Limited Transmission ofblaCTX-M-9-Type-Positive Escherichia coli between Humans and Poultry in Vietnam

ABSTRACTWe examined whetherEscherichia coliisolates that produce CTX-M-9-type extended-spectrum β-lactamases (ESBL) are transferred between humans and chickens in a Vietnamese community. The phylogenetic group compositions, sequence types, antimicrobial resistance profiles, the prevalence of plasmid antibiotic resistance genes, and the plasmid replicon types generally differed between the human and chickenE. coliisolates. Our results suggest that transmission of theblaCTX-M-9-positiveE. colibetween humans and poultry was limited.

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F Plasmids Are the Major Carriers of Antibiotic Resistance Genes in Human-Associated Commensal Escherichia coli

mSphere ◽

10.1128/msphere.00709-20 ◽

2020 ◽

Vol 5 (4) ◽

Author(s):

Craig Stephens ◽

Tyler Arismendi ◽

Megan Wright ◽

Austin Hartman ◽

Andres Gonzalez ◽

...

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Transposable Elements ◽

Dna Sequencing ◽

Resistance Genes ◽

Bacterial Pathogens ◽

Acquired Resistance ◽

Antibiotic Resistance Genes ◽

Content Type ◽

E Coli

ABSTRACT The evolution and propagation of antibiotic resistance by bacterial pathogens are significant threats to global public health. Contemporary DNA sequencing tools were applied here to gain insight into carriage of antibiotic resistance genes in Escherichia coli, a ubiquitous commensal bacterium in the gut microbiome in humans and many animals, and a common pathogen. Draft genome sequences generated for a collection of 101 E. coli strains isolated from healthy undergraduate students showed that horizontally acquired antibiotic resistance genes accounted for most resistance phenotypes, the primary exception being resistance to quinolones due to chromosomal mutations. A subset of 29 diverse isolates carrying acquired resistance genes and 21 control isolates lacking such genes were further subjected to long-read DNA sequencing to enable complete or nearly complete genome assembly. Acquired resistance genes primarily resided on F plasmids (101/153 [67%]), with smaller numbers on chromosomes (30/153 [20%]), IncI complex plasmids (15/153 [10%]), and small mobilizable plasmids (5/153 [3%]). Nearly all resistance genes were found in the context of known transposable elements. Very few structurally conserved plasmids with antibiotic resistance genes were identified, with the exception of an ∼90-kb F plasmid in sequence type 1193 (ST1193) isolates that appears to serve as a platform for resistance genes and may have virulence-related functions as well. Carriage of antibiotic resistance genes on transposable elements and mobile plasmids in commensal E. coli renders the resistome highly dynamic. IMPORTANCE Rising antibiotic resistance in human-associated bacterial pathogens is a serious threat to our ability to treat many infectious diseases. It is critical to understand how acquired resistance genes move in and through bacteria associated with humans, particularly for species such as Escherichia coli that are very common in the human gut but can also be dangerous pathogens. This work combined two distinct DNA sequencing approaches to allow us to explore the genomes of E. coli from college students to show that the antibiotic resistance genes these bacteria have acquired are usually carried on a specific type of plasmid that is naturally transferrable to other E. coli, and likely to other related bacteria.

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bla OXA-48-like genome architecture among carbapenemase-producing Escherichia coli and Klebsiella pneumoniae in the Netherlands

Microbial Genomics ◽

10.1099/mgen.0.000512 ◽

2021 ◽

Vol 7 (5) ◽

Author(s):

Antoni P. A. Hendrickx ◽

Fabian Landman ◽

Angela de Haan ◽

Sandra Witteveen ◽

Marga G. van Santen-Verheuvel ◽

...

