Insertion sequence ISEcp1B is involved in expression and mobilization of a bla(CTX-M) beta-lactamase gene

Cryptic environmental conjugative plasmid recruits a novel hybrid transposon resulting in a new plasmid with higher dispersion potential

Cryptic conjugative plasmids lack antibiotic-resistance genes (ARGs). These plasmids can capture ARGs from the vast pool of the environmental metagenome, but the mechanism to recruit ARGs remains to be elucidated. To investigate the recruitment of ARGs by a cryptic plasmid, we sequenced and conducted mating experiments with Escherichia coli SW4848 (collected from a lake) that has a cryptic IncX (IncX4) plasmid and an IncF (IncFII/IncFIIB) plasmid with five genes that confer resistance to aminoglycosides (strA and strB), sulfonamides (sul2), tetracycline [tet(A)], and trimethoprim (dfrA5). In a conjugation experiment, a novel hybrid Tn21/Tn1721 transposon of 22,570 bp (designated Tn7714) carrying the five ARG mobilized spontaneously from the IncF plasmid to the cryptic IncX plasmid. The IncF plasmid was found to be conjugative when it was electroporated into E. coli DH10B (without the IncX plasmid). Two parallel conjugations with the IncF and the new IncX (carrying the novel Tn7714 transposon) plasmids in two separate E. coli DH10B as donors and E. coli J53 as the recipient revealed that the conjugation rate of the new IncX plasmid (with the novel Tn7714 transposon and five ARGs) is more than two orders of magnitude larger than the IncF plasmid. For the first time, this study shows experimental evidence that cryptic environmental plasmids can capture and transfer transposons with ARGs to other bacteria, creating novel multidrug-resistant conjugative plasmids with higher dispersion potential.

IMPORTANCE

Cryptic conjugative plasmids are extrachromosomal DNA molecules without antibiotic-resistance genes (ARGs). Environmental bacteria carrying cryptic plasmids with a high conjugation rate threaten public health because they can capture clinically relevant ARGs and rapidly spread them to pathogenic bacteria. However, the mechanism to recruit ARG by cryptic conjugative plasmids in environmental bacteria has not been observed experimentally. Here, we document the first translocation of a transposon with multiple clinically relevant ARGs to a cryptic environmental conjugative plasmid. The new multidrug-resistant conjugative plasmid has a conjugation rate that is two orders of magnitude higher than the original plasmid that carries the ARG (i.e., the new plasmid from the environment can spread ARG more than two orders of magnitude faster). Our work illustrates the importance of studying the mobilization of ARGs in environmental bacteria. It sheds light on how cryptic conjugative plasmids recruit ARGs, a phenomenon at the root of the antibiotic crisis.

Occurrence and characteristics of blaOXA-181-carrying Klebsiella aerogenes from swine in China

OBJECTIVES

Klebsiella aerogenes is a largely understudied opportunistic pathogen that can cause sepsis and lead to high mortality rates. In this study, we reported the occurrence of carbapenem-resistant blaOXA-181-carrying Klebsiella aerogenes from swine in China and elucidate their genomic characteristics.

METHODS

A total of 126 samples, including 109 swine fecal swabs, 14 environmental samples, and three feed samples were collected from a pig farm in China. The samples were enriched with LB broth culture and then inoculated into MacConkey agar plates for bacterial isolation. After PCR detection of carbapenemases genes, the blaOXA-181-carrying isolates were subjected to antimicrobial susceptibility testing, and whole-genome sequence analysis.

RESULTS

Four Klebsiella aerogenes isolates carrying the blaOXA-181 gene were obtained from swine faecal samples. All the 4 strains were belonged to ST438. The blaOXA-181 genes were located in IncX3-ColKP3 hybrid plasmids with the core genetic structure of IS26-ΔIS3000-ΔISEcp1-blaOXA-181-ΔlysR-ΔereA-ΔrepA-ISKpn19-tinR-qnrS1-ΔIS2-IS26, which suggests the potential for horizontal transfer and further dissemination of this resistance gene among Enterobacteriaceae and other sources.

CONCLUSIONS

This study represents the first instance of OXA-181-producing K. aerogenes being identified from swine faeces in China. It is crucial to maintain continuous monitoring and ongoing attention to the detection of K. aerogenes carrying blaOXA-181 and other resistance genes in pigs.

Comparative genomics of an extensively drug resistant strain Klebsiella pneumoniae IITR008 with international high-risk clonal lineage ST147 isolated from river water

Carbapenem resistant Klebsiella pneumoniae causing severe infection resulting in morbidity and mortality have become a global health concern. K. pneumoniae with sequence type ST147 is an international high-risk clonal lineage, genomic studies have been done on K. pneumoniae ST147 isolated from clinical origin but genomic data for environmental K. pneumoniae ST147 is very scarce. Herein, K. pneumoniae IITR008, an extensively drug resistant and potentially hypervirulent bacterium, was isolated from Triveni Sangam, the confluence of three rivers where religious congregations are organized. Phenotypic, genomic and comparative genomic analysis of strain IITR008 was performed. Antibiotic susceptibility profiling revealed resistance to 9 different classes of antibiotics including ß-lactams, ß-lactam combination agents, carbapenem, aminoglycoside, macrolide, quinolones, cephams, phenicol, and folate pathway antagonists and was found to be susceptible to only tetracycline. The strain IITR008 possesses hypervirulence genes namely, iutA and iroN in addition to numerous virulence factors coding for adherence, regulation, iron uptake, secretion system and toxin. Both the IITR008 chromosome and plasmid pIITR008_75 possess a plethora of clinically relevant antibiotic-resistant genes (ARGs) including blaCTX-M-15, blaTEM-1, and blaSHV-11, corroborating the phenotypic resistance. Comparative genomic analysis with other ST147 K. pneumoniae provided insights on the phylogenetic clustering of IITR008 with a clinical strain isolated from a patient in Czech with recent travel history in India and other clinical strains isolated from India and Pakistan. According to the 'One Health' perspective, surveillance of antibiotic resistance in the environment is crucial to impede its accelerated development in diverse ecological niches.

Global spread characteristics of CTX-M-type extended-spectrum β-lactamases: A genomic epidemiology analysis

BACKGROUND

Extended-spectrum β-lactamases (ESBLs) producing bacteria have spread worldwide and become a global public health concern. Plasmid-mediated transfer of ESBLs is an important route for resistance acquisition.

METHODS

We collected 1345 complete sequences of plasmids containing CTX-Ms from public database. The global transmission pattern of plasmids and evolutionary dynamics of CTX-Ms have been inferred. We applied the pan-genome clustering based on plasmid genomes and evolution analysis to demonstrate the transmission events.

FINDINGS

Totally, 48 CTX-Ms genotypes and 186 incompatible types of plasmids were identified. The geographical distribution of CTX-Ms showed significant differences across countries and continents. CTX-M-14 and CTX-M-55 were found to be the dominant genotypes in Asia, while CTX-M-1 played a leading role in Europe. The plasmids can be divided into 12 lineages, some of which forming distinct geographical clusters in Asia and Europe, while others forming hybrid populations. The Inc types of plasmids are lineage-specific, with the CTX-M-1_IncI1-I (Alpha) and CTX-M-65_IncFII (pHN7A8)/R being the dominant patterns of cross-host and cross-regional transmission. The IncI-I (Alpha) plasmids with the highest number, were presumed to form communication groups in Europe-Asia and Asia-America-Oceania, showing the transmission model as global dissemination and regional microevolution. Meanwhile, the main kinetic elements of blaCTX-Ms showed genotypic preferences. ISEcpl and IS26 were most frequently involved in the transfer of CTX-M-14 and CTX-M-65, respectively. IS15 has become a crucial participant in mediating the dissemination of blaCTX-Ms. Interestingly, blaTEM and blaCTX-Ms often coexisted in the same transposable unit. Furthermore, antibiotic resistance genes associated with aminoglycosides, sulfonamides and cephalosporins showed a relatively high frequency of synergistic effects with CTX-Ms.

