Insights into the impact of flhF inactivation on Campylobacter jejuni colonization of chick and mice gut

Sludge amended soil induced multidrug and heavy metal resistance in endophytic Exiguobacterium sp. E21L: genomics evidences

The emergence of multidrug-resistant bacteria in agro-environments poses serious risks to public health and ecological balance. In this study, Exiguobacterium sp. E21L, an endophytic strain, was isolated from carrot leaves cultivated in soil amended with sewage treatment plant-derived sludge. The strain exhibited resistance to clinically relevant antibiotics, including beta-lactams, fluoroquinolones, aminoglycosides, and macrolides, with a high Multi-Antibiotic Resistance Index of 0.88. Whole-genome sequencing revealed a genome of 3.06 Mb, encoding 3894 protein-coding genes, including antimicrobial resistance genes (ARGs) such as blaNDM, ermF, tetW, and sul1, along with heavy metal resistance genes (HMRGs) like czcD, copB, and nikA. Genomic islands carrying ARGs and stress-related genes suggested potential horizontal gene transfer. The strain demonstrated robust biofilm formation, high cell hydrophobicity (> 80%), and significant auto-aggregation (90% at 48 h), correlating with genes associated with motility, quorum sensing, and stress adaptation. Notably, phenotypic assays confirmed survival under simulated gastrointestinal conditions, emphasizing its resilience in host-associated environments. Comparative genomics positioned Exiguobacterium sp. E21L near Exiguobacterium chiriqhucha RW-2, with a core genome of 2716 conserved genes. Functional annotations revealed genes involved in xenobiotic degradation, multidrug efflux pumps, and ABC-type transporters, indicating versatile resistance mechanisms and metabolic capabilities. The presence of ARGs, HMRGs, and MGEs (mobile genetic elements) highlights the potential role of Exiguobacterium sp. E21L as a reservoir for resistance determinants in agricultural ecosystems. These findings emphasized the need for stringent regulations on sludge-based fertilizers and advanced sludge treatment strategies to mitigate AMR risks in agro-environments.

Mechanistic concepts involved in biofilm associated processes of Campylobacter jejuni: persistence and inhibition in poultry environments

Campylobacter species, predominantly Campylobacter jejuni, remains a significant zoonotic pathogen worldwide, with the poultry sector being the primary vector for human transmission. In recent years. there has been a notable rise in the incidence of human campylobacteriosis, necessitating a deeper understanding of the pathogen's survival mechanisms and transmission dynamics. Biofilm presence significantly contributes to C. jejuni persistence in poultry and subsequent food product contamination, and this review describes the intricate processes involved in biofilm formation. The ability of Campylobacter to form biofilms on various surfaces, including stainless steel, plastic, and glass, is a critical survival strategy. Campylobacter biofilms, with their remarkable resilience, protect the pathogen from environmental stresses such as desiccation, pH extremes, biocides and sanitizing agents. This review explores the molecular and genetic mechanisms of C. jejuni biofilm formation, highlighting regulatory genes involved in motility, chemotaxis, and stress responses. Flagellar proteins, particularly flaA, flaB, flaG, and adhesins like cadF and flpA, are identified as the main molecular components in biofilm development. The role of mixed-species biofilms, where C. jejuni integrates into existing biofilms of other bacteria to enhance pathogen resilience, is also discussed. This review also considers alternative interventions to control C. jejuni in poultry production, in the context of increasing antibiotic resistance. It explores the effectiveness of prebiotics, probiotics, synbiotics, bacteriocins, bacteriophages, vaccines, and organic acids, with a focus on their mechanisms of action in reducing bacterial colonization and biofilm formation. Studies show that mixtures of organic acids and compounds like Carvacrol and Eugenol significantly downregulate genes linked with motility and adhesion, thereby disrupting biofilm integrity. It discusses the impact of environmental factors, such as temperature and oxygen levels on biofilm formation, providing insights into how industrial conditions can be manipulated to reduce contamination. This paper stresses the need for a multifaceted approach to control Campylobacter in poultry, integrating molecular and genetic insights with practical interventions. By advancing our understanding of biofilm dynamics and gene regulation, we aim to inform the development of more effective strategies to enhance food safety and protect public health.

