Role of Plasmids in the Ecology and Evolution of "High-Risk" Extraintestinal Pathogenic Escherichia coli Clones

Major F plasmid clusters are linked with ColV and pUTI89-like marker genes in bloodstream isolates of Escherichia coli

BACKGROUND

F plasmids are abundant in E. coli, carrying a variety of genetic cargo involved in fitness, pathogenicity, and antimicrobial resistance. ColV and pUTI89-like plasmids have drawn attention for their potential roles in various forms of extra-intestinal pathogenicity. However, the rates of their carriage and the overall diversity of F plasmids in E. coli bloodstream infections (BSI E. coli) remain unknown.

METHODS

We performed a t-SNE-based cluster analysis of predicted F plasmids from a collection of 4711 BSI E. coli draft genomes to describe their diversity and abundance. We also screened them for markers of ColV and pUTI89-like plasmids, F plasmid replicon sequence types (RST) and E. coli sequence types (ST) to understand how genetic features were related to plasmid clusters.

RESULTS

Predicted F plasmids in BSI E. coli draft genomes were embedded within five major clusters based on a model of complete F plasmid sequences. Nearly half of the clustered sequences belonged to two major clusters, which were associated with ColV and pUTI89-like marker genes, respectively. Genomes from the ColV cluster featured F2:A-:B1 and F24:A-B1 RSTs in association with ST95, ST58 and ST88, whilst the pUTI89-like cluster was mostly F29:A-:B10 linked to ST73, ST69, ST95 and ST131. Plasmids associated with different lineages of ST131 formed additional major clusters, whilst F51:A-:B10 plasmids in ST73 were also common.

CONCLUSIONS

ColV and pUTI89-like plasmid markers are predominant in BSI E. coli that carry F plasmids. These markers are associated with distinct clusters of plasmids across diverse sequence types of E. coli. We hypothesise that their abundance in BSI E. coli is partially driven by carriage of backbone genes previously shown to contribute to virulence in models of bloodstream infection. Their carriage by pandemic E. coli STs suggests clonal expansion also plays a role in their success in BSI. Ecological pathways via which these plasmids evolve, and spread are likely to be distinct as other studies show ColV is strongly associated with poultry and food animal production, whereas pUTI89-like plasmids appear to be mostly human-restricted.

CRISPR-Cas9-mediated IncF plasmid curing in extraintestinal pathogenic Escherichia coli

IMPORTANCE

Understanding the role of IncF plasmids in the success of drug-resistant bacteria has far-reaching implications for tackling antibiotic resistance. The study's use of a novel CRISPR-Cas9-mediated plasmid-curing system provides a precision tool for dissecting the specific impact of IncF plasmids on ExPEC clones, especially high-risk, multidrug-resistant strains like ST131, ST1193, and ST410. The study offers a crucial stepping stone for future research into understanding how these plasmids influence more complex aspects of bacterial behavior, such as cell invasion and in vivo fitness.

Identification of plasmids in avian-associated Escherichia coli using nanopore and illumina sequencing

BACKGROUND

Avian pathogenic Escherichia coli (APEC) are the causative agents of colibacillosis in chickens, a disease which has significant economic impact on the poultry industry. Large plasmids detected in APEC are known to contribute to strain diversity for pathogenicity and antimicrobial resistance, but there could be other plasmids that are missed in standard analysis. In this study, we determined the impact of sequencing and assembly factors for the detection of plasmids in an E. coli whole genome sequencing project.

RESULTS

Hybrid assembly (Illumina and Nanopore) combined with plasmid DNA extractions allowed for detection of the greatest number of plasmids in E. coli, as detected by MOB-suite software. In total, 79 plasmids were identified in 19 E. coli isolates. Hybrid assemblies were robust and consistent in quality regardless of sequencing kit used or if long reads were filtered or not. In contrast, long read only assemblies were more variable and influenced by sequencing and assembly parameters. Plasmid DNA extractions allowed for the detection of physically smaller plasmids, but when averaged over 19 isolates did not significantly change the overall number of plasmids detected.

CONCLUSIONS

Hybrid assembly can be reliably used to detect plasmids in E. coli, especially if researchers are focused on large plasmids containing antimicrobial resistance genes and virulence factors. If the goal is comprehensive detection of all plasmids, particularly if smaller sized vectors are desired for biotechnology applications, the addition of plasmid DNA extractions to hybrid assemblies is prudent. Long read sequencing is sufficient to detect many plasmids in E. coli, however, it is more prone to errors when expanded to analyze a large number of isolates.

HlyF, an underestimated virulence factor of uropathogenic Escherichia coli

OBJECTIVES

Urinary tract infections (UTIs) are primarily caused by uropathogenic Escherichia coli (UPEC). This study aims to elucidate the role of the virulence factor HlyF in the epidemiology and pathophysiology of UTIs and investigate the dissemination of plasmids carrying the hlyF gene.