CONCLUSIONS

We recognized the dominant blaCTX-Ms and mainstream plasmids of different continents. The results of this study provide support for a more effective response to the risks associated with the evolution of blaCTX-Ms-bearing plasmids, and lay the foundation for genotype-specific epidemiological surveillance of resistance, which are of important public health implications.

Understanding the rapid spread of antimicrobial resistance genes mediated by IS26

Insertion sequences (ISs) promote the transmission of antimicrobial resistance genes (ARGs) across bacterial populations. However, their contributions and dynamics during the transmission of resistance remain unclear. In this study, we selected IS26 as a representative transposable element to decipher the relationship between ISs and ARGs and to investigate their transfer features and transmission trends. We retrieved 2656  translocatable  IS 26 -bounded  units with  ARGs (tIS26-bUs-ARGs) in complete bacterial genomes from the NCBI RefSeq database. In total, 124 ARGs spanning 12 classes of antibiotics were detected, and the average contribution rate of IS26 to these genes was 41.2%. We found that  IS 26 -bounded  units (IS26-bUs) mediated extensive ARG dissemination within the bacteria of the Gammaproteobacteria class, showing strong transfer potential between strains, species, and even phyla. The IS26-bUs expanded in bacterial populations over time, and their temporal expansion trend was significantly correlated with antibiotic usage. This wide dissemination could be due to the nonspecific target site preference of IS26. Finally, we experimentally confirmed that the introduction of a single copy of IS26 could lead to the formation of a composite transposon mediating the transmission of "passenger" genes. These observations extend our knowledge of the IS26 and provide new insights into the mediating role of ISs in the dissemination of antibiotic resistance.

Genomic characteristics of two strains of ESBL-producing Klebsiella pneumoniae ST268 isolated from different samples of one patient

OBJECTIVES

This study reports the whole-genome sequences of two strains of extended-spectrum beta-lactamase (ESBL)-producing and multidrug-resistant (MDR) K. pneumoniae ST268 and explores their acquired antibiotic resistance genes (ARGs) and the mobile genetic elements (MGEs).

METHODS

Two strains of K. pneumoniae ST268 were isolated from different samples of one patient. Assessment of antimicrobial susceptibility was performed, and then whole-genome sequencing was conducted. Acquired ARGs, insertion sequences, and transposons harboured by the two strains of K. pneumoniae ST268 were identified, and then the genetic contexts associated with the ARGs were analysed systematically.

RESULTS

Two strains of K. pneumoniae ST268 were found to carry the 118.6-kb hybrid IncFIIK:IncQ1:repBR1701 plasmid. All the acquired ARGs carried by the IncF plasmid were found to be situated on the 25.3-kb MDR region bracketed by ISKpn19 and IS26, which was widely present in the plasmids in 14 STs of strains in K. pneumoniae but also in IncF plasmids from Shigella flexneri and Klebsiella quasipneumoniae. Notably, the IncF plasmids harbouring the 25.3-kb MDR region were geographically distributed mainly in China, and the pKP161637-1/pKP160802-1 in our study was the first report on the IncF plasmid carrying the 25.3-kb MDR region bracketed in K. pneumoniae ST268.

CONCLUSIONS

Two strains of ESBL-producing K. pneumoniae ST268 with a MDR IncF plasmid were identified in a hospital in China. The ARGs were identified on the 25.3-kb MDR region, bracketed by ISKpn19 and IS26, of the IncF plasmids, which were present not only in the K. pneumoniae but also in the S. flexneri and K. quasipneumoniae.

Comparative genomic analysis of strong biofilm-forming Klebsiella pneumoniae isolates uncovers novel ISEcp1-mediated chromosomal integration of a full plasmid-like sequence

BACKGROUND

The goal of the current study was to elucidate the genomic background of biofilm formation in Klebsiella pneumoniae.

METHODS

Clinical isolates were screened for biofilm formation using the crystal violet assay. Antimicrobial resistance (AMR) profiles were assessed by disk diffusion and broth microdilution tests. Biofilm formation was correlated to virulence and resistance genes screened by PCR. Draft genomes of three isolates that form strong biofilm were generated by Illumina sequencing.

RESULTS

Only the siderophore-coding gene iutA was significantly associated with more pronounced biofilm formation. ST1399-KL43-O1/O2v1 and ST11-KL15-O4 were assigned to the multidrug-resistant strain K21 and the extensively drug-resistant strain K237, respectively. ST1999-KL38-O12 was assigned to K57. Correlated with CRISPR/Cas distribution, more plasmid replicons and prophage sequences were identified in K21 and K237 compared to K57. The acquired AMR genes (blaOXA-48, rmtF, aac(6')-Ib and qnrB) and (blaNDM-1, blaCTX-M, aph(3')-VI, qnrS, and aac(6')-Ib-cr) were found in K237 and K21, respectively. The latter showed a novel ISEcp1-mediated chromosomal integration of replicon type IncM1 plasmid-like structure harboring blaCTX-M-14 and aph(3')-VI that uniquely interrupted rcsC. The plasmid-mediated heavy metal resistance genes merACDEPRT and arsABCDR were spotted in K21, which also exclusively carried the acquired virulence genes mrkABCDF and the hypervirulence-associated genes iucABCD-iutA, and rmpA/A2. Pangenome analysis revealed NTUH-K2044 accessory genes most frequently shared with K21.

CONCLUSIONS

While less virulent to Galleria mellonella than ST1999 (K57), the strong biofilm former, multidrug-resistant, NDM-producer K. pneumoniae K21 (ST1399-KL43-O1/O2v1) carries a novel chromosomally integrated plasmid-like structure and hypervirulence-associated genes and represents a serious threat to countries in the area.

Whole-Genome Sequencing of an Escherichia coli ST69 Strain Harboring blaCTX-M-27 on a Hybrid Plasmid

Objective

Escherichia coli is a common Gram-negative human pathogen. The emergence of E. coli with multiple-antibiotic-resistant phenotypes has become a serious health concern. This study reports the whole-genome sequences of third-generation cephalosporin-resistant (3GC-R) and multidrug-resistant (MDR) E. coli EC6868 and explores the acquired antibiotic-resistance genes (ARGs) as well as their genetic contexts.

Methods

E. coli EC6868 was isolated from a vaginal secretion sample of a pregnant patient in China. The antimicrobial susceptibility was assessed, and whole-genome sequencing was conducted. The acquired ARGs, insertion sequence (IS) elements, and integrons within the genome of E. coli EC6868 were identified, and the genetic contexts associated with the ARGs were analyzed systematically.

Results

E. coli EC6868 was determined to belong to ST69 and harbored a 144.9-kb IncF plasmid (pEC6868-1) with three replicons (Col156, IncFIBAP001918, and IncFII). The ESBL gene blaCTX-M-27 was located on the structure "∆ISEcp1-blaCTX-M-27-IS903B", which was widely present in the species of Enterobacteriales. Other ARGs carried by plasmid pEC6868-1 were mainly located on the 18.9-kb IS26-composite transposon (five copies of intact IS26 and one copy of truncated IS26) composing of IS26-mphA-mrx(A)-mphR(A)-IS6100, ∆TnAs3-eamA-tet(A)-tetR(A)-aph(6)-Id-aph(3")-Ib-sul2-IS26, and a class 1 integron, which was widely present on IncF plasmids of E. coli, mainly distributed in ST131, ST38, and ST405. Notably, pEC6868 in our study was the first report on a plasmid harboring the 18.9-kb structure in E. coli ST69 in China.

Conclusion

The 3GC-R E. coli ST69 strain with an MDR IncF plasmid carrying blaCTX-M-27 and other ARGs, conferring resistance to aminoglycosides, macrolides, sulfonamides, tetracycline, and trimethoprim, was identified in a hospital in China. Mobile genetic elements including ISEcp1, IS903B, IS26, Tn3, IS6100 and class 1 integron were found within the MDR region, which could play important roles in the global dissemination of these resistance genes.

