Listeria Monocytogenes Strains Research Articles

Amoxicillin and ceftriaxone: a synergistic association against Listeria monocytogenes

Abstract Among 15 strains of Listeria monocytogenes tested, a synergy between amoxicillin and ceftriaxone was observed in 14 (93%) using MIC strips, 12 (80%) using checkerboard methods and for two of the 3 strains tested with time killing curve. This association may be an alternative treatment for listeriosis in the future.

Profile of pathogenic bacteria isolated from cow's milk in N'Djamena: associated risk factors and antibiotic resistance

Raw milk and its derivatives are foodstuffs vulnerable to contamination by microorganisms including pathogenic bacteria and failure to comply with hygiene rules. The objective of this study was to determine the profile of pathogenic bacteria isolated from cow's milk and to evaluate the effectiveness of antibiotics commonly used in veterinary and human medicine against these bacteria in Chad. This was a prospective and analytical study based on bacteriological examination including 180 milk samples collected in 10 districts of N'Djamena. The isolation, identification and testing of sensitivity of isolated bacteria to antibiotics were carried out under standard food bacteriology conditions. Among 180 milk samples which were screened by bacteriological examination, 71 (34.44%) cases were positive. The bacterial strains isolated were: Staphylococcus aureus (38.03%), Streptococcus agalactiae (18.31%), Staphylococcus hyicus (11.27%), Streptococcus uberis (7.04%), Escherichia coliO157H7 (7.04%), Streptococcus pyogenes (5.63%), Aeromonas hydrophila (5.63%), Listeria monocytogenes (4.22%) and Mycobacterium tuberculosis (2.81%). The risk factors most frequently associated with milk contamination were hand milking (100%) followed by unsanitary environment (65%), 35% of milks were sold in reused bottles and 58% of vendors and producers were uneducated. The antibiogram of the 69 isolated bacterial agents showed reduced sensitivities to beta-lactams and aminoglycosides, and varied resistance to cyclins and fluoroquinolones. Streptomycin remains an aminoglycoside most sensitive to all strains of pathogenic bacteria with an average level of 95.7%. Staphylococci (Staphylococcus aureus and Staphylococcus hyicus) developed an average resistance of 80.15% to methycillin, 80.1% to vancomycin and all bacteria showed an average resistance of 85% to metronidazole. Streptococci strains (Streptococcus agalactiae, Streptococcus uberis and Streptococcus pyogenes) were very sensitive (76.3%) to vancomycin. The isolated Listeria monocytogenes strains were 100%sensitive to aminoglycosides and beta-lactams. The two-strains of Mycobacterium tuberculosis detected by GeneXpert had a profile of 50%sensitivity and 50%resistance to rifampicin. This study not only made it possible to know the high rate and frequency of pathogenic bacteria in cow's milk as well as the associated risk factors, but also showed a reduction in sensitivity of bacteria to aminopenicillins and aminoglycosides, a strong resistance of Staphylococcus aureus to methicillin and vancomycin and a high sensitivity of streptococci to vancomycin.

The combined effect of chitosan and High Hydrostatic Pressure on Listeria monocytogenes and Escherichia coli

This study explores the combined effect of different High Hydrostatic Pressures (HHP; 200–300 MPa) with various chitosan concentrations (up to 0.2%) on five Listeria monocytogenes strains and one of Escherichia coli, at temperatures 20 & 35 °C. Cells were resuspended in ACES buffer 1 h prior to HHP. A synergistic effect of chitosan and HHP was reported for first time in the above bacterial species tested. Synergistic effect up to 1 log reduction was observed at 300 MPa and chitosan at 20 °C against L.monocytogenes LO28 with FBR13 being the most sensitive strain at 250 MPa and 0.1% chitosan. Higher combined effect was found at 35 °C compared to 20 °C at 200 MPa highlighting for first time the significant role of temperature in the above synergistic action. Pressure and temperature had a greater impact on inactivation and synergism than chitosan concentrations. Synergistic effect (1 log reduction) was also observed in E. coli K12 at 0.1% chitosan and 200 MPa. Industrial relevanceThis study presents the significance of combining HHP with natural antimicrobials to control L. monocytogenes and E. coli. Even though the technology is used for 3 decades in the food industry, its cost is still relatively high. Therefore, it is important to investigate novel ways to reduce the pressure intensity resulting in reduced costs, lower energy consumption and a broader product portfolio. This research demonstrates for first time the synergistic action of chitosan and HHP on L. monocytogenes and E. coli and the significant role of temperature that could contribute in the enhancement of the antimicrobial effect and optimization of the processing conditions. This aligns also with the growing demand for more sustainable and natural systems regarding the food production.

