Long polar fimbriae contribute to pathogenic Escherichia coli infection to host cells

Removal of intracellular and extracellular antibiotic resistance genes and virulence factor genes using electricity-intensified constructed wetlands

Constructed wetland (CW) is considered a promising technology for the removal of emerging contaminants. However, its removal performance for antibiotic resistance genes (ARGs) is not efficient and influence of virulence factor genes (VFGs) have not been elucidated. Here, removal of intracellular and extracellular ARGs as well as VFGs by electricity-intensified CWs was comprehensively evaluated. The two electrolysis-intensified CWs can improve the removal of intracellular ARGs and MGEs to 0.96- and 0.85-logs, respectively. But cell-free extracellular ARGs (CF-eARGs) were significantly enriched with 1.8-logs in the electrolysis-intensified CW. Interestingly, adding Fe-C microelectrolysis to the electrolysis-intensified CW is conducive to the reduction of CF-eARGs. However, the detected number and relative abundances of intracellular and extracellular VFGs were increased in all of the three CWs. The biofilms attached onto the substrates and rhizosphere are also hotspots of both intracellular and particle-associated extracellular ARGs and VFGs. Structural equation models and correlation analysis indicated that ARGs and VFGs were significantly cooccurred, suggesting that VFGs may affect the dynamics of ARGs. The phenotypes of VFGs, such as biofilm, may act as protective matrix for ARGs, hindering the removal of resistance genes. Our results provide novel insights into the ecological remediation technologies to enhance the removal of ARGs.

Escherichia coli in urban marine sediments: interpreting virulence, biofilm formation, halotolerance, and antibiotic resistance to infer contamination or naturalization

Marine sediments have been suggested as a reservoir for pathogenic bacteria, including Escherichia coli. The origins, and properties promoting survival of E. coli in marine sediments (including osmotolerance, biofilm formation capacity, and antibiotic resistance), have not been well-characterized. Phenotypes and genotypes of 37 E. coli isolates from coastal marine sediments were characterized. The isolates were diverse: 30 sequence types were identified that have been previously documented in humans, livestock, and other animals. Virulence genes were found in all isolates, with more virulence genes found in isolates sampled from sediment closer to the effluent discharge point of a wastewater treatment plant. Antibiotic resistance was demonstrated phenotypically for one isolate, which also carried tetracycline resistance genes on a plasmid. Biofilm formation capacity varied for the different isolates, with most biofilm formed by phylogroup B1 isolates. All isolates were halotolerant, growing at 3.5% NaCl. This suggests that the properties of some isolates may facilitate survival in marine environments and can explain in part how marine sediments can be a reservoir for pathogenic E. coli. As disturbance of sediment could resuspend bacteria, this should be considered as a potential contributor to compromised bathing water quality at nearby beaches.

Flagella are an important virulence factor in the subclinical persistence of Escherichia coli in bovine mammary gland

We compared the virulence profile and REP-PCR genotypes of Escherichia coli strains isolated from subclinical and clinical mastitis cases and dairy farm environments in Minas Gerais State, Brazil, to determine virulence factors and genotypes potentially associated with subclinical persistence in the udder. The virulence profile was obtained by the search for three virulence genes: lpfA (long polar fimbriae), fliC (flagella), and escN (type III secretion system). Subclinical isolates exhibited mainly the fliC gene (33.33%) and fliC + escN genes (30.30%). Clinical isolates exhibited mainly fliC + escN genes (50%) and environmental isolates the lpfA + escN genes (58.04%). Strains isolated from subclinical mastitis showed 6.75 times more positivity to fliC than environmental isolates. Thirty-four genotypes were observed in the REP-PCR analysis, and clinical mastitis isolates indicated more genetic proximity to dairy farm environment isolates than subclinical mastitis isolates. In conclusion, the results suggested that flagella may be an important virulence factor for mammary persistent E. coli infection in cattle, however, none of the E. coli REP-PCR genotypes were associated with subclinical infection.