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

The Netherlands ◽

Resistance Genes ◽

Type Species ◽

Antibiotic Resistance Genes ◽

Gene Content ◽

Content Type ◽

E Coli ◽

Link Type

Carbapenem-hydrolysing enzymes belonging to the OXA-48-like group are encoded by bla OXA-48-like alleles and are abundant among Enterobacterales in the Netherlands. Therefore, the objective here was to investigate the characteristics, gene content and diversity of the bla OXA-48-like carrying plasmids and chromosomes of Escherichia coli and Klebsiella pneumoniae collected in the Dutch national surveillance from 2014 to 2019 in comparison with genome sequences from 29 countries. A combination of short-read genome sequencing with long-read sequencing enabled the reconstruction of 47 and 132 complete bla OXA-48-like plasmids for E. coli and K. pneumoniae , respectively. Seven distinct plasmid groups designated as pOXA-48-1 to pOXA-48-5, pOXA-181 and pOXA-232 were identified in the Netherlands which were similar to internationally reported plasmids obtained from countries from North and South America, Europe, Asia and Oceania. The seven plasmid groups varied in size, G+C content, presence of antibiotic resistance genes, replicon family and gene content. The pOXA-48-1 to pOXA-48-5 plasmids were variable, and the pOXA-181 and pOXA-232 plasmids were conserved. The pOXA-48-1, pOXA-48-2, pOXA-48-3 and pOXA-48-5 groups contained a putative conjugation system, but this was absent in the pOXA-48-4, pOXA-181 and pOXA-232 plasmid groups. pOXA-48 plasmids contained the PemI antitoxin, while the pOXA-181 and pOXA-232 plasmids did not. Furthermore, the pOXA-181 plasmids carried a virB2-virB3-virB9-virB10-virB11 type IV secretion system, while the pOXA-48 plasmids and pOXA-232 lacked this system. A group of non-related pOXA-48 plasmids from the Netherlands contained different resistance genes, non-IncL-type replicons or no replicons. Whole genome multilocus sequence typing revealed that the bla OXA-48-like plasmids were found in a wide variety of genetic backgrounds in contrast to chromosomally encoded bla OXA-48-like alleles. Chromosomally localized bla OXA-48 and bla OXA-244 alleles were located on genetic elements of variable sizes and comprised regions of pOXA-48 plasmids. The bla OXA-48-like genetic element was flanked by a direct repeat upstream of IS1R, and was found at multiple locations in the chromosomes of E. coli . Lastly, K. pneumoniae isolates carrying bla OXA-48 or bla OXA-232 were mostly resistant for meropenem, whereas E. coli bla OXA-48, bla OXA-181 and chromosomal bla OXA-48 or bla OXA-244 isolates were mostly sensitive. In conclusion, the overall bla OXA-48-like plasmid population in the Netherlands is conserved and similar to that reported for other countries, confirming global dissemination of bla OXA-48-like plasmids. Variations in size, presence of antibiotic resistance genes and gene content impacted pOXA-48, pOXA-181 and pOXA-232 plasmid architecture.

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Phylum barrier and Escherichia coli intra-species phylogeny drive the acquisition of antibiotic-resistance genes

Microbial Genomics ◽

10.1099/mgen.0.000489 ◽

2021 ◽

Vol 7 (8) ◽

Author(s):

Marie Petitjean ◽

Bénédicte Condamine ◽

Charles Burdet ◽

Erick Denamur ◽

Etienne Ruppé

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Resistance Genes ◽

Type Species ◽

Antibiotic Resistance Genes ◽

Resistance Pattern ◽

Content Type ◽

E Coli ◽

Link Type ◽

Specific Distribution

Escherichia coli is a ubiquitous bacterium that has been widely exposed to antibiotics over the last 70 years. It has adapted by acquiring different antibiotic-resistance genes (ARGs), the census of which we aim to characterize here. To do so, we analysed 70 301 E. coli genomes obtained from the EnteroBase database and detected 1 027 651 ARGs using the AMRFinder, Mustard and ResfinderFG ARG databases. We observed a strong phylogroup and clonal lineage specific distribution of some ARGs, supporting the argument for epistasis between ARGs and the strain genetic background. However, each phylogroup had ARGs conferring a similar antibiotic class resistance pattern, indicating phenotypic adaptive convergence. The G+C content or the type of ARG was not associated with the frequency of the ARG in the database. In addition, we identified ARGs from anaerobic, non- Proteobacteria bacteria in four genomes of E. coli , supporting the hypothesis that the transfer between anaerobic bacteria and E. coli can spontaneously occur but remains exceptional. In conclusion, we showed that phylum barrier and intra-species phylogenetic history are major drivers of the acquisition of a resistome in E. coli .

