Transferable Resistance to Highest Priority Critically Important Antibiotics for Human Health in Escherichia coli Strains Obtained From Livestock Feces in Uruguay

Analysis of Antimicrobial Resistance in Bacterial Pathogens Recovered from Food and Human Sources: Insights from 639,087 Bacterial Whole-Genome Sequences in the NCBI Pathogen Detection Database

Understanding the role of foods in the emergence and spread of antimicrobial resistance necessitates the initial documentation of antibiotic resistance genes within bacterial species found in foods. Here, the NCBI Pathogen Detection database was used to query antimicrobial resistance gene prevalence in foodborne and human clinical bacterial isolates. Of the 1,843,630 sequence entries, 639,087 (34.7%) were assigned to foodborne or human clinical sources with 147,788 (23.14%) from food and 427,614 (76.88%) from humans. The majority of foodborne isolates were either Salmonella (47.88%), Campylobacter (23.03%), Escherichia (11.79%), or Listeria (11.3%), and the remaining 6% belonged to 20 other genera. Most foodborne isolates were from meat/poultry (95,251 or 64.45%), followed by multi-product mixed food sources (29,892 or 20.23%) and fish/seafood (6503 or 4.4%); however, the most prominent isolation source varied depending on the genus/species. Resistance gene carriage also varied depending on isolation source and genus/species. Of note, Klebsiella pneumoniae and Enterobacter spp. carried larger proportions of the quinolone resistance gene qnrS and some clinically relevant beta-lactam resistance genes in comparison to Salmonella and Escherichia coli. The prevalence of mec in S. aureus did not significantly differ between meat/poultry and multi-product sources relative to clinical sources, whereas this resistance was rare in isolates from dairy sources. The proportion of biocide resistance in Bacillus and Escherichia was significantly higher in clinical isolates compared to many foodborne sources but significantly lower in clinical Listeria compared to foodborne Listeria. This work exposes the gaps in current publicly available sequence data repositories, which are largely composed of clinical isolates and are biased towards specific highly abundant pathogenic species. We also highlight the importance of requiring and curating metadata on sequence submission to not only ensure correct information and data interpretation but also foster efficient analysis, sharing, and collaboration. To effectively monitor resistance carriage in food production, additional work on sequencing and characterizing AMR carriage in common commensal foodborne bacteria is critical.

Genomic epidemiology of third-generation cephalosporin-resistant Escherichia coli from Argentinian pig and dairy farms reveals animal-specific patterns of co-resistance and resistance mechanisms

Control measures are being introduced globally to reduce the prevalence of antibiotic resistance (ABR) in bacteria on farms. However, little is known about the current prevalence and molecular ecology of ABR in bacterial species with the potential to be key opportunistic human pathogens, such as Escherichia coli, on South American farms. Working with 30 dairy cattle farms and 40 pig farms across two provinces in central-eastern Argentina, we report a comprehensive genomic analysis of third-generation cephalosporin-resistant (3GC-R) E. coli, which were recovered from 34.8% (cattle) and 47.8% (pigs) of samples from fecally contaminated sites. Phylogenetic analysis revealed substantial diversity suggestive of long-term horizontal and vertical transmission of 3GC-R mechanisms. CTX-M-15 and CTX-M-2 were more often produced by isolates from dairy farms, while CTX-M-8 and CMY-2 and co-carriage of amoxicillin/clavulanate resistance and florfenicol resistance were more common in isolates from pig farms. This suggests different selective pressures for antibiotic use in these two animal types. We identified the β-lactamase gene blaROB, which has previously only been reported in the family Pasteurellaceae, in 3GC-R E. coli. blaROB was found alongside a novel florfenicol resistance gene, ydhC, also mobilized from a pig pathogen as part of a new composite transposon. As the first comprehensive genomic survey of 3GC-R E. coli in Argentina, these data set a baseline from which to measure the effects of interventions aimed at reducing on-farm ABR and provide an opportunity to investigate the zoonotic transmission of resistant bacteria in this region.

