Listeria monocytogenes in ready to eat meat products from Zambia: phenotypical and genomic characterization of isolates

The contamination of ready to eat foods (RTE) products due to Listeria monocytogenes could compromise the products safety becoming a great risk for the consumers. The high presence of L. monocytogenes in RTE products has been described worldwide, but few data are available about these products from African countries. The aims of this study were to report the presence of L. monocytogenes in Zambian RTE products, providing genomic characterization and data on similarity with African circulating strains using whole genome sequencing (WGS). A total of 304 RTE products, produced by different Zambian manufacturers, were purchased at retail, from major supermarkets located in Lusaka, Zambia, comprising 130 dairy and 174 meat products. L. monocytogenes was detected only in 18 (10.3%) RTE meat products of the 174 samples tested. The MLST analysis grouped the 18 L. monocytogenes isolates in 7 clonal complexes (CCs): CC1 (n = 5), CC2 (n = 4), CC9 (n = 4), CC5 (n = 2), CC121 (n = 1), CC155 (n = 1), and CC3 (n = 1). According to the cgMLST results, several clusters were detected, in particular belonging to hyper-virulent clones CC1 and CC2. Regarding the virulence factors, a complete L. monocytogenes Pathogenicity Island 3 (LIPI-3) was present both in the CC1 and CC3, in addition to LIPI-1. Several resistance genes and mobile genetic elements were detected, including Stress Islands, the bcrABC cassette and Tn6188_qac transposon, plasmids and intact prophages. Despite being a first preliminary work with a limited number of samples and isolates, this study helped to increase existing knowledge on contaminated RTE products in Zambia, confirming the presence of hyper-virulent L. monocytogenes CCs, which could play an important role in human diseases, posing a public health concern for consumers.


Introduction
The consumption of convenience foods, such as sliced and prepackaged ready to eat (RTE) products, has increased worldwide.The RTE meat and dairy products require no post-processing heating or other additional antimicrobial treatments before consumption, hence the contamination of pathogenic microorganisms, such as Listeria monocytogenes, could compromise the safety of the products becoming a great risk for the final consumers (Calvo-Arrieta et al., 2021).
The presence of L. monocytogenes in RTE products has been worldwide described and confirmed, including European Union (European Food Safety Authority, 2022) and South Africa (SA) (Matle et al., 2019).The contamination of RTE products can occur along the entire food production chain as L. monocytogenes is widely distributed in primary production areas and in food production environments (FPE) of food producing plants (FPP), processing and packaging plants, storage facilities and retail shops (Gupta and Achyut, 2022).L. monocytogenes is ubiquitous and able to survive at low refrigeration temperatures, low pH and high salt concentrations, but also to develop biofilms, increasing the risks of food contamination (Lee et al., 2019;Osek and Wieczorek, 2022).L. monocytogenes contamination is associated with poor food processing practices and cross-contaminations in FPP, involving mainly RTE, such as vegetables, fish, dairy and meat products (Dufailu et al., 2021).
Listeria monocytogenes is a foodborne pathogen that can cause listeriosis, a potentially severe foodborne disease in human and animals (Maury et al., 2019).In healthy people, more frequently L. monocytogenes is a cause a febrile gastroenteritis, whereas in susceptible people, such as children, elderly, immunocompromised and pregnant women, it may lead to septicemia, meningitis, abortion and eventually death (Osek and Wieczorek, 2022).Even if rare, an occurrence of respiratory infection caused by L. monocytogens has been reported in Italy (Guidi et al., 2021a).
Few data are available regarding the prevalence of L. monocytogenes in RTE food products from African countries (Garedew et al., 2015;Oyinloye, 2016;Matle et al., 2019), however, one of the biggest listeriosis outbreak, with 1,060 cases, was reported in SA between 2017 and 2018, due to polony, a RTE processed meat product (Smith et al., 2019;Thomas et al., 2020).
The aims of this study were to report the presence of L. monocytogenes in Zambian RTE products, provide data on the genomic characterization of isolated strains and evaluate their similarity with strains circulating in other African countries using whole genome sequencing (WGS).