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Discovery ofmcr-1-Mediated Colistin Resistance in a Highly VirulentEscherichia coliLineage

mSphere ◽

10.1128/msphere.00486-18 ◽

2018 ◽

Vol 3 (5) ◽

Cited By ~ 12

Author(s):

Brian M. Forde ◽

Hosam M. Zowawi ◽

Patrick N. A. Harris ◽

Leah Roberts ◽

Emad Ibrahim ◽

...

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Resistance Genes ◽

Antibiotic Resistance Genes ◽

Neonatal Meningitis ◽

Colistin Resistance ◽

Content Type ◽

E Coli ◽

Virulence Potential ◽

High Virulence

ABSTRACTResistance to last-line polymyxins mediated by the plasmid-borne mobile colistin resistance gene (mcr-1) represents a new threat to global human health. Here we present the complete genome sequence of anmcr-1-positive multidrug-resistantEscherichia colistrain (MS8345). We show that MS8345 belongs to serotype O2:K1:H4, has a large 241,164-bp IncHI2 plasmid that carries 15 other antibiotic resistance genes (including the extended-spectrum β-lactamaseblaCTX-M-1) and 3 putative multidrug efflux systems, and contains 14 chromosomally encoded antibiotic resistance genes. MS8345 also carries a large ColV-like virulence plasmid that has been associated withE. colibacteremia. Whole-genome phylogeny revealed that MS8345 clusters within a discrete clade in the sequence type 95 (ST95) lineage, and MS8345 is very closely related to the highly virulent O45:K1:H4 clone associated with neonatal meningitis. Overall, the acquisition of a plasmid carrying resistance to colistin and multiple other antibiotics in this virulentE. colilineage is concerning and might herald an era where the empirical treatment of ST95 infections becomes increasingly more difficult.IMPORTANCEEscherichia coliST95 is a globally disseminated clone frequently associated with bloodstream infections and neonatal meningitis. However, the ST95 lineage is defined by low levels of drug resistance amongst clinical isolates, which normally provides for uncomplicated treatment options. Here, we provide the first detailed genomic analysis of anE. coliST95 isolate that has both high virulence potential and resistance to multiple antibiotics. Using the genome, we predicted its virulence and antibiotic resistance mechanisms, which include resistance to last-line antibiotics mediated by the plasmid-bornemcr-1gene. Finding an ST95 isolate resistant to nearly all antibiotics that also has a high virulence potential is of major clinical importance and underscores the need to monitor new and emerging trends in antibiotic resistance development in this important global lineage.

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The Conjugation Window in an Escherichia coli K-12 Strain with an IncFII Plasmid

Applied and Environmental Microbiology ◽

10.1128/aem.00948-20 ◽

2020 ◽

Vol 86 (17) ◽

Cited By ~ 1

Author(s):

Brendan Headd ◽

Scott A. Bradford

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Antibiotic Resistance Genes ◽

Time Frame ◽

Environmental Aspect ◽

Content Type ◽

E Coli ◽

Donor Cells ◽

K 12 ◽

Regulatory Controls

ABSTRACT Many studies have examined the role that conjugation plays in disseminating antibiotic resistance genes in bacteria. However, relatively little research has quantitively examined and modeled the dynamics of conjugation under growing and nongrowing conditions beyond a couple of hours. We therefore examined growing and nongrowing cultures of Escherichia coli over a 24-h period to understand the dynamics of bacterial conjugation in the presence and absence of antibiotics with pUUH239.2, an IncFII plasmid containing multiantibiotic- and metal-resistant genes. Our data indicate that conjugation occurs after E. coli cells divide and before they have transitioned to a nongrowing phase. The result is that there is only a small window of opportunity for E. coli to conjugate with pUUH239.2 under both growing and nongrowing conditions. Only a very small percentage of the donor cells likely are capable of even undergoing conjugation, and not all transconjugants can become donor cells due to molecular regulatory controls and not being in the correct growth phase. Once a growing culture enters stationary phase, the number of capable donor cells decreases rapidly and conjugation slows to produce a plateau. Published models did not provide accurate descriptions of conjugation under nongrowing conditions. We present here a modified modeling approach that accurately describes observed conjugation behavior under growing and nongrowing conditions. IMPORTANCE There has been growing interest in horizontal gene transfer of antibiotic resistance plasmids as the antibiotic resistance crisis has worsened over the years. Most studies examining conjugation of bacterial plasmids focus on growing cultures of bacteria for short periods, but in the environment, most bacteria grow episodically and at much lower rates than in the laboratory. We examined conjugation of an IncFII antibiotic resistance plasmid in E. coli under growing and nongrowing conditions to understand the dynamics of conjugation under which the plasmid is transferred. We found that conjugation occurs in a narrow time frame when E. coli is transitioning from a growing to nongrowing phase and that the conjugation plateau develops because of a lack of capable donor cells in growing cultures. From an environmental aspect, our results suggest that episodic growth in nutrient-depleted environments could result in more conjugation than sustained growth in a nutrient rich environment.

