Inactivation of Listeria innocua on frankfurters that contain potassium lactate and sodium diacetate by flash pasteurization

ABSTRACT:  Listeria monocytogenes , a psychrotrophic foodborne pathogen, is a recurring postprocess contaminant on ready-to-eat meat (RTE) products, including frankfurters. Potassium lactate (PL) and sodium diacetate (SDA) are FDA-approved antimicrobials that inhibit the growth of L. monocytogenes when incorporated into the formulation of fine emulsion sausage. Flash (steam) pasteurization (FP) has been shown to reduce levels of L. monocytogenes , and its surrogate L. innocua , on frankfurter surfaces. The ability of FP to inactivate and prevent the growth of the L. monocytogenes surrogate L. innocua in a pilot plant setting was investigated. FP treatment (1.5 s, 121 °C) of single layers of frankfurters that were surface-inoculated with either 5, 4, or 3 log CFU/g of L. innocua immediately before FP (1.5 s, 121 °C) resulted in log reductions of 1.97 (± 0.11), 2.03 (± 0.10), or 2.07 (± 0.14), respectively. Inoculum level had no effect on the inactivation of L. innocua . Following 8 wk of refrigerated storage (4 °C), L. innocua levels decreased by 0.5 log in non-FP-treated frankfurter packs, while the 2 log reduction of L. innocua was maintained for FP-treated frankfurters. FP (1.5 s, 121 °C) had no effect on frankfurter color or texture. Because the numbers of L. monocytogenes associated with contaminations of ready-to-eat meats are typically very low, the use of FP in combination with PL and SDA has the potential to reduce the number of frankfurter recalls and foodborne illness outbreaks.     

Control of Listeria monocytogenes in ready-to-eat meats containing sodium levulinate, sodium lactate, or a combination of sodium lactate and sodium diacetate

ABSTRACT:  This study investigated the use of sodium levulinate to prevent outgrowth of Listeria monocytogenes in refrigerated ready-to-eat (RTE) meat products. Turkey breast roll and bologna were formulated to contain 1%, 2%, or 3% (w/w) sodium levulinate, 2% sodium lactate, a 2% combination of sodium lactate and sodium diacetate (1.875% sodium lactate and 0.125% sodium diacetate), or no antimicrobial (control). Samples of the RTE products were sliced, inoculated with 10² to 10³ CFU/cm² of a 5-strain cocktail of L. monocytogenes , vacuum packaged, and stored at refrigeration temperature for 0 to 12 wk. Counts reached 10⁸ CFU/cm² on control turkey roll product after 8 wk, and over 10⁷ CFU/cm² on control bologna after 12 wk. Addition of 2% or more sodium levulinate to turkey roll and 1% or more sodium levulinate to bologna completely prevented growth of L. monocytogenes during 12 wk of refrigerated storage. A consumer taste panel with pathogen-free samples found no differences in the overall liking among the preparations of turkey roll or among preparations of bologna. These results show that sodium levulinate is at least as effective at inhibiting outgrowth of L. monocytogenes in RTE meat products as the current industry standards of lactate or lactate and diacetate, and levulinate addition does not alter the overall liking of the RTE meat products.     

Modeling the lag phase and growth rate of Listeria monocytogenes in ground ham containing sodium lactate and sodium diacetate at various storage temperatures

ABSTRACT:  Refrigerated ready-to-eat (RTE) meats contaminated with Listeria monocytogenes were implicated in several listeriosis outbreaks. Lactate and diacetate have been shown to control L. monocytogenes in RTE meats. The objective of this study was to examine and model the effect of lactate (1.0% to 4.2%) and diacetate (0.05% to 0.2%) in ground ham on the lag phase duration (LPD, h) and growth rate (GR, log CFU/h) of L. monocytogenes at a range of temperatures (0 to 45 °C). A 6-strain mixture of L. monocytogenes was inoculated into ground ham containing lactate and diacetate, and stored at various temperatures. The LPD and GR of L. monocytogenes in ham as affected by lactate, diacetate, and storage temperature were analyzed and accurately represented with mathematical equations. Resulting LPD and GR equations for storage temperatures within the range of 0 to 36 °C significantly represented the experimental data with a regression coefficient of 0.97 and 0.96, respectively. Significant factors ( P < 0.05) that affected the LPD were temperature, lactate, diacetate, and the interactions of all three, whereas only temperature and the interactions between temperature and lactate and diacetate had a significant effect on GR. At suboptimal growth temperatures (≤12 °C) the increase of lactate and diacetate concentrations, individually or in combination, extended the LPD. The effect of higher concentrations of both additives on reducing the GR was observed only at temperatures that were more suitable for growth of L. monocytogenes , that is, 15 to 35 °C. These data may be used to assist in determining concentrations of lactate and diacetate in cooked ham products to control the growth of L. monocytogenes over a wide range of temperatures during manufacturing, distribution, and storage.     