IMPORTANCE

Little is known about the ecology of critically important antibiotic resistance among bacteria with the potential to be opportunistic human pathogens (e.g., Escherichia coli) on South American farms. By studying 70 pig and dairy cattle farms in central-eastern Argentina, we identified that third-generation cephalosporin resistance (3GC-R) in E. coli was mediated by mechanisms seen more often in certain species and that 3GC-R pig E. coli were more likely to be co-resistant to florfenicol and amoxicillin/clavulanate. This suggests that on-farm antibiotic usage is key to selecting the types of E. coli present on these farms. 3GC-R E. coli and 3GC-R plasmids were diverse, suggestive of long-term circulation in this region. We identified the de novo mobilization of the resistance gene blaROB from pig pathogens into E. coli on a novel mobile genetic element, which shows the importance of surveying poorly studied regions for antibiotic resistance that might impact human health.

Phenotypic and genotypic characterization of extended spectrum beta-lactamase producing E. coli harboring carbapenem and colistin-resistant genes from poultry farms in Egypt

Background

eEscherichia coli (E. coli) bacteria that produce extended spectrum beta-lactamase (ESBL) is associated with a high prevalence of human illnesses worldwide. The emergence of resistance to carbapenem and colistin compounds poses further challenges to the treatment options for these illnesses. This study aimed to evaluate the phenotypic and genotypic pattern of resistance to carbapenem and colistin in ESBL-producing E. coli. Escherichia coli isolates collected from the respiratory tract of chickens in El-Sharkia government, Egypt.

Methods

A total of 250 lung samples were collected from 50 poultry farms. These samples were then subjected to isolation, identification, and serotyping of E. coli. The presence of antimicrobial resistance was identified by disc diffusion testing. The occurrence of ESBL phenotypes was also assessed using the double disc synergy method. PCR/sequencing techniques were employed to examine the presence of ESBL (β-lactamase (bla)-TEM, blaSHV, and blaCTX-M), colistin (mcr-1), and carbapenem (blaNDM, blaVIM, and blaKPC) resistance genes.

Results

The findings revealed that 140 out of 250 (56%) were identified as E. coli. All E. coli isolates had a high level of multi-antimicrobial resistance (MAR) with an index value greater than 0.2, and 65.7% of them were confirmed to produce ESBL. Out of the 92 ESBL phenotypes, 55 (59.7%), 32 (34.7%), 18 (19.6%), and 37 (40.2%) isolates harbor b laTEM-3, b laSHV-4, b laCTX-M-1, a nd blaCTX-M-14 genes, respectively. The blaNDM-1 gene was identified in all 40 phenotypes that exhibited resistance to carbapenem, accounting for 28.5% of all strains of E. coli and 43.4% of ESBL isolates. The VIM and KPC genes were not detected in any of the samples. Furthermore, there was a significant prevalence of the mobilized colistin resistance (mcr)-1 gene, with 64 (69.5%) of the ESBL isolates exhibiting this gene.

Conclusion

The prevalence of ESBL-producing E. coli, particularly those resistant to carbapenem and colistin, poses a significant public health risk in society.

Klebsiella quasipneumoniae subsp. similipneumoniae ST1859 O5:KL35 from Soil: First Report of qnrE1 in the Environment

A Klebsiella quasipneumoniae subsp. similipneumoniae strain, named S915, belonging to the ST1859 O5:KL35, and harboring the plasmid-mediated quinolone resistance qnrE1 gene, was isolated from a soil sample cultivated with lettuce in Brazil. The core genome multilocus sequence typing analysis revealed that S915 strain was most related to a clinical strain of Brazil. Comparative genomic analysis showed that ST1859 O5:KL35 strains have been circulating in clinical settings and are closely related to multidrug resistance and multimetal tolerance. Strain S915 presented a plasmid contig co-harboring the qnrE1 gene and tellurite tolerance operon. The region harboring the qnrE1 gene (ISEcp1-qnrE1-araJ-ahp) shared high similarity with others from infected humans, ready-to-eat dish, and food-producing animals in Brazil. This is the first report of the plasmid-mediated qnrE1 gene in the environment. Our findings evidence the initial dissemination of the qnrE1 gene in the environment by the introduction of a clinical strain, which may be spread to different sectors, representing a One Health challenge.