Evaluation of the performance of a three-strains lactic acid bacteria cocktail for the control of Listeria monocytogenes on marinated lean pork

The aim of this study was to evaluate the addition of a cocktail of three lactic acid bacteria (LAB) (Lactococcus lactis, Lacticaseibacillus paracasei and Lactiplantibacillus plantarum) as a protective culture into marinated pork. The pork was artificially inoculated with two Listeria monocytogenes strains and stored for 12 days. Two packagings were used: vacuum or modified atmosphere packaging (MAP). LAB, L. monocytogenes, psychrotrophic bacteria, pH, aw, color, the metataxonomic profile and the sensorial quality of the product were evaluated. The growth of L. monocytogenes under vacuum and MAP was reduced with the use of the LAB up to 0.8 and 0.7 log10 CFU/g, respectively. LAB counts gradually increased, which was accompanied by a slight decrease in pH. In LAB samples, psychrotrophic bacteria showed a reduction at day 12 as compared to non-inoculated samples. Some minor differences were also observed among samples for color and sensory parameters. Regardless of the type of packaging, the microbiota of the marinated pork was dominated initially by Photobacterium and subsequently during storage by a diversity of LAB. The application of LAB could help to obtain a safe product, although further evaluation would be required to optimize the application of the LAB cocktail in real-scale commercial scenarios.

Antimicrobial and antioxidant competence of sustainable grumixama leaves extracts in nanoemulsion system

The spontaneous emulsification method was used to produce nanoemulsions loaded with grumixama leaves extracts (GLE) to protect and improve its functionality as a natural additive in food. Nanoemulsions were characterized for physicochemical stability, morphology, thermal analyses, antioxidant capacity, and antimicrobial activity. The formulations showed encapsulation efficiency (EE%) >89%, sizes between 182 and 290nm, low polydispersity, and zeta potential near -30mV. The formulations were kinetically stable since these parameters remained constant for up to 180 days at 4°C. The nanoemulsion with 125mg GLE exhibited better droplet structure, which favored greater phenolic compounds protection and thermal resistance. The antioxidant capacity of all formulations remained stable over 30 days. The nanoemulsions acted as a bactericidal agent (MBC/MIC ratio ≤ 4) against Staphylococcus aureus, Bacillus cereus, and Listeria monocytogenes strains. However, GLE-loaded nanoemulsions offer a sustainable and functional alternative for use as a natural additive to meet trends such as a clean label.

Phenotypic microarray characterization of hemolytic and non-hemolytic strains of Listeria monocytogenes

Limited information is available on the phenotypic characteristics of Listeriamonocytogenes that may affect its virulence of L.monocytogenes. The study focused on comparing the differences between two strains of L. monocytogenes, one hemolytic (LLO+) and one non-hemolytic (tLLO). Using Phenotype Microarray (PM) technology, carbon, nitrogen, and phosphorus-sulfur source utilization by the strains was performed and the KEGG pathway involvement in substrate utilization was analyzed. Of the 285 substrates screened, the results suggested that d-gluconic acid and l-serine may play a role in L. monocytogenes hemolytic activity towards LLO production by generating pyruvate as an intermediate and amino acid biosynthesis, which may play an important role in virulence protein translation. d-gluconic acid and l-serine showed no effect on the tLLO strain in PM analysis and validation tests. Notably, the scope of this study was limited to these two strains of L. monocytogenes. While these findings provide valuable insights into the metabolic differences between hemolytic and non-hemolytic strains, further research is necessary to expand this understanding to a broader range of strains and explore additional factors that may influence LLO functionality.

