limit of detection (&lt;2 log CFU per frank) on franks with or without KL and treated with ACS or LA throughout 12 weeks at 4.5° C. L. monocytogenes counts remained at the minimum level of detection on all franks treated with the ACS dip, which indicated a residual bactericidal effect when L. monocytogenes populations were monitored over 12 weeks. L. monocytogenes numbers were also reduced, but not to the same degree in franks made without or with KL and treated with LA. These results revealed the effectiveness of ACS (bactericidal effect) or LA (bacteriostatic effect) as postprocessing dipping solutions to inhibit or control the growth of L. monocytogenes on vacuum-packaged frankfurters stored at 4.5° C for up to 12 weeks.

Radiosensitivity of Listeria monocytogenes at Various Temperatures and Cell Concentrations

1995 ◽  
Vol 58 (7) ◽  
pp. 748-751 ◽  
Author(s):  
LINDA S. ANDREWS ◽  
DOUGLAS L. MARSHALL ◽  
ROBERT M. GRODNER
Keyword(s):  
Regression Analysis ◽  
Listeria Monocytogenes ◽  
Total Dose ◽  
Gram Negative Bacteria ◽  
Initial Cell Concentration ◽  
Food Borne ◽  
Colony Forming Units ◽  
Radiation Resistant ◽  
D Values ◽  
D Value

Among food-borne pathogens, Listeria monocytogenes is more radiation resistant than gram-negative bacteria of the genera Salmonella and Vibrio. This study was designed to determine if initial cell concentration and/or temperature at the time of irradiation influences the radiosensitivity of L. monocytogenes. Concentrations of 103, 106, and 109 CFU (colony-forming units)/ml of L. monocytogenes Scott A were suspended in tryptic soy broth and exposed to 0 to 5 kGy of gamma radiation (1.25 MeV) at 20, 4, and −80°C. Survivors were enumerated and irradiation D-values were calculated using regression analysis and total-dose methods. A 103 CFU/ml population was destroyed with a &lt;2 kGy dose. The irradiation D-value of 0.43 kGy when calculated by regression analysis for frozen (−80°C) cultures of 106 CFU/ml was significantly lower (P &lt; 0.05) than those (0.58 and 0.62 kGy) at 20° and 4°C, respectively. However, the −80°C D-value was not significantly different (0.61 kGy) when calculated by the total dose required to eliminate all recovery. At 109 CFU/ml, a D-value (calculated by both methods) of 0.42 kGy was obtained at both 4° and −80°C, which was significantly lower (P &lt; 0.05) than 0.50 kGy for 20°C suspensions. The temperature of irradiation only influenced the radiosensitivity of L. monocytogenes at 109 CFU/ml.

Failure Analysis of Flip-Chip Interconnections Through Acoustic Microscopy

1996 ◽  
Author(s):  
O. Diaz de Leon ◽  
M. Nassirian ◽  
C. Todd ◽  
R. Chowdhury
Keyword(s):  
Failure Analysis ◽  
Large Scale ◽  
Flip Chip ◽  
Ultrasonic Waves ◽  
Acoustic Microscopy ◽  
Acoustic Microscope ◽  
Chip Technology ◽  
Ball Joints ◽  
Non Destructive ◽  
Scanning Acoustic Microscope

Abstract Integration of circuits on semiconductor devices with resulting increase in pin counts is driving the need for improvements in packaging for functionality and reliability. One solution to this demand is the Flip- Chip concept in Ultra Large Scale Integration (ULSI) applications [1]. The flip-chip technology is based on the direct attach principle of die to substrate interconnection.. The absence of bondwires clearly enables packages to become more slim and compact, and also provides higher pin counts and higher-speeds [2]. However, due to its construction, with inherent hidden structures the Flip-Chip technology presents a challenge for non-destructive Failure Analysis (F/A). The scanning acoustic microscope (SAM) has recently emerged as a valuable evaluation tool for this purpose [3]. C-mode scanning acoustic microscope (C-SAM), has the ability to demonstrate non-destructive package analysis while imaging the internal features of this package. Ultrasonic waves are very sensitive, particularly when they encounter density variations at surfaces, e.g. variations such as voids or delaminations similar to air gaps. These two anomalies are common to flip-chips. The primary issue with this package technology is the non-uniformity of the die attach through solder ball joints and epoxy underfill. The ball joints also present defects as open contacts, voids or cracks. In our acoustic microscopy study packages with known defects are considered. It includes C-SCAN analysis giving top views at a particular package interface and a B-SCAN analysis that provides cross-sectional views at a desired point of interest. The cross-section analysis capability gives confidence to the failure analyst in obtaining information from a failing area without physically sectioning the sample and destroying its electrical integrity. Our results presented here prove that appropriate selection of acoustic scanning modes and frequency parameters leads to good reliable correlation between the physical defects in the devices and the information given by the acoustic microscope.

Biofilm Formation and Associated Genes in Listeria Monocytogenes

2017 ◽  
Vol 12 (3) ◽  
Author(s):  
S. R. Warke ◽  
V. C. Ingle ◽  
N. V. Kurkure ◽  
P. A. Tembhurne ◽  
Minakshi Prasad ◽  
...  
Keyword(s):  
Public Health ◽  
Listeria Monocytogenes ◽  
Multiplex Pcr ◽  
Food Processing ◽  
Biofilm Formation ◽  
Milk Samples ◽  
Biofilm Production ◽  
Food Borne ◽  
Serious Infections ◽  
Microtiter Assay

Listeria monocytogenes, an opportunistic food borne pathogen can cause serious infections in immunocompromised individuals. L. monocytogenes is capable of producing biofilm on the surface of food processing lines and instruments.The biofilm transfers contamination to food products and impose risk to public health. In the present study biofilm producing ability of L. monocytogenes isolates were investigated phenotypically and genotypically by microtiter assay and multiplex PCR, respectively. Out of 38 L. monocytogenes isolates 14 were recovered from animal clinical cases, 12 bovine environment and 12 from milk samples. A total of 3 (21.42%) clinical, 2 (16.66%) environment and 3 (25%) milk samples respectively, revealed biofilm production in microtiter assay. Cumulative results showed that 23 (60.52%) out of 38 strains of L. monocytogenes were positive for luxS and flaA gene and 1 (2.63%) was positive only for the flaA gene.

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