Virulence behavior of uropathogenic Escherichia coli strains in the host model Caenorhabditis elegans

A new killing assay with the Caenorhabditis elegans PX627 mutant to assess the virulence of uropathogenic Escherichia coli strains

The nematode Caenorhabditis elegans (C. elegans) is a prime invertebrate host model for studying uropathogenic Escherichia coli (UPEC) pathogenesis. The aim of this work was to develop a new C. elegans killing assay based on feeding bacteria by the nematode throughout its life from the egg. With this model, the lifespan of C. elegans rrf-3, temperature-sterile, mutant, and PX627, auxin-inducible infertile, mutant fed UPEC strains, was compared. The behavior of three clinical UPEC strains and the non-pathogenic Escherichia coli OP50 strain was analyzed. Survival curves were generated by the Kaplan-Meier method and compared by the log-rank test over 10 days of follow-up. There was no significant difference between the survival curves obtained with each of the two C. elegans mutants (PX627 and rrf-3) fed with each of the strains of E. coli (OP50, G1722, G1473 or ER41). The UPEC strains were classified according to their virulence in vivo in the C. elegans PX627 mutant. The most virulent strain was ER41 which harbored the virulence genes fimA, papC and hlyA, expressed hemolysis in vitro and showed no antibiotic resistance. The least virulent strain was G1722 which only harbored the two adhesion factor genes, was not hemolytic and was resistant to multiple antibiotics. The C. elegans PX627 mutant fed with UPEC bacteria from the egg stage is a simple and inexpensive invertebrate animal model for assessing the in vivo virulence of different strains. The early exposure of C. elegans to pathogenic bacteria at the egg stage, without the need to change the incubation temperature, is an advantage over previously described C. elegans killing assays.

Genotypic characteristics of Uropathogenic Escherichia coli isolated from complicated urinary tract infection (cUTI) and asymptomatic bacteriuria-a relational analysis

Background

Uropathogenic Escherichia coli (UPEC) is the predominant agent causing various categories of complicated urinary tract infections (cUTI). Although existing data reveals that UPEC harboured numerous virulence determinants to aid its survival in the urinary tract, the reason behind the occurrence of differences in the clinical severity of uninary tract infections (UTI) demonstrated by the UPEC infection is poorly understood. Therefore, the present study aims to determine the distribution of virulence determinants and antimicrobial resistance among different phylogroups of UPEC isolated from various clinical categories of cUTI and asymptomatic bacteriuria (ASB) E. coli isolates. The study will also attempt a relational analysis of the genotypic characteristics of cUTI UPEC and ASB E. coli isolates.

Methods

A total of 141 UPEC isolates from cUTI and 160 ASB E. coli isolates were obtained from Universiti Malaya Medical Centre (UMMC). Phylogrouping and the occurrence of virulence genes were investigated using polymerase chain reaction (PCR). Antimicrobial susceptibility of the isolates to different classes of antibiotics was determined using the Kirby Bauer Disc Diffusion method.

Results

The cUTI isolates were distributed differentially among both Extraintestinal Pathogenic E. coli (ExPEC) and non-ExPEC phylogroups. Phylogroup B2 isolates were observed to possess the highest average aggregative virulence score (7.17), a probable representation of the capability to cause severe disease. Approximately 50% of the cUTI isolates tested in this study were multidrug resistant against common antibiotics used to treat UTI. Analysis of the occurrence of virulence genes among different cUTI categories demonstrated that UPEC isolates of pyelonephritis and urosepsis were highly virulent and had the highest average aggregative virulence scores of 7.80 and 6.89 respectively, compared to other clinical categories. Relational analysis of the occurrence of phylogroups and virulence determinants of UPEC and ASB E. coli isolates showed that 46.1% of UPEC and 34.3% of ASB E. coli from both categories were distributed in phylogroup B2 and had the highest average aggregative virulence score of 7.17 and 5.37, respectively. The data suggest that UPEC isolates which carry virulence genes from all four virulence genes groups studied (adhesions, iron uptake systems, toxins and capsule synthesis) and isolates from phylogroup B2 specifically could predispose to severe UTI involving the upper urinary tract. Therefore, specific analysis of the genotypic characteristics of UPEC could be further explored by incorporating the combination of virulence genes as a prognostic marker for predicting disease severity, in an attempt to propose a more evidence driven treatment decision-making for all UTI patients. This will go a long way in enhancing favourable therapeutic outcomes and reducing the antimicrobial resistance burden among UTI patients.