Antimicrobial activity of lactic acid bacteria against Listeria monocytogenes on frankfurters formulated with and without lactate/diacetate

Contamination by Listeria monocytogenes has been a constant public health threat for the ready-to-eat (RTE) meat industry due to the potential for high mortalities from listeriosis. Lactic acid bacteria (LAB) have shown protective action against various pathogenic bacteria. The aim of this study was to evaluate the antilisterial activity of a combination of three LAB strains (Lactiguard®) on L. monocytogenes. The combination of the LAB was inhibitory to L. monocytogenes inoculated onto frankfurters not containing lactate/diacetate after 8 weeks of refrigerated storage (0.6 log reduction compared to L. monocytogenes only control), and when a cell free extract (CFS) of the LAB was added with LAB even more inhibition was obtained (1.2 log reduction compared with L. monocytogenes only). In frankfurters containing lactate/diacetate the LAB and the LAB plus CFS were more effective in reducing growth of L. monocytogenes after 8 weeks of refrigerated storage (2 and 3.3 log reductions respectively).     

Effects and interactions of sodium lactate, sodium diacetate, and pediocin on the thermal inactivation of starved Listeria monocytogenes on bologna

The effects and interactions of temperature (56.3-60 °C), sodium lactate (SL; 0-4.8%), sodium diacetate (SDA; 0-2.5%), and pediocin (0-10,000 AU) on starved Listeria monocytogenes (10⁷ CFU/g) on bologna were investigated. Bologna slices containing SL and SDA in the formulation were dipped in pediocin, surface inoculated, and treated at various temperatures using combinations of parameters determined by central composite design. D-values were calculated. The observed D-values ranged from 2.8 min at 60 °C to 24.61 min at 56.3 °C. Injury ranged from 9.1 to 76% under various conditions. The observed D-values were analyzed using second order response surface regression for temperature, SL, SDA, and pediocin, and a predictive model was developed. Predicted D-values were calculated and ranged from 3.7 to 19 min for various combinations of parameters. Temperature alone reduced the predicted D-values from 33.96 min at 56.3 °C to 11.51 min at 60 °C. Addition of SL showed a protective effect. Other combination treatments either reduced or increased D-values depending on temperature. The combination of SL and SDA was effective at lower temperatures, however, higher levels of SDA at higher temperatures made the organism more heat resistant. Pediocin (up to 5000 AU) with increasing temperature and SDA reduced D-values. Depending on temperature and concentration, the interactions between various additives can affect thermal inactivation of L. monocytogenes on bologna. Starvation rendered L. monocytogenes more susceptible to heat and additives.     

Control of Listeria Monocytogenes by Lauric Arginate on Frankfurters Formulated with or without Lactate/Diacetate

ABSTRACT:  Listeria monocytogenes  (Lm) is a food safety concern that can be associated with ready-to-eat (RTE) meat and poultry products because of its persistence in the processing environment. Listeriosis has a fatality rate of 28% in immuno-compromised individuals. RTE meats receive a lethal heat treatment but may become contaminated by Lm after this treatment. Federal regulators and manufacturers of RTE meats are working to find additional ways to control postprocess contamination by Lm in RTE meats. This research was initiated to validate combinations of antimicrobials that would produce an immediate lethality of at least 1 log of Lm on artificially contaminated frankfurters, and also suppress Lm growth to less than 2 logs throughout the extended shelf life at refrigerated temperatures (4 °C). Based on our studies, 22-ppm lauric arginate (LAE, ethyl-N-dodecanoyl-L-arginate hydrochloride) gave more than a 1-log reduction of Lm surface inoculated onto frankfurters within 12 h. The combination of either 1.8%/0.13% or 2.1%/0.15% potassium lactate/sodium diacetate (L/D) in combination with 22 ppm LAE caused more than a 2-log reduction at 12 h. Storage studies revealed that complementary interactions of L/D and LAE also met the 2nd requirement. This combination initially reduced Lm by 2 logs and suppressed growth to less than 2 logs even at the end of the 156-d storage life for frankfurters. These results confirmed that the combination of L/D with LAE as a postprocessing–prepackaging application could be useful in complying with the USDA's Alternative 1 that requires validation for the control of Lm on RTE frankfurters.     

