Incidence of Listeria spp. in fish and environment of fish markets in Northern Greece

The incidence of Listeria spp. in the salt-water edible fish and in the environment of fish markets in Thessaloniki, Northern Greece was studied. One hundred and twenty raw/fresh fish bought at the fish markets of Thessaloniki (Northern Greece), were sampled and tested for presence of Listeria species using a two step enrichment procedure, followed by plating on two selective agars and subsequent biochemical identification of the isolates. Five fish samples were positive for Listeria spp. and in only one sample L. monocytogenes was detected. Also, 100 samples of knives, hands, boxes etc were sampled and 18 samples were positive for Listeria spp. and five for L. monocytogenes. L. innocua was more common being detected in four fish samples and 13 environmental samples. L. seeligeri was detected only in one environmental sample. Our findings indicate that only a few fish were contaminated with Listeria spp., while the level of contamination of the environment of fish markets was higher.     

Detection of Listeria monocytogenes in food,equivalent to EN ISO 11290-1 or ISO 10560, by a three-days polymerase chain reaction-based method

A method is presented for the detection of Listeria monocytogenes in food, which produces definitive results on the third day after the sample collection. The method is equivalent to EN ISO 11290-1 or ISO 10560 in terms of the same detection limit of 10⁰ cfu per 25 or 10 g and 100% relative accuracy. The version alternative to EN ISO 11290-1 begins with a primary enrichment in half Fraser broth (24 h), secondary enrichment in Fraser broth (24 h) and post-enrichment in brain heart infusion broth (5 h). The version alternative to ISO 10560 begins with enrichment in Listeria enrichment broth (48 h) and post-enrichment in tryptone soya broth (5 h). These steps are followed by bacterial cell lysis by boiling, PCR oriented to inlB gene using a mimic internal control, and agarose gel electrophoresis. At the evaluation of the method on model food samples artificially contaminated with decimal dilutions of a L. monocytogenes culture (cheese, smoked fish, ready-to-eat meat products; 21 samples altogether), a detection limit of 10⁰ cfu per 25 or 10 g was determined. Dead L. monocytogenes cells did not cause false positivity, as determined using model food samples artificially contaminated with decimal dilutions of dead L. monocytogenes cells. At the evaluation of the method on naturally contaminated food samples (same as above, 140 samples altogether) identical results (8 positives) as with the reference method were obtained.     

Prevalence of Listeria spp. in ready to eat foods (RTE) from Algiers (Algeria)

The aim of this study was to establish the occurrence of Listeria spp., especially Listeria monocytogenes in ready to eat RTE food marketed in Algiers (Algeria).A total of 227 samples were collected from different producers and retailers.All samples were analyzed using a conventional cultivation method AFNOR V08-055.Out of 227 samples tested, 21 (9.3%) tested positive for Listeria spp. among them, 6 (2.6%) tested positive for L. monocytogenes. L. innocua was the most common Listeria species found being detected in 11 samples (4.8%), although both Listeria ivanovii and Listeria welshimeri were detected in 3 (1.3%) and 1 (0.4%) food samples respectively.The study of the antimicrobial sensitivity of Listeria monocytogenes strains showed no resistance.The study has enabled us to detect these contaminants in a wide range of RTE foods, to suggest that contamination likely occurs after heat treatment, and to assess the danger represented by this category of food for populations at risk.     

Successful management of Listeria spp. in an avocado processing facility

Listeria monocytogenes can grow and multiply in various food matrices and cause severe human illness. Apart from the influence on consumer health, L. monocytogenes contamination of ready-to-eat (RTE) food products causes major economic losses due to product recalls. Control of foodborne pathogens in RTE food products is a challenge, specifically in foods that cannot undergo a heat-treatment during processing. The aim of this study was to develop control strategies for the management of L. monocytogenes in an avocado processing facility, additional to a quality control system. An in-house monitoring system (IMS) was established to test specifically for Listeria spp. in the final products and processing environment, including floors, equipment, work areas and personnel. Guacamole and environmental samples were collected and tested on-site for Listeria with the ISO 11290-1 method. Based on the prevalence of Listeria, the facility introduced new strategies in processing to counter cross contamination. Results from the 2014 guacamole production season showed almost complete eradication of Listeria spp. in final products (0.17%, n = 1170) and the processing facility (0.79%, n = 1520). This is a major achievement since the highest incidence of Listeria spp. over a period of five years was measured at 11.39% (n = 948) in the final product during the 2013 season and 13.44% (n = 1927) in the processing facility in 2011. These results indicate that successful management of Listeria spp. in an avocado processing facility can be accomplished with in-house monitoring of the listerial population and subsequent adjustments to the processing system.     