Differential mechanism between Listeria monocytogenes strains with different virulence contaminating ready-to-eat sausages during the simulated gastrointestinal tract

Listeria monocytogenes exhibits varying levels of pathogenicity when entering the host through contaminated food. However, little is known regarding the stress response and environmental tolerance mechanism of different virulence strains to host gastrointestinal (GI) stimuli. This study analyzed the differences in the survival and genes of stress responses among two strains of L. monocytogenes 10403S (serotype 1/2a, highly virulent strain) and M7 (serotype 4a, low-virulence strain) during simulated gastrointestinal digestion. The results indicated that L. monocytogenes 10403S showed greater acid and bile salt tolerance than L. monocytogenes M7, with higher survival rates and less cell deformation and cell membrane permeability during the in vitro digestion. KEGG analysis of the transcriptomes indicated that L. monocytogenes 10403S displayed significant activity in amino acid metabolism, such as glutamate and arginine, associated with acid tolerance. Additionally, L. monocytogenes 10403S demonstrated a higher efficacy in promoting activities that preserve bacterial cell membrane integrity and facilitate flagellar protein synthesis. These findings will contribute valuable practical insights into the tolerance distinctions among different virulence strains of L. monocytogenes in the GI environment.

Genomic Approach of Listeria monocytogenes Strains Isolated from Deli-Meats in Mexico.

Listeria monocytogenes is a foodborne pathogen that causes listeriosis worldwide. In México, L. monocytogenes has been identified as a hazard of deli-meats. However, the genomic analysis that supports the transmission of L. monocytogenes strains via deli-meats and its role as a source for virulence and resistance genes is lacking. Here, we present four high-quality genome drafts of L. monocytogenes strains isolated from deli-meats in Mexico. In silico typing was used to determine the serotype, lineage, clonal complexes (CC), and multilocus sequence (ST). Also, comparative genomics were performed to explore the diversity, virulence, mobile elements, antimicrobial resistant and stress survival traits. The genome sequence size of these strains measured 3.05 ± 0.07Mb with a mean value of 37.9%G+C. All strains belonged to linage I, which was divided into two groups: 4b, CC2, ST1 (n = 3) and 1/2b, CC5, ST5 (n = 1). The pangenome and core genome contained 3493 and 2625 genes, respectively. The strains harbor the L. monocytogenes pathogenicity island-1 (LIPI-1) and the same multidrug resistance pattern (fosX, norB, mprF, lin) via in silico analysis. Comparative analysis delineated the genomes as essentially syntenic, whose genomic differences were due to phage insertion. These results expand what is known about the biology of the L. monocytogenes strains isolated from deli-meats in Mexico and warns of the risk that these strains belong to epidemic linage and harbor virulence genes linked to human disease.

A Mini-Review of Anti-Listerial Compounds from Marine Actinobacteria (1990-2023).

Among the foodborne illnesses, listeriosis has the third highest case mortality rate (20-30% or higher). Emerging drug-resistant strains of Listeria monocytogenes, a causative bacterium of listeriosis, exacerbate the seriousness of this public health concern. Novel anti-Listerial compounds are therefore needed to combat this challenge. In recent years, marine actinobacteria have come to be regarded as a promising source of novel antimicrobials. Hence, our aim was to provide a narrative of the available literature and discuss trends regarding bioprospecting marine actinobacteria for new anti-Listerial compounds. Four databases were searched for the review: Academic Search Ultimate, Google Scholar, ScienceDirect, and South African Thesis and Dissertations. The search was restricted to peer-reviewed full-text manuscripts that discussed marine actinobacteria as a source of antimicrobials and were written in English from 1990 to December 2023. In total, for the past three decades (1990-December 2023), only 23 compounds from marine actinobacteria have been tested for their anti-Listerial potential. Out of the 23 reported compounds, only 2-allyoxyphenol, adipostatins E-G, 4-bromophenol, and ansamycins (seco-geldanamycin B, 4.5-dihydro-17-O-demethylgeldanamycin, and seco-geldanamycin) have been found to possess anti-Listerial activity. Thus, our literature survey reveals the scarcity of published assays testing the anti-Listerial capacity of bioactive compounds sourced from marine actinobacteria during this period.