Gamma irradiation as a means to eliminate Listeria monocytogenes from frozen chicken meat

Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D₁₀, dose required for 10% survival—0.15 kGy) at 0–5°C. The cells showed higher radiation survival when irradiated under frozen condition, with a D₁₀ of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre^?1) was evidenced by even higher D₁₀ values (0.5 kGy) at both 0–5°C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 × 10³) colony-forming unit (cfu) g^?1 and high (5 × 10⁶ cfu g^?1) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2–4°C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10³ cfu cells of L monocytogenes g^?1 from air-packed frozen chicken meat.     

Evaluation of Changes in Listeria monocytogenes Populations on Frankfurters at Different Stages from Manufacturing to Consumption

ABSTRACT: This study evaluated the fate of inoculated Listeria monocytogenes on frankfurters stored under conditions simulating those that may be encountered between manufacturing and consumption. Frankfurters with or without 1.5% potassium lactate and 0.1% sodium diacetate (PL/SD) were inoculated (1.8 ± 0.1 log CFU/cm²) with a 10‐strain composite of L. monocytogenes, vacuum‐packaged, and stored under conditions simulating predistribution storage (24 h, 4 °C), temperature abuse during transportation (7 h, 7 °C followed by 7 h, 12 °C), and storage before purchase (60 d, 4 °C; SBP). At 0, 20, 40, and 60 d of SBP, samples were exposed to conditions simulating delivery from stores to homes or food establishments (3 h, 23 °C), and then opened or held vacuum‐packaged at 4 or 7 °C for 14 d (SHF). Pathogen counts remained relatively constant on frankfurters with PL/SD regardless of product age and storage conditions; however, they increased on product without antimicrobials. In vacuum‐packaged samples, during SHF at 4 °C, the pathogen grew faster (P < 0.05) on older product (20 d of SBP) compared to product that was fresh (0 d of SBP); a similar trend was observed in opened packages. At 7 °C, the fastest growth (0.35 ± 0.02 log CFU/cm²/d) was observed on fresh product in opened packages; in vacuum‐packages, growth rates on fresh and aged products were similar. By day 40 of SBP the pathogen reached high numbers and increased slowly or remained unchanged during SHF. This information may be valuable in L. monocytogenes risk assessments and in development of guidelines for storage of frankfurters between package opening and product consumption.     

Ultraviolet Light (254 nm) Inactivation of Listeria monocytogenes on Frankfurters That Contain Potassium Lactate and Sodium Diacetate

ABSTRACT:  Listeria monocytogenes , a psychrotrophic foodborne pathogen, is an occasional postprocess contaminant on ready-to-eat meat (RTE) products including frankfurters. Ultraviolet C light (UVC) is an FDA-approved technology for the decontamination of food surfaces. In this study, the ability of UVC to inactivate L. monocytogenes on frankfurters that contained potassium lactate (PL) and sodium diacetate (SDA), either before or after packaging, was investigated. UVC irradiation of frankfurters that were surface-inoculated with L. monocytogenes resulted in a 1.31, 1.49, and 1.93 log reduction at doses of 1, 2, and 4 J/cm², respectively. UVC treatment had no effect on frankfurter color or texture at UVC doses up to 4 J/cm². Frankfurter meat treated with UVC doses up to 16 J/cm² did not increase mutagenesis in bacterial or human cells, either with or without exogenous metabolic activation. UVC treatment of single-layer frankfurter packs at a dose of 2 J/cm² resulted in a 0.97 (± 0.14) log reduction of L. monocytogenes . Following 8 wk of refrigerated storage L. monocytogenes levels decreased by only 0.65 log in non-UVC-treated frankfurter packs compared with 2.5 log in the UVC-treated packs. Because the numbers of L. monocytogenes associated with contaminations of ready-to-eat meats are typically very low, the use of UVC in combination with potassium lactate and sodium diacetate has the potential to reduce the number of frankfurter recalls and foodborne illness outbreaks.     