Annotation and Comparative Genomics of Prokaryotic Transposable Elements

The data generated in nearly 30 years of bacterial genome sequencing has revealed the abundance of transposable elements (TE) and their importance in genome and transcript remodeling through the mediation of DNA insertions and deletions, structural rearrangements, and regulation of gene expression. Furthermore, what we have learned from studying transposition mechanisms and their regulation in bacterial TE is fundamental to our current understanding of TE in other organisms because much of what has been observed in bacteria is conserved in all domains of life. However, unlike eukaryotic TE, prokaryotic TE sequester and transmit important classes of genes that impact host fitness, such as resistance to antibiotics and heavy metals and virulence factors affecting animals and plants, among other acquired traits. This provides dynamism and plasticity to bacteria, which would otherwise be propagated clonally. The insertion sequences (IS), the simplest form of prokaryotic TE, are autonomous and compact mobile genetic elements. These can be organized into compound transposons, in which two similar IS can flank any DNA segment and render it transposable. Other more complex structures, called unit transposons, can be grouped into four major families (Tn3, Tn7, Tn402, Tn554) with specific genetic characteristics. This chapter will revisit the prominent structural features of these elements, focusing on a genomic annotation framework and comparative analysis. Relevant aspects of TE will also be presented, stressing their key position in genome impact and evolution, especially in the emergence of antimicrobial resistance and other adaptive traits.

IS26 mediated blaCTX-M-65 amplification in Escherichia coli increase the antibiotic resistance to cephalosporin in vivo

OBJECTIVES

To characterize two Escherichia coli strains isolated from a patient pre- and post-treatment, using β-lactams and β-lactam/β-lactamase inhibitor combinations (BLBLIs).

METHODS

A combination of antibiotic susceptibility testing (AST) with whole genome sequencing using Illumina and Oxford Nanopore platforms. Long-read sequencing and reverse transcription-quantitative PCR were performed to determine the copy numbers and expression levels of antibiotic resistance genes (ARGs), respectively. Effect on fitness costs were assessed by growth rate determination.

RESULTS

The strain obtained from the patient after the antibiotic treatment (XH989) exhibited higher resistance to cefepime, BLBLIs and quinolones compared with the pre-treatment strain (XH987). Sequencing revealed IS26-mediated duplications of a IS26-fosA3-blaCTX-M-65 plasmid-embedded element in strain XH989. Long-read sequencing (7.4 G data volume) indicated a variation in copy numbers of blaCTX-M-65 within one single culture of strain XH989. Increased copy numbers of the IS26-fosA3-blaCTX-M-65 element were correlated with higher CTX-M-65 expression level and did not impose fitness costs, while facilitating faster growth under high antibiotic concentrations.

CONCLUSION

Our study is an example from the clinic how BLBLIs and β-lactams exposure in vivo possibly promoted the amplification of an IS26-multiple drug resistance (MDR) region. The observation of a copy number variation seen with the blaCTX-M-65 gene in the plasmid of the post-treatment strain expands our knowledge of insertion sequence dynamics and evolution during treatment.

Visualizing and quantifying structural diversity around mobile resistance genes

Understanding the evolution of mobile genes is important for understanding the spread of antimicrobial resistance (AMR). Many clinically important AMR genes have been mobilized by mobile genetic elements (MGEs) on the kilobase scale, such as integrons and transposons, which can integrate into both chromosomes and plasmids and lead to rapid spread of the gene through bacterial populations. Looking at the flanking regions of these mobile genes in diverse genomes can highlight common structures and reveal patterns of MGE spread. However, historically this has been a largely descriptive process, relying on gene annotation and expert knowledge. Here we describe a general method to visualize and quantify the structural diversity around genes using pangraph to find blocks of homologous sequence. We apply this method to a set of 12 clinically important beta-lactamase genes and provide interactive visualizations of their flanking regions at https://liampshaw.github.io/flanking-regions. We show that nucleotide-level variation in the mobile gene itself generally correlates with increased structural diversity in its flanking regions, demonstrating a relationship between rates of mutational evolution and rates of structural evolution, and find a bias for greater structural diversity upstream. Our framework is a starting point to investigate general rules that apply to the horizontal spread of new genes through bacterial populations.

The emergence of carbapenemase-producing Enterobacterales in hospitals: a major challenge for a debilitated healthcare system in Lebanon

Background

Carbapenem- and extended-spectrum cephalosporin-resistant Enterobacterales (CR-E and ESCR-E, respectively) are increasingly isolated worldwide. Information about these bacteria is sporadic in Lebanon and generally relies on conventional diagnostic methods, which is detrimental for a country that is struggling with an unprecedented economic crisis and a collapsing public health system. Here, CR-E isolates from different Lebanese hospitals were characterized.

Materials and methods

Non-duplicate clinical ESCR-E or CR-E isolates (N = 188) were collected from three hospitals from June 2019 to December 2020. Isolates were identified by MALDI-TOF, and their antibiotic susceptibility by Kirby-Bauer disk diffusion assay. CR-E isolates (n = 33/188) were further analyzed using Illumina-based WGS to identify resistome, MLST, and plasmid types. Additionally, the genetic relatedness of the CR-E isolates was evaluated using an Infrared Biotyper system and compared to WGS.

Results

Using the Kirby-Bauer disk diffusion assay, only 90 isolates out of the 188 isolates that were collected based on their initial routine susceptibility profile by the three participating hospitals could be confirmed as ESCR-E or CR-E isolates and were included in this study. This collection comprised E. coli (n = 70; 77.8%), K. pneumoniae (n = 13; 14.4%), Enterobacter spp. (n = 6; 6.7%), and Proteus mirabilis (n = 1; 1.1%). While 57 were only ESBL producers the remaining 33 isolates (i.e., 26 E. coli, five K. pneumoniae, one E. cloacae, and one Enterobacter hormaechei) were resistant to at least one carbapenem, of which 20 were also ESBL-producers. Among the 33 CR-E, five different carbapenemase determinants were identified: blaNDM-5 (14/33), blaOXA-244 (10/33), blaOXA-48 (5/33), blaNDM-1 (3/33), and blaOXA-181 (1/33) genes. Notably, 20 CR-E isolates were also ESBL-producers. The analysis of the genetic relatedness revealed a substantial genetic diversity among CR-E isolates, suggesting evolution and transmission from various sources.

Conclusion

This study highlighted the emergence and broad dissemination of blaNDM-5 and blaOXA-244 genes in Lebanese clinical settings. The weak AMR awareness in the Lebanese community and the ongoing economic and healthcare challenges have spurred self-medication practices. Our findings highlight an urgent need for transformative approaches to combat antimicrobial resistance in both community and hospital settings.

Phenotypic and genotypic antimicrobial resistance correlation and plasmid characterization in Salmonella spp. isolates from Italy reveal high heterogeneity among serovars

Introduction

The spread of antimicrobial resistance among zoonotic pathogens such as Salmonella is a serious health threat, and mobile genetic elements (MGEs) carrying antimicrobial resistance genes favor this phenomenon. In this work, phenotypic antimicrobial resistance to commonly used antimicrobials was studied, and the antimicrobial resistance genes (ARGs) and plasmid replicons associated with the resistances were determined.

Methods

Eighty-eight Italian Salmonella enterica strains (n = 88), from human, animal and food sources, isolated between 2009 and 2019, were selected to represent serovars with different frequency of isolation in human cases of salmonellosis. The presence of plasmid replicons was also investigated.

Results and discussion

Resistances to sulphonamides (23.9%), ciprofloxacin (27.3%), ampicillin (29.5%), and tetracycline (32.9%) were the most found phenotypes. ARGs identified in the genomes correlated with the phenotypical results, with blaTEM-1B, sul1, sul2, tetA and tetB genes being frequently identified. Point mutations in gyrA and parC genes were also detected, in addition to many different aminoglycoside-modifying genes, which, however, did not cause phenotypic resistance to aminoglycosides. Many genomes presented plasmid replicons, however, only a limited number of ARGs were predicted to be located on the contigs carrying these replicons. As an expectation of this, multiple ARGs were identified on contigs with IncQ1 plasmid replicon in strains belonging to the monophasic variant of Salmonella Typhimurium. In general, high variability in ARGs and plasmid replicons content was observed among isolates, highlighting a high level of heterogeneity in Salmonella enterica. Irrespective of the serovar., many of the ARGs, especially those associated with critically and highly important antimicrobials for human medicine were located together with plasmid replicons, thus favoring their successful dissemination.