Clinically relevant antibiotic resistance in Escherichia coli from black kites in southwestern Siberia: a genetic and phenotypic investigation

Wild birds including raptors can act as vectors of clinically relevant bacteria with antibiotic resistance. The aim of this study was to investigate the occurrence of antibiotic-resistant Escherichia coli in black kites (Milvus migrans) inhabiting localities in proximity to human-influenced environments in southwestern Siberia and investigate their virulence and plasmid contents. A total of 51 E. coli isolates mostly with multidrug resistance (MDR) profiles were obtained from cloacal swabs of 35 (64%, n = 55) kites. Genomic analyses of 36 whole genome sequenced E. coli isolates showed: (i) high prevalence and diversity of their antibiotic resistance genes (ARGs) and common association with ESBL/AmpC production (27/36, 75%), (ii) carriage of mcr-1 for colistin resistance on IncI2 plasmids in kites residing in proximity of two large cities, (iii) frequent association with class one integrase (IntI1, 22/36, 61%), and (iv) presence of sequence types (STs) linked to avian-pathogenic (APEC) and extra-intestinal pathogenic E. coli (ExPEC). Notably, numerous isolates had significant virulence content. One E. coli with APEC-associated ST354 carried qnrE1 encoding fluoroquinolone resistance on IncHI2-ST3 plasmid, the first detection of such a gene in E. coli from wildlife. Our results implicate black kites in southwestern Siberia as reservoirs for antibiotic-resistant E. coli. It also highlights the existing link between proximity of wildlife to human activities and their carriage of MDR bacteria including pathogenic STs with significant and clinically relevant antibiotic resistance determinants. IMPORTANCE Migratory birds have the potential to acquire and disperse clinically relevant antibiotic-resistant bacteria (ARB) and their associated antibiotic resistance genes (ARGs) through vast geographical regions. The opportunistic feeding behavior associated with some raptors including black kites and the growing anthropogenic influence on their natural habitats increase the transmission risk of multidrug resistance (MDR) and pathogenic bacteria from human and agricultural sources into the environment and wildlife. Thus, monitoring studies investigating antibiotic resistance in raptors may provide essential data that facilitate understanding the fate and evolution of ARB and ARGs in the environment and possible health risks for humans and animals associated with the acquisition of these resistance determinants by wildlife.

Shiga Toxin-Producing Escherichia coli (STEC) Associated with Calf Mortality in Uruguay

In Uruguay, the mortality of dairy calves due to infectious diseases is high. Escherichia coli is a natural inhabitant of the intestinal microbiota, but can cause several infections. The aim of the work was to characterize E. coli isolates from intestinal and extraintestinal origin of dead newborn calves. Using PCR, virulence gene characteristics of pathogenic E. coli were searched. The pathogenic E. coli were molecularly characterized and the phylogroup, serogroup and the Stx subtype were determined. Antibiotic susceptibility was determined using the Kirby-Bauer disk diffusion method and plasmid-mediated quinolone resistance (PMQR) genes with PCR. Finally, clonal relationships were inferred using PFGE. Gene characteristics of the Shiga toxin-producing E. coli (STEC), Enteropathogenic E. coli (EPEC) and Necrotoxigenic E. coli (NTEC) were identified. The prevalence of the iucD, afa8E, f17, papC, stx1, eae and ehxA genes was high and no f5, f41, saa, sfaDE, cdtIV, lt, sta or stx2 were detected. The prevalence of STEC gene stx1 in the dead calves stood out and was higher compared with previous studies conducted in live calves, and STEC LEE+ (Enterohemorrhagic E. coli (EHEC)) isolates with stx1/eae/ehxA genotypes were more frequently identified in the intestinal than in the extraintestinal environment. E. coli isolates were assigned to phylogroups A, B1, D and E, and some belonged to the O111 serogroup. stx1a and stx1c subtypes were determined in STEC. A high prevalence of multi-resistance among STEC and qnrB genes was determined. The PFGE showed a high diversity of pathogenic strains with similar genetic profiles. It can be speculated that EHEC (stx1/eae/ehxA) could play an important role in mortality. The afa8E, f17G1 and papC genes could also have a role in calf mortality. Multidrug resistance defies disease treatment and increases the risk of death, while the potential transmissibility of genes to other species constitutes a threat to public health.