Listeria detection in microscale solid state inoculation with minimal selective agents

The food industry needs a simple, reliable, and cost-effective primary screening protocol for routine inspection of bacterial contamination. Microscale inoculation technique is proposed as an alternative method for Listeria detection. This proposed novel technique shows a good correlation with standard spread plate technique for the enumeration of pure Listeria cultures (R² = 0.96, P < 0.0001). The commonly used selective agents in Listeria media (PALCAM, MOX, and OCLA) were assessed for their inhibitory effect on Listeria monocytogenes, Listeria innocua, and Listeria ivanovii using the microscale inoculation technique. The concentration of selective agents was lowered to inhibit competitive bacteria with minimum impact on the growth of Listeria. At the standard concentration, all three media showed less inhibition on L. monocytogenes and L. innocua than on L. ivanovii. OCLA had less inhibitory effect on the three species than did MOX and PALCAM. The comparison between ISO 11290-1 and microscale with 25% of selective agent concentration on detection of Listeria in 36 naturally contaminated food samples revealed that the microscale technique agreed well with the ISO method (Cohen KAPPA = 0.83). Reduction of selective agent concentration to 25% of the conventional formulas resulted in substantial improvement in detectability of Listeria spp. without significantly reducing specificity. The detection sensitivity of the Listeria colonies in food samples was significantly improved by microscale inoculation with 25% of the inhibitors on the three selective media at 24 and 48 h incubation (ANOVA, P = 0.039). At 48 h incubation the improvement was from 95%, 90%, and 85% (ISO method with regular strength inhibitors) to 100%, 100%, and 90% (microscale) on OCLA, MOX, and PALCAM respectively. There was no discrepancy between the microscale and the ISO method in detection of L. monocytogenes in the food samples. The optimization of Listeria detection improves sensitivity of detection as well as reducing media volume which may reduce costs and waste generated.     

Occurrence of Listeria spp. in dairy plants in Southern Italy and molecular subtyping of isolates using AFLP

We report the detection of Listeria spp. and Listeria monocytogenes in 34 dairy plants. In total, 547 of food, product contact surface and floor drain samples were collected along the product lines. Nineteen cheese factories (55.8%) were contaminated by Listeria spp. Of these 20.6% were L. monocytogenes positive. Listeria spp. was found in 6.8% of food samples, 11.3% of product contact surfaces and 40.6% of floor drains. L. monocytogenes was found in 2.4% of food samples, 4.9% of product contact surfaces and 18.8% of floor drains. Twentyfive L. monocytogenes isolates were serotyped using commercial specific antisera and genotyped using Amplified Fragment Length Polymorphism (AFLP) analysis. AFLP genotyping discriminated the four species of Listeria isolated and different genotypes for each species, moreover it could identify persistent genotypes in some dairy facilities. Listeria spp. and L. monocytogenes are widely spread in the dairy sector and probably contaminate foods during the production process. Facility-based monitoring can identify possible routes of transmission and thus allow establishment of more effective strategies to prevent food contamination.     

Presence of Listeria monocytogenes in Turkish style fermented sausage (sucuk)

Turkish style fermented sausage (sucuk) is a well-known and very popular meat product produced in Turkey. The growth of Listeria monocytogenes in fermented sausage and other meat products may cause serious health problems for consumers. The aim of this study is to assess the presence of L. monocytogenes in sucuk sold in Istanbul. During the period of February 2004–January 2005, a total of 300 sucuk samples were obtained from various markets located in Istanbul and the presence of L. monocytogenes was analyzed according to “Food and Drug Administration” (FDA) method. The results were found to be positive for Listeria spp. and L. monocytogenes as 63 (21%) and 35 (11.6%) respectively.     