High Prevalence of Plasmid-Mediated Quinolone Resistance among ESBL/AmpC-Producing Enterobacterales from Free-Living Birds in Poland

In this study, we investigated the occurrence of plasmid-mediated quinolone resistance (PMQR) in extended-spectrum β-lactamase- (ESBL) and/or AmpC-type β-lactamase-producing Enterobacterales isolates from free-living birds in Poland. The prevalence of the qnrB19 gene was 63%, and the distribution of isolates in terms of bacterial species was as follows: 67% (22/33) corresponded to Escherichia coli, 83% (5/6) to Rahnella aquatilis, 44% (4/9) to Enterobacter cloacae and 33% (1/3) to Klebsiella pneumoniae. The qnrB19 gene was also found in a single isolate of Citrobacter freundii. The molecular characteristics of qnrB19-positive isolates pointed to extended-spectrum beta lactamase CTX-M as the most prevalent one (89%) followed by TEM (47%), AmpC (37%) and SHV (16%). This study demonstrates the widespread occurrence of PMQR-positive and ESBL/AmpC-producing Enterobacterales isolates in fecal samples from wild birds. In this work, plasmid pAM1 isolated from Escherichia coli strain SN25556 was completely sequenced. This plasmid is 3191 nucleotides long and carries the qnrB19 gene, which mediates decreased susceptibility to quinolones. It shares extensive homology with other previously described small qnrB19-harboring plasmids. The nucleotide sequence of pAM1 showed a variable region flanked by an oriT locus and a Xer recombination site. The presence of a putative recombination site was detected, suggesting that interplasmid recombination events might have played a role in the development of pAM1. Our results highlight the broad geographical spread of ColE-type Qnr resistance plasmids in clinical and environmental isolates of Enterobacterales. As expected from the results of phenotypic susceptibility testing, no resistance genes other than qnrB19 were identified.

Genetic characterization of ESBL-producing and ciprofloxacin-resistant Escherichia coli from Belgian broilers and pigs

Background

The increasing number of infections caused by Escherichia coli resistant to clinically important antibiotics is a global concern for human and animal health. High overall levels of extended-spectrum beta-lactamase (ESBL)-producing and ciprofloxacin-resistant (ciproR) Escherichia coli in livestock are reported in Belgium. This cross-sectional study aimed to genotypically characterize and trace ESBL-and ciproR-E. coli of Belgian food-producing animals.

Methods

A total of 798 fecal samples were collected in a stratified-random sampling design from Belgian broilers and sows. Consequently, 77 ESBL-E. coli and 84 ciproR-E. coli were sequenced using Illumina MiSeq. Minimum inhibitory concentration (MIC) for fluoroquinolones and cephalosporins were determined. Molecular in silico typing, resistance and virulence gene determination, and plasmid identification was performed. Scaffolds harboring ESBL or plasmid-mediated quinolone resistance (PMQR) genes were analyzed to detect mobile genetic elements (MGEs) and plasmid origins. Core genome allelic distances were used to determine genetic relationships among isolates.

Results

A variety of E. coli sequence types (ST) (n = 63), resistance genes and virulence profiles was detected. ST10 was the most frequently encountered ST (8.1%, n = 13). The pandemic multidrug-resistant clone ST131 was not detected. Most farms harbored more than one ESBL type, with blaCTX-M-1 (41.6% of ESBL-E. coli) being the most prevalent and blaCTX M-15 (n = 3) being the least prevalent. PMQR genes (15.5%, n = 13) played a limited role in the occurrence of ciproR-E. coli. More importantly, sequential acquisition of mutations in quinolone resistance-determining regions (QRDR) of gyrA and parC led to increasing MICs for fluoroquinolones. GyrA S83L, D87N and ParC S80I mutations were strongly associated with high-level fluoroquinolone resistance. Genetically related isolates identified within the farms or among different farms highlight transmission of resistant E. coli or the presence of a common reservoir. IncI1-I(alpha) replicon type plasmids carried different ESBL genes (blaCTX-M-1, blaCTX-M-32 and blaTEM-52C). In addition, the detection of plasmid replicons with associated insertion sequence (IS) elements and ESBL/PMQR genes in different farms and among several STs (e.g., IncI1-I(alpha)/IncX3) underline that plasmid transmission could be another important contributor to transmission of resistance in these farms.

Conclusion

Our findings reveal a multifaceted narrative of transmission pathways. These findings could be relevant in understanding and battling the problem of antibiotic resistance in farms.

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.

Using a combination of short- and long-read sequencing to investigate the diversity in plasmid- and chromosomally encoded extended-spectrum beta-lactamases (ESBLs) in clinical Shigella and Salmonella isolates in Belgium

For antimicrobial resistance (AMR) surveillance, it is important not only to detect AMR genes, but also to determine their plasmidic or chromosomal location, as this will impact their spread differently. Whole-genome sequencing (WGS) is increasingly used for AMR surveillance. However, determining the genetic context of AMR genes using only short-read sequencing is complicated. The combination with long-read sequencing offers a potential solution, as it allows hybrid assemblies. Nevertheless, its use in surveillance has so far been limited. This study aimed to demonstrate its added value for AMR surveillance based on a case study of extended-spectrum beta-lactamases (ESBLs). ESBL genes have been reported to occur also on plasmids. To gain insight into the diversity and genetic context of ESBL genes detected in clinical isolates received by the Belgian National Reference Center between 2013 and 2018, 100 ESBL-producing Shigella and 31 ESBL-producing Salmonella were sequenced with MiSeq and a representative selection of 20 Shigella and six Salmonella isolates additionally with MinION technology, allowing hybrid assembly. The bla _CTX-M-15 gene was found to be responsible for a rapid rise in the ESBL Shigella phenotype from 2017. This gene was mostly detected on multi-resistance-carrying IncFII plasmids. Based on clustering, these plasmids were determined to be distinct from the circulating plasmids before 2017. They were spread to different Shigella species and within Shigella sonnei between multiple genotypes. Another similar IncFII plasmid was detected after 2017 containing bla _CTX-M-27 for which only clonal expansion occurred. Matches of up to 99 % to plasmids of various bacterial hosts from all over the world were found, but global alignments indicated that direct or recent ESBL-plasmid transfers did not occur. It is most likely that travellers introduced these in Belgium and subsequently spread them domestically. However, a clear link to a specific country could not be made. Moreover, integration of bla _CTX-M in the chromosome of two Shigella isolates was determined for the first time, and shown to be related to ISEcp1. In contrast, in Salmonella, ESBL genes were only found on plasmids, of which bla _CTX-M-55 and IncHI2 were the most prevalent, respectively. No matching ESBL plasmids or cassettes were detected between clinical Shigella and Salmonella isolates. The hybrid assembly data allowed us to check the accuracy of plasmid prediction tools. MOB-suite showed the highest accuracy. However, these tools cannot replace the accuracy of long-read and hybrid assemblies. This study illustrates the added value of hybrid assemblies for AMR surveillance and shows that a strategy where even just representative isolates of a collection used for hybrid assemblies could improve international AMR surveillance as it allows plasmid tracking.