In Vitro Probiotic Properties and In Vivo Anti-Ageing Effects of Lactoplantibacillus plantarum PFA2018AU Strain Isolated from Carrots on Caenorhabditis elegans

Lactic acid bacteria (LAB) share and provide several beneficial effects on human health, such as the release of bioactive metabolites, pathogen competition, and immune stimulation. The two major reservoirs of probiotic microorganisms are the human gastro-intestinal tract and fermented dairy products. However, other sources, such as plant-based foods, represent important alternatives thanks to their large distribution and nutritive value. Here, the probiotic potential of autochthonous Lactiplantibacillus plantarum PFA2018AU, isolated from carrots harvested in Fucino highland, Abruzzo (Italy), was investigated through in vitro and in vivo approaches. The strain was sent to the biobank of Istituto Zooprofilattico Sperimentale della Lombardia ed Emilia Romagna in Italy for the purpose of patent procedures under the Budapest Treaty. The isolate showed high survival capability under in vitro simulated gastro-intestinal conditions, antibiotic susceptibility, hydrophobicity, aggregation, and the ability to inhibit the in vitro growth of Salmonella enterica serovar Typhimurium, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus pathogens. Caenorhabditis elegans was used as the in vivo model in order to analyse prolongevity and anti-ageing effects. L. plantarum PFA2018AU significantly colonised the gut of the worms, extended their lifespan, and stimulated their innate immunity. Overall, these results showed that autochthonous LAB from vegetables, such as carrots, have functional features that can be considered novel probiotic candidates.

Virulence potential of antimicrobial-resistant extraintestinal pathogenic Escherichia coli from retail poultry meat in a Caenorhabditis elegans model

Healthy poultry can be a reservoir for extraintestinal pathogenic Escherichia coli (ExPEC), some of which could be multidrug resistant to antimicrobials. These ExPEC strains could contaminate the environment and/or food chain representing thus, food safety and human health risk. However, few studies have shown the virulence of poultry-source antimicrobial-resistant (AMR) ExPEC in humans. This study characterized AMR ExPEC and investigated the virulence potential of some of their isolates in a Caenorhabditis elegans infection model. A total of 46 E. coli isolates from poultry (chicken, n = 29; turkey, n = 12) retail meats and chicken feces (n = 4), or humans (n = 1) were sequenced and identified as ExPEC. Except eight, all remaining 38 ExPEC isolates were resistant to at least one antibiotic and carried corresponding antimicrobial resistance genes (ARGs). About 27 of the 46 ExPEC isolates were multidrug-resistant (≥3 antibiotic classes). Seven ExPEC isolates from chicken or turkey meats were of serotype O25:H4 and sequence type (ST) 131 which clustered with an isolate from a human urinary tract infection (UTI) case having the same serotype and ST. The C. elegans challenge model using eight of studied ExPEC isolates harboring various ARGs and virulence genes (VGs) showed that regardless of their ARG or VG numbers in tested poultry meat and feces, ExPEC significantly reduced the life span of the nematode (P < 0.05) similarly to a human UTI isolate. This study indicated the pathogenic potential of AMR ExPEC from retail poultry meat or feces, but more studies are warranted to establish their virulence in poultry and human. Furthermore, relationships between specific resistance profiles and/or VGs in these E. coli isolates for their pathogenicity deserve investigations.

Neem Oil or Almond Oil Nanoemulsions for Vitamin E Delivery: From Structural Evaluation to in vivo Assessment of Antioxidant and Anti-Inflammatory Activity

Purpose

Vitamin E (VitE) may be classified in "the first line of defense" against the formation of reactive oxygen species. Its inclusion in nanoemulsions (NEs) is a promising alternative to increase its bioavailability. The aim of this study was to compare O/W NEs including VitE based on Almond or Neem oil, showing themselves antioxidant properties. The potential synergy of the antioxidant activities of oils and vitamin E, co-formulated in NEs, was explored.

Patients and Methods

NEs have been prepared by sonication and deeply characterized evaluating size, ζ-potential, morphology (TEM and SAXS analyses), oil nanodroplet feature, and stability. Antioxidant activity has been evaluated in vitro, in non-tumorigenic HaCaT keratinocytes, and in vivo through fluorescence analysis of C. elegans transgenic strain. Moreover, on healthy human volunteers, skin tolerability and anti-inflammatory activity were evaluated by measuring the reduction of the skin erythema induced by the application of a skin chemical irritant (methyl-nicotinate).