Assessment of Prevalence and Diversity of Antimicrobial Resistant Escherichia coli from Retail Meats in Southern California

Retail meat products may serve as reservoirs and conduits for antimicrobial resistance, which is frequently monitored using Escherichia coli as indicator bacteria. In this study, E. coli isolation was conducted on 221 retail meat samples (56 chicken, 54 ground turkey, 55 ground beef, and 56 pork chops) collected over a one-year period from grocery stores in southern California. The overall prevalence of E. coli in retail meat samples was 47.51% (105/221), with E. coli contamination found to be significantly associated with meat type and season of sampling. From antimicrobial susceptibility testing, 51 isolates (48.57%) were susceptible to all antimicrobials tested, 54 (51.34%) were resistant to at least 1 drug, 39 (37.14%) to 2 or more drugs, and 21 (20.00%) to 3 or more drugs. Resistance to ampicillin, gentamicin, streptomycin, and tetracycline were significantly associated with meat type, with poultry counterparts (chicken or ground turkey) exhibiting higher odds for resistance to these drugs compared to non-poultry meats (beef and pork). From the 52 E. coli isolates selected to undergo whole-genome sequencing (WGS), 27 antimicrobial resistance genes (ARGs) were identified and predicted phenotypic AMR profiles with an overall sensitivity and specificity of 93.33% and 99.84%, respectively. Clustering assessment and co-occurrence networks revealed that the genomic AMR determinants of E. coli from retail meat were highly heterogeneous, with a sparsity of shared gene networks.

Phenotypic and genotypic survey of antibiotic resistance in Salmonella enterica isolates from dairy farms in Uruguay

Salmonella enterica is an important zoonotic pathogen that is frequently identified in dairy farming systems. An increase in antibiotic resistance has led to inadequate results of treatments, with impacts on animal and human health. Here, the phenotypic and genotypic susceptibility patterns of Salmonella isolates from dairy cattle and dairy farm environments were evaluated and compared. A collection of 75 S. enterica isolates were evaluated, and their phenotypic susceptibility was determined. For genotypic characterization, the whole genomes of the isolates were sequenced, and geno-serotypes, sequence types (STs) and core-genome-sequence types were determined using the EnteroBase pipeline. To characterize antibiotic resistance genes and gene mutations, tools from the Center for Genomic Epidemiology were used. Salmonella Dublin (SDu), S. Typhimurium (STy), S. Anatum (SAn), S. Newport (SNe), S. Agona (Sag), S. Montevideo (SMo) and IIIb 61:i:z53 were included in the collection. A single sequence type was detected per serovar. Phenotypic non-susceptibility to streptomycin and tetracycline was very frequent in the collection, and high non-susceptibility to ciprofloxacin was also observed. Multidrug resistance (MDR) was observed in 42 isolates (56.0%), with SAn and STy presenting higher MDR than the other serovars, showing non-susceptibility to up to 6 groups of antibiotics. Genomic analysis revealed the presence of 21 genes associated with antimicrobial resistance (AMR) in Salmonella isolates. More than 60% of the isolates carried some gene associated with resistance to aminoglycosides and tetracyclines. Only one gene associated with beta-lactam resistance was found, in seven isolates. Two different mutations were identified, parC_T57S and acrB_R717Q, which confer resistance to quinolones and azithromycin, respectively. The accuracy of predicting antimicrobial resistance phenotypes based on AMR genotypes was 83.7%. The genomic approach does not replace the phenotypic assay but offers valuable information for the survey of circulating antimicrobial resistance. This work represents one of the first studies evaluating phenotypic and genotypic AMR in Salmonella from dairy cattle in South America.

Characterization of ESBL-producing Escherichia spp. and report of an mcr-1 colistin-resistance Escherichia fergusonni strain from minced meat in Pamplona, Colombia

Foods of animal origin are increasingly considered a source of extended spectrum β-lactamase (ESBL) producing bacteria which can disseminate throughout the food chain and become a health concern for humans. This work aimed to evaluate the occurrence of ESBL-producing Escherichia coli in 100 retail minced meat samples taken in markets in Pamplona, Colombia. A total of 19 ESBL-producing isolates were obtained, 18 identified as E. coli and one as E. fergusonii. Fifteen isolates (78.9 %) carried bla_CTX-M and bla_TEM genes, one (5.2 %) bla_SHV and bla_TEM genes, one isolate (5.2 %) carried bla_CTX-M and one (5.2 %) bla_SHV alone. The majority of CTX-M-positive E. coli isolates carried the bla_CTX-M-15 gene (13 isolates), being the bla_CTX-M-9, bla_CTX-M-2, and bla_CTX-M-8 (one isolate each) also detected. Two SHV-positive isolates presented the bla_SHV-5 and bla_SHV-12 allele. The isolate identified as E. fergusonii was positive for bla_CTX-M-65 gene and mcr-1 gene. Sixteen isolates (84.2 %) belonged to phylogroups A and B1 and grouped together in the phylogenetic tree obtained by MLST; phylogroups E and F were also detected. Transfer of ESBL resistance was demonstrated for the E. fergusonii isolate. Whole genome sequencing of this isolate revealed the presence of plasmids carrying additional resistance genes. This investigation showed the high prevalence of ESBL-producing E. coli in retail samples of minced meat. Also, the isolation of a strain of E. fergusonii is an additional concern, as some resistance genes are located in mobile elements, which can be transmitted to other bacteria. These evidences support the increasing public health concern considering the spreading of resistance genes through the food chain.