Phenotypic, genotypic and proteomic variations between poor and robust colonizing Campylobacter jejuni strains

Campylobacter jejuni is one of the major causes of bacterial gastrointestinal disease in humans worldwide. This foodborne pathogen colonizes the intestinal tracts of chickens, and consumption of chicken and poultry products is identified as a common route of transmission. We analyzed two C. jejuni strains after oral challenge with 105 CFU/ml of C. jejuni per chick; one strain was a robust colonizer (A74/C) and the other a poor colonizer (A74/O). We also found extensive phenotypic differences in growth rate, biofilm production, and in vitro adherence, invasion, intracellular survival, and transcytosis. Strains A74/C and A74/O were genotypically similar with respect to their whole genome alignment, core genome, and ribosomal MLST, MLST, flaA, porA, and PFGE typing. The global proteomes of the two congenic strains were quantitatively analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and 618 and 453 proteins were identified from A74/C and A74/O isolates, respectively. Cluster of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that carbon metabolism and motility proteins were distinctively overexpressed in strain A74/C. The robust colonizer also exhibited a unique proteome profile characterized by significantly increased expression of proteins linked to adhesion, invasion, chemotaxis, energy, protein synthesis, heat shock proteins, iron regulation, two-component regulatory systems, and multidrug efflux pump. Our study underlines phenotypic, genotypic, and proteomic variations of the poor and robust colonizing C. jejuni strains, suggesting that several factors may contribute to mediating the different colonization potentials of the isogenic isolates.

Molecular structures mediating adhesion of Campylobacter jejuni to abiotic and biotic surfaces

Microaerophilic, Gram-negative Campylobacter jejuni is the causative agent of campylobacteriosis, the most common bacterial gastrointestinal infection worldwide. Adhesion is the crucial first step in both infection or interaction with the host and biofilm formation, and is a critical factor for bacterial persistence. Here we describe the proteins and other surface structures that promote adhesion to various surfaces, including abiotic surfaces, microorganisms, and animal and human hosts. In addition, we provide insight into the distribution of adhesion proteins among strains from different ecological niches and highlight unexplored proteins involved in C. jejuni adhesion. Protein-protein, protein-glycan, and glycan-glycan interactions are involved in C. jejuni adhesion, with different factors contributing to adhesion to varying degrees under different circumstances. As adhesion is essential for survival and persistence, it represents an interesting target for C. jejuni control. Knowledge of the adhesion process is incomplete, as different molecular and functional aspects have been studied for different structures involved in adhesion. Therefore, it is important to strive for an integration of different approaches to obtain a clearer picture of the adhesion process on different surfaces and to consider the involvement of proteins, glycoconjugates, and polysaccharides and their cooperation.

A secreted sirtuin from Campylobacter jejuni contributes to neutrophil activation and intestinal inflammation during infection

Histone modifications control numerous processes in eukaryotes, including inflammation. Some bacterial pathogens alter the activity or expression of host-derived factors, including sirtuins, to modify histones and induce responses that promote infection. In this study, we identified a deacetylase encoded by Campylobacter jejuni which has sirtuin activities and contributes to activation of human neutrophils by the pathogen. This sirtuin is secreted from the bacterium into neutrophils, where it associates with and deacetylates host histones to promote neutrophil activation and extracellular trap production. Using the murine model of campylobacteriosis, we found that a mutant of this bacterial sirtuin efficiently colonized the gastrointestinal tract but was unable to induce cytokine production, gastrointestinal inflammation, and tissue pathology. In conclusion, these results suggest that secreted bacterial sirtuins represent a previously unreported class of bacterial effector and that bacterial-mediated modification of host histones is responsible for the inflammation and pathology that occurs during campylobacteriosis.