Growth, biofilm formation, and motility of Listeria monocytogenes strains isolated from food and clinical samples located in Shanghai (China)

Listeria monocytogenes is a common foodborne pathogen that frequently causes global outbreaks. In this study, the growth characteristics, biofilm formation ability, motility ability and whole genome of 26 L. monocytogenes strains isolated from food and clinical samples in Shanghai (China) from 2020 to 2022 were analyzed. There are significant differences among isolates in terms of growth, biofilm formation, motility, and gene expression. Compared with other sequence type (ST) types, ST1930 type exhibited a significantly higher maximum growth rate, the ST8 type demonstrated a stronger biofilm formation ability, and the ST121 type displayed greater motility ability. Furthermore, ST121 exhibited significantly high mRNA expression levels compared with other ST types in virulence genes mpl, fbpA and fbpB, the quorum sensing gene luxS, starvation response regulation gene relA, and biofilm adhesion related gene bapL. Whole-genome sequencing (WGS) analyses indicated the isolates of lineage I were mostly derived from clinical, and the isolates of lineage II were mostly derived from food. The motility ability, along with the expression of genes associated with motility (motA and motB), exhibited a significantly higher level in lineage II compared with lineage I. The isolates from food exhibited significantly higher motility ability compared with isolates from clinical. By integrating growth, biofilm formation, motility phenotype with molecular and genotyping information, it is possible to enhance comprehension of the association between genes associated with these characteristics in L. monocytogenes.

Deletion of Nox from Listeria monocytogenes Strain EGDe Enhances Bacterial Virulence and Reduces the Production of Reactive Oxygen Species and Inflammatory Factors In Vivo.

The foodborne pathogens have a serious threat to human health, especially Listeria monocytogenes. NADPH oxidase (NOX) is involved in cellular respiration and the production of reactive oxygen species (ROS), acting as messengers to host cells during the infection. However, the role of nox in the process of L. monocytogenes infection is unclear. In this study, we examined the impact of nox in L. monocytogenes by gene deletion. The results of cell experiment showed that knocking out nox from L. monocytogenes strain EGDe resulted in a twofold increase invasion ability to Caco-2 cells compared with that of wild-type strain (WT), but did not affect adhesion ability. Animal infection assays also showed that bacterial loads in the liver and spleen of mice challenged with EGDe-Δnox were approximately two times higher compared with those challenged with the WT strain. On the one hand, quantitative real-time polymerase chain reaction revealed that deletion of nox leads to upregulation of genes related to the internalization of L. monocytogenes (inlA, inlB, and inlC). More importantly, the expression of listeriolysin-positive regulatory (prfA) gene increased by three times in vivo compared with that of WT. On the other hand, the deletion of nox resulted in a reduction of the upregulation of proinflammatory factors in EGDe-Δnox compared with the WT and complementary strains. Thus, our study revealed that nox affected the virulence of L. monocytogenes by upregulating the expression of virulence genes and regulating the production of ROS and inflammatory factors in vivo.

Detection of Pathogenic Serogroups and Virulence Genes in Listeria monocytogenes Strains Isolated from Beef and Beef Products Retailed in Gauteng Province, South Africa, Using Phenotypic and Polymerase Chain Reaction (PCR)-Based Methods.