Worldwide Prevalence of mcr-mediated Colistin-Resistance Escherichia coli in Isolates of Clinical Samples, Healthy Humans, and Livestock-A Systematic Review and Meta-Analysis

Background: Antimicrobial resistance is a serious public-health problem throughout the world. Escherichia coli, the most common Gram-negative microorganism, has developed different resistance mechanisms, making treating infections difficult. Colistin is considered a last-resort drug in the treatment of infections caused by E. coli. Plasmid-mediated mobile-colistin-resistant (mcr) genes in E. coli, now disseminated globally, are considered a major public-health threat. Humans, chickens, and pigs are the main reservoirs for E. coli and the sources of antibiotic resistance. Hence, an up-to-date and precise estimate of the global prevalence of mcr resistance genes in these reservoirs is necessary to understand more precisely the worldwide spread and to more effectively implement control and prevention strategies. Methodology: Publications were identified in the PubMed database on the basis of the PRISMA guidelines. English full-text articles were selected from December 2014 to March 2021. Descriptive statistics and a meta-analysis were performed in Excel and R software, respectively. Colistin resistance was defined as the molecular-genetic detection of the mcr genes. The crude and estimated prevalence were calculated for each host and continent. The studies were divided into two groups; community-based when they involved isolates from healthy humans, chickens, or pigs, and clinical studies when they involved only hospital, outpatient, or laboratory isolates. Results: A total of 1278 studies were identified and 218 were included in this systematic review and meta-analysis, divided into community studies (159 studies) and clinical studies (59 studies). The general prevalence of mcr-mediated colistin-resistant E. coli (mcrMCRE) was 6.51% (n = 11,583/177,720), reported in 54 countries and on five continents; Asia with 119 studies followed by Europe with 61 studies registered the most articles. Asia reported the major diversity of mcr-variants (eight of nine, except mcr-2). Worldwide, chickens and pigs proved to be the principal reservoir of mcr with an estimated prevalence of 15.8% and 14.9%, respectively. Healthy humans and clinical isolates showed a lower prevalence with 7.4% and 4.2% respectively. Conclusions: In this systematic review and meta-analysis, the worldwide prevalence of mcr in E. coli isolated from healthy humans, chickens, and pigs was investigated. A wide prevalence and distribution of mcr genes was demonstrated on all continents in E. coli isolates from the selected reservoirs. Understanding the epidemiology and occurrence in the reservoirs of mcr in E. coli on different continents of the world facilitates tracing how mcr genes are transmitted and determining the infection risks for humans. This knowledge can be used to reduce the incidence of zoonotic transmission by implementing the appropriate control programs.

Antimicrobial resistance and genetic background of non-typhoidal Salmonella enterica strains isolated from human infections in São Paulo, Brazil (2000-2019)