Sample collection and Listeria monocytogenes detection
Between October 2019 and February 2020, a total of 304 RTE Zambian products were collected; all the products were randomly selected and purchased at retail, from the major supermarkets located in Lusaka, Zambia.The RTE products considered in this study are usually consumed in the cities which has more wealthy people who prefer easy and fast made foods, hence the choice of selection site.The RTE product categories included 130 dairy products (milk drink n = 94, cheese n = 18, ice cream n = 16, butter n = 2) and 174 meat products (polony n = 84, ham n = 43, sausage n = 21, biltong n = 15, and salami n = 11).All products were produced in Zambia by local manufacturers, in particular: 16 different meat (M) and 23 different dairy (D) manufacturers.The sample identification, product type, RTE category, data of sampling and Zambian producer manufacturer were reported in Supplementary Table S1.
From the supermarkets, the packaged samples were placed in a cool box with ice, kept at 8°C and transported to the Central Veterinary Research Institute (CVRI) laboratory on the same day.The RTE products were processed immediately on arrival at the laboratory and tested for L. monocytogenes detection, according to ISO (International Organization for Standardization) (2017).Briefly, 25 g of each sample was cultured in 225 mL of Half Fraser enrichment broth (Oxoid, Hampshire, England) for 24 h ± 2 h at 30°C ± 1°C.After the incubation, 0.1 mL of the culture was poured into 10 mL of Fraser broth (Oxoid, Hampshire, England), incubated for 24 h ± 2 h at 37°C ± 1°C.A loopful of both culture suspensions were streaked on to two selective media plates: Agar Listeria according to Ottaviani and Agosti (ALOA) agar (Biolife, Milan, Italy) and Oxford agar (Oxoid, Hampshire, England) and both incubated at 37°C ± 1°C for 24-48 h.Suspect presumptive colonies of L. monocytogenes (small, convex bluish-green colonies with opaque white halo on ALOA plate and gray colonies with black zones and sunken center on Oxford plate) were selected in order to perform all confirmation tests reported in the ISO11290-1:2017 (i.e., hemolysis, sugar fermentation).All the L. monocytogenes isolates were stored in microbank tubes (Pro Lab Diagnostics, TX, USA) at −20°C and sent, with frozen transport, to the Italian National Reference Laboratory for L. monocytogenes (NRL-Lm) of Istituto Zooprofilattico Sperimentale dell' Abruzzo e del Molise (IZSAM) for further phenotypical and genomic characterization.

Antimicrobial susceptibility testing
All the L. monocytogenes isolates were tested for antimicrobial susceptibility (AST) by broth microdilution method with the Sensititre OptiRead Automated Fluorometric Plate Reading System (Thermo Scientific, Monza, Italy), in order to verify the susceptibility profile of L. monocytogenes strains.The minimum inhibitory concentration (MIC) was in vitro assessed using the Haemophilus spp.and Streptococcus pneumoniae Sensititre plate HPB1 (Thermo Scientific, Monza, Italy).
Listeria monocytogenes isolates, stored in microbank tubes (Pro Lab Diagnostics, TX, USA) in the NRL-Lm at −80°C, were cultured in Brain Heart Infusion (BHI) broth for 20-24 h at 37°C ± 1°C.A loop was  S2).The MIC value of cefixime was inferred based on cefuroxime susceptibility considering as reference Streptococcus pneumoniae.All the extended dilution range of tested antimicrobials are summarized in Supplementary Table S3.

Whole genome sequencing and bioinformatics analysis
Listeria monocytogenes isolates, stored in microbank tubes (Pro Lab Diagnostics, Round Rock, TX, USA) in the NRL-Lm at −80°C, were firstly streaked on ALOA agar (Liofilchem, Roseto degli Abruzzi, Teramo, Italy), incubated at 37°C ± 1°C for 24-48 h.The DNA extraction was performed on each strain according to Portmann et al. (2018), with minor modifications, firstly adding lysozyme from chicken egg solution (20 mg/mL) (Sigma-Aldrich, Milan, Italy) and, then, using the QIAamp DNA Mini Kit (Qiagen Hilden, Germany), following the manufacturer's protocol.The purity of the extracts was evaluated by Biospectrometer fluorescence (Eppendorf, Milan, Italy), measuring the absorbance (A), in particular A260/280 and A260/230 values.
Starting from 1 ng of input DNA, the Nextera XT DNA chemistry (Illumina, San Diego, CA) was used for library preparation, according to the manufacturer's protocols.WGS was performed on the NextSeq 500 platform (Illumina, San Diego, CA, US) with the NextSeq 500/550 mid output reagent cartridge v2 (300 cycles, standard 150-bp paired-end reads).