South Africa recently (2017-18) experienced the largest outbreak of human listeriosis in the world caused by L. monocytogenes following the consumption of "polony," a ready-to-eat meat product. Most (59%) cases originated from Gauteng province, South Africa. As a follow-up study to the outbreak, we used standard bacteriological and molecular methods to determine the prevalence of pathogenic and virulent serogroups of L. monocytogenes in various beef and beef products retailed in Gauteng province, South Africa. The overall prevalence of Listeria spp. was 28% (112/400), comprising Listeria monocytogenes (9.3%), Listeria innocua (16.3%), and Listeria welshimeri (2.5%) (p < 0.001). It is crucial to have detected that the region (p=0.036), type of product (p=0.032), and temperature at storage (p=0.011) significantly affected the occurrence of L. monocytogenes in beef products. It is alarming that pathogenic serogroups 4b-4d-4e (51.4%) and 1/2a-3a (43.2%) were detected among the isolates of L. monocytogenes. Importantly, they were all carriers of seven virulence-associated genes (hlyA, inlB, plcA, iap, inlA, inlC, and inlJ). Our study also demonstrated that 16.7% of "polony" samples investigated were contaminated with L. monocytogenes. Considering that pathogenic and virulent L. monocytogenes contaminated beef and beef products retailed in South Africa, the food safety risk posed to consumers remains and cannot be ignored. Therefore, it is imperative to reduce the contamination of these products with L. monocytogenes during beef production, processing, and retailing to avoid future outbreaks of human listeriosis in the country.

An update on the taxonomy and functional properties of the probiotic Enterococcus faecium SF68.

Enterococcus faecium SF68 (SF68) is a well-known probiotic with a long history of safe use. Recent changes in the taxonomy of enterococci have shown that a novel species, Enterococcus lactis, is closely related with E. faecium and occurs together with other enterococci in a phylogenetically well-defined E. faecium species group. The close phylogenetic relationship between the species E. faecium and E. lactis prompted a closer investigation into the taxonomic status of E. faecium SF68. Using phylogenomics and ANI, the taxonomic analysis in this study showed that probiotic E. faecium SF68, when compared to other E. faecium and E. lactis type and reference strains, could be re-classified as belonging to the species E. lactis. Further investigations into the functional properties of SF68 showed that it is potentially capable of bacteriocin production, as a bacteriocin gene cluster encoding the leaderless bacteriocin EntK1 together with putative Lactococcus lactis bacteriocins LsbA, and LsbB-like putative immunity peptide (LmrB) were found located in an operon on plasmid pF9. However, bacteriocin expression was not studied. Competitive exclusion experiments in co-culture over 7 days at 37°C showed that the probiotic SF68 could inhibit the growth of specific E. faecium and Listeria monocytogenes strains, while showing little or no inhibitory activity towards an entero-invasive Escherichia coli and a Salmonella Typhimurium strain, respectively. In cell culture experiments with colon carcinoma HT29 cells, the probiotic SF68 was also able to strain-specifically inhibit adhesion and/or invasion of enterococcal and L. monocytogenes strains, while such adhesion and invasion inhibition effects were less pronounced for E. coli and Salmonella strains. This study therefore provides novel data on the taxonomy and functional properties of SF68, which can be reclassified as Enterococcus lactis SF68, thereby enhancing the understanding of its probiotic nature.

Cross-Phosphorylation between AgrC Histidine Kinase and the Noncognate Response Regulator Lmo1172 in Listeria monocytogenes under Benzalkonium Chloride Stress.