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Detection of Phylogenetic Groups and Drug Resistance Genes of Escherichia coli Causing Urinary Tract Infection in Southwest Iran

Jundishapur Journal of Microbiology ◽

10.5812/jjm.112547 ◽

2021 ◽

Vol 14 (2) ◽

Author(s):

Mostafa Boroumand Boroumand ◽

Mohsen Naghmachi ◽

Mohammad Amin Ghatee

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Urinary Tract ◽

Resistance Genes ◽

Antibiotic Resistance Genes ◽

Phylogenetic Group ◽

Phylogenetic Groups ◽

E Coli ◽

Pcr Method ◽

Tract Infections

Background: Many bacteria can cause urinary tract infections (UTIs), among which Escherichia coli is the most common causative agent. E. coli strains are divided into eight phylogenetic groups based on the new Quadroplex-PCR method, which are different in terms of patterns of resistance to antibiotics, virulence, and environmental characteristics. Objectives: This study aimed to determine the phylogenetic groups and the prevalence of drug resistance genes in E. coli strains causing UTIs. Methods: In this descriptive cross-sectional study, 129 E. coli isolates obtained from the culture of patients with UTIs were evaluated for phylogenetic groups using the new method of Clermont et al. The identification of phylogenetic groups and antibiotic resistance genes was performed using the multiplex polymerase chain reaction (PCR) method. Results: In this study, concerning the distribution of phylogenetic groups among E. coli isolates, the phylogenetic group B2 (36.4%) was the most common phylogenetic group, followed by phylogroups C (13.2%), clade I (10.1%), D (9.3%), and A (3.1%) while groups B1 and F were not observed in any of the isolates, and 20.2% had an unknown state. Also, out of 129 E. coli isolates, the total frequency of tetA, tetB, sul1, sul2, CITM, DfrA, and qnr resistance genes was 59.7%, 66.7, 69, 62, 30.2, 23.3, and 20.2%, respectively. In this study, there was a significant relationship between antibiotics (P = 0.026), cefotaxime (P = 0.003), and nalidixic acid (P = 0.044) and E. coli phylogenetic groups. No significant relationship was observed between E. coli phylogenetic groups and antibiotic resistance genes. Conclusions: The results of this study showed that strains belonging to group B2 had the highest prevalence among other phylogroups, and also, the frequency of antibiotic resistance genes and drug-resistant isolates had a higher prevalence in this phylogroup. These results show that phylogroup B2 has a more effective role in causing urinary tract infections compared to other phylogroups, and this phylogroup can be considered a genetic reservoir of antibiotic resistance.

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Draft Genome Sequences of Cefepime-Resistant and -Susceptible Escherichia coli Strains and Imipenem-Resistant and -Susceptible Pseudomonas aeruginosa Strains

Microbiology Resource Announcements ◽

10.1128/mra.00749-21 ◽

2021 ◽

Vol 10 (48) ◽

Author(s):

Kendra Batchelder ◽

Liz Ward ◽

Elsa Collins ◽

Caitlin Miles ◽

Stefania Palm ◽

...

Keyword(s):

Escherichia Coli ◽

Pseudomonas Aeruginosa ◽

Antibiotic Resistance ◽

Resistance Genes ◽

Draft Genome ◽

Antibiotic Resistance Genes ◽

Genome Sequences ◽

Content Type ◽

E Coli

Draft genome sequences of Escherichia coli and Pseudomonas aeruginosa strains collected from clinical infections were used to determine the prevalence of newly emerging antibiotic resistance genes in Maine. Comparisons between cefepime-resistant and -susceptible E. coli strains and imipenem-resistant and -susceptible P. aeruginosa strains are being conducted.