The L. monocytogenes genomes in this study were also characterized in silico using BIGSdb-Lm database tools (accessed on February 2022), querying for: "Virulence, " "Antibiotic resistance, " "Metal and disinfectant resistance" and "Stress Islands." The identification of mobile genetic elements, such as prophages and plasmids, was performed using PHASTER (accessed on February 2022)3 and PlasmidFinder 2.1 (accessed on February 2022) 4 platforms, respectively.
In addition, a genomic comparison based on AD was performed between L. monocytogenes genomes and genomic data available at the National Center for Biotechnology Information (NCBI), related to previous studies on food, environmental and clinical samples from African countries.
The genome assemblies were deposited at DDBJ/ENA/GenBank under the BioProject PRJNA965923.

Listeria monocytogenes detection
Out of the 304 RTE food tested, L. monocytogenes was detected in 18 (10.3%) of the 174 RTE meat products samples and none from dairy products.Data in detail were reported in the Table 1.

Antimicrobial susceptibility testing
The phenotypical AST results are reported in Figure 1 and Supplementary Table S4.All the 18 L. monocytogenes isolates showed a resistant phenotypic profile to cephalosporins (cefaclor, cefepime, cefixime, ceftriaxone, and cefuroxime) confirming their natural resistance to this molecule.In the case of penicillin, except one (2021.TE.16), all isolates were susceptible to ampicillin.Two strains were resistant to tetracycline (2021.TE.14 and 2021.TE.16), and finally one strain (2021.TE.11) was resistant to trimethoprim/sulfamethoxazole (miscellaneous agents).
For chloramphenicol, one isolate was susceptible; all the other strains showed a MIC value greater than the maximum value of concentration of this compound in the plate and makes results not interpretable.In the case of quinolones, for sparfloxacin, eight strains were susceptible, while all the other strains showed a MIC value greater than the maximum value of concentration of this compound in the plate making results not interpretable; whereas for levofloxacin, all the strains were susceptible.Finally, all strains were susceptible to Additionally, the identification of antimicrobial resistance genes stated that in all the L. monocytogenes isolates tested intrinsic core genes were observed, in particular: fosX, mprF, norB, sul, conferring resistance to fosfomycin, quinolones and cationic peptides and sulfonamides, respectively.
Regarding the virulence factors, all the CCs detected had a complete L. monocytogenes Pathogenicity Island 1 (LIPI-1), while a complete LIPI-3 was present both in the CC1 and CC3 isolates.All the CCs carried vip, virR, and virS genes and a full-length inlA for Internalin A and inlB for Internalin B. However, only in CC9 and CC121 isolates, a premature stop codon (PMSC) mutation was detected in the inlA.
The resistance to stresses, the Stress Survival Islet 1 (SSI-1) was carried by all the CC9, CC5, CC3 and CC155 isolates.Only the CC121 clone, indeed, highlighted the presence of SSI-2.The bcrABC cassette was present in 4 CC1 isolates, and in all the CC9 and CC5 L. monocytogenes isolates.Only the CC5 and CC155 revealed the presence of cadA gene.The Tn6188_qac transposon for Benzalkonium Chloride (BC) tolerance was observed in CC121, in one CC1 and CC2 L. monocytogenes, together with the Tn6188_tetR.The CC121 isolate carried out other transposons (Tn6188_tnpA, Tn6188_tnpB, Tn6188_tnpC).
Regarding mobile genetic elements, plasmids were identified in 9 isolates; the most frequent was plasmid Plm33 (n = 5), detected in all the CC9 and in CC3 isolates, followed by plasmid N1-011A (n = 2) in CC5 isolates.Plasmids pLM5578 and pLGUG1 were observed only in CC121 and in one CC2 isolates, respectively.Eight different intact prophages regions were found across 17 of the 18 L. monocytogenes isolates of this study.The prevalent one was the NC_028871, followed by NC_04990, NC_021539, NC_003216, NC_009813, NC_024387, NC_009815 and NC_028929, reported here as NCBI Reference Sequence.
The comparison between L. monocytogenes detected in Zambia and those selected from NCBI, available from SA, showed the presence of several relatedness's.In regards to CC1 isolates (Figure 2), 3 AD was observed between one CC1 isolate from biltong (2021.TE.14) and one isolated in 2016 from a retail (processed meat-beef) in Gauteng (SA) (SAMN18679582).Similarly, 26 AD was observed between our strain (2021.TE.3) from ham sample and one L. monocytogenes isolated from a butchery (processed meat-beef) in Limpopo (SA) in 2016 (SAMN18679598).