Prevalence of Listeria spp. and antibiotic susceptibility of Listeria monocytogenes isolated from raw chicken and ready-to-eat chicken products in Jordan

Listeria monocytogenes is the causal agent of listeriosis, a disease that can be serious and is often fatal in susceptible individuals. The objective of the study was to determine the prevalence of Listeria spp. in raw chicken and ready-to-eat (RTE) chicken products in Amman, Jordan and the antimicrobial resistance of L. monocytogenes isolates. A total of 280 raw chicken and RTE chicken products (chicken-shawirma, chicken-burger, chicken-sausage and mortadella) were collected from Amman abattoir and local retail markets in Amman city. Listeria spp. were isolated by the conventional International Organization for Standardization (ISO) method and L. monocytogenes identified by biochemical and Polymerase Chain Reaction (PCR). Results of conventional method showed that out of total 280 samples, 141 (50%) were found to be contaminated with Listeria spp. [L. monocytogenes (18.2%), Listeria ivanovi (26.1%), Listeria grayi (3.5%), Listeria seeligeri (1.8), Listeria welshimeri (0.7%)]. The PCR confirmed all L. monocytogenes isolates (51 isolates: 15 from raw dressed broiler chicken, 23 from chicken-burger, 9 from chicken-sausage, and 4 from chicken-shawirma). Five of the tested L. monocytogenes isolates were resistance to two antibiotics (tilimicosin and tetracycline) among the ten tested antibiotics as determined by microbroth dilution method. The results presented in this study indicate the potential risk of contamination of RTE chicken products with L. monocytogenes.     

Investigation on prevalence of Listeria spp. and Listeria monocytogenes in animal-derived foods by multiplex PCR assay targeting novel genes

Chilled and frozen animal-derived food can be contaminated by Listeria spp., emerging foodborne pathogens in food industry. The objective of this study was to mine novel target genes by comparative genomics approach for multiplex PCR detection and differentiation of Listeria monocytogenes and other Listeria spp. in food. Multiplex PCR assay targeting the genetic markers LMOf2365_2721, AX25_00730, lin1814, int, lwe1673, and Oxidoreductase gene, resulted in the amplification of DNA fragments of 583 bp, 703 bp, 421 bp, 994 bp, 345 bp, and 201 bp from L. monocytogenes, Listeria ivanovii, Listeria innocua, Listeria seeligeri, Listeria welshimeri, and Listeria grayi, respectively. The detection limits of the multiplex assays were as low as 89 fg/μL genomic DNA and 910 CFU/mL of bacterial culture. The prevalence of Listeria spp. was determined using the developed multiplex PCR assay and standard microbiological method in a total of 200 food samples collected from different supermarkets and traditional agri-product markets in Nanjing, China. A total of 28 samples were found to be positive for the presence of Listeria, including 10.9% (6/55) of livestock meat samples, 22% (11/50) of poultry samples, 15% (6/40) of shellfish samples, 13.3% (4/30) of octopus samples and 4% (1/25) of freshwater fish samples. Of these, 13 isolates were classified as L. monocytogenes, 11 were classified as L. innocua, 2 were classified as L. ivanovii and 3 were classified as L. welshimeri. These results demonstrate that the multiplex PCR assay based on novel target genes is able to rapidly detect the Listeria spp. in 12 h with high accuracy and sensitivity, which may be used in the future for detection of Listeria spp. in animal-derived food products.     

Prevalence and antimicrobial resistance patterns of Listeria species isolated from poultry products marketed in Iran

In the present study, a total of 402 poultry product samples composed of raw, ready-to-cook (RTC) and ready-to-eat (RTE) products were examined for the presence of Listeria spp. The total contamination rate with Listeria spp. in poultry products was 33.3% with a higher rate of contamination in warm seasons than in cold seasons. The most species recovered was Listeria innocua (46.3%); the remaining isolates were Listeria monocytogenes (38.8%), Listeria ivanovii (9.7%) and Listeria seeligeri (5.22%). L. monocytogenes was detected in 14.1%, 12.2% and 11.4% of raw, RTC and RTE poultry products, respectively. Serotype 4b (44.9%) was the predominant serotype of L. monocytogenes isolates followed by 1/2a (40.8%), 1/2b (10.2%) and 1/2c (4.08%). Considering seasonal variability, 1/2a was the most prevalent serotype in warm seasons, while 4b was predominant in cold seasons. The Listeria spp. particularly L. monocytogenes isolates were highly resistant to ampicillin, penicillin, fluroquinolones and tetracycline. The results indicate that high prevalence of Listeria spp. especially L. monocytogenes in poultry products, and resistance of the isolates to the antimicrobials commonly used to treat human listeriosis could be a potential health hazard for consumers. In addition, prevalence of L. monocytogenes serotype 4b that involved in the majority of foodborne outbreaks of human listeriosis is a public health concern.     