The impact of lipid A modification on biofilm and related pathophysiological phenotypes, endotoxicity, immunogenicity, and protection of Salmonella Typhimurium

This study presents the engineering of a less endotoxic Salmonella Typhimurium strain by manipulating the lipid-A structure of the lipopolysaccharide (LPS) component. Salmonella lipid A was dephosphorylated by using lpxE from Francisella tularensis. The 1-phosphate group from lipid-A was removed selectively, resulting in a close analog of monophosphoryl lipid A. We observed a significant impact of ∆pagL on major virulence factors such as biofilm formation, motility, persistency, and immune evasion. In correlation with biofilm and motility retardation, adhesion and invasion were elevated but with reduced intracellular survival, a favorable phenotype prospect of a vaccine strain. Western blotting and silver staining confirmed the absence of the O-antigen and truncated lipid-A core in the detoxified Salmonella mutant. In vitro and in vivo studies demonstrated that the dephosphorylated Salmonella mutant mediated lower pro-inflammatory cytokine secretion than the wild-type strain. The vaccine strains were present in the spleen and liver for five days and were cleared from the organs by day seven. However, the wild-type strain persisted in the spleen, liver, and brain, leading to sepsis-induced death. Histological evaluations of tissue samples further confirmed the reduced endotoxic activity of the detoxified Salmonella mutant. The detoxification strategy did not compromise the level of protective immunity, as the vaccine strain could enhance humoral and cellular immune responses and protect against the wild-type challenge in immunized mice.

Mouse models for bacterial enteropathogen infections: insights into the role of colonization resistance

Globally, enteropathogenic bacteria are a major cause of morbidity and mortality.1-3 Campylobacter, Salmonella, Shiga-toxin-producing Escherichia coli, and Listeria are among the top five most commonly reported zoonotic pathogens in the European Union.4 However, not all individuals naturally exposed to enteropathogens go on to develop disease. This protection is attributable to colonization resistance (CR) conferred by the gut microbiota, as well as an array of physical, chemical, and immunological barriers that limit infection. Despite their importance for human health, a detailed understanding of gastrointestinal barriers to infection is lacking, and further research is required to investigate the mechanisms that underpin inter-individual differences in resistance to gastrointestinal infection. Here, we discuss the current mouse models available to study infections by non-typhoidal Salmonella strains, Citrobacter rodentium (as a model for enteropathogenic and enterohemorrhagic E. coli), Listeria monocytogenes, and Campylobacter jejuni. Clostridioides difficile is included as another important cause of enteric disease in which resistance is dependent upon CR. We outline which parameters of human infection are recapitulated in these mouse models, including the impact of CR, disease pathology, disease progression, and mucosal immune response. This will showcase common virulence strategies, highlight mechanistic differences, and help researchers from microbiology, infectiology, microbiome research, and mucosal immunology to select the optimal mouse model.

Characterization of Campylobacter jejuni-Neutrophil Interactions

Campylobacter jejuni is the leading cause of bacterial-derived gastroenteritis worldwide, infecting 96 million individuals annually. During infection, inflammation and tissue pathology occur in the lower gastrointestinal tract, including the recruitment of leukocytes. Neutrophils are the most abundant leukocyte in humans, and recruitment is associated with bacterial infections and the development of various inflammatory disorders, including inflammatory bowel disease. Neutrophils possess three main antibacterial functions: phagocytosis and degradation of microbes, degranulation to release antimicrobial proteins, and extrusion of neutrophil extracellular traps (NETs). Because neutrophils are recruited to the site of C. jejuni infection and they are associated with damaging inflammation in other diseases, it is imperative to understand the immunopathology that occurs during C. jejuni infection and thoroughly study the neutrophil response to the pathogen. Detailed protocols for human and ferret neutrophil isolations, neutrophil gentamicin protection assay, neutrophil activation flow cytometry assay, NET induction and quantification, and neutrophil western blot analysis are included in this article. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Isolation of human and ferret neutrophils Basic Protocol 2: Neutrophil gentamicin protection assay Basic Protocol 3: Neutrophil activation flow cytometry analyses Basic Protocol 4: Neutrophil extracellular trap induction and quantification Basic Protocol 5: Western blot detection of neutrophil-derived antimicrobial proteins.