Discussion
To date, very few data are available on L. monocytogenes in RTE foods from Zambia and in Zambian products.Our findings highlighted the presence of L. monocytogenes mainly in ham and polony; the latter was the same type of product involved in the SA outbreak (Smith et al., 2019).Previous studies conducted in Zambia reported the prevalence of L. monocytogenes in 74% of poultry dressed carcasses (Mpundu et al., 2022a) and 26.3% in cattle carcasses (Mpundu et al., 2022b).
Data are available from African countries, reporting the presence of L. monocytogenes in different matrices, such as foods, animal and environmental samples, in Nigeria, SA, Egypt, Ethiopia, and Botswana (Dufailu et al., 2021).In particular data related to L. monocytogenes in East Africa, Ethiopia, reported a prevalence of 6.25% in RTE food of animal origin (Garedew et al., 2015), lower than our findings.In Nigeria, a prevalence of 7% was detected in raw meat samples from Rivers State (Odu and Okonko, 2017), while 91.8% in chicken flocks and meat in Oyo (Ishola et al., 2016).In Lafia (Nigeria), the 64.4% of isolates from beef and chevon were confirmed to be L. monocytogenes (Chuku et al., 2020).Additionally, in locally made soft cheeses the 12.4% of isolates were L. monocytogenes (Oyinloye, 2016).In a study, Matle et al. (2019), conducted in meat samples from SA over several years, reported L. monocytogenes in 13.5% of RTE foods collected, higher than the one obtained in our study.The presence of L. monocytogenes in the RTE meat placed on markets could be mainly due to inadequate hygiene management systems (Matle et al., 2019), which is a problem in many African countries.
It emerged in this study that several FPP considered presented more than one RTE meat category contaminated by L. monocytogenes.The subsequent placing on the market of these contaminated products and their availability for the consumers, poses a high risk especially for vulnerable people.The risk associated with RTE products depends mainly on the effectiveness of control measures applied by food business operators (FBOs), including good hygiene and good manufacturing practices, both at processing and retail (European Food Safety Authority, 2022).In smaller retail store and local manufacturers, inadequate equipment for the preparation of RTE foods may also increase the contamination risk of the final products.In addition, inadequate procedures applied to clean and sanitize FPE (i.e., cutting boards) may increase the cross-contamination of other food products and the persistence of L. monocytogenes.Moreover, the presence of L. monocytogenes is reported in animals (Heredia and García, 2018), then the contamination of processed foods could be also related to inadequate management of animals, agriculture and farming practices, not only to the post-processing phases.
In literature is well known that listeriosis cases are predominantly associated with RTE foods, including RTE meat products (European Food Safety Authority, 2022).As reported, in the USA, the main listeriosis cases were caused by meat products sliced at retail (Forauer et al., 2021).Food products sliced in retail shops presented a higher bacterial contamination than products prepared in FPP (Forauer et al., 2021), hence RTE food preparation at retail shops could increase the risk of cross-contamination of products from different FBOs (Kurpas et al., 2018).
The WGS approach provided crucial information regarding the CCs distribution and the genomic characteristics of L. monocytogenes isolated from Zambian RTE meat foods, especially related to CC1 and CC2 clones, the main CCs detected in the RTE products tested.CC1 and CC2 are both well known to be hyper-virulent clones, often associated with clinical infections (Maury et al., 2016), their presence in RTE foods is a crucial concern for consumer safety.In literature, CC1 clone was often isolated in the pork-meat production sector and it is frequently associated with dairy sector (Félix et al., 2018).The presence of hyper-virulent clones in foods has been reported worldwide, including African countries, suggesting the L. monocytogenes adaptation to food products (Matle et al., 2020;Mafuna et al., 2021).The clustering conducted in this study with other public available African L. monocytogenes genomes, showed that one CC1 isolate from biltong sample, seems to be closely related to CC1 strain previously detected in 2016 from a SA processed meat.