Benzalkonium chloride (BC) is widely used for disinfection in the food industry. However, Listeria monocytogenes strains with resistance to BC have been reported recently. In L. monocytogenes, the Agr communication system consists of a membrane-bound peptidase AgrB, a precursor peptide AgrD, a histidine kinase (HK) AgrC, and a response regulator (RR) AgrA. Our previous study showed that the agr genes are significantly upregulated by BC adaptation. This study aimed to investigate the role of the Agr system in BC resistance in L. monocytogenes. Our results showed that the Agr system was involved in BC resistance. However, a direct interaction between BC and AgrC was not observed, nor between BC and AgrA. These results indicated that BC could induce the Agr system via an indirect action. Both AgrBD and AgrC were required for growth under BC stress. Nevertheless, when exposed to BC, the gene deletion mutant ∆agrA strain exhibited better growth performance than its parental strain. The RR Lmo1172 played a role in BC resistance in the ∆agrA strain, suggesting that Lmo1172 may be an alternative to AgrA in the phosphotransfer pathway. Phosphorylation of Lmo1172 by AgrC was observed in vitro. The cognate HK Lmo1173 of Lmo1172 was not involved in BC stress, regardless of whether it was as the wild-type or the ∆agrA mutant strain. Our evidence suggests that the HK AgrC cross-phosphorylates its noncognate RR Lmo1172 to cope with BC stress when the cognate RR AgrA is absent. In vivo, further studies will be required to detect phosphotransfer of AgrC/AgrA and AgrC/Lmo1172.

Evaluating of Antioxidant and Antibacterial Characteristics Ginkgo Biloba Leaves

Introduction: Reactive oxygen species cause disease by damaging the chemical compounds in our body. On the other hand, drug resistance is becoming a serious issue in infection treatment, globally. Ginkgo biloba has many therapeutically features. The objective of this study was to evaluate antioxidant and antibacterial activity of Iranian Ginkgo’s leaf extracts.&#x0D; Methods: In this experimental study, aqueous, ethanolic (%70) and methanolic (%80) extracts were made using Ginkgo. Total Phenolic and Flavonoids Content were measured by folin– ciocalteu reagent and Chloride Aluminum color assays. The extracts’ antioxidant activity was assessed by their potential in scavenging DPPH free radicals. Disc Diffusion assay was carried out to test antibacterial potency against two strains of bacteria (Enterococcus faecalis, Listeria monocytogenes). Data analysis was performed using factorial experiment within a completely randomized design. SPSS version 16 software and Duncan's multiple range tests were used to compare the means.&#x0D; Results: Based on results, all three extracts contained extensive amount of phenolic and especially flavonoid compounds with methanolic extract being the richest in phenolic and flavonoids while aqueous extract having the least of these compounds. The most antioxidant activity was found in methanolic extract of 300 mg/mL concentration with %84.73 (P&lt;0.05) and the least was in aqueous extract of 40 mg/mL with %18.17 (P&lt;0.05) ROS scavenging rate, this result was proportional to the measured bioactive components of the extracts. Antibacterial activity in 200 mg/mL concentration of methanolic extract was maximum against Enterococcus faecalis while it was minimum at 50 mg/µl concentration of aqueous extract against Listeria monocytogenes strain. Antibacterial activity of all three extracts was found out to be concentration dependent.&#x0D; Conclusion: The results indicated that Ginkgo leaves are rich in phenolic and flavonoids contents that may be reason behind their notable antioxidant and antibacterial activity. Thus, Ginkgo could be a treasure trove of antioxidants and therapeutic compounds. However, more studies are required in regard to Ginkgo’s various characteristics.

A stochastic approach for modelling the in-vitro effect of osmotic stress on growth dynamics and persistent cell formation in Listeria monocytogenes