Listeria spp. in the raw milk and dairy products in Antakya,Turkey

In this study, the presence of Listeria spp. was investigated in a total of 157 raw milk and dairy product samples sold in Antakya (Antioch). The prevalence of Listeria spp. in raw milk and Turkish white cheese samples was found to be 2.12% and 8.23%, respectively. Listeria monocytogenes was not isolated from raw milk and found in only two cheese samples (2.35%). No Listeria spp. were isolated in any of the butter and yoghurt samples.     

Occurrence of Listeria spp. in Brazilian fresh sausage and control of Listeria monocytogenes using bacteriophage P100

Since the 1980s, an increase in outbreaks of human listeriosis linked to contaminated food has been a concern of health authorities. Intensively manipulated foods, such as Brazilian fresh sausage, are frequently responsible for food-borne diseases. In this work the occurrence of Listeria monocytogenes and the efficacy of bacteriophage P100 (LISTEX?) to control the microorganism was evaluated in Brazilian fresh sausage. Eighty samples were analyzed, 40 each of swine and chicken Brazilian fresh sausage. Listeria spp. were isolated from 12 samples (15%), of which three (3.75%) were positive for L. monocytogenes. L. monocytogenes strains isolated belonged to serotype 1/2a. L. monocytogenes 1/2a was inoculated in Brazilian fresh sausage (2.1 × 10⁴ cfu/g) with the bacteriophage added thereafter (3.0 × 10⁷ pfu/g). Samples were analysed immediately (day zero) and then stored at 4 °C for 10 days. The bacteriophage P100 reduced L. monocytogenes counts by 2.5 log units at both 0 and 10 days compared to controls without bacteriophage. In spite of this, the populations of L. moncytogenes increased over the 10 day storage. Our data demonstrate that in one of the samples the use of the bacteriophage dropped the bacteria count below the level of direct detection. This study demonstrates a new alternative for pathogen control in the food industry, especially in the processes used to produce Brazilian fresh sausage.     

Prevalence and antimicrobial resistance of Listeria species isolated from milk and dairy products in Iran

The objective of this study was to determine the prevalence of Listeria spp. in milk and dairy products in Isfahan province, Iran. From March 2007 to September 2009, a total of 594 samples of various milk and dairy products were obtained from randomly selected retail stores. Using conventional bacteriologic method, 55 samples (9.3%) were positive for Listeria spp. The highest prevalence of Listeria was found in raw sheep milk samples (22.6%), followed by cheese samples (18.9%). The most species recovered was Listeria innocua (58.2%); the remaining isolates were Listeria monocytogenes (32.7%) and Listeria seeligari (9.1%). Overall, 54 Listeria isolates (98.2%) were resistant to one or more antimicrobial agents. Resistance to nalidixic acid was the most common finding (96.4%). All Listeria isolates were susceptible to vancomycin. The results of this study indicate the potential risk of infection with Listeria in people consuming raw and unpasteurized milk and dairy products.     

Rapid and specific detection of Listeria monocytogenes in smoked salmon with BAX®-PCR

Members of the genus Listeria are ubiquitous, and are therefore also common to the food and the environment. Among them, only Listeria monocytogenes has a pathogenic potential, and can cause infectious diseases (listeriosis) in humans. Conventional microbiological testing methods are labour-intensive and time consuming (4–5 days), and often require a number of different culture media for final isolation and confirmatory tests. In order to overcome these limitations, numerous rapid methods have been developed in recent years. DNA-based methods such as the polymerase chain reaction (PCR) have increasingly been used for rapid and sensitive detection of L. monocytogenes. Among the various available PCR assays, we used the BAX^® system (with two different detection procedures: gel detection and automated detection) to screen for L. monocytogenes in samples of vacuum packaged cold smoked salmon. A total of 27 samples were used for this study. The method was compared to the German standard microbiological detection method according to DIN 11290-1 and -2. Detection of Listeria and L. monocytogenes from salmon samples was performed using Palcam enrichment medium, followed by plating on both Palcam agar and ALOA agar. The BAX^® assay gave identical results for 26 food samples compared to the standard method, including 15 positives. Only in one case the BAX^® system gave a false-positive result, probably due to the amplification of DNA from nonviable cells of L. monocytogenes. In naturally contaminated food samples, the BAX^® method gave good results after 24–48 h. Application of this rapid method is simple and time saving.     