Results

Results confirm that Vitamin E can be formulated in highly stable NEs showing good antioxidant activity on keratinocyte and on C. elegans. Interestingly, only Neem oil NEs showed some anti-inflammatory activity on healthy volunteers.

Conclusion

From the obtained results, Neem over Almond oil is a more appropriate candidate for further studies on this application.

A Multiwell-Plate Caenorhabditis elegans Assay for Assessing the Therapeutic Potential of Bacteriophages against Clinical Pathogens

In order to establish phage therapy as a standard clinical treatment for bacterial infections, testing of every phage to ensure the suitability and safety of the biological compound is required. While some issues have been addressed over recent years, standard and easy-to-use animal models to test phages are still rare. Testing of phages in highly suitable mammalian models such as mice is subjected to strict ethical regulations, while insect larvae such as the Galleria mellonella model suffer from batch-to-batch variations and require manual operator skills to inject bacteria, resulting in unreliable experimental outcomes. A much simpler model is the nematode Caenorhabditis elegans, which feeds on bacteria, a fast growing and easy to handle organism that can be used in high-throughput screening. In this study, two clinical bacterial strains of Escherichia coli, one Klebsiella pneumoniae, and one Enterobacter cloacae strain were tested on the model system together with lytic bacteriophages that we isolated previously. We developed a liquid-based assay, in which the efficiency of phage treatment was evaluated using a scoring system based on microscopy and counting of the nematodes, allowing increasing statistical significance compared to other assays such as larvae or mice. Our work demonstrates the potential to use Caenorhabditis elegans to test the virulence of strains of Klebsiella pneumoniae, Enterobacter cloacae, and EHEC/EPEC as well as the efficacy of bacteriophages to treat or prevent infections, allowing a more reliable evaluation for the clinical therapeutic potential of lytic phages. IMPORTANCE Validating the efficacy and safety of phages prior to clinical application is crucial to see phage therapy in practice. Current animal models include mice and insect larvae, which pose ethical or technical challenges. This study examined the use of the nematode model organism C. elegans as a quick, reliable, and simple alternative for testing phages. The data show that all the four tested bacteriophages can eliminate bacterial pathogens and protect the nematode from infections. Survival rates of the nematodes increased from <20% in the infection group to >90% in the phage treatment group. Even the nematodes with poly-microbial infections recovered during phage cocktail treatment. The use of C. elegans as a simple whole-animal infection model is a rapid and robust way to study the efficacy of phages before testing them on more complex model animals such as mice.

Evaluation of Biofilm Formation and Virulence Genes and Association with Antibiotic Resistance Patterns of Uropathogenic Escherichia coli Strains in Southwestern Iran

Background: Uropathogenic Escherichia coli (UPEC) strains, encoding superficial and secretory virulence factors, can lead to colonization and facilitation of bacterial growth in the host urinary tract, causing Urinary Tract Infection (UTI). Objectives: This study determined the ability of biofilm formation by the Congo red agar method, the presence of virulence genes using the multiplex polymerase chain reaction (PCR) method, and the relationship between biofilm formation and antibiotic resistance patterns and virulence genes in E. coli clinical isolates in Yasuj. Methods: This cross-sectional study was performed on 144 UPEC isolates collected in 2017. Biofilm formation was detected by the Congo red agar phenotypic assay and virulence factors by the multiplex PCR method. Antibiotic resistance tests were performed by the Kirby-Bauer method. Results: Out of 144 isolates of E. coli, 22 (19.4%) isolates showed to be strong biofilm producers, 27 (23.8%) moderate biofilm producers, and 64 (56.3%) weak biofilm producers. A significant relationship was observed between biofilm-producing strains and resistance to ampicillin (P = 0.020) and cotrimoxazole (P = 0.038). The virulence genes in strong biofilm producers included iutA (95%), FimH (93%), ompT (90%), PAI (90%), and TraT (81%) genes. The phylogroup B2 carried the most virulence genes. A significant correlation was observed between E. coli phylogenetic groups and aer (P = 0.019), iroN (P = 0.042), and ompT (P = 0.032) virulence genes. Conclusions: The results of this study showed a high prevalence of virulence genes, and antibiotic-resistant E. coli strains capable of biofilm formation. The results of this study may help elucidate the pathogenesis of UPEC and facilitate better treatment strategies for patients with UTIs in this geographic area.