Epidemiology of Plasmid Lineages Mediating the Spread of Extended-Spectrum Beta-Lactamases among Clinical Escherichia coli

The prevalence of extended-spectrum beta-lactamases (ESBLs) among clinical isolates of Escherichia coli has been increasing, with this spread driven by ESBL-encoding plasmids. However, the epidemiology of ESBL-disseminating plasmids remains understudied, obscuring the roles of individual plasmid lineages in ESBL spread. To address this, we performed an in-depth genomic investigation of 149 clinical ESBL-like E. coli isolates from a tertiary care hospital. We obtained high-quality assemblies for 446 plasmids, revealing an extensive map of plasmid sharing that crosses time, space, and bacterial sequence type boundaries. Through a sequence-based network, we identified specific plasmid lineages that are responsible for the dissemination of major ESBLs. Notably, we demonstrate that IncF plasmids separate into 2 distinct lineages that are enriched for different ESBLs and occupy distinct host ranges. Our work provides a detailed picture of plasmid-mediated spread of ESBLs, demonstrating the extensive sequence diversity within identified lineages, while highlighting the genetic elements that underlie the persistence of these plasmids within the clinical E. coli population. IMPORTANCE The increasing incidence of nosocomial infections with extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli represents a significant threat to public health, given the limited treatment options available for such infections. The rapid ESBL spread is suggested to be driven by localization of the resistance genes on conjugative plasmids. Here, we identify the contributions of different plasmid lineages in the nosocomial spread of ESBLs. We provide further support for plasmid-mediated spread of ESBLs but demonstrate that some ESBL genes rely on dissemination through plasmids more than the others. We identify key plasmid lineages that are enriched in major ESBL genes and highlight the encoded genetic elements that facilitate the transmission and stable maintenance of these plasmid groups within the clinical E. coli population. Overall, our work provides valuable insight into the dissemination of ESBLs through plasmids, furthering our understating of factors underlying the increased prevalence of these genes in nosocomial settings.

Antibiotic Resistance Profiles and Molecular Characteristics of blaCTX-M-15-Carrying Salmonella enterica Serovar Enteritidis Isolates from Healthy and Diseased Chickens in Korea

Extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica serovar Enteritidis has emerged as a public health concern. The main objectives of this study were therefore to determine the antimicrobial susceptibility profiles of Salmonella Enteritidis and to investigate the molecular characteristics of identified ESBL-producing isolates. In the study, 237 Salmonella Enteritidis isolates (232 isolates from chickens, 4 from cattle, and 1 from a pig) were recovered from carcasses and fecal samples of healthy and diseased food animals between 2010 and 2017. Ceftiofur resistance was noted only in chicken isolates (43%, 102/237), with the highest in healthy chickens and their carcasses (48.3%, 83/172) compared with that in diseased chickens (31.7%, 19/60). All of the ceftiofur-resistant isolates exhibited resistance to multiple antimicrobials. Indeed, a relatively higher percentage of ceftiofur-resistant isolates demonstrated resistance to the tested aminoglycosides and tetracycline compared with the ceftiofur-susceptible strains. In this study, bla_CTX-M-15 was the only ESBL gene detected in all of the ceftiofur-resistant isolates. The bla_CTX-M-15-carrying isolates belonged to 11 different pulsotypes. The bla_CTX-M-15 gene was transferred from 20.6% (21/102) of the bla_CTX-M-15-harboring isolates to a recipient Escherichia coli J53. The coexistence of IncHI2/ST2 and IncFIIs/ST1 plasmids was noted in the majority (81.8%, 18/22) of the transconjugants. E. coli J53 transconjugants carrying bla_CTX-M-15 gene showed distinct genetic environments, predominantly ISEcp1-bla_CTX-M-15-orf477 (15/21, 71.4%). This study demonstrated that healthy chickens and their carcasses act as reservoirs of bla_CTX-M-15-carrying Salmonella Enteritidis that can potentially be transmitted to humans.

In silico characterization of IncX3 plasmids carrying blaOXA-181 in Enterobacterales

Carbapenem-resistant Enterobacterales poses a global urgent antibiotic resistance threat because of its ability to transfer carbapenemase genes to other bacteria via horizontal gene transfer mediated by mobile genetic elements such as plasmids. Oxacillinase-181 (OXA-181) is one of the most common OXA-48-like carbapenemases, and OXA-181-producing Enterobacterales has been reported in many countries worldwide. However, systematic research concerning the overall picture of plasmids harboring bla_OXA-181 in Enterobacterales is currently scarce. In this study, we aimed to determine the phylogeny and evolution of bla_OXA-181-positive (gene encoding OXA-181) plasmids. To characterize the plasmids harboring bla_OXA-181 in Enterobacterales, we identified 81 bla_OXA-181-positive plasmids from 35,150 bacterial plasmids downloaded from the NCBI RefSeq database. Our results indicated that diverse plasmid types harbored bla_OXA-181 but was predominantly carried by IncX3-type plasmids. We systematically compared the host strains, plasmid types, conjugative transfer regions, and genetic contexts of bla_OXA-181 among the 66 bla_OXA-181-positive IncX3 plasmids. We found that IncX3 plasmids harboring bla_OXA-181 were mostly ColKP3-IncX3 hybrid plasmids with a length of 51 kb each and were mainly distributed in Escherichia coli and Klebsiella pneumoniae. Most of the IncX3 plasmids harboring bla_OXA-181 were human origin. Almost all the bla_OXA-181-positive IncX3 plasmids were found to carry genes coding for relaxases of the MOB_P family and VirB-like type IV secretion system (T4SS) gene clusters, and all the 66 IncX3 plasmids were found to carry the genes encoding type IV coupling proteins (T4CPs) of the VirD4/TraG subfamily. Most IncX3 plasmids harbored both bla_OXA-181 and qnrS1 in their genomes, and the two antibiotic resistance genes were found to a composite transposon bracketed by two copies of insertion sequence IS26 in the same orientation. Our findings provide important insights into the phylogeny and evolution of bla_OXA-181-positive IncX3 plasmids and further address their role in acquiring and spreading bla_OXA-181 genes in Enterobacterales.

Complete Genome Sequence of a Multidrug-Resistant Klebsiella pneumoniae Environmental Isolate from Zanzibar, Tanzania, Harboring Novel Insertion Elements and Two bla CTX-M-15 Genes

Here, we report the annotated whole-genome sequence of Klebsiella pneumoniae strain KP_3b, isolated in Zanzibar, Tanzania, from plastic litter. The strain is extended-spectrum β-lactamase (ESBL) producing and multidrug resistant, encoding 17 resistance genes, most of which are located on a 230,544-bp plasmid. The isolate contains two copies of the bla_CTX-M-15 gene and novel insertion elements.

Hidden dissemination of carbapenem-susceptible OXA-48-producing Proteus mirabilis

OBJECTIVES

To detect a potential hidden dissemination of the blaOXA-48 gene among Proteus mirabilis isolates obtained from a single centre.

METHODS

P. mirabilis from diverse clinical samples presenting an ESBL phenotype or obtained from blood cultured from 2017 to 2019 were evaluated. Bacterial identification was performed using MALDI-TOF MS. MICs were determined using International Organization for Standardization (ISO) standard microdilution and interpreted following EUCAST guidelines. WGS was performed using both short- and long-read technologies and assemblies were done using Unicycler. Resistomes were assessed using the ResFinder database. SNPs were detected using the PATRIC bioinformatics platform. Cloning experiments were performed using the pCRII-TOPO cloning kit.

RESULTS

Thirty-one out of 108 (28.7%) isolates were positive for blaOXA-48 and blaCTX-M-15. Twenty-nine out of 31 of the isolates were susceptible to temocillin, piperacillin/tazobactam, ertapenem and meropenem, whereas only 2/31 showed a resistance phenotype against these antibiotics. Both blaOXA-48 and blaCTX-M-15 genes were detected within the same chromosomally integrated new transposon in all isolates. The resistant isolates displayed a single mutation located in the putative promoter upstream of blaOXA-48. Cloning experiments confirmed that the mutation was responsible for the resistance phenotype.

CONCLUSIONS

The presence of a chromosomal copy of blaOXA-48 did not confer resistance to carbapenems, but a single mutation in the promoter could lead to an increase in resistance. This study shows a hidden circulation of OXA-48-positive, but carbapenem- and piperacillin/tazobactam-susceptible, P. mirabilis isolates that can become resistant to β-lactams after a single mutation.