Occurrence and traceability of Listeria monocytogenes strains isolated from sheep's milk cheese-making plants environment

The aim of the study was to conduct an extensive survey on Listeria monocytogenes and Listeria spp. environmental contamination in 13 cheese-making plants. A total of 409 environmental and food samples were collected during years 2011–2013. Listeria spp. contamination was observed in all the facilities, while L. monocytogenes was recovered from 12 facilities with a prevalence ranging between 3.0% and 22.6%. Floor drains were the most contaminated sampling sites (48.8% of positive samples), serving as harbourage site for subsequent contamination. Out of 616 isolates, 277 (45.0%) were Listeria innocua, 274 (44.5%) L. monocytogenes, 41 (6.6%) Listeria ivanovii, 14 (2.3%) Listeria welshimeri and 10 (1.6%) Listeria gravyi. Serotyping carried out by PCR and agglutination method for L. monocytogenes revealed that 169 strains (61.7%) were serotype 1/2a, 65 (23.7%) 4b, 20 (7.3%) 1/2b, 10 (3.6%) 3a, 7 (2.5%) 1/2c and 3 (1.1%) 3b. PFGE conducted on L. monocytogenes isolates using AscI and ApaI restriction enzymes, yielded 6 clusters. Two predominant PFGE clusters were observed including respectively 36 and 32 strains. Within cheese-making plants, L. monocytogenes showed wide variability with strains distributed up to 4 different clusters. Pulsotypes isolated from raw milk filter were never detected in the processing environment, indicating that the contamination originated from sources other than raw milk. The isolation of strains with similar profile from different sampling sites, within and among cheese-making plants, indicated the possible transfer of L. monocytogenes contamination along production lines and from one facility to another. Strains recovered from food were confirmed as originating from the processing environment.     

Prevalence and antibiotic susceptibility of Listeria spp. isolated from raw meat and retail foods

Listeria and particularly Listeria monocytogenes is an important foodborne pathogen that can cause listeriosis with flu-like symptoms in healthy people, and severe complications in immunocompromised subjects, children, pregnant women and the elderly. A research survey was conducted to check the presence of Listeria spp. in raw meat and retail products and to analyse their antibiotic resistances. Total prevalence was 11.7%: in raw meat was 21.4%; in ham it was 5.2%; in fresh soft cheese it was 3.49%; in sandwiches it was 5.88%, while we found no isolates in smoked salmon and only two in ready salads (1.23%). The highest percentage of prevalence of L. monocytogenes was found in samples of ham (37.5%), lower percentages were in sandwiches (25.0%), in raw meat samples (23.6%), in fresh soft cheeses (20.0%), while ready salads and smoked salmons were not contaminated. The susceptibility of 168 strains of Listeria spp. was determined by disk diffusion method: we found 51 (30.4%) strains resistant to three or more antibiotics. All isolated strains, except one, are susceptible or at least to one of the first choice antibiotics (ampicillin and gentamycin) or to trimethoprim–sulfamethoxazole used as antibiotic of second choice in the treatment of human listeriosis. Strains isolated from ready-to-eat food show high level of resistance to ampicillin, gentamycin and meticillin. Meticillin is used normally, in treatment of Enterococcus spp. human infection; L. monocytogenes can transfer antibiotic resistance genes from plasmids and transposons to Enterococcus spp. in vitro and in vivo causing an increase of these bacteria resistant to meticillin. L. monocytogenes, in the last decades, is becoming resistant to a lot of antibiotics, a continued surveillance on its incidence on raw foods and on emerging resistances are important to identify food that can represent a risk of infection for the population, particularly for immunocompromised, children, pregnant women and the elderly to ensure effective treatment of human listeriosis with effective antibiotics.     