Leuconostoc mesenteroides Strains Isolated from Carrots Show Probiotic Features

Lactic acid bacteria (LAB) share several beneficial effects on human organisms, such as bioactive metabolites’ release, pathogens’ competition and immune stimulation. This study aimed at determining the probiotic potential of autochthonous lactic acid bacteria isolated from carrots. In particular, the work reported the characterization at the species level of four LAB strains deriving from carrots harvested in Fucino highland, Abruzzo (Italy). Ribosomal 16S DNA analysis allowed identification of three strains belonging to Leuconostoc mesenteroides and a Weissella soli strain. In vitro and in vivo assays were performed to investigate the probiotic potential of the different isolates. Among them, L. mesenteroides C2 and L. mesenteroides C7 showed high survival percentages under in vitro simulated gastro-intestinal conditions, antibiotic susceptibly and the ability to inhibit in vitro growth against Salmonella enterica serovar Typhimurium, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus pathogens. In parallel, the simple model Caenorhabditis elegans was used for in vivo screenings. L. mesenteroides C2 and L. mesenteroides C7 strains significantly induced pro-longevity effects, protection from pathogens’ infection and innate immunity stimulation. Overall, these results showed that some autochthonous LAB from vegetables such as carrots have functional features to be considered as novel probiotic candidates.

Adherent-Invasive and Non-Invasive Escherichia coli Isolates Differ in Their Effects on Caenorhabditis elegans' Lifespan

The adherent-invasive Escherichia coli (AIEC) pathotype has been implicated in the pathogenesis of inflammatory bowel diseases in general and in Crohn’s disease (CD) in particular. AIEC strains are primarily characterized by their ability to adhere to and invade intestinal epithelial cells. However, the genetic and phenotypic features of AIEC isolates vary greatly as a function of the strain’s clonality, host factors, and the gut microenvironment. It is thus essential to identify the determinants of AIEC pathogenicity and understand their role in intestinal epithelial barrier dysfunction and inflammation. We reasoned that soil nematode Caenorhabditis elegans (a simple but powerful model of host-bacterium interactions) could be used to study the virulence of AIEC vs. non- AIEC E. coli strains. Indeed, we found that the colonization of C. elegans (strain N2) by E. coli impacted survival in a strain-specific manner. Moreover, the AIEC strains’ ability to invade cells in vitro was linked to the median lifespan in C. elegans (strain PX627). However, neither the E. coli intrinsic invasiveness (i.e., the fact for an individual strain to be characterized as invasive or not) nor AIEC’s virulence levels (i.e., the intensity of invasion, established in % from the infectious inoculum) in intestinal epithelial cells was correlated with C. elegans’ lifespan in the killing assay. Nevertheless, AIEC longevity of C. elegans might be a relevant model for screening anti-adhesion drugs and anti-invasive probiotics.

Bacterial processing of glucose modulates C. elegans lifespan and healthspan

Intestinal microbiota play an essential role in the health of a host organism. Here, we define how commensal Escherichia coli (E. coli) alters its host after long term exposure to glucose using a Caenorhabditis elegans-E. coli system where only the bacteria have direct contact with glucose. Our data reveal that bacterial processing of glucose results in reduced lifespan and healthspan including reduced locomotion, oxidative stress resistance, and heat stress resistance in C. elegans. With chronic exposure to glucose, E. coli exhibits growth defects and increased advanced glycation end products. These negative effects are abrogated when the E. coli is not able to process the additional glucose and by the addition of the anti-glycation compound carnosine. Physiological changes of the host C. elegans are accompanied by dysregulation of detoxifying genes including glyoxalase, glutathione-S-transferase, and superoxide dismutase. Loss of the glutathione-S-transferase, gst-4 shortens C. elegans lifespan and blunts the animal's response to a glucose fed bacterial diet. Taken together, we reveal that added dietary sugar may alter intestinal microbial E. coli to decrease lifespan and healthspan of the host and define a critical role of detoxification genes in maintaining health during a chronic high-sugar diet.