Salmonella enterica causes Salmonellosis, an important infection in humans and other animals. The number of multidrug-resistant (MDR) phenotypes associated with Salmonella spp. isolates is increasing worldwide, causing public health concern. Here, we aim to characterize the antimicrobial-resistant phenotype of 789 non-typhoidal S. enterica strains isolated from human infections in the state of São Paulo, Brazil, along 20 years (2000-2019). Among the non-susceptible isolates, 31.55, 14.06, and 13.18% were resistant to aminoglycosides, tetracycline, and β-lactams, respectively. Moreover, 68 and 11 isolates were considered MDR and Extended Spectrum β-Lactamase (ESBL) producers, respectively, whereas one isolate was colistin-resistant. We selected four strains to obtain a draft of the Genome Sequence; one S. Infantis (ST32), one S. Enteritidis (ST11), one S. I 4,[5],12:i:- (ST19), and one S. Typhimurium (ST313). Among them, three presented at least one of the following antimicrobial resistance genes (AMR) linked to mobile DNA: bla_TEM-1B, dfrA1, tetA, sul1, floR, aac(6')-laa, and qnrE1. This is the first description of the plasmid-mediated quinolone resistance (PMQR) gene qnrE1 in a clinical isolate of S. I 4,[5],12:i:-. The S. Typhimurium is a colistin-resistant isolate, but did not harbor mcr genes, but it presented mutations within the mgrB, pmrB, and pmrC regions that might be linked to the colistin-resistant phenotype. The virulence pattern of the four isolates resembled the virulence pattern of the highly pathogenic S. Typhimurium UK-1 reference strain in assays involving the in vivo Galleria mellonella model. In conclusion, most isolates studied here are susceptible, but a small percentage present an MDR or ESBL-producer and pathogenic phenotype. Sequence analyses revealed plasmid-encoded AMR genes, such as β-lactam and fluoroquinolone resistance genes, indicating that these characteristics can be potentially disseminated among other bacterial strains.

Multidrug-Resistant and Genetic Characterization of Extended-Spectrum Beta-Lactamase-Producing E. coli Recovered from Chickens and Humans in Egypt

Simple Summary

Feeding food chain animals with sub-therapeutic doses for prophylaxis or for growth-promoting purposes has led to the emergence of resistant bugs such as ESBL-E. coli. Infections caused by these superbugs are tremendously associated with treatment failures and high morbidity/mortality rates. Scarce information is currently available on the relation between the incidence of ESBL-E. coli in human and food chain animals in Egypt. The current study analyzed chicken and human fecal samples for isolation and characterization of ESBL-producing E. coli followed by sequencing the isolates. Significant similarities were detected between human and chicken isolates, indicating the possibility of zoonotic transmission. In conclusion, the study encouraged managing the use of antibiotics in veterinary field, to reduce the selection and spread of life-threating bugs to humans.

Abstract

Colonization of food chain animals such as chickens with extended-spectrum β-lactamases (ESBL) poses a major health threat to human. The current study aimed to determine the phenotypic and genotypic relationship between ESBL-producing E. coli from diseased human and chickens in Egypt. A total of 56 out of 120 chicken farms (46.7%) and 9 human samples (100%) were phenotypically and genotypically identified with at least one ESBL-phenotype/gene. Chicken isolates showed a high proportion of beta lactamase from CTX-M group 9 > TEM > PER families, followed by CTX-M group 1 > SHV > GES > OXA group10 > VEB > OXA group2 families, while human isolates only contained the CTX-M family. A high incidence of ESBL genes from the CTX-M family was recognized in both human and chicken isolates. Furthermore, nucleotide identity showed high similarity between chicken and human isolates. In conclusion, the current study traced phenotypes and genotypes of ESBL-producing E. coli from chickens and human samples in Egypt, reporting degrees of similarity that suggest potential zoonotic transmission. Our data highlighted the significant importance of chicken as a major food source not only in Egypt but all over the world in the spreading of ESBL-producing E. coli to human.

Imported One-Day-Old Chicks as Trojan Horses for Multidrug-Resistant Priority Pathogens Harboring mcr-9, rmtG and Extended-Spectrum β-Lactamase Genes