Properties of refrigerated ground beef treated with potassium lactate and sodium diacetate

BACKGROUND: Ground meat is product that perishes easily and therefore various preservatives are applied to prolong its shelf life. The aim of this study was to investigate the effect of potassium lactate and sodium diacetate (Protec K‐DI preparation) on general proteolytic activity, protein degradation, texture, colour and water‐holding capacity of vacuum‐packaged ground beef. RESULTS: The activity of endogenous proteolytic enzymes, and hence the rate of protein hydrolysis changed significantly (P < 0.05) during refrigerated storage. The proteolysis was more intensive in the meat with the preservative than in a control sample. According to the results of SDS‐PAGE, the level of myosin in ground beef decreased with increasing storage time, whereas the preservative did not have a significant effect (P > 0.05) on these changes. However, its impact was the most significant in the case of tropomyosin and troponin T content, as well as changes of 30 kDa protein content. The preservative as well as the increase in storage time influenced an increase in content of polypeptides, peptides and some amino acids in the samples, and had an inhibiting effect on unfavourable changes in ground beef hardness. The preservative addition allowed the meat to maintain desired meat colour, and the main pigment during refrigerated storage was oxymyoglobin (MbO₂). CONCLUSION: Results showed that the Protec K‐DI preparation can be useful in minced meat production as a good stabiliser of colour and texture despite the increase observed in proteolytic activity after the preservative addition. Copyright © 2007 Society of Chemical Industry     

Protein variations in Listeria monocytogenes exposed to sodium lactate, sodium diacetate, and their combination

Most studies of the effect of adverse conditions on survival of Listeria monocytogenes have focused on stress caused by acid or sodium chloride. However, no information is available on resistance of this pathogen to stress caused by salts of organic acids. Sodium lactate and sodium diacetate are generally recognized as safe substances and are approved as ingredients for use in foods. We evaluated antilisterial properties of each of these salts and the enhanced inhibition effected by their combination in ready-to-eat meat products at pH 6.3. Changes in proteins found in this pathogen were studied in the presence of the salts in a chemically defined medium at the same pH using a proteomic approach. The total numbers of protein spots obtained from two-dimensional electrophoresis were 198, 150, and 131 for sodium diacetate, sodium lactate, and the control, respectively. Sodium diacetate treatment produced the highest number of unmatched proteins (124 versus 53 in lactate), the greatest increase in expression (20 versus 5 in lactate), and the highest number of novel proteins (90 versus 45 in lactate). The number of repressed proteins was highest in the combination treatment (41 versus -30 in the single salt treatment). Six proteins that increased or decreased by > or = 10-fold were further investigated; oxidoreductase and lipoprotein were upregulated, and DNA-binding protein, alpha amylase, and two SecA proteins were downregulated or completely suppressed by the salt treatment. Identification of all protein spots is essential for comparison with proteins induced or suppressed under other stress conditions.     

单核细胞增生李斯特氏菌的PCR检测方法

研究比较了裂解法、热煮沸法、试验盒法提取单增李斯特氏菌DNA的效果 ,认为Promega试剂盒法提取的DNA ,得率高、纯度好。同时根据单增李斯特氏菌的毒力相关基因的 5对引物 ,进行了引物的特异性研究 ,结果发现inlA引物、inlB引物、plcA引物特异性好 ,可以用于食品中单增李斯特氏菌的检测     

Combining pediocin with postpackaging irradiation for control of Listeria monocytogenes on frankfurters