METHODS

An epidemiological analysis was conducted on a representative collection of 225 UPEC strains isolated from community-acquired infections. Selected hlyF+ strains were fully sequenced using a combination of Illumina and Nanopore technologies. To investigate the impact of HlyF, a murine model of UTI was utilized to compare clinical signs, bacterial loads in the bladder, kidney, and spleen, onset of bacteraemia, and inflammation through cytokine quantification among wild-type hlyF+ strains, isogenic mutants, and complemented mutants.

RESULTS

Our findings demonstrate that 20% of UPEC encode the HlyF protein. These hlyF+ UPEC strains exhibited enhanced virulence, frequently leading to pyelonephritis accompanied by bloodstream infections. Unlike typical UPEC strains, hlyF+ UPEC strains demonstrate a broader phylogroup distribution and possess a unique array of virulence factors and antimicrobial resistance genes, primarily carried by ColV-like plasmids. In the murine UTI model, expression of HlyF was linked to the UPECs' capacity to induce urosepsis and elicit an exacerbated inflammatory response, setting them apart from typical UPEC strains.

DISCUSSION

Overall, our results strongly support the notion that HlyF serves as a significant virulence factor for UPECs, and the dissemination of ColV-like plasmids encoding HlyF warrants further investigation.

Commensal Fitness Advantage May Contribute to the Global Dissemination of Multidrug-Resistant Lineages of Bacteria-The Case of Uropathogenic E. coli

It is widely accepted that favorable fitness in commensal colonization is one of the prime facilitators of clonal dissemination in bacteria. The question arises as to what kind of fitness advantage may be wielded by uropathogenic strains of the two predominant fluoroquinolone- and multidrug-resistant clonal groups of E. coli-ST131-H30 and ST1193, which has permitted their unprecedented pandemic-like global expansion in the last few decades. The colonization-associated genes' content, carriage of low-cost plasmids, and integrons with weak promoters could certainly contribute to the fitness of the pandemic groups, although those genetic factors are common among other clonal groups as well. Also, ST131-H30 and ST1193 strains harbor fluoroquinolone-resistance conferring mutations targeting serine residues in DNA gyrase (GyrA-S83) and topoisomerase IV (ParC-S80) that, in those clonal backgrounds, might result in a commensal fitness benefit, i.e., beyond the antibiotic resistance per se. This fitness gain might have contributed not only to the widespread dissemination of these major clones in the healthcare setting but also to their long-term colonization of healthy individuals and, thus, circulation in the community, even in a low or no fluoroquinolone use environment. This evolutionary shift affecting commensal E. coli, initiated by mutations co-favorable in both antibiotics-treated patients and healthy individuals warrants more in-depth studies to monitor further changes in the epidemiological situation and develop effective measures to reduce the antibiotic resistance spread.

Epistatic interactions between the high pathogenicity island and other iron uptake systems shape Escherichia coli extra-intestinal virulence

The intrinsic virulence of extra-intestinal pathogenic Escherichia coli is associated with numerous chromosomal and/or plasmid-borne genes, encoding diverse functions such as adhesins, toxins, and iron capture systems. However, the respective contribution to virulence of those genes seems to depend on the genetic background and is poorly understood. Here, we analyze genomes of 232 strains of sequence type complex STc58 and show that virulence (quantified in a mouse model of sepsis) emerged in a sub-group of STc58 due to the presence of the siderophore-encoding high-pathogenicity island (HPI). When extending our genome-wide association study to 370 Escherichia strains, we show that full virulence is associated with the presence of the aer or sit operons, in addition to the HPI. The prevalence of these operons, their co-occurrence and their genomic location depend on strain phylogeny. Thus, selection of lineage-dependent specific associations of virulence-associated genes argues for strong epistatic interactions shaping the emergence of virulence in E. coli.

The Significance of Epidemic Plasmids in the Success of Multidrug-Resistant Drug Pandemic Extraintestinal Pathogenic Escherichia coli