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Comparative Genome Analysis of an Extensively Drug-Resistant Isolate of Avian Sequence Type 167 Escherichia coli Strain Sanji with Novel In Silico Serotype O89b:H9

mSystems ◽

10.1128/msystems.00242-18 ◽

2019 ◽

Vol 4 (1) ◽

Cited By ~ 5

Author(s):

Xiancheng Zeng ◽

Xuelin Chi ◽

Brian T. Ho ◽

Damee Moon ◽

Christine Lambert ◽

...

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Resistance Genes ◽

In Silico ◽

Antibiotic Resistance Genes ◽

Secretion System ◽

Sequence Type ◽

Content Type ◽

E Coli ◽

Multiple Paths

ABSTRACT Extensive drug resistance (XDR) is an escalating global problem. Escherichia coli strain Sanji was isolated from an outbreak of pheasant colibacillosis in Fujian province, China, in 2011. This strain has XDR properties, exhibiting sensitivity to carbapenems but no other classes of known antibiotics. Whole-genome sequencing revealed a total of 32 known antibiotic resistance genes, many associated with insertion sequence 26 (IS26) elements. These were found on the Sanji chromosome and 2 of its 6 plasmids, pSJ_255 and pSJ_82. The Sanji chromosome also harbors a type 2 secretion system (T2SS), a type 3 secretion system (T3SS), a type 6 secretion system (T6SS), and several putative prophages. Sanji and other ST167 strains have a previously uncharacterized O-antigen (O89b) that is most closely related to serotype O89 as determined on the basis of analysis of the wzm-wzt genes and in silico serotyping. This O89b-antigen gene cluster was also found in the genomes of a few other pathogenic sequence type 617 (ST617) and ST10 complex strains. A time-scaled phylogeny inferred from comparative single nucleotide variant analysis indicated that development of these O89b-containing lineages emerged about 30 years ago. Comparative sequence analysis revealed that the core genome of Sanji is nearly identical to that of several recently sequenced strains of pathogenic XDR E. coli belonging to the ST167 group. Comparison of the mobile elements among the different ST167 genomes revealed that each genome carries a distinct set of multidrug resistance genes on different types of plasmids, indicating that there are multiple paths toward the emergence of XDR in E. coli. IMPORTANCE E. coli strain Sanji is the first sequenced and analyzed genome of the recently emerged pathogenic XDR strains with sequence type ST167 and novel in silico serotype O89b:H9. Comparison of the genomes of Sanji with other ST167 strains revealed distinct sets of different plasmids, mobile IS elements, and antibiotic resistance genes in each genome, indicating that there exist multiple paths toward achieving XDR. The emergence of these pathogenic ST167 E. coli strains with diverse XDR capabilities highlights the difficulty of preventing or mitigating the development of XDR properties in bacteria and points to the importance of better understanding of the shared underlying virulence mechanisms and physiology of pathogenic bacteria.

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Limited and Strain-Specific Transcriptional and Growth Responses to Acquisition of a Multidrug Resistance Plasmid in Genetically Diverse Escherichia coli Lineages

mSystems ◽

10.1128/msystems.00083-21 ◽

2021 ◽

Vol 6 (2) ◽

Author(s):