Combined comparative genomics and clinical modeling reveals plasmid-encoded genes are independently associated with Klebsiella infection

Members of the Klebsiella pneumoniae species complex frequently colonize the gut and colonization is associated with subsequent infection. To identify genes associated with progression from colonization to infection, we undertook a case-control comparative genomics study. Concordant cases (N = 85), where colonizing and invasive isolates were identical strain types, were matched to asymptomatically colonizing controls (N = 160). Thirty-seven genes are associated with infection, 27 of which remain significant following adjustment for patient variables and bacterial phylogeny. Infection-associated genes are not previously characterized virulence factors, but instead a diverse group of stress resistance, regulatory and antibiotic resistance genes, despite careful adjustment for antibiotic exposure. Many genes are plasmid borne, and for some, the relationship with infection is mediated by gut dominance. Five genes were validated in a geographically-independent cohort of colonized patients. This study identifies several genes reproducibly associated with progression to infection in patients colonized by diverse Klebsiella.

How Do Transposable Elements Activate Expression of Transcriptionally Silent Antibiotic Resistance Genes?

The rapidly emerging phenomenon of antibiotic resistance threatens to substantially reduce the efficacy of available antibacterial therapies. Dissemination of resistance, even between phylogenetically distant bacterial species, is mediated mainly by mobile genetic elements, considered to be natural vectors of horizontal gene transfer. Transposable elements (TEs) play a major role in this process—due to their highly recombinogenic nature they can mobilize adjacent genes and can introduce them into the pool of mobile DNA. Studies investigating this phenomenon usually focus on the genetic load of transposons and the molecular basis of their mobility. However, genes introduced into evolutionarily distant hosts are not necessarily expressed. As a result, bacterial genomes contain a reservoir of transcriptionally silent genetic information that can be activated by various transposon-related recombination events. The TEs themselves along with processes associated with their transposition can introduce promoters into random genomic locations. Thus, similarly to integrons, they have the potential to convert dormant genes into fully functional antibiotic resistance determinants. In this review, we describe the genetic basis of such events and by extension the mechanisms promoting the emergence of new drug-resistant bacterial strains.

Interspecies Transmission of CMY-2-Producing Escherichia coli Sequence Type 963 Isolates between Humans and Gulls in Australia

We have provided the first comprehensive genomic study of E. coli ST963 by analyzing various genomic and phenotypic data sets of isolates from Australian silver gulls and comparison with genomes from geographically dispersed regions of human and animal origin. Our study suggests the emergence of a specific bla CMY-2 -carrying E. coli ST963 clone in Australia that is widely spread across the continent by humans and birds.

Molecular characterization of resistance determinants and mobile genetic elements of ESBL producing multidrug-resistant bacteria from freshwater lakes in Kashmir, India

BACKGROUND

Antibiotic resistance conceded as a global concern is a phenomenon that emerged from the bacterial response to the extensive utilization of antimicrobials. The expansion of resistance determinants through horizontal transfer is linked with mobile genetic elements (MGEs) like transposons, insertion sequences, and integrons. Heavy metals also create consequential health hazards. Metal resistance gene in alliance with antibiotic resistance genes (ARGs) and MGEs is assisting bacteria to attain exalted quantity of resistance.

METHODOLOGY

The present work was carried out to study ARGs blaCTX-M, AmpC, qnrS, MGEs like ISecp1, TN3, TN21, and Int I by performing PCR and sequencing from Wular and Dal lakes of Kashmir; India. The genetic environment analysis of blaCTX-M-15 was carried out using PCR amplification, and sequencing approach followed by in-silico docking and mutational studies. Co-occurrence of ARGs and HMRGs was determined. Plasmid typing was done using PCR-based replicon typing (PBRT) and conjugation assay was also performed.

RESULTS

Out of 201 isolates attained from 16 locations, 33 were ESBLs producers. 30 ESBL displaying isolates were perceived positive for CTX-M gene, followed by AmpC (17), qnrS (13), ISecp1 (15), TN3 (11), TN21 (11), Int I (18), and SulI (14). The genetic environment of blaCTX-M-15 was observed as (ISEcp1-blaCTX-M-15-orf477), classical promoter-10 TACAAT and -35 TTGAA was found at the 3' region. The 3D structure of CTX-M-15 and ISEcp1 was generated and CTX-M-15-ISEcp1 (R299L) docking and mutation showed a reduction in hydrogen bonds. Co-occurrence of antibiotics and HMRGs (mer, sil, and ars) was found in 18, 14, and 8 isolates. PBRT analysis showed the presence of Inc. groups- B/O, F, I1, HI1, FIA, HI2, N, FIB, L/M. Molecular analysis of transconjugants showed the successful transfer of ARGs, MGEs, and HMRGs in the E. coli J53 AZ^R strain.

CONCLUSION

This study highlights the occurrence of ESBL producing bacteria in the aquatic environment of Kashmir India that can serve as a reservoir of ARGs. It also discussed the molecular mechanisms of MGEs which can help in containing the spread of antibiotic resistance.

Antimicrobial resistance of Escherichia coli, Enterobacter spp., Klebsiella pneumoniae and Enterococcus spp. isolated from the feces of giant panda

Background

Escherichia coli, Enterobacter spp., Klebsiella pneumoniae and Enterococcus spp., common gut bacteria in giant pandas, include opportunistic pathogens. The giant panda is an endangered species, classified as vulnerable by the World Wildlife Foundation. Continuous monitoring for the emergence of antimicrobial resistance (AMR) among bacterial isolates from giant pandas is vital not only for their protection but also for public health.

Results

A total of 166 E. coli, 68 Enterobacter spp., 116 K. pneumoniae and 117 Enterococcus spp. isolates were collected from fecal samples of 166 giant pandas. In the antimicrobial susceptibility tests, 144 E. coli isolates, 66 Enterobacter spp. isolates, 110 K. pneumoniae isolates and 43 Enterococcus spp. isolates were resistant to at least one antimicrobial. The resistant isolates carried antimicrobial resistance genes (ARGs), including sul3, bla_TEM, bla_SHV and tetA. The differences in the prevalence of the bla types implied that the genetic basis for β-lactam resistance among the E. coli, Enterobacter spp. and K. pneumoniae isolates was different. The strain K. pneumoniae K85 that was resistant to sixteen antimicrobials was selected for whole genome sequencing. The genome contained Col440I, IncFIB_K and IncFII_K plasmids and altogether 258 ARGs were predicted in the genome; 179 of the predicted ARGs were efflux pump genes. The genetic environment of the β-lactamase genes bla_CTX-M-3 and bla_TEM-1 in the K. pneumoniae K85 genome was relatively similar to those in other sequenced K. pneumoniae genomes. In comparing the giant panda age groups, the differences in the resistance rates among E. coli, K. pneumoniae and Enterobacter spp. isolates suggested that the infections in giant pandas of different age should be treated differently.

Conclusions

Antimicrobial resistance was prevalent in the bacterial isolates from the giant pandas, implying that the gut bacteria may pose serious health risks for captive giant pandas. The resistance genes in the genome of K. pneumoniae K85 were associated with insertion sequences and integron-integrase genes, implying a potential for the further spread of the antimicrobial resistance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02514-0.

Plant pathogenic bacterium can rapidly evolve tolerance to an antimicrobial plant allelochemical

Crop losses to plant pathogens are a growing threat to global food security and more effective control strategies are urgently required. Biofumigation, an agricultural technique where Brassica plant tissues are mulched into soils to release antimicrobial plant allelochemicals called isothiocyanates (ITCs), has been proposed as an environmentally friendly alternative to agrochemicals. Whilst biofumigation has been shown to suppress a range of plant pathogens, its effects on plant pathogenic bacteria remain largely unexplored. Here, we used a laboratory model system to compare the efficacy of different types of ITCs against Ralstonia solanacearum plant bacterial pathogen. Additionally, we evaluated the potential for ITC‐tolerance evolution under high, intermediate, and low transfer frequency ITC exposure treatments. We found that allyl‐ITC was the most efficient compound at suppressing R. solanacearum growth, and its efficacy was not improved when combined with other types of ITCs. Despite consistent pathogen growth suppression, ITC tolerance evolution was observed in the low transfer frequency exposure treatment, leading to cross‐tolerance to ampicillin beta‐lactam antibiotic. Mechanistically, tolerance was linked to insertion sequence movement at four positions in genes that were potentially associated with stress responses (H‐NS histone like protein), cell growth and competitiveness (acyltransferase), iron storage ([2‐Fe‐2S]‐binding protein) and calcium ion sequestration (calcium‐binding protein). Interestingly, pathogen adaptation to the growth media also indirectly selected for increased ITC tolerance through potential adaptations linked with metabolism and antibiotic resistance (dehydrogenase‐like protein) and transmembrane protein movement (Tat pathway signal protein). Together, our results suggest that R. solanacearum can rapidly evolve tolerance to allyl‐ITC plant allelochemical which could constrain the long‐term efficiency of biofumigation biocontrol and potentially shape pathogen evolution with plants.