Frankfurters, in 1-link, 5-link, or 10-link packages, were surface inoculated with a five-strain mixture of Listeria monocytogenes (3.40 or 5.20 log CFU/g) after treatment with 3,000 arbitrary units (AU) or 6,000 AU of pediocin (in ALTA 2341) per link. The frankfurters were vacuum packaged, after which the 1-link and 5-link packages were irradiated at 1.2 or 2.3 kGy and the 10-link packages were irradiated at 1.4 or 3.5 kGy. L. monocytogenes was enumerated following the treatments. Selected treatments were subsequently evaluated during storage at 4, 10, and 25 degrees C for up to 12 weeks. Combination of pediocin with postpackaging irradiation at 1.2 kGy or more was necessary to achieve a 50% reduction of L. monocytogenes on frankfurters in 1-link or 5-link packages. The combination of 6,000 AU of pediocin and irradiation at 2.3 kGy or more was effective in all package sizes for inhibition of the pathogen for 12 weeks at 4 or 10 degrees C. There was a synergistic effect between pediocin and irradiation for inhibition of L. monocytogenes. Storage at 4 degrees C enhanced the antilisterial effects of the treatment combinations, with little or no growth of the pathogen in 1-link or 5-link packages during 12 weeks of storage. In general, these treatments did not affect the sensory quality of frankfurters.     

Inhibition of Listeria monocytogenes by exposure to a combination of nisin and cold-pressed terpeneless Valencia oil

Listeria monocytogenes is an important foodborne pathogen and its control in foods is a significant challenge. This study evaluated the effectiveness of nisin and cold-pressed terpeneless Valencia oil (CPTVO) on limiting L. monocytogenes growth. Disk diffusion assays were performed to determine the effects of CPTVO and nisin individually and in combination. Together, these antimicrobials produced a zone of inhibition that was significantly larger (P < 0.05) than zones correlating to CPTVO or nisin individually. Furthermore, L. monocytogenesΔsigB had an increased sensitivity to the combination treatment. Growth experiments performed in brain heart infusion (BHI) broth revealed the effects of nisin and CPTVO, individually and in combination on L. monocytogenes growth rate. When L. monocytogenes was grown in BHI containing 0.025% CPTVO and 26 IU/mL nisin, no growth inhibition was observed relative to the control. However, exposure to CPTVO at 0 h followed by the introduction of nisin at 15 h resulted in a statistically significant (P < 0.05) reduction in growth. This approach to inhibiting L. monocytogenes has potential as an all-natural, generally-recognized-as-safe multiple hurdle intervention that may be applicable for ready-to-eat products in which L. monocytogenes is likely to cause foodborne illness.     

Antimicrobial activity of lactic acid bacteria against Listeria monocytogenes on frankfurters formulated with and without lactate/diacetate

Contamination by Listeria monocytogenes has been a constant public health threat for the ready-to-eat (RTE) meat industry due to the potential for high mortalities from listeriosis. Lactic acid bacteria (LAB) have shown protective action against various pathogenic bacteria. The aim of this study was to evaluate the antilisterial activity of a combination of three LAB strains (Lactiguard®) on L. monocytogenes. The combination of the LAB was inhibitory to L. monocytogenes inoculated onto frankfurters not containing lactate/diacetate after 8 weeks of refrigerated storage (0.6 log reduction compared to L. monocytogenes only control), and when a cell free extract (CFS) of the LAB was added with LAB even more inhibition was obtained (1.2 log reduction compared with L. monocytogenes only). In frankfurters containing lactate/diacetate the LAB and the LAB plus CFS were more effective in reducing growth of L. monocytogenes after 8 weeks of refrigerated storage (2 and 3.3 log reductions respectively).     

Inhibition of Listeria monocytogenes by food antimicrobials applied singly and in combination