Prevalence of Listeria spp. at a poultry processing plant in Brazil and a phage test for rapid confirmation of suspect colonies

Sites and occurrence of Listeria contamination in an industrial poultry processing plant were investigated by sampling carcasses at varying stages of processing and testing the hands and gloves of food handlers as well as the chilling water used in the process. In the course of nine visits to a local processing plant we collected a total of 121 samples: 66 from carcasses, 37 from workers' hands and gloves and 18 from the water used for chilling. Except for the water samples Listeria was isolated at all sampling sites. The species most often isolated was Listeria innocua, which accounted for 28 of the 31 (90.3%) isolates. The frequency of Listeria in the chicken carcasses was similar at bleeding, defeathering and end of evisceration stages (33.3%), reduced during scalding (16.7%), and rose immediately after initial evisceration stage (50%) to peak after packaging (76.2%). The carcasses were contaminated by L. monocytogenes serotypes 1b and 1c only during packaging. The prevalence of Listeria spp. on workers' hands and gloves was 46% mostly with L. innocua (40.5%) followed by L. monocytogenes 1b (11.8%). Chilling water presented more than 100 ppm of chlorine, which could explain why the samples were negative to Listeria. As the contamination by Listeria in the carcasses progressively rose both in number, species and strains during processing it seems reasonable to conclude that those carcasses become contaminated at the processing level. Improvement and innovation measures to control bacteria in general at the processing plant level are necessary to effectively reduce final product contamination by L. monocytogenes. In the course of this work we introduced a bacteriophage susceptibility test to confirm suspected Listeria colonies which was able to reduce the time of analysis to a minimum of 30 h depending on the isolation technique employed.     

Listeria monocytogenes in raw salad vegetables sold at retail level in Malaysia

A range of commercially available vegetables (n = 306) that are consumed in the minimally processed state in Malaysia was examined for the presence of Listeria spp. and Listeria monocytogenes to provide information on the occurrence of such organisms in these vegetables. Analysis was carried out using the most probable number–polymerase chain reaction (MPN–PCR) method. It was found that Listeria spp. and L. monocytogenes could be detected in 33.3% and 22.5% of the vegetables respectively. L. monocytogenes was more frequently detected in Vigna unguiculata (Japanese parsley) at 31.3% and Oenanther stolonifera (yardlong bean) at 27.2%.     

Influence of Listeria innocua on the growth of Listeria monocytogenes

The growth of Listeria monocytogenes and Listeria innocua strains was monitored during this study: (i) in TSB–YE media and (ii) in a food matrix (pasteurized milk) according to the ISO 11290-1 methodology. Different inocula concentrations and mixtures were tested. The response was shown to be strain dependent. In TSB–YE the inhibition of a L. monocytogenes strain was observed in just one of the three mixtures (L. monocytogenes_1340 with L. innocua_11288) showing a reduction of 1.37 log cfu/ml after 42.5 h and 1.85 log after 66.5 h of incubation. In pasteurized milk the inhibition of L. monocytogenes by L. innocua was always observed when L. innocua was present in higher concentrations than L. monocytogenes. The reverse was also observed but only in one mixture (cocktail of six L. monocytogenes with L. innocua_2030c) when the initial concentration of L. monocytogenes was 100 times higher than L. innocua suggesting the phenomenon of quorum sensing. Furthermore, inhibitory activity was not caused by bacteriocins, and no correlation between the growth rate and inhibition was demonstrated.     

Detection of Listeria in milk using non-targeted metabolic profiling of Listeria monocytogenes: A proof-of-concept application

Listeria is represented by ten known species, comprising pathogenic and non-pathogenic variants. Listeria monocytogenes is the type species and is primarily pathogenic to humans and causes serious illness. As a result, most countries have a zero tolerance towards the presence of Listeria in foods. Therefore, in order to  ensure food safety, robust techniques for detection are required. This paper describes a proof-of-concept application of a metabolomic technique for the rapid detection of Listeria, applied to nutrient media and a complex food sample (milk) inoculated with a pathogenic Listeria strain (L. monocytogenes). It was found that a profile of intracellular and extracellular metabolites associated with L. monocytogenes could be obtained using gas chromatography coupled to orthogonal acceleration time-of-flight mass spectrometry (GC-oaToFMS). Chemometric analysis showed that it is possible to differentiate between the uninoculated samples and samples inoculated with Listeria based on L. monocytogenes metabolic activity. This research demonstrates that metabolomics has the potential for rapidly identifying food contaminated with Listeria and could provide a means for enhancing monitoring programmes and ensuring food safety.