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The Genetic Determinants of Listeria monocytogenes Resistance to Bacteriocins Produced by Lactic Acid Bacteria
Background: Listeria monocytogenes is a Gram-positive bacterium responsible for listeriosis, a serious foodborne disease that can lead to serious health complications. Pregnant women, newborns, the elderly, and patients with weakened immune systems are particularly susceptible to infection. Due to the ability of L. monocytogenes to survive in extreme environmental conditions, such as low temperatures, high salinity, and acidity, this bacterium poses a serious threat to food production plants and is particularly difficult to eliminate from these plants. One of the promising solutions to reduce the presence of this bacterium in food products is bacteriocins as natural control agents. These are substances with antibacterial activity produced by other bacteria, mainly lactic acid bacteria (LAB), which can effectively inhibit the development of pathogens such as L. monocytogenes. The use of bacteriocins in the food industry is beneficial due to their natural origin, specificity of action, and consumer safety. However, the problem of resistance to these substances exists. Results: This review focuses on the mechanisms of bacteriocin resistance, such as modifications of bacteriocin docking receptors, changes in the structure of the cell wall and membrane, and the occurrence of cross-resistance to different bacteriocins. Genetic factors determining these mechanisms and strategies to cope with the problem of resistance are also presented. Conclusions: Research on this issue is crucial for developing effective preventive methods that will enable the safe and long-term use of bacteriocins in food production.
Characteristics of Intestinal Barrier State and Immunoglobulin-Bound Fraction of Stool Microbiota in Advanced Melanoma Patients Undergoing Anti-PD-1 Therapy
The gut microbiota is recognized as one of the extrinsic factors that modulate the clinical outcomes of immune checkpoint inhibitors (ICIs), such as inhibitors targeting programmed cell death protein 1 (PD-1), in cancer patients. However, the link between intestinal barrier, which mutually interacts with the gut microbiota, and therapeutic effects has not been extensively studied so far. Therefore, the primary goal of this study was to investigate the relationship between intestinal barrier functionality and clinical outcomes of anti-PD-1 therapy in patients with advanced melanoma. Fecal samples were collected from 64 patients before and during anti-PD-1 therapy. The levels of zonulin, calprotectin, and secretory immunoglobulin A (SIgA), which reflect intestinal permeability, inflammation, and immunity, respectively, were measured in fecal samples (n = 115) using an Enzyme-Linked Immunosorbent Assay (ELISA). Moreover, the composition of the immunoglobulin (Ig)-bound (n = 108) and total stool microbiota (n = 117) was determined by the V3–V4 region of 16S rRNA gene sequencing. ELISA indicated a higher baseline concentration of fecal SIgA in patients with favorable clinical outcomes than those with unfavorable ones. Moreover, high baseline concentrations of intestinal barrier state biomarkers correlated with survival outcomes. In the cases of fecal zonulin and fecal SIgA, there was a positive correlation, while in the case of fecal calprotectin, there was a negative correlation. Furthermore, there were differences in the microbial profiles of the Ig-bound stool microbiota between patients with favorable and unfavorable clinical outcomes and their changes during treatment. Collectively, these findings indicate an association between intestinal barrier functionality and clinical outcomes of anti-PD-1 therapy in advanced melanoma patients.
Charakterystyka frakcji mikrobioty jelitowej związanej z wydzielniczymi immunoglobulinami A (SlgA) u pacjentów z zaawansowanym czerniakiem poddanych immunoterapii anty-PD-1
Circulating Microbial Cell-Free DNA in Health and Disease
Human blood contains low biomass of circulating microbial cell-free DNA (cfmDNA) that predominantly originates from bacteria. Numerous studies have detected circulating cfmDNA in patients with infectious and non-infectious diseases, and in healthy individuals. Remarkable differences were found in the microbial composition of healthy subjects and patients compared to cohorts with various diseases or even patients with diversified prognoses, implying that these alterations may be associated with disease development. Although the function of circulating cfmDNA needs to be elucidated (whether it acts as a bystander of dysbiosis or a key player in disease development), several studies have demonstrated its potential as a non-invasive biomarker that may improve diagnosis and treatment efficacy. The origin of circulating cfmDNA is still the subject of much deliberation, but studies have identified members of various microbiome niches, including the gut, oral cavity, airways, and skin. Further studies investigating the origin and function of circulating cfmDNA are needed. Moreover, low-biomass microbiome studies are prone to contamination, therefore stringent negative experimental control reactions and decontamination frameworks are advised in order to detect genuine circulating cfmDNA.