Genomic Diversity, Virulence Gene, and Prophage Arrays of Bovine and Human Shiga Toxigenic and Enteropathogenic Escherichia coli Strains Isolated in Hungary

Escherichia coli belonging to the enterohemorrhagic (EHEC), Shiga toxin-producing (STEC) and atypical enteropathogenic (aEPEC) pathotypes are significant foodborne zoonotic pathogens posing serious health risks, with healthy cattle as their main reservoir. A representative sampling of Hungarian cattle farms during 2017-2018 yielded a prevalence of 6.5 and 5.8% for STEC and aEPEC out of 309 samples. The draft genomes of twelve STEC (of them 9 EHEC) and four aEPEC of bovine origin were determined. For comparative purposes, we also included 3 EHEC and 2 aEPEC strains of human origin, as well four commensal isolates and one extraintestinal pathogenic E. coli (ExPEC) obtained from animals in a final set of 26 strains for a WGS-based analysis. Apart from key virulence genes, these isolates harbored several additional virulence genes with arrays characteristic for the site of isolation. The most frequent insertion site of Shiga toxin (stx) encoding prophages was yehV for the Stx1 prophage and wrbA and sbcB for Stx2. For O157:H7 strains, the locus of enterocyte effacement pathogenicity island was present at the selC site, with integration at pheV for other serotypes, and pheU in the case of O26:H11 strains. Several LEE-negative STEC and aEPEC as well as commensal isolates carried additional prophages, with an average of ten prophage regions per isolate. Comparative phylogenomic analysis showed no clear separation between bovine and human lineages among the isolates characterized in the current study. Similarities in virulence gene arrays and close phylogenetic relations of bovine and human isolates underline the zoonotic potential of bovine aEPEC and STEC and emphasize the need for frequent monitoring of these pathogens in livestock.

Genomic characterization of high-risk E. coli and E. hormaechei clones recovered from a single tertiary-care hospital in Pakistan

Aims

Spread of carbapenem‐resistant Enterobacterales have become a global problem. We characterized extended‐spectrum β‐lactamase (ESBL)‐producing Enterobacterales from urinary tract infections cases from Allied Hospital Faisalabad, Pakistan.

Methods and Results

Eleven (22%, 11/50) ESBL‐producing Enterobacterales (Escherichia coli; n = 10 and Enterobacter hormaechei; n = 1) were recovered and processed through VITEK‐2, PCR, rep‐PCR followed by whole‐genome sequencing (WGS) of ESBL‐producing Ent. hormaechei and carbapenem‐resistant E. coli isolates. Plasmid transferability of bla_NDM‐1‐producers was assayed by conjugation experiments. All ESBL strains carried the bla_CTX‐M‐15 gene. Of these bla_CTX‐M‐15 producing E. coli, four also carried bla_NDM‐1 located on transferable plasmids. All E. coli strains belonged to ST448 and displayed similar genetic features including genes for antimicrobial resistance, heavy metal, biocides and virulence. Genomic features of a multidrug‐resistant (MDR) Ent. hormaechei were also reported for the first time in Pakistan.

Conclusion

Our findings indicate that bla_NDM‐1 producing E. coli ST448 is a multidrug, heavy metals and biocides‐resistant strain. Therefore, the screening of these isolates may be effective in limiting the MDR bacteria spread in hospitalized patients and within the community.

Significance and Impact of this Study

Spread of multi‐drug‐resistant ESBL‐producing bacteria in the clinical settings of Pakistan is a serious challenge and further limiting treatment options in the country. WGS could be used as a tool in the nationwide antibiotic surveillance programme to explore insights of spread and outbreak.