Ultra-deep long-read sequencing detects IS-mediated gene duplications as a potential trigger to generate arrays of resistance genes and a mechanism to induce novel gene variants such as blaCTX-M-243

BACKGROUND

Extended-spectrum β-lactamases (ESBLs) are enzymes that can render their hosts resistant to various β-lactam antibiotics. CTX-M-type enzymes are the most prevalent ESBLs and the main cause of resistance to third-generation cephalosporins in Enterobacteriaceae. The number of described CTX-M types is continuously rising, currently comprising over 240 variants. During routine screening we identified a novel blaCTX-M gene.

OBJECTIVES

To characterize a novel blaCTX-M variant harboured by a multidrug-resistant Escherichia coli isolate of sequence type ST354.

METHODS

Antibiotic susceptibilities were determined using broth microdilution. Genome and plasmid sequences were reconstructed using short- and long-read sequencing. The novel blaCTX-M locus was analysed using long-read and Sanger sequencing. Plasmid polymorphisms were determined in silico on a single plasmid molecule level.

RESULTS

The novel blaCTX-M-243 allele was discovered alongside a nearly identical blaCTX-M-104-containing gene array on a 219 kbp IncHI2A plasmid. CTX-M-243 differed from CTX-M-104 by only one amino acid substitution (N109S). Ultra-deep (2300-fold coverage) long-read sequencing revealed dynamic scaling of the blaCTX-M genetic contexts from one to five copies. Further antibiotic resistance genes such as blaTEM-1 also exhibited sequence heterogeneity but were stable in copy number.

CONCLUSIONS

We identified the novel ESBL gene blaCTX-M-243 and illustrate a dynamic system of varying blaCTX-M copy numbers. Our results highlight the constant emergence of new CTX-M family enzymes and demonstrate a potential evolutionary platform to generate novel ESBL variants and possibly other antibiotic resistance genes.

Integron Functionality and Genome Innovation: An Update on the Subtle and Smart Strategy of Integrase and Gene Cassette Expression Regulation

Integrons are considered hot spots for bacterial evolution, since these platforms allow one-step genomic innovation by capturing and expressing genes that provide advantageous novelties, such as antibiotic resistance. The acquisition and shuffling of gene cassettes featured by integrons enable the population to rapidly respond to changing selective pressures. However, in order to avoid deleterious effects and fitness burden, the integron activity must be tightly controlled, which happens in an elegant and elaborate fashion, as discussed in detail in the present review. Here, we aimed to provide an up-to-date overview of the complex regulatory networks that permeate the expression and functionality of integrons at both transcriptional and translational levels. It was possible to compile strong shreds of evidence clearly proving that these versatile platforms include functions other than acquiring and expressing gene cassettes. The well-balanced mechanism of integron expression is intricately related with environmental signals, host cell physiology, fitness, and survival, ultimately leading to adaptation on the demand.

Antimicrobial resistance genes and genetic characteristics of multidrug-resistant Escherichia coli in a veterinary hospital in Taiwan

Introduction. Antimicrobial resistance associated with animal hosts is easily transmitted to humans either by direct contact with resistant organisms or by transferring resistance genes into human pathogens.Gap statement. There are limited studies on antimicrobial resistance genes and genetic elements of multidrug-resistant (MDR) Escherichia coli in veterinary hospitals in Taiwan.Aim. The aim of this study was to investigate antimicrobial resistance genes in multidrug-resistant Escherichia coli from animals.Methodology. Between January 2014 and August 2015, 95 multidrug-resistant Escherichia coli isolates were obtained from pigs (n=66), avians (n=18), and other animals (n=11) in a veterinary hospital in Taiwan. Susceptibility testing to 24 antimicrobial agents of 14 antimicrobial classes was performed. Antimicrobial resistance genes, integrons, and insertion sequences were analysed by polymerase chain reaction and nucleotide sequencing. Pulsed-field gel electrophoresis (PFGE), and multi-locus sequence typing were used to explore the clonal relatedness of the study isolates.Results. Different antimicrobial resistance genes found in these isolates were associated with resistance to β-lactams, tetracycline, phenicols, sulfonamides, and aminoglycosides. Fifty-five of 95 E. coli isolates (55/95, 57.9 %) were not susceptible to extended-spectrum cephalosporins, and bla _CTX-M-55 (11/55, 20.0 %) and bla _CMY-2 (40/55, 72.7 %) were the most common extended-spectrum β-lactamase (ESBL) and AmpC genes, respectively. Both bla _CTX-M and bla _CMY-2 were present on conjugative plasmids that contained the insertion sequence ISEcp1 upstream of the bla genes. Plasmid-mediated FOX-3 β-lactamase-producing E. coli was first identified in Taiwan. Forty isolates (40/95, 42 %) with class 1 integrons showed seven resistance phenotypes. Genotyping of 95 E. coli isolates revealed 91 different XbaI pulsotypes and 52 different sequence types. PFGE analysis revealed no clonal outbreaks in our study isolates.Conclusion. This study showed a high diversity of antimicrobial resistance genes and genotypes among MDR E. coli isolated from diseased livestock in Taiwan. To our knowledge, this is the first report of plasmid-mediated ESBL in FOX-3 β-lactamase-producing E. coli isolates in Taiwan. MDR E. coli isolates from animal origins may contaminate the environment, resulting in public health concerns, indicating that MDR isolates from animals need to be continuously investigated.

RamAp, an efflux pump regulator carried by an IncHI2 plasmid

In investigating the epidemiological trends of Salmonella enterica serovar Goldcoast, we have previously identified several closely related strains with different MICs to azithromycin and quinolones. Genome sequencing and comparison of two very similar MDR strains, R18.0877 and R18.1656, has led to the identification of an extra plasmid-borne ramA gene, ramAp, on the large IncHI2 plasmid carried by R18.0877. The ramAp is located in a 953-bp region on the plasmid, which is identical to that of the Klebsiella quasipneumoniae chromosomal ramA loci. A truncated ISEcp1 located at the adjacent upstream of the putative regulatory region of the ramAp may likely contribute to its mobilization and expression. Introducing the ramAp and the truncated ISEcp1 into E. coli have resulted in elevated expression of efflux pump genes and elevated MICs to chloramphenicol, azithromycin, nalidixic acid, ciprofloxacin, sulfamethoxazole, trimethoprim, tetracycline, and tigecycline. The ramAp is an extra efflux pump activator gene that potentially could be transmitted with the IncHI2 plasmid among bacteria. It is plausible that, with high interspecific conservation, the plasmid-encoded regulator reduces drug susceptibility by activating existing efflux pump systems of the host and thus can be regarded as a new type of auxiliary antimicrobial resistance determinant. Sequences of similar plasmids were found worldwide. Its impact on the emergence of antimicrobial resistance among bacterial pathogens is worrisome.

Molecular detection of blaCTX-M gene to predict phenotypic cephalosporin resistance and clinical outcome of Escherichia coli bloodstream infections in Vietnam

BACKGROUND

Blood stream infections (BSI) caused by Extended Spectrum Beta-Lactamases (ESBLs) producing Enterobacteriaceae is a clinical challenge leading to high mortality, especially in developing countries. In this study, we sought to describe the epidemiology of ESBL-producing Escherichia coli strains isolated from Vietnamese individuals with BSI, to investigate the concordance of genotypic-phenotypic resistance, and clinical outcome of ESBL E. coli BSI.