Influence of supplementation with iron and probiotic bacteria Lactobacillus plantarum and Lactobacillus curvatus on selected parameters of inflammatory state in rats on a high-fat iron-deficient diet
AbstractBACKGROUNDA high‐fat (HF) diet, diet iron deficiency and iron supplementation may affect inflammatory parameters. Probiotics influence both iron metabolism and inflammation. We compared the inflammatory state in rats on a HF iron‐deficient diet receiving oral iron, Lactobacillus plantarum and Lactobacillus curvatus in different combinations.METHODSThis was a two‐stage experiment. In groups C (n = 8) and HF (n = 8), rats ate a control or HF diet, respectively, for 16 weeks. In the group HFDEF (n = 48), rats ate a HF iron‐deficient diet for 8 weeks (first stage) and were subsequently divided into 6 groups (n = 8 each) receiving the following for a further 8 weeks (second stage): HFDEF – a HF iron‐deficient diet; HFDEFFe – a HF iron‐deficient diet with iron; HFDEFLp and HFDEFLc – a HF iron‐deficient diet with L. plantarum or L. curvatus, respectively; and HFDEFFeLp and HFDEFFeLc – a HF iron‐deficient diet with iron and L. plantarum or L. curvatus, respectively. Body composition analysis and blood sampling was performed. Markers of iron status and levels of total antioxidant status (TAS), C‐reactive protein (CRP), tumour necrosis factor alpha (TNF‐α) and interleukin 6 (IL‐6) were measured in the blood.RESULTSTAS was higher in the HFDEF group (756.57 ± 489.53 ng mL−1) versus the HFDEFLc group (187.04 ± 47.84 ng mL−1; P = 0.022). No more differences were found between groups, or in TAS, CRP, TNF‐α and IL‐6 concentrations. Also, no differences were found between groups for alanine and aspartate aminotransferases, glucose, total cholesterol, low‐ and high‐density lipoproteins and triglycerides. TAS level was positively correlated with ferritin concentration, IL‐6 with TAS and TNF‐α with hepcidin level.CONCLUSIONSSupplementation with L. plantarum, L. curvatus and iron in combinations exerts no influence on inflammatory status, lipid profile, hepatic function and serum fasting glucose in rats on a HF iron‐deficient diet. © 2024 Society of Chemical Industry.
High Prevalence of Virulence-Associated Genes and Length Polymorphism in actA and inlB Genes Identified in Listeria monocytogenes Isolates from Meat Products and Meat-Processing Environments in Poland
Listeria monocytogenes is a human pathogen that has the ability to cause listeriosis, a disease with possible fatal outcomes. The typical route of infection is ingestion of the bacteria with contaminated food. In this study, 13 virulence-associated genes were examined with PCR in the genomes of 153 L. monocytogenes isolates collected from meat products and processing environments in Poland. All isolates possessed genes from LIPI-1—hly, actA, plcA, plcB and mpl—as well as four internalins: inlA, inlB, inlC, inlJ. Invasion-associated protein iap, as well as genes prfA and sigB, encoding regulatory proteins, were also detected in all isolates. Gene flaA, encoding flagellin, was detected in 113 (74%) isolates. This was the only gene that was not detected in all isolates, as its presence is serotype-dependent. Gene actA showed polymorphism with longer and shorter variants in PCR amplicons. Two isolates were characterized by truncated inlB genes, lacking 141 bp in their sequence, which was confirmed by gene sequencing. All isolates were positive in hemolysis assays, proving the synthesis of functional PrfA and Hly proteins. Four genotypes of L. monocytogenes based on actA polymorphism and two genotypes based on inlB polymorphism were distinguished within the isolates’ collection.
Analiza wolnego pozakomórkowego DNA o pochodzeniu bakteryjnym u pacjentów z zaawansowanym czerniakiem poddanych immunoterapii anty-PD-1
Gene emrC Associated with Resistance to Quaternary Ammonium Compounds Is Common among Listeria monocytogenes from Meat Products and Meat Processing Plants in Poland
(1) Background: L. monocytogenes is a food pathogen of great importance, characterized by a high mortality rate. Quaternary ammonium compounds (QACs), such as benzalkonium chloride (BC), are often used as disinfectants in food processing facilities. The effectiveness of disinfection procedures is crucial to food safety. (2) Methods: A collection of 153 isolates of L. monocytogenes from meat processing industry was analyzed for their sensitivity to BC using the agar diffusion method. Genes of interest were detected with PCR. (3) Results: Genes emrC, bcrABC, and qacH were found in 64 (41.8%), 6 (3.9%), and 1 isolate (0.7%), respectively, and 79 isolates (51.6%) were classified as having reduced sensitivity to BC. A strong correlation between carrying QACs resistance-related genes and phenotype was found (p-value < 0.0001). Among 51 isolates originating from bacon (collected over 13 months), 48 had the emrC gene, which could explain their persistent presence in a processing facility. Isolates with the ilsA gene (from LIPI-3) were significantly (p-value 0.006) less likely to carry QACs resistance-related genes. (4) Conclusions: Reduced sensitivity to QACs is common among L. monocytogenes from the meat processing industry. Persistent presence of these bacteria in a processing facility is presumably caused by emrC-induced QACs resistance.