Virulence factors of foodborne pathogen Campylobacterjejuni

Campylobacter jejuni is a highly frequent cause of gastrointestinal foodborne disease in humans throughout the world. Disease outcomes vary from mild to severe diarrhea, and in rare cases the Guillain-Barré syndrome or reactive arthritis can develop as a post-infection complication. Transmission to humans usually occurs via the consumption of a range of foods, especially those associated with the consumption of raw or undercooked poultry meat, unpasteurized milk, and water-based environmental sources. When associated to food or water ingestion, the C. jejuni enters the human host intestine via the oral route and colonizes the distal ileum and colon. When it adheres and colonizes the intestinal cell surfaces, the C. jejuni is expected to express several putative virulence factors, which cause damage to the intestine either directly, by cell invasion and/or production of toxin(s), or indirectly, by triggering inflammatory responses. This review article highlights various C. jejuni characteristics - such as motility and chemotaxis - that contribute to the biological fitness of the pathogen, as well as factors involved in human host cell adhesion and invasion, and their potential role in the development of the disease. We have analyzed and critically discussed nearly 180 scientific articles covering the latest improvements in the field.

Feeding Malic Acid to Chickens at Slaughter Age Improves Microbial Safety with Regard to Campylobacter

Simple Summary

Chicken meat has become a popular food that is consumed worldwide. However, chicken flocks suffer from Campylobacter infection during their rearing period. Campylobacter is the most serious pathogen colonizing chicken flocks which could be transmitted through the food chain and threaten public health. The traditional strategy of using antibiotics to inhibit pathogens in chicken flocks is no longer acceptable due to the increasing risk of antibiotic resistance. Thus, finding alternative antimicrobial agents has become a priority in recent years. In this study, malic acid was supplied to flocks in order to find an effective means of reducing the contamination of Campylobacter and to evaluate its potential effects on poultry production. By using malic acid-supplemented drinking water for 5 days before slaughtering, the Campylobacter carriage was significantly decreased in the treated group compared to the control group. Malic acid has no adverse effects on chickens, though it could change the composition of chicken meat by increasing the moisture content and decreasing the fat content and it could be applied as a potential antimicrobial agent in poultry production.

Abstract

This study supplied malic acid-supplemented drinking water to flocks that were naturally Campylobacter-positive and assessed the effect of feeding malic acid to chickens on Campylobacter reduction and poultry production. In Experiment 1, chickens were provided with malic acid-supplemented drinking water for three weeks. The contamination loads of Campylobacter were decreased by 0.91–0.98 log after the first week of use (p < 0.05). However, this effect did not persist over time and significant decontamination could not be found in the second and third weeks of application. Thus, in Experiment 2 malic acid-supplemented drinking water was given to chickens for a period of five days at slaughter age. The Campylobacter carriage was found to be effectively decreased by 1.05–1.55 log (p < 0.05). Malic acid had no adverse effects on chicken body weight, weight gain, intestinal indices, or the microbiota. In addition, it could change the composition of chicken meat since the moisture content was increased by 5.12–5.92% (p < 0.05) and the fat content was decreased by 1.60% (p < 0.05). Our study provides an effective means for reducing the contamination of Campylobacter during the chicken rearing period and this method can be applied to promote the safe development of poultry farming and its products.

Population Biology and Comparative Genomics of Campylobacter Species

The zoonotic pathogen Campylobacter is the leading cause for bacterial foodborne infections in humans. Campylobacters are most commonly transmitted via the consumption of undercooked poultry meat or raw milk products. The decreasing costs of whole genome sequencing enabled large genome-based analyses of the evolution and population structure of this pathogen, as well as the development of novel high-throughput molecular typing methods. Here, we review the evolutionary development and the population diversity of the two most clinically relevant Campylobacter species; C. jejuni and C. coli. The state-of-the-art phylogenetic studies showed clustering of C. jejuni lineages into host specialists and generalists with coexisting lifestyles in chicken and livestock-associated hosts, as well as the separation of C. coli isolates of riparian origin (waterfowl, water) from C. coli isolated from clinical and farm-related samples. We will give an overview of recombination between both species and the potential impact of horizontal gene transfer on host adaptation in Campylobacter. Additionally, this review briefly places the current knowledge of the population structure of other Campylobacter species such as C. lari, C. concisus and C. upsaliensis into perspective. We also provide an overview of how molecular typing methods such as multilocus sequence typing (MLST) and whole genome MLST have been used to detect and trace Campylobacter outbreaks along the food chain.