Antimicrobial resistance is a critical issue that is no longer restricted to hospital settings, but also represents a growing problem involving intensive animal production systems. In this study, we have performed a microbiological and molecular investigation of priority pathogens carrying transferable resistance genes to critical antimicrobials in one-day-old chickens imported from Brazil to Uruguay. Bacterial identification was performed by MALDI-TOF mass spectrometry and antibiotic susceptibility was determined by Sensititre. Antimicrobial resistance genes were sought by polymerase chain reaction and clonality was assessed by PFGE. Four multidrug-resistant (MDR) representative strains were sequenced by Illumina and/or Oxford Nanopore Technologies. Twenty-eight MDR isolates identified as Escherichia coli (n= 14), Enterobacter cloacae (n= 11) and Klebsiella pneumoniae (n= 3). While resistance to oxyiminocephalosporins was due to bla_CTX-M-2, bla_CTX-M-8, bla_CTX-M-15, bla_CTX-M-55 and bla_CMY-2, plasmid-mediated quinolone resistance was associated with qnrB19, qnrE1, and qnrB2 genes. Finally, resistance to aminoglycosides and fosfomycin was due to the presence of 16S rRNA methyltransferase rmtG and fosA-type genes, respectively. Short and long-read genome sequencing of E. cloacae ODC-Eclo3 strain revealed the presence of IncQ/rmtG (pUR-EC3.1, 7400-pb), IncHI2A/mcr-9.1/bla_CTX-M-2 [pUR-EC3.2, ST16 (pMLST), 408,436-bp] and IncN2/qnrB19/aacC3/aph(3'')-Ib (pUR-EC3.3) resistance plasmids. Strikingly, the bla_CTX-M-2 gene was carried by a novel Tn1696-like composite transposon designated Tn7337. In summary, we report that imported one-day-old chicks can act as Trojan horses for the hidden spread of WHO critical priority MDR pathogens harboring mcr-9, rmtG and extended-spectrum β-lactamase genes in poultry farms, which is a critical issue within a One Health perspective. Importance section Antimicrobial resistance is considered a significant problem for global health, including within the concept of "One Health", therefore, the food chain is a link that connects human and animal health directly. In this work, we searched for microorganisms resistant to antibiotics considered critical for human health in intestinal microbiota of one-day-old baby chicks imported to Uruguay from Brazil. We described antibiotic-resistant genes to antibiotics named as to watch or reserve for the WHO, such as rmtG or mcr9.1, which confers resistance to all the aminoglycosides and colistin, respectively, among others genes, and their presence in new mobile genetic elements that favor its dissemination. The sustained entry of these microorganisms evades the sanitary measures implemented by the countries and production establishments to reduce the selection of resistant microorganisms. These silently imported resistant microorganisms could explain a considerable part of the antimicrobial resistance problems found in the production stages of the system.

Global colistin use: A review of the emergence of resistant Enterobacterales and the impact on their genetic basis

The dramatic global rise of MDR and XDR Enterobacterales in human medicine forced clinicians to the reintroduction of colistin as last-resort drug. Meanwhile, colistin is used in the veterinary medicine since its discovery, leading to a steadily increasing prevalence of resistant isolates in the livestock and meat-based food sector. Consequently, transmission of resistant isolates from animals to humans, acquisition via food and exposure to colistin in the clinic are reasons for the increased prevalence of colistin-resistant Enterobacterales in humans in the last decades. Initially, resistance mechanisms were caused by mutations in chromosomal genes. However, since the discovery in 2015, the focus has shifted exclusively to mobile colistin resistances (mcr). This review will advance the understanding of chromosomal-mediated resistance mechanisms in Enterobacterales. We provide an overview about genes involved in colistin resistance and the current global situation of colistin-resistant Enterobacterales. A comparison of the global colistin use in veterinary and human medicine highlights the effort to reduce colistin sales in veterinary medicine under the One Health approach. In contrast, it uncovers the alarming rise in colistin consumption in human medicine due to the emergence of MDR Enterobacterales, which might be an important driver for the increasing emergence of chromosome-mediated colistin resistance.

Potential sources and characteristic occurrence of mobile colistin resistance (mcr) gene-harbouring bacteria recovered from the poultry sector: a literature synthesis specific to high-income countries