Strain specific motility patterns and surface adhesion of virulent and probiotic Escherichia coli

Bacterial motility provides the ability for bacterial dissemination and surface exploration, apart from a choice between surface colonisation and further motion. In this study, we characterised the movement trajectories of pathogenic and probiotic Escherichia coli strains (ATCC43890 and M17, respectively) at the landing stage (i.e., leaving the bulk and approaching the surface) and its correlation with adhesion patterns and efficiency. A poorly motile strain JM109 was used as a control. Using specially designed and manufactured microfluidic chambers, we found that the motion behaviour near surfaces drastically varied between the strains, correlating with adhesion patterns. We consider two bacterial strategies for effective surface colonisation: horizontal and vertical, based on the obtained results. The horizontal strategy demonstrated by the M17 strain is characterised by collective directed movements within the horizontal layer during a relatively long period and non-uniform adhesion patterns, suggesting co-dependence of bacteria in the course of adhesion. The vertical strategy demonstrated by the pathogenic ATCC43890 strain implies the individual movement of bacteria mainly in the vertical direction, a faster transition from bulk to near-surface swimming, and independent bacterial behaviour during adhesion, providing a uniform distribution over the surface.

An overview on mastitis-associated Escherichia coli: Pathogenicity, host immunity and the use of alternative therapies

Escherichia coli is one of the leading causes of bovine mastitis; it can cause sub-clinical, and clinical mastitis characterized by systemic changes, abnormal appearance of milk, and udder inflammation. E. coli pathogenicity in the bovine udder is due to the interaction between its virulence factors and the host factors; it was also linked to the presence of a new pathotype termed mammary pathogenic E. coli (MPEC). However, the presence of this pathotype is commonly debated. Its main virulence factor is the lipopolysaccharide (LPS) that is responsible for causing an endotoxic shock, and inducing a strong immune response by binding to the toll-like receptor 4 (TLR4), and stimulating the expression of chemokines (such as IL-8, and RANTES) and pro-inflammatory cytokines (such as IL-6, and IL-1β). This strong immune response could be used to develop alternative and safe approaches to control E. coli causing bovine mastitis by targeting pro-inflammatory cytokines that can damage the host tissue. The need for alternative treatments against E. coli is due to its ability to resist many conventional antibiotics, which is a huge challenge for curing ill animals. Therefore, the aim of this review was to highlight the pathogenicity of E. coli in the mammary gland, discuss the presence of the new putative pathotype, the mammary pathogenic E. coli (MPEC) pathotype, study the host's immune response, and the alternative treatments that are used against mastitis-associated E. coli.

Regulation of ydiV-induced biological characteristics permits Escherichia coli evasion of the host STING inflammatory response

Mammary gland-derived Escherichia coli (E. coli) is an important pathogen causing dairy cow mastitis. YdiV, with EAL-like domains, inhibits flagellum biogenesis and motility and affects c-di-GMP (eubacterial signaling molecule) concentration changes in bacteria. However, the pathophysiological role of ydiV in host-pathogen cross-talk still needs to be elucidated. In this study, firstly constructed the ydiV mutant (NJ17ΔydiV) and ydiV complementary (cNJ17ΔydiV) E. coli strains to infect mouse mammary epithelial cells (EpH4-Ev) and macrophages (RAW264.7), as well as mouse mammary glands, respectively. Then biological characteristics, adaptor molecules in related signaling pathways, proinflammatory cytokines and the extent of host cell damage was evaluated. Compared with E. coli NJ17 infected mice, the bacterial load in the mammary gland of NJ17ΔydiV was significantly lower and the extent of the damage was alleviated. Notably, the deletion of ydiV significantly aggravated cell damage in RAW264.7 cells and compared with the wild-type strain, NJ17ΔydiV significantly activated the STING/TBK1/IRF3 pathway in macrophages. In EpH4-Ev cells, although STING did not sense E. coli NJ17 invasion, IRF3 was activated by the NJ17ΔydiV strain. Taken together, ydiV deletion significantly affects a variety of biological characteristics and induces severe cell damage, while the STING/TBK1/IRF3 pathway actively participated in pathogen elimination in the host. This study highlights a new role for ydiV in E. coli infection and provides a foundation for further studies to better understand host-bacteria interactions and potential prophylactic strategies for infectious diseases.