Epidemic IncF plasmids have been pivotal in the selective advantage of multidrug-resistant (MDR) extraintestinal pathogenic Escherichia coli (ExPEC). These plasmids have offered several advantages to their hosts that allowed them to coevolve with the bacterial host genomes and played an integral role in the success of ExPEC. IncF plasmids are large, mosaic, and often contain various types of antimicrobial resistance (AMR) and virulence associated factor (VAF) genes. The presence of AMR, VAF genes, several addition/restriction systems combined with truncated transfer regions, led to the fixation of IncF plasmids in certain ExPEC MDR clones, such as ST131 and ST410. IncF plasmids entered the ST131 ancestral lineage in the mid 1900s and different ST131 clade/CTX-M plasmid combinations coevolved over time. The IncF_CTX-M-15/ST131-C2 subclade combination emerged during the early 2000s, spread rapidly across the globe, and is one of the greatest clone/plasmid successes of the millennium. The ST410-B3 subclade containing bla_CTX-M-15 incorporated the NDM-5 carbapenemase gene into existing IncF platforms, providing an additional positive selective advantage that included the carbapenems. A "plasmid-replacement" clade scenario occurred in the histories of ST131 and ST410 as different subclades gained different AMR genes on different IncF platforms. The use of antimicrobial agents will generate selection pressures that enhance the risks for the continuous emergence of MDR ExPEC clone/IncF plasmid combinations. The reasons for clade/IncF replacements and associations between certain clades and specific IncF plasmid types are unknown. Such information will aid in designing management and prevention strategies to combat AMR.

Pathogenome comparison and global phylogeny of Escherichia coli ST1485 strains

Escherichia coli ST1485 strains belong to the clinically important phylogroup F and have disseminated worldwide in humans, animals, and the environment. Here, we elucidated the pathogenome of a global collection of E. coli ST1485 isolates from diverse sources retrieved from public databases and a high-quality sequenced complete genome of colistin-resistant E. coli strain CFSAN061771 isolated from raw milk cheese which designated as a reference strain. CFSAN061771 belongs to O83:H42-ST1485 pathotype and carries a conjugative ColV plasmid, pCFSAN061771_01, combining extraintestinal virulence genes (ompt, sitA, iroN, etsC, traT, cvaC, hylF, iss, tsh, mchf, iucC, iutA) with a multidrug resistance island (blaTEM-1, aph(6)-Id, aph(3″)-Ib, sul2, dfrA14). Comparative genomic analysis revealed a high frequency of pCFSAN061771_01-like plasmids in E. coli ST1485. A notable evolutionary genetic event in E. coli ST1485 strains is the acquisition of a pCFSAN061771_02-like plasmid, which confers resistance to several antimicrobials, tellurium, and quaternary ammonium compounds. The identical virulence and antibiotic resistance profiles identified in some human and animal strains are worrisome. This is the first study to emphasize the significance of E. coli ST1485 as a global high-risk virulent and multidrug-resistant clone with zoonotic potential.

Effects of TolC on the pathogenicity of porcine extraintestinal pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC) is a well-known critical pathogenic zoonosis that causes extraintestinal infections in humans and animals by affecting their immune organs. Recently, research on the outer membrane protein of E. coli, tolerant colicin (TolC), a virulent protein in the formation of the ExPEC efflux pump, has been an attractive subject. However, the pathogenic mechanisms remain unclear. This study aimed to explore the role of TolC in the pathogenesis of the ExPEC strain PPECC42; a complementation strain (Cm-TolC) and an isogenic mutant (ΔTolC) were constructed. Loss of TolC drastically impaired the virulence of ExPEC in an experimental mouse model. ΔTolC showed a substantial decrease in the porcine aortic vascular endothelial cell (PAVEC) adherence, invasion, and pro-inflammatory response, in contrast to that of the wild type, with a reduced survival ratio in both the bacterial load and whole blood in mice. ΔTolC also showed decreased expression of necroptosis signals such as receptor-interacting protein kinase 1, phosphorylated mixed-lineage kinase domain-like protein, and mitochondrial proteins such as phosphoglycerate mutase family member 5. Our data suggest that TolC is closely associated with ExPEC pathogenesis. These results provide scientific grounds for exploring the potential of TolC as an effective drug target for controlling ExPEC infection, screening new inhibitors, and developing new drugs. This will allow for further prevention and control of ExPEC infection.