Steven Dunn ◽

Laura Carrilero ◽

Michael Brockhurst ◽

Alan McNally

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Multidrug Resistance ◽

Resistance Genes ◽

Antibiotic Resistance Genes ◽

Growth Responses ◽

Fitness Costs ◽

Transcriptional Responses ◽

Content Type ◽

E Coli

ABSTRACT Multidrug-resistant (MDR) Escherichia coli strains are a major global threat to human health, wherein multidrug resistance is primarily spread by MDR plasmid acquisition. MDR plasmids are not widely distributed across the entire E. coli species, but instead are concentrated in a small number of clones. Here, we test if diverse E. coli strains vary in their ability to acquire and maintain MDR plasmids and if this relates to their transcriptional response following plasmid acquisition. We used strains from across the diversity of E. coli strains, including the common MDR lineage sequence type 131 (ST131) and the IncF plasmid pLL35, carrying multiple antibiotic resistance genes. Strains varied in their ability to acquire pLL35 by conjugation, but all were able to stably maintain the plasmid. The effects of pLL35 acquisition on cefotaxime resistance and growth also varied among strains, with growth responses ranging from a small decrease to a small increase in growth of the plasmid carrier relative to the parental strain. Transcriptional responses to pLL35 acquisition were limited in scale and highly strain specific. We observed transcriptional responses at the operon or regulon level—possibly due to stress responses or interactions with resident mobile genetic elements (MGEs). Subtle transcriptional responses consistent across all strains were observed affecting functions, such as anaerobic metabolism, previously shown to be under negative frequency-dependent selection in MDR E. coli. Overall, there was no correlation between the magnitudes of the transcriptional and growth responses across strains. Together, these data suggest that fitness costs arising from transcriptional disruption are unlikely to act as a barrier to dissemination of this MDR plasmid in E. coli. IMPORTANCE Plasmids play a key role in bacterial evolution by transferring adaptive functions between lineages that often enable invasion of new niches, including driving the spread of antibiotic resistance genes. Fitness costs of plasmid acquisition arising from the disruption of cellular processes could limit the spread of multidrug resistance plasmids. However, the impacts of plasmid acquisition are typically measured in lab-adapted strains rather than natural isolates, which act as reservoirs for the maintenance and transmission of plasmids to clinically relevant strains. Using a clinical multidrug resistance plasmid and a diverse collection of E. coli strains isolated from clinical infections and natural environments, we show that plasmid acquisition had only limited and highly strain-specific effects on bacterial growth and transcription under laboratory conditions. These findings suggest that fitness costs arising from transcriptional disruption are unlikely to act as a barrier to transmission of this plasmid in natural populations of E. coli.

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Molecular Epidemiology of Dairy Cattle-AssociatedEscherichia coliCarryingblaCTX-MGenes in Washington State

Applied and Environmental Microbiology ◽

10.1128/aem.02430-17 ◽

2018 ◽

Vol 84 (6) ◽

Cited By ~ 11

Author(s):

Josephine A. Afema ◽

Sara Ahmed ◽

Thomas E. Besser ◽

Lisa P. Jones ◽

William M. Sischo ◽

...

Keyword(s):

Escherichia Coli ◽

Dairy Cattle ◽

Molecular Epidemiology ◽

Washington State ◽

M Gene ◽

Antimicrobial Drugs ◽

Content Type ◽

E Coli ◽

Plasmid Replicon ◽

Sequence Types

ABSTRACTAn increase in the prevalence of commensalEscherichia colicarryingblaCTX-Mgenes among dairy cattle was observed between 2008 and 2012 in Washington State. To study the molecular epidemiology of this change, we selected 126blaCTX-M-positive and 126blaCTX-M-negative isolates for determinations of the multilocus sequence types (MLSTs) and antibiotic resistance phenotypes fromE. coliobtained during a previous study. For 99 isolates, we also determined theblaCTX-Malleles using PCR and sequencing and identified the replicon types ofblaCTX-M-carrying plasmids. TheblaCTX-M-negativeE. coliisolates comprised 76 sequence types (STs) compared with 32 STs inblaCTX-M-positiveE. coliisolates. TheblaCTX-M-positiveE. coliisolates formed three MLST clonal complexes, accounting for 83% of these isolates; 52% ofblaCTX-M-negativeE. coliisolates clustered into 10 clonal complexes, and the remainder were singletons. Overall,blaCTX-M-negativeE. coliisolates had more diverse genotypes that were distinct to farms, whereasblaCTX-M-positiveE. coliisolates had a clonal population structure and were widely disseminated on farms in both regions included in the study. Plasmid replicon types included IncI1 which predominated, followed by IncFIB and IncFIA/FIB.blaCTX-M-15was the predominant CTX-M gene allele, followed byblaCTX-M-27andblaCTX-M-14. There was no significant association between plasmid replicon types and bacterial STs, and neither clonal complexes nor major plasmid groups were associated with two discrete dairy-farming regions of Washington State.IMPORTANCEInfections caused by extended-spectrum β-lactamase (ESBL)-producingEscherichia colioccur globally and present treatment challenges because of their resistance to multiple antimicrobial drugs. Cattle are potential reservoirs of ESBL-producingEnterobacteriaceae, and so understanding the causes of successful dissemination ofblaCTX-Mgenes in commensal bacteria will inform future approaches for the prevention of antibiotic-resistant pathogen emergence.

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