Persistent bacteria (or persisters) can be defined as a microbial subpopulation that, exposed to bactericidal treatment, is killed more slowly than the rest of the population they are part of. They stochastically originate in response to environmental stressors or spontaneously without external signals. When transferred into a fresh medium, persisters can resume active replication although they spend more time adapting to the new conditions remaining in the lag phase longer. They were studied for decades for their ability to survive antibiotic treatments while studies on their formation in food and potential impact on their safety are lacking. The most common food preservation techniques may act as stressors that trigger the formation of persistent bacteria able to survive bactericidal treatments and grow later in foods during storage. This study aimed to investigate a possible relationship between exposure to different salt concentrations (osmotic stress) and the amount of persisters triggered in a strain of Listeria monocytogenes. Furthermore, we described this phenomenon from a mathematical perspective through predictive microbiology models commonly used in the food field. The lag time distribution of a L. monocytogenes ATCC 7644 strain grown in broth with additional 2 %, 4 % and 6 % NaCl was evaluated using the software ScanLag. It uses office scanners to automatically record the colony growth on agar plates and evaluate the frequency distribution of their appearance times (lag phase) by automated image analysis. The same broth cultures were diluted to equalize salt concentration and transferred into a fresh broth to evaluate how the previous salt exposure impacted their growth kinetics. The observed growth curves were reproduced using predictive models in which the mean duration of the lag phase of the whole population took into account the occurrence of persisters with a longer lag phase. The models were solved first using a deterministic approach and then a stochastic one introducing a stochastic term that mimics the variability of lag phase duration due to the persisters occurrence. Results showed that the growth of L. monocytogenes in broth with additional NaCl might trigger the formation of persistent cells whose number increased consistently with salt concentrations. The proposed predictive approach reproduced the observed real curves in strong agreement, especially through the stochastic resolution of the models. Persistence is currently a neglected bacterial defence strategy in the food sector but the persisters' formation during production cannot be excluded; therefore, further insights on the topic are certainly desirable.

Characterization of Listeria monocytogenes Strains Isolated in Palermo (Sicily and Italy) during the Years 2018-2020 from Severe Cases of Listeriosis.

Listeria monocytogenes (LM), the etiological agent of listeriosis, can cause foodborne zoonosis. In this study, we characterized 23 strains that caused human severe listeriosis in Palermo (Sicily, Italy) during the period of 2018-2020. In addition, we assessed the phenotypic susceptibility of clinical isolates to antibiotics in accordance with EUCAST guidelines. The serogroup was determined through the use of PCR, while MLST and MVLST were identified through the sequencing of housekeeping genes. Finally, susceptibility to antibiotics was assessed by means of the Phoenix automatic system. Patients hospitalized with listeriosis were predominantly males (56% vs. 44% of females). The cases not associated with pregnancy included patients >65 years of age (60%), two of whom were affected by cancer, while cases associated with pregnancy included two pregnant women and three preterm infants. The data collected showed that the main pathologies shown by patients were meningitis (60.9%) and bacteremia (39.1%). The LM strains were isolated from the blood (52%), cerebrospinal fluid (26%), cerebrospinal fluid + blood (13%), blood + a nasal swab (4%), and ascitic fluid (4%). The predominant serogroup was IVb (96%), whereas only one strain belonged to serogroup IIa (4%). Among the strains with serotypes 4b, 4d, and 4e, ST2/VT21 (92%) and ST6/VT19 (4%) were determined, while only isolates with serotypes 1/2a and3a show ST155/VT45 (CC155). This study reveals the widespread circulation of a clinical strain (ST2/VT21) associated with suspected food contamination, demonstrating the importance of carrying out molecular epidemiological surveillance. Our clinical isolates were susceptible to the beta-lactams assayed, in agreement with the literature data.

Tacrolimus Pharmacotherapy: Infectious Complications and Toxicity in Organ Transplant Recipients; An Updated Review.