According to our results, both CC1 and CC2, carried a full-length internalins, inlA and inlB, which are considered one of the most influent factors for L. monocytogenes invasiveness (Su et al., 2019).Increased hyper-virulence and bacterial colonization has been reported in isolates with a full-length inlA and a complete LIPI-1 and LIPI-3 (Maury et al., 2016;Yin et al., 2019), suggesting that some isolates have increased virulence potential (Gray et al., 2021).In addition to a complete LIPI-1, CC1 isolates also harbored a complete LIPI-3, encoding the production of Listeriolysin S, a hemolytic and cytotoxic factor also observed to be released in acid stress (Tavares et al., 2020).
Previous studies reported that CC9 and CC121 were often associated with meat products, including RTE, and FPP worldwide, also in African countries (Matle et al., 2020;Mafuna et al., 2021).As known, L. monocytogenes is able to resist under stress conditions, supporting its spread in many types of foods (Kurpas et al., 2018).In particular, CC9 and CC121 are well known to be better adapted to meat processing environments (Maury et al., 2019;Centorotola et al., 2021;Guidi et al., 2021b).Specific factors are reported to be crucial for L. monocytogenes resistance to the environmental stress.In particular, the presence of SSI-1 ensures resistances to low pH, high osmolarity, bile and nisin, while SSI-2 confers resistances to alkaline and oxidative stresses (Maury et al., 2019).According to our results, SSI-1 was observed in L. monocytogenes strains belonging to different Minimum spanning tree (MST) based on the cgMLST profiles of L. monocytogenes CC1.In red were reported the strains from this study, in light yellow were reported the public available genomic data (external) African strains from NCBI.The MST was visualized using GrapeTree (https://github.com/achtman-lab/GrapeTree) and graphically elaborated by Adobe Illustrator to highlight the genomic relatedness (red square).
clones, whereas the SSI-2 genes were mainly found in CC121 isolates (Harter et al., 2017).The presence of these genes increases the survival, resistance and persistence capacity of L. monocytogenes in the FPP, increasing the risk for consumers.In addition, the presence of Tn6188_qac transposon confers tolerance to BC disinfectant, mainly used for sanitation in food processing plants.In this study, in fact, CC9 was one of the main clones observed in the RTE meat products tested, and this finding indicates a need for improvement in the FPP sanitation.However, a PMSC mutation was detected in the inlA gene, confirming CC9 and CC121 clones as hypo-virulent (Maury et al., 2019;Guidi et al., 2021b).Moreover, L. monocytogenes strains showing PMSC in inlA were reported in literature, isolated both from clinical case (Magagna et al., 2023) and animal (Sévellec et al., 2020).Our results showed the CC5 as one of the main clones in RTE meat products, as reported also in China (Wang et al., 2015).In the study of Maury et al. (2016), CC5 was not classified as a hyper-virulent clone, but further studies are needed.This clone caused several outbreak cases, such as the cantaloupe case in the USA in 2011 (Lomonaco et al., 2013) and in a previous study by Zhang et al. (2019), the CC5 was reported as the second common clone in clinical L. monocytogenes strains in Beijing (China).
Regarding the minor CCs detected in this study, CC155 strains were mostly found in farm and environmental samples, but also this clone was detected worldwide both in food samples and in clinical cases (Matle et al., 2020).L. monocytogenes CC3 was reported as prevalent in a study conducted on cooked food tested in China and also in clinical samples (Wang et al., 2018).Similarly to previous data (Chen et al., 2019), and like CC1, the CC3 isolate reported in this study harbored a complete LIPI-3 that could be responsible for the increasing of virulence (Vilchis-Rangel et al., 2019).CC3 strains were also reported in poultry RTE foods during a previous outbreak in SA (Matle et al., 2020).