Circulating Cell-Free Microbial DNA Signatures and Plasma Soluble CD14 Level Are Associated with Clinical Outcomes of Anti-PD-1 Therapy in Advanced Melanoma Patients
An accumulating number of studies suggest the potential of circulating cell-free microbial DNA (cfmDNA) as a non-invasive biomarker in various diseases, including cancers. However, its value in the prediction or prognosis of clinical outcomes of immune checkpoint inhibitors (ICIs) is poorly explored. The circulating cfmDNA pool may also reflect the translocation of various microbial ligands to the circulatory system and may be associated with the increased release of soluble CD14 (sCD14) by myeloid cells. In the present study, blood samples were collected from advanced melanoma patients (n = 66) before and during the anti-PD-1 therapy (approximately 3 and 12 months after the start). Then, V3-V4 16S rRNA gene sequencing was performed to analyze the circulating cfmDNA extracted from plasma samples. Moreover, the concentration of plasma sCD14 was measured using ELISA. As a result, the differences in the circulating cfmDNA profiles were found between patients with favorable and unfavorable clinical outcomes of the anti-PD-1 and baseline signatures correlated with progression-free survival and overall survival. Moreover, there was a higher concentration of plasma sCD14 in patients with unfavorable clinical outcomes. High baseline sCD14 level and its increase during the therapy prognosticated worse survival outcomes. Taken together, this preliminary study indicates the potential of circulating cfmDNA signatures and plasma sCD14 levels as biomarkers of clinical outcomes of ICIs.
Phage-Based Control of Listeria innocua in the Food Industry: A Strategy for Preventing Listeria monocytogenes Persistence in Biofilms
Listeria innocua, though considered non-pathogenic, frequently coexists with Listeria monocytogenes in industrial environments, aiding its survival in biofilms. These biofilms pose a significant challenge in food processing facilities, as they protect bacteria from disinfectants and facilitate their spread. The aim of this review was to identify bacteriophages as a promising method for eliminating Listeria biofilms from the food industry. Lytic bacteriophages show great potential in combating Listeria biofilms. Commercially available products, such as PhageGuard Listex™ (P100) (Micreos Food Safety, Wageningen, The Netherlands), effectively reduce both L. monocytogenes and L. innocua in food products and on production surfaces. Additionally, phage-derived enzymes, such as endolysins, can degrade biofilms, eliminating bacteria without compromising food quality. The following article highlights that although bacteriophages present a promising biocontrol method, further research is necessary to assess their long-term effectiveness, particularly regarding bacterial resistance. To maximize efficacy, a combination of strategies such as phage cocktails and disinfectants is recommended to enhance biofilm eradication and minimize food contamination risks.
Influence of supplementation with probiotic bacteria Lactiplantibacillus plantarum and Latilactobacillus curvatus on selected parameters of duodenum iron metabolism in rats on a high-fat, iron-deficient diet
Genoserotyping of Listeria monocytogenes strains originating from meat products and meat processing environments
Background. Listeria monocytogenes is a foodborne human pathogen and a causative factor of listeriosis, which is an illness with a high mortality rate. Serotyping is a method for differentiating L. monocytogenes isolates based on unique combinations of somatic (O) and flagellar (H) antigens on the surface of their cells. Standard serotyping involves agglutination methods, which require using antisera. However, there are also genoserotyping methods which allow to categorise L. monocytogenes isolates into particular groups of serotypes (referred to as serogroups) based on genetic analyses. Differentiating L. monocytogenes isolates is an important issue in terms of food safety, surveillance and traceability of contamination sources. In this work, we present results of the genoserotyping of 153 L. monocytogenes isolates originating from meat products and meat processing environments at Polish processing plants. Two protocols were used for genoserotyping analyses: the first one allows to differentiate between four most common serotypes (1/2a, 1/2b, 1/2c and 4b) and the second one allows to distinguish hipervirulent serovar 4h from other serotypes. Results and conclusion. Results achieved using both methods were consistent and all isolates were categorised into corresponding serogroups within the two methodologies. Most of the isolates (73.9 %) were characterised as members of the IIa serogroup (representing the 1/2a, 3a serovars). The IVb (4b, 4d, 4e) serogroup was the second most common (and comprised 18.3 % of isolates), followed by IIb (1/2b, 3b, 7) and IIc (1/2c, 3c), however, the last two groups were equally numerous (and each of them comprised 3.9 % of all isolates). None of the collected isolates belonged to the serogroup representing the 4a, 4c, 4ab and 4h serotypes.