In vitro and in vivo lipidomics as a tool for probiotics evaluation

The probiotic bacteria are helpful for nutritional and therapeutic purposes, and they are commercially available in various forms, such as capsules or powders. Increasing pieces of evidence indicate that different growth conditions and variability in manufacturing processes can determine the properties of probiotic products. In recent years, the lipidomic approach has become a useful tool to evaluate the impact that probiotics induce in host physiology. In this work, two probiotic formulations with identical species composition, produced in two different sites, the USA and Italy, were utilized to feed Caenorhabditis elegans, strains and alterations in lipid composition in the host and bacteria were investigated. Indeed, the multicellular organism C. elegans is considered a simple model to study the in vivo effects of probiotics. Nematodes fat metabolism was assessed by gene expression analysis and by mass spectrometry-based lipidomics. Lipid droplet analysis revealed a high accumulation of lipid droplets in worms fed US-made products, correlating with an increased expression of genes involved in the fatty acid synthesis. We also evaluated the lifespan of worms defective in genes involved in the insulin/IGF-1-mediated pathway and monitored the nuclear translocation of DAF-16. These data demonstrated the involvement of the signaling in C. elegans responses to the two diets. Lipidomics analysis of the two formulations was also conducted, and the results indicated differences in phosphatidylglycerol (PG) and phosphatidylcholine (PC) contents that, in turn, could influence nematode host physiology. Results demonstrated that different manufacturing processes could influence probiotics and host properties in terms of lipid composition. KEY POINTS: • Probiotic formulations impact on Caenorhabditis elegans lipid metabolism; • Lipidomic analysis highlighted phospholipid abundance in the two products; • Phosphocholines and phosphatidylglycerols were analyzed in worms fed the two probiotic formulations.

A Combined Proteomics, Metabolomics and In Vivo Analysis Approach for the Characterization of Probiotics in Large-Scale Production

The manufacturing processes of commercial probiotic strains may be affected in different ways in the attempt to optimize yield, costs, functionality, or stability, influencing gene expression, protein patterns, or metabolic output. Aim of this work is to compare different samples of a high concentration (450 billion bacteria) multispecies (8 strains) formulation produced at two different manufacturing sites, United States of America (US) and Italy (IT), by applying a combination of functional proteomics, metabolomics, and in vivo analyses. Several protein-profile differences were detected between IT- and US-made products, with Lactobacillus paracasei, Streptococcus thermophilus, and Bifidobacteria being the main affected probiotics/microorganisms. Performing proton nuclear magnetic spectroscopy (¹H-NMR), some discrepancies in amino acid, lactate, betaine and sucrose concentrations were also reported between the two products. Finally, we investigated the health-promoting and antiaging effects of both products in the model organism Caenorhabditis elegans. The integration of omics platforms with in vivo analysis has emerged as a powerful tool to assess manufacturing procedures.

Pmr-1 gene affects susceptibility of Caenorhabditis elegans to Staphylococcus aureus infection through glycosylation and stress response pathways' alterations

Calcium signaling can elicit different pathways involved in an extreme variety of biological processes. Calcium levels must be tightly regulated in a spatial and temporal manner in order to be efficiently and properly utilized in the host physiology. The Ca²⁺-ATPase, encoded by pmr-1 gene, was first identified in yeast and localized to the Golgi and it appears to be involved in calcium homeostasis. PMR-1 function is evolutionary conserved from yeast to human, where mutations in the orthologous gene ATP2C1 cause Hailey-Hailey disease. In this work, we used the Caenorhabditis elegans model system to gain insight into the downstream response elicited by the loss of pmr-1 gene. We found that pmr-1 knocked down animals not only showed defects in the oligosaccharide structure of glycoproteins at the cell surface but also were characterized by reduced susceptibility to bacterial infection. Although increased resistance to the infection might be related to lack of regular recognition of C. elegans surface glycoproteins by microbial agents, we provide genetic evidence that pmr-1 interfered nematodes mounted a stronger innate immune response to Gram-positive bacterial infection. Thus, our observations indicate pmr-1 as a candidate gene implicated in mediating the worm's innate immune response.

Virulence behavior of uropathogenic Escherichia coli strains in the host model Caenorhabditis elegans

Urinary tract infections (UTIs) are among the most common bacterial infections in humans. Although a number of bacteria can cause UTIs, most cases are due to infection by uropathogenic Escherichia coli (UPEC). UPEC are a genetically heterogeneous group that exhibit several virulence factors associated with colonization and persistence of bacteria in the urinary tract. Caenorhabditis elegans is a tiny, free-living nematode found worldwide. Because many biological pathways are conserved in C. elegans and humans, the nematode has been increasingly used as a model organism to study virulence mechanisms of microbial infections and innate immunity. The virulence of UPEC strains, characterized for antimicrobial resistance, pathogenicity-related genes associated with virulence and phylogenetic group belonging was evaluated by measuring the survival of C. elegans exposed to pure cultures of these strains. Our results showed that urinary strains can kill the nematode and that the clinical isolate ECP110 was able to efficiently colonize the gut and to inhibit the host oxidative response to infection. Our data support that C. elegans, a free-living nematode found worldwide, could serve as an in vivo model to distinguish, among uropathogenic E. coli, different virulence behavior.