Abstract: Combining food antimicrobials can enhance inhibition of Listeria monocytogenes in ready-to-eat (RTE) meats. A broth dilution assay was used to compare the inhibition of L. monocytogenes resulting from exposure to nisin, acidic calcium sulfate, ɛ-poly-L-lysine, and lauric arginate ester applied singly and in combination. Minimum inhibitory concentrations (MICs) were the lowest concentrations of single antimicrobials producing inhibition following 24 h incubation at 35 °C. Minimum bactericidal concentrations (MBCs) were the lowest concentrations that decreased populations by ≥3.0 log₁₀ CFU/mL. Combinations of nisin with acidic calcium sulfate, nisin with lauric arginate ester, and ɛ-poly-L-lysine with acidic calcium sulfate were prepared using a checkerboard assay to determine optimal inhibitory combinations (OICs). Fractional inhibitory concentrations (FICs) were calculated from OICs and were used to create FIC indices (FIC_Is) and isobolograms to classify combinations as synergistic (FIC_I < 1.00), additive/indifferent (FIC_I= 1.00), or antagonistic (FIC_I > 1.00). MIC values for nisin ranged from 3.13 to 6.25 μg/g with MBC values at 6.25 μg/g for all strains except for Natl. Animal Disease Center (NADC) 2045. MIC values for ɛ-poly-L-lysine ranged from 6.25 to 12.50 μg/g with MBCs from 12.50 to 25.00 μg/g. Lauric arginate ester at 12.50 μg/g was the MIC and MBC for all strains; 12.50 mL/L was the MIC and MBC for acidic calcium sulfate. Combining nisin with acidic calcium sulfate synergistically inhibited L. monocytogenes; nisin with lauric arginate ester produced additive-type inhibition, while ɛ-poly-L-lysine with acidic calcium sulfate produced antagonistic-type inhibition. Applying nisin along with acidic calcium sulfate should be further investigated for efficacy on RTE meat surfaces. Practical Application: This study demonstrates the potential for combinations of antimicrobials to result in greater pathogen inhibition as compared to the application of a single antimicrobial. The data presented in this study can aid the food industry in developing more efficient and effective application of antimicrobials. These findings should also prompt further studies validating the inhibitory effect of combinations of antimicrobials on ready-to-eat surfaces.     

Sodium lactate,sodium diacetate and pediocin: Effects and interactions on the thermal inactivation of Listeria monocytogenes on bologna

The effects and interactions of temperature (56.3–60 °C), sodium lactate (SL; 0–4.8%), sodium diacetate (SD; 0–0.25%) and pediocin (0–10,000 AU) on Listeria monocytogenes on bologna were studied and a predictive inactivation model was developed. Bologna was manufactured with different SL/SD concentrations in the formulation, dipped in pediocin solution and treated at different temperatures using combinations of parameters determined by central composite design. D-values were calculated and analyzed using second order response regression. Predicted D-values were also calculated. The observed D-values for L. monocytogenes on bologna ranged from 2.10 to 35.59 min. Temperature alone decreased predicted D-values from 99.02 min at 56.3 °C to 44.71 min at 60.0 °C. Adding SL decreased D-values (85.43–22.71 min) further; however, heat and SD combined was the most effective for reducing L. monocytogenes on bologna. An SD level of 0.25% at 58.2 °C had the overall lowest predicted D-value (15.95 min). Combination treatments increased or decreased D-values, depending on the temperature. Pediocin (2500 and 5000 AU) and heat decreased D-values, but exhibited a protective effect at higher concentrations (≥7500 AU). The results showed that interactions between additives in formulations can vary at different temperatures/concentrations, thereby affecting thermal inactivation of foodborne pathogens in meat products. Hence, food processors should modify food formulations carefully, and verify with adequate testing so that product safety is not compromised.     

单核细胞增生李斯特菌进化家系的研究进展

单核细胞增生李斯特菌（以下简称单增李斯特菌）是危害严重的食源性致病菌之一,作为一种兼性厌氧的革兰氏阳性短杆菌,广泛存在于食品、环境及动物宿主体内。根据分子特征和流行情况的不同,可将其分成4 个进化家系,不同家系的菌株毒力和致病性各不相同。本文分析归纳了单增李斯特菌不同进化家系的特点,总结概述了其致病性和流行特征等,以期为研究与单增李斯特菌家系有关的食源性疾病提供一定参考。     

Recent developments in molecular sub-typing of Listeria monocytogenes

As a vast majority of the human listeriosis cases are caused by serotypes 1/2a, 1/2b and 4b strains, it is imperative that strains from clinical as well as from food and environment are further characterised so that accurate and timely epidemiological determination of sources of the contamination can be established to minimise the disease burden. Recent developments in the field of genomics provide a great opportunity to use these tools towards the development of molecular sub-typing techniques with a greater degree of discrimination spanning the entire length of the genome. This brief review summarises a few of these DNA-based techniques with an emphasis on DNA microarray and other whole genome sequencing-based approaches and their usefulness in Listeria monocytogenes sub-typing and outbreak investigations.