METHODS

A total of 459 hospitalized patients with BSI were screened between October 2014 and May 2016. 115 E. coli strains from 115 BSI patients were isolated and tested for antibiotic resistance using the VITEK®2 system. The ESBL phenotype was determined by double disk diffusion method following the guideline of Clinical and Laboratory Standards Institute. Screening for beta-lactamase (ESBL and carbapenemase) genes was performed using a multiplex-PCR assay.

RESULTS

58% (67/115) of the E. coli strains were ESBL-producers and all were susceptible to both imipenem and meropenem. Resistance to third-generation cephalosporin was common, 70% (81/115) were cefotaxime-resistant and 45% (52/115) were ceftazidime-resistant. blaCTX-M was the most common ESBL gene detected (70%; 80/115) The sensitivity and specificity of blaCTX-M-detection to predict the ESBL phenotype was 87% (76-93% 95% CI) and 54% (39-48% 95% CI), respectively. 28%% (22/80) of blaCTX-M were classified as non-ESBL producers by phenotypic testing for ESBL production. The detection of blaCTX-M in ESBL-negative E. coli BSI was associated with fatal clinical outcome (27%; 6/22 versus 8%; 2/26, p = 0.07).

CONCLUSION

A high prevalence of ESBL-producing E. coli isolates harbouring blaCTX-M was observed in BSI patients in Vietnam. The genotypic detection of blaCTX-M may have added benefit in optimizing and guiding empirical antibiotic therapy of E. coli BSI to improve clinical outcome.

Extended-spectrum β-lactamases: an update on their characteristics, epidemiology and detection

Extended-spectrum β-lactamase (ESBL)-producing Gram-negative pathogens are a major cause of resistance to expanded-spectrum β-lactam antibiotics. Since their discovery in the early 1980s, they have spread worldwide and an are now endemic in Enterobacterales isolated from both hospital-associated and community-acquired infections. As a result, they are a global public health concern. In the past, TEM- and SHV-type ESBLs were the predominant families of ESBLs. Today CTX-M-type enzymes are the most commonly found ESBL type with the CTX-M-15 variant dominating worldwide, followed in prevalence by CTX-M-14, and CTX-M-27 is emerging in certain parts of the world. The genes encoding ESBLs are often found on plasmids and harboured within transposons or insertion sequences, which has enabled their spread. In addition, the population of ESBL-producing Escherichia coli is dominated globally by a highly virulent and successful clone belonging to ST131. Today, there are many diagnostic tools available to the clinical microbiology laboratory and include both phenotypic and genotypic tests to detect β-lactamases. Unfortunately, when ESBLs are not identified in a timely manner, appropriate antimicrobial therapy is frequently delayed, resulting in poor clinical outcomes. Several analyses of clinical trials have shown mixed results with regards to whether a carbapenem must be used to treat serious infections caused by ESBLs or whether some of the older β-lactam-β-lactamase combinations such as piperacillin/tazobactam are appropriate. Some of the newer combinations such as ceftazidime/avibactam have demonstrated efficacy in patients. ESBL-producing Gram-negative pathogens will continue to be major contributor to antimicrobial resistance worldwide. It is essential that we remain vigilant about identifying them both in patient isolates and through surveillance studies.

Successful Dissemination of Plasmid-Mediated Extended-Spectrum β-Lactamases in Enterobacterales over Humans to Wild Fauna

Background: The emergence of multidrug-resistant bacteria remains poorly understood in the wild ecosystem and at the interface of habitats. Here, we explored the spread of Escherichia coli containing IncI1-ST3 plasmid encoding resistance gene cefotaximase-Munich-1 (bla_CTX-M-1) in human-influenced habitats and wild fauna using a genomic approach. Methods. Multilocus sequence typing (MLST), single-nucleotide polymorphism comparison, synteny-based analysis and data mining approaches were used to analyse a dataset of genomes and circularised plasmids. Results. CTX-M-1 E. coli sequence types (STs) were preferentially associated with ecosystems. Few STs were shared by distinct habitats. IncI1-ST3-bla_CTX-M-1 plasmids are disseminated among all E. coli phylogroups. The main divergences in plasmids were located in a shuffling zone including bla_CTX-M-1 inserted in a conserved site. This insertion hot spot exhibited diverse positions and orientations in a zone-modulating conjugation, and the resulting synteny was associated with geographic and biological sources. Conclusions. The ecological success of IncI1-ST3-bla_CTX-M-1 appears less linked to the spread of their bacterial recipients than to their ability to transfer in a broad spectrum of bacterial lineages. This feature is associated with the diversity of their shuffling conjugation region that contain bla_CTX-M-1. These might be involved in the resistance to antimicrobials, but also in their spread.

Genetic Environments of Plasmid-Mediated blaCTXM-15 Beta-Lactamase Gene in Enterobacteriaceae from Africa

The most widely distributed blaCTX-M gene on a global scale is blaCTX-M-15. The dissemination has been associated with clonal spread and different types of mobile genetic elements. The objective of this review was to describe the genetic environments of the blaCTX-M-15 gene detected from Enterobacteriaceae in published literature from Africa. A literature search for relevant articles was performed through PubMed, AJOL, and Google Scholar electronic databases; 43 articles from 17 African countries were included in the review based on the eligibility criteria. Insertion sequences were reported as part of the genetic environment of blaCTX-M-15 gene in 32 studies, integrons in 13 studies, and plasmids in 23 studies. In this review, five insertion sequences including ISEcp1, IS26, orf447, IS903, and IS3 have been detected which are associated with the genetic environment of blaCTX-M-15 in Africa. Seven different genetic patterns were seen in the blaCTX-M-15 genetic environment. Insertion sequence ISEcp1 was commonly located upstream of the end of the blaCTX-M-15 gene, while the insertion sequence orf477 was located downstream. In some studies, ISEcp1 was truncated upstream of blaCTX-M-15 by insertion sequences IS26 and IS3. The class 1 integron (Intl1) was most commonly reported to be associated with blaCTX-M-15 (13 studies), with Intl1/dfrA17–aadA5 being the most common gene cassette array. IncFIA-FIB-FII multi-replicons and IncHI2 replicon types were the most common plasmid replicon types that horizontally transferred the blaCTX-M-15 gene. Aminoglycoside-modifying enzymes, and plasmid-mediated quinolone resistance genes were commonly collocated with the blaCTX-M-15 gene on plasmids. This review revealed the predominant role of ISEcp1, Intl1 and IncF plasmids in the mobilization and continental dissemination of the blaCTX-M-15 gene in Africa.

Plasmid-mediated Kluyvera-like arnBCADTEF operon confers colistin (hetero)resistance to Escherichia coli

The use of colistin as a last resort antimicrobial is compromised by the emergence of resistant enterobacteria with acquired determinants like mcr genes, mutations that activate the PmrAB system and by still unknown mechanisms. This work analyzed 74 E. coli isolates from healthy swine, turkey or bovine, characterizing their colistin resistance determinants. The mcr-1 gene, detected in 69 isolates, was the main determinant found among which 45% were carried by highly mobile plasmids, followed by four strains lacking previously known resistance determinants or two with mcr-4 (one in addition to mcr-1), whose phenotypes were not transferred by conjugation. Although a fraction of isolates carrying mcr-1 or mcr-4 genes also presented missense polymorphisms in pmrA or pmrB, constitutive activation of PmrAB was not detected, in contrast to strains with mutations that confer colistin resistance. The expression of mcr genes negatively controls the transcription of the arnBCADTEF operon itself, a down-regulation that was also observed in the four isolates lacking known resistance determinants, three of them sharing the same macrorestriction and plasmid profiles. Genomic sequencing of one of these strains, isolated from a bovine in 2015, revealed a IncFII plasmid of 62.1 Kb encoding an extra copy of the arnBCADTEF operon closely related to Kluyvera ascorbata homologs. This element, called pArnT1, was cured by ethidium bromide and the cells lost resistance to colistin in parallel. Furthermore, a susceptible E. coli strain acquired heteroresistance after transformation with pArnT1 or pBAD24 carrying the Kluyvera-like arnBCADTEF operon, revealing it as a new colistin resistance determinant.

Whole genome sequencing of Salmonella enterica serovar Saintpaul for elucidating the