The comparison between L. monocytogenes detected in Zambian RTE and those selected from NCBI, available from SA, showed the presence of several relatedness's, in particular for hyper-virulent CCs such as CC1 and CC2.This findings was crucial, highlighting how is important to continue to detect and characterize African L. monocytogenes strains in order to improve knowledge on strains circulation, surveillance and the monitoring of any possible clusters or new outbreak.About antimicrobial resistance L. monocytogenes strains of this study showed to be widely susceptible to clinically relevant classes of antibiotics (penicillin, carbapenems and quinolones) similar to previous reports (Wiśniewski et al., 2022).Our results also confirmed the intrinsic resistance to broad-spectrum cephalosporin antibiotics, commonly used in therapy of bacterial infections (Krawczyk-Balska and Markiewicz, 2016).WGS identification of antimicrobial resistance genes revealed that in all the L. monocytogenes tested, intrinsic core genes were observed, as expected, according to what is found in literature (Kurpas et al., 2020).Two strains showed to be phenotypically resistant to tetracycline, despite the absence of tet genes.This could be driven by adaptive mechanism such as the antimicrobial resistance determinants Minimum spanning tree (MST) based on the cgMLST profiles of L. monocytogenes CC2 (A), CC9 (B), and CC5 (C).In red were reported the strains from this study, in light yellow were reported the public available genomic data (external) African strains from NCBI.The MST was visualized using GrapeTree (https://github.com/achtman-lab/GrapeTree)and graphically elaborated by Adobe Illustrator to highlight the genomic relatedness (red square).exchange with other bacteria through horizontal gene transfer or plasmid mobilization (Wiśniewski et al., 2022).Just one strains showed a resistant phenotype against trimethoprim-sulfamethoxazole concordant with the presence of sul gene.However, all the strains resulted susceptible to the antimicrobials used as first choice for the therapy of human listeriosis (Baquero et al., 2020).Listeria spp.isolated from different parts of Africa are generally susceptible to ciprofloxacin, but resistant to penicillin (Dufailu et al., 2021).Previous studies reported the increase in resistance of L. monocytogenes strains to antibiotics of different classes (Godreuil et al., 2003;Swetha et al., 2021).Keet and Rip (2021) described the presence of isolates susceptible to all antibiotics tested in RTE food, at the same time some isolates were resistant to erythromycin and tetracycline and some strains from polony were multi-drug resistant.
According to literature, the presence of genetic mobile elements, such as plasmids and prophages, increases the L. monocytogenes resistance.Interestingly, several studies indicated that some plasmids might confer increasing tolerance to stresses, heavy metals, quaternary ammonium compounds, salt, oxidative, heat, and cold stress (Mafuna et al., 2021;Schmitz-Esser et al., 2021).According to previous studies, among the hyper-virulent clones, few strains carried plasmids; on the contrary, the hypo-virulent clones normally show a higher number of plasmids (Schmitz-Esser et al., 2021).With the additional presence of disinfectant resistances, such as the bcrABC cassette and the Tn6188_ qac for BC tolerance, various prophages and plasmids involved in stress response, the hyper-virulent clones could resist several stresses and probably persist in the environment for years.Data from literature highlighted the distribution of the hyper-virulent clones and their ability to contaminate, during the years and for long time, food products, food processing plants in Africa, increasing risk for human (Mafuna et al., 2021).

Conclusion
Although there has been listeriosis cases reported worldwide, L. monocytogenes data from Africa remains limited.Despite being a first preliminary work with a limitation in the sampling plan and a limited number of samples and isolates, this study reported our findings providing justification for a more complete surveys in future work, and helping to increase existing knowledge on contaminated RTE products circulating in Africa countries.Furthermore, this study highlighted interesting results about L. monocytogenes in Zambian RTE meat foods, confirming the presence of hyper-virulent CCs, which could play an important role in human diseases, posing a public health concern for consumers.Moreover, the presence of stress resistance factors could help these hyper-virulent clones to adapt, survive and persist over the years, as described by relatedness found in this study with other L. monocytogenes isolated in SA, during the years, from different matrices.
This preliminary study was conducted in order to test local Zambian foods available in local supermarkets, but also to allow generalizable findings.Further studies should be conducted on RTE products from Zambia and other African country, in order to deeply investigate the worldwide diffusion and the genomic characteristics of L. monocytogenes strains with particular attention on hyper-virulent clones aiming to improve worldwide surveillance and food safety.
In the future it will become crucial to improve the sampling plan, test more RTE foods and food environmental samples, but also to collect and characterize by WGS more L. monocytogenes isolates, especially from each positive sample, improving data and knowledge on L. monocytogenes in food products from Africa.
Due to the global increasing request, trade and consumption of foreign foods, it would be necessary to improve hygiene conditions and standardize procedures for hygiene and sanitation in food processing plants in Africa countries.Moreover, it could be useful to apply a better practices related to animal, agriculture and farming management in order to reduce L. monocytogenes in preharvest animals and consequentially in RTE meat products.According to One Health approach, it will be important compare available L. monocytogenes WGS data with clinical strains, in order to identify any clusters, including any potential connections to listeriosis cases and outbreaks.

TABLE 1
Identification of 18 samples positive for L. monocytogenes and related ready to eat category, local producer manufacturer, BioSample accession number and clonal complex results of the related L. monocytogenes isolates.