Understanding the sources, prevalence, phenotypic and genotypic characteristics of mcr gene-harbouring bacteria (MGHB) in the poultry sector is crucial to supplement existing information. Through this, the plasmid-mediated colistin resistance (PMCR) could be tackled to improve food safety and reduce public health risks. Therefore, we conducted a literature synthesis of potential sources and characteristic occurrence of MGHB recovered from the poultry sector specific to the high-income countries (HICs). Colistin (COL) is a last-resort antibiotic used for treating deadly infections. For more than 60 years, COL has been used in the poultry sector globally, including the HICs. The emergence and rapid spread of mobile COL resistance (mcr) genes threaten the clinical use of COL. Currently, ten mcr genes (mcr-1 to mcr-10) have been described. By horizontal and vertical transfer, the mcr-1, mcr-2, mcr-3, mcr-4, mcr-5, and mcr-9 genes have disseminated in the poultry sector in HICs, thus posing a grave danger to animal and human health, as harboured by Escherichia coli, Klebsiella pneumoniae, Salmonella species, and Aeromonas isolates. Conjugative and non-conjugative plasmids are the major backbones for mcr in poultry isolates from HICs. The mcr-1, mcr-3 and mcr-9 have been integrated into the chromosome, making them persist among the clones. Transposons, insertion sequences (IS), especially ISApl1 located downstream and upstream of mcr, and integrons also drive the COL resistance in isolates recovered from the poultry sector in HICs. Genes coding multi-and extensive-drug resistance and virulence factors are often co-carried with mcr on chromosome and plasmids in poultry isolates. Transmission of mcr to/among poultry strains in HICs is clonally unrestricted. Additionally, the contact with poultry birds, manure, meat/egg, farmer's wears/farm equipment, consumption of contaminated poultry meat/egg and associated products, and trade of poultry-related products continue to serve as transmission routes of MGHB in HICs. Indeed, the policymakers, especially those involved in antimicrobial resistance and agricultural and poultry sector stakeholders-clinical microbiologists, farmers, veterinarians, occupational health clinicians and related specialists, consumers, and the general public will find this current literature synthesis very useful.

Polymyxin resistance in Enterobacterales: overview and epidemiology in the Americas

The worldwide spread of carbapenem- and polymyxin-resistant Enterobacterales represents an urgent public-health threat. However, for most countries in the Americas, the available data are limited, although Latin America has been suggested as a silent spreading reservoir for isolates carrying plasmid-mediated polymyxin resistance mechanisms. This work provides an overall update on polymyxin and polymyxin resistance and focuses on uses, availability and susceptibility testing. Moreover, a comprehensive review of the current polymyxin resistance epidemiology in the Americas is provided. We found that reports in the English and Spanish literature show widespread carbapenemase-producing and colistin-resistant Klebsiella pneumoniae in the Americas determined by the clonal expansion of the pandemic clone ST258 and mgrB-mediated colistin resistance. In addition, widespread IncI2 and IncX4 plasmids carrying mcr-1 in Escherichia coli come mainly from human sources; however, plasmid-mediated colistin resistance in the Americas is underreported in the veterinary sector. These findings demonstrate the urgent need for the implementation of polymyxin resistance surveillance in Enterobacterales as well as appropriate regulatory measures for antimicrobial use in veterinary medicine.

Description of novel resistance islands harbouring blaCTX-M-2 in IncC type 2 plasmids

OBJECTIVES

We sequenced two IncA/C plasmids harbouring bla_CTX-M-2 in Klebsiella pneumoniae clinical isolates and compared their antibiotic resistance islands.

METHODS

Transconjugants were obtained from two clinical K. pneumoniae isolates harbouring bla_CTX-M-2. Plasmid DNA from transconjugants underwent short-read whole-genome sequencing, reads were assembled, and gaps were closed by PCR and sequencing. Determination of plasmid replicons, antibiotic resistance genes, identification and characterisation of insertion sequence (IS) elements, and comparison with publicly available plasmid sequences were performed.

RESULTS

bla_CTX-M-2 was located in a complex class 1 integron In35::ISCR1::bla_CTX-M-2, inserted in two different transposons designated Tn7057 and Tn7058, that reside in the resistance islands of plasmids pUR-KP0923 and pUR-KP1025, respectively. The general modules of both transposons were In35::ISCR1::bla_CTX-M-2-Tn1000-like-Tn2*-ISKpn11-12-13 variable module-ΔTn21. In Tn7057 there was ΔIS10R-catA2 associated with an additional ISKpn13. Both plasmids belonged to IncC type 2 and ST3. pUR-KP0923 was 167 138 bp in length and had a 37 926-bp resistance island at position 4 (RI-4). Plasmid pUR-KP1025 was 168 128 bp with a RI-4 of 36 222 bp.

CONCLUSION

This report describes the molecular nature of two transposons (Tn7057 and Tn7058) harbouring bla_CTX-M-2 that reside in IncC type 2 ST3 plasmids. These transposons mediate resistance to oxyimino-cephalosporins, gentamicin and, in the case of Tn7057, chloramphenicol. CTX-M-2 is an important extended-spectrum β-lactamase (ESBL) to South American epidemiology. It is remarkable that despite being only two plasmid sequences, the information revealed here could contribute to a better understanding of the resistance islands from IncC type 2 plasmids.