Diversity of Non-O157 Shiga Toxin-Producing Escherichia coli Isolated from Cattle from Central and Southern Chile

Simple Summary

Cattle are the main reservoir of Shiga toxin-producing E. coli (STEC), foodborne pathogens that cause severe disease and outbreaks. However, not all STEC cause human illnesses or have the same virulence potential. Characterizing strains isolated worldwide allows insights into how strains spread and which isolates have a more significant risk potential. This study described STEC isolation rates from cattle in Chile and characterized 30 isolates. We obtained 93 STEC isolates from 56/446 (12.6%) fecal cattle samples. Then, 30 non-O157 STEC isolates were selected for complete characterization; we found isolates of 16 different sequence types and 17 serotypes. One isolate was resistant to tetracycline and carried resistance genes against the drug. Surveyed virulence genes (n = 31) were present from 13% to 100% of isolates, and one isolate carried 26/31 virulence genes. Most isolates (90%; 27/30) carried the stx2 gene, which is frequently linked to strains causing severe disease. A phylogenetic reconstruction demonstrated that isolates clustered based on serotypes, independent of their geographical origin (Central or Southern Chile). These results indicate that cattle in Chile carry a wide diversity of STEC potentially pathogenic for humans based on the presence of virulence genes.

Abstract

Cattle are the main reservoir of Shiga toxin-producing Escherichia coli (STEC), one of the world’s most important foodborne pathogens. The pathogen causes severe human diseases and outbreaks. This study aimed to identify and characterize non-O157 STEC isolated from cattle feces from central and southern Chile. We analyzed 446 cattle fecal samples and isolated non-O157 STEC from 12.6% (56/446); a total of 93 different isolates were recovered. Most isolates displayed β-glucuronidase activity (96.8%; 90/93) and fermented sorbitol (86.0%; 80/93), whereas only 39.8% (37/93) were resistant to tellurite. A subgroup of 30 representative non-O157 STEC isolates was selected for whole-genome sequencing and bioinformatics analysis. In silico analysis showed that they grouped into 16 different sequence types and 17 serotypes; the serotypes most frequently identified were O116:H21 and O168:H8 (13% each). A single isolate of serotype O26:H11 was recovered. One isolate was resistant to tetracycline and carried resistance genes tet(A) and tet(R); no other isolate displayed antimicrobial resistance or carried antimicrobial resistance genes. The intimin gene (eae) was identified in 13.3% (4/30) of the genomes and 90% (27/30) carried the stx2 gene. A phylogenetic reconstruction demonstrated that the isolates clustered based on serotypes, independent of geographical origin. These results indicate that cattle in Chile carry a wide diversity of STEC potentially pathogenic for humans based on the presence of critical virulence genes.

Role of long polar fimbriae type 1 and 2 in pathogenesis of mammary pathogenic Escherichia coli

Escherichia coli is a leading cause of bovine mastitis worldwide. The bacteria can rapidly grow in milk and elicit a strong lipopolysaccharide (LPS)/toll-like receptor-4 (TLR4)-dependent inflammatory response. Recently, the long polar fimbriae (LPF) were identified as a promising virulence factor candidate widely distributed in mammary pathogenic E. coli (MPEC) strains. Mammary pathogenic E. coli possess 2 lpf loci encoding LPF1 and LPF2, respectively. By deleting the major fimbrial subunit gene, lpfA, we found that both LPF1 and LPF2 contribute to MPEC adhesion, invasion, and biofilm formation in vitro. The lpf1A and lpf2A mutants showed reduced cytotoxicity in our in vitro cell infection model. Furthermore, we observed that LPF2 induced a mild TLR4-independent proinflammatory response. The median lethal dose (LD50) of both ∆lpf2A and ∆lpf1A∆lpf2A mutants to BALB/c mice increased by 0.38 and 0.15 logs, respectively, whereas that of wild-type strain MPJS13 was 8.69 logs. In contrast, LPF1 deficiency significantly enhanced the LPS/TLR4-mediated inflammatory response in mammary epithelial cells, and the LD50 of the mutant decreased to 8.18 logs. In conclusion, our data suggested that LPF are important in MPEC colonization of mammary cells and may provide a benefit to bacterial intracellular survival that induces persistent bovine mastitis.