Genomic and Temporal Trends in Canine ExPEC Reflect Those of Human ExPEC

Companion animals and humans are known to share extraintestinal pathogenic Escherichia coli (ExPEC), but the extent of E. coli sequence types (STs) that cause extraintestinal diseases in dogs is not well understood. Here, we generated whole-genome sequences of 377 ExPEC collected by the University of Melbourne Veterinary Hospital from dogs over an 11-year period from 2007 to 2017. Isolates were predominantly from urogenital tract infections (219, 58.1%), but isolates from gastrointestinal specimens (51, 13.5%), general infections (72, 19.1%), and soft tissue infections (34, 9%) were also represented. A diverse collection of 53 STs were identified, with 18 of these including at least five sequences. The five most prevalent STs were ST372 (69, 18.3%), ST73 (31, 8.2%), ST127 (22, 5.8%), ST80 (19, 5.0%), and ST58 (14, 3.7%). Apart from ST372, all of these are prominent human ExPEC STs. Other common ExPEC STs identified included ST12, ST131, ST95, ST141, ST963, ST1193, ST88, and ST38. Virulence gene profiles, antimicrobial resistance carriage, and trends in plasmid carriage for specific STs were generally reflective of those seen in humans. Many of the prominent STs were observed repetitively over an 11-year time span, indicating their persistence in the dogs in the community, which is most likely driven by household sharing of E. coli between humans and their pets. The case of ST372 as a dominant canine lineage observed sporadically in humans is flagged for further investigation. IMPORTANCE Pathogenic E. coli that causes extraintestinal infections (ExPEC) in humans and canines represents a significant burden in hospital and veterinary settings. Despite the obvious interrelationship between dogs and humans favoring both zoonotic and anthropozoonotic infections, whole-genome sequencing projects examining large numbers of canine-origin ExPEC are lacking. In support of anthropozoonosis, we found that most STs from canine infections are dominant human ExPEC STs (e.g., ST73, ST127, ST131) with similar genomic traits, such as plasmid carriage and virulence gene burden. In contrast, we identified ST372 as the dominant canine ST and a sporadic cause of infection in humans, supporting zoonotic transfer. Furthermore, we highlight that, as is the case in humans, STs in canine disease are consistent over time, implicating the gastrointestinal tract as the major community reservoir, which is likely augmented by exposure to human E. coli via shared diet and proximity.

A role for ColV plasmids in the evolution of pathogenic Escherichia coli ST58

Escherichia coli ST58 has recently emerged as a globally disseminated uropathogen that often progresses to sepsis. Unlike most pandemic extra-intestinal pathogenic E. coli (ExPEC), which belong to pathogenic phylogroup B2, ST58 belongs to the environmental/commensal phylogroup B1. Here, we present a pan-genomic analysis of a global collection of 752 ST58 isolates from diverse sources. We identify a large ST58 sub-lineage characterized by near ubiquitous carriage of ColV plasmids, which carry genes encoding virulence factors, and by a distinct accessory genome including genes typical of the Yersiniabactin High Pathogenicity Island. This sub-lineage includes three-quarters of all ExPEC sequences in our study and has a broad host range, although poultry and porcine sources predominate. By contrast, strains isolated from cattle often lack ColV plasmids. Our data indicate that ColV plasmid acquisition contributed to the divergence of the major ST58 sub-lineage, and different sub-lineages inhabit poultry, swine and cattle.

Close genetic linkage between human and companion animal extraintestinal pathogenic Escherichia coli ST127

Escherichia coli ST127, a recently emerged global pathogen noted for high virulence gene carriage, is a leading cause of urinary tract and blood stream infections. ST127 is frequently isolated from humans and companion animals; however, it is unclear if they are distinct or related populations of ST127. We performed a phylogenomic analysis of 299 E. coli ST127 of diverse epidemiological origin to characterize their population structure, genetic determinants of virulence, antimicrobial resistance, and repertoire of mobile genetic elements with a focus on plasmids. The core gene phylogeny was divided into 13 clusters, the largest of which (BAP4) contained the majority of human and companion animal origin isolates. This dominant cluster displayed genetic differences to the remainder of the phylogeny, most notably alternative gene alleles encoding important virulence factors including lipid A, flagella, and K capsule. Furthermore, numerous close genetic linkages (<30 SNPs) between human and companion animal isolates were observed within the cluster. Carriage of antimicrobial resistance genes in the collection was limited, but virulence gene carriage was extensive. We found evidence of pUTI89-like virulence plasmid carriage in over a third of isolates, localised to four of the major phylogenetic clusters. Our study supports global scale repetitive transfer of E. coli ST127 lineages between humans and companion animals, particularly within the dominant BAP4 cluster.

Complete sequence of classic F-type plasmid pRK100 shows unique conservation over time and geographic location

Plasmids exhibit great diversity of gene content and host ranges and are famous for quick adaptation to the genetic background of the bacterial host cell. In addition to observing ever evolving plasmids, some plasmids have conserved backbones: a stable core composition and arrangement of genes in addition to variable regions. There are a few reports of extremely conserved plasmids. Here we report the complete sequence of pRK100 plasmid - a large, well-characterized conjugative F-like plasmid found in an Escherichia coli strain isolated from a urinary tract infection patient in 1990. The sequence shows that the 142 kb-long pRK100 plasmid is nearly identical to plasmids circulating in distant geographical locations and found in different host E. coli strains between 2007 and 2017. We also performed additional functional characterization of pRK100. Our results showed that pRK100 does not have a strong pathogenicity phenotype in porcine primary bladder epithelial cell culture. Moreover, the conjugation of pRK100 seems to strongly depend on recipient characteristics. These observations and identification of the pRK100 plasmid in different strain genotypes leave the extreme sequence conservation and broad distribution of this plasmid unexplained.