After allogeneic organ transplantation, in order to reduce the risk of rejection, tacrolimus is given. In fact, infection is reported as one of the most common side effects of tacrolimus that might be associated with graft failure. This study aims to review the association between the occurrence of infections due to toxicity following the administration of tacrolimus in organ transplant recipients. Scientific literature on the pharmacotherapy of tacrolimus after organ transplantation, infections, and neurotoxicity were searched using PUBMED.Gov (https://pubmed.ncbi.nlm.nih.gov/), Web of Science, and Scopus (n=108). All articles were screened, and the data associated with the topic of interest was extracted. The primary outcome was infection and neurotoxicity. Total area under the curve exposure, the ratio of parent drug/metabolites of tacrolimus was reported to be correlated with aggressive events such as infection episodes. A trough/dose ratio may demonstrate the net state of immunosuppression and drug-related events. The most frequent infectious complication of tacrolimus after organ transplantation was reported as urinary tract infections (UTIs). Virulent strains of recombinant Listeria monocytogenes, in addition to an increase in bacterial burden in the liver and spleen tissues, were reported in experimental animal studies. Patient survival was significantly lower in recipients with UTIs in the first post-transplant month. A higher degree of immunosuppression was associated with recurrent UTIs and drug-resistant organisms. By inhibiting the cerebral immune system, tacrolimus could cause neurodegeneration. Transplant type, gut dysmotility, acute or chronic condition before transplant surgery, use of azole, antifungal, hematocrit, tacrolimus methods of detection, the total area under the curve, and duration of hospital stay could define the risk of infection through the first month of transplant surgery. In addition, neurological and infectious complications could be associated with the higher amounts of tacrolimus trough levels (C0). Polypharmacy based on tacrolimus, antiviral, and antifungal drugs, in addition to neurotoxicity, could increase the risk of opportunistic infections such as cytomegalovirus within the first year of organ transplantation.

Molecular characterization of Listeria monocytogenes strains isolated from imported food in China from 14 countries/regions, 2003-2018.

Listeria monocytogenes (Lm) is associated with severe foodborne infections and ubiquitous in the nature. Identification of characteristics of Lm transmission through trading of food products is essential for rapidly tracking Lm sources and controlling dissemination of listeriosis. In this study, a total of 44 Lm strains were isolated from food products originating from 14 countries/regions during 2003-2018 at the Shanghai port. The genomes of these Lm strains were sequenced by high-throughput sequencing. Multilocus sequence typing (MLST) analysis showed that 43 isolates were divided into 17 sequence types (STs). The distribution of STs was decentralized, with the dominant ST2 accounting for only 18.18% of the strains. The LM63 strain did not match with any of the existing STs. Core-genome MLST (cgMLST) analysis based on 1748 core genes categorized the 44 strains into 30 cgMLST types (CTs), with CT10153 and CT7892 as the most predominant CTs. Notably, LM63 and LM67 shared the same CT in the cgMLST analysis. The phylogenetic analysis based on single-copy homologous genes revealed that the 44 Lm strains were primarily classified into two lineages. The SNP analysis also indicated that these strains were roughly divided into two clades, with strains in the first clade mainly collected earlier than those in the second clade, which were predominantly collected from 2010 onwards. The analysis using the virulence factor database (VFDB) indicated that the virulence gene inlJ was the most prevalent among these 44 strains. Notably, ddrA, msbA, and sugC were enriched in this dataset, requiring further clarification of their roles in Listeria through future studies. These results might provide a clue for understanding of the global epidemiology and surveillance of Lm and present insights for implementing effective measures to reduce or prevent Listeria contamination outbreaks in imported food products.

The influence of nutrients on biofilm formation of an ST87 strain of Listeria monocytogenes

Biofilm development by pathogenic organisms plays a pivotal role in certain foodborne illnesses. Listeria monocytogenes, specifically the sequence type 87 (ST87), has been widely identified in China. This study aimed to monitor the dynamic process of biofilm formation by a food-isolated L. monocytogenes ST87 strain under diverse nutritional conditions. Results showed that this strain can consistently exhibit high viable cell counts in both nutrient-rich and nutrient-limited conditions. By utilizing cell counting, we discovered the ability of L. monocytogenes ST87 to form biofilms in various nutritional environments, including beef juice and vegetable juice, maintaining levels above 2 Log10 CFU/cm2. Notably, biofilm formation was expedited under nutrient-limited conditions, with cell counts under nutrient-limited vegetable juice presenting significantly higher than that under the nutrient-rich one. The analysis of the composition of extracellular polymeric substances (EPS) showed a consistent pattern between viable cell count and extracellular protein variation within the biofilms. Moreover, an evaluation of nutritional components (protein, fat, total sugar, ash, and pH) in the culture medium unveiled a positive correlation between extracellular substances and pH, but a negative correlation was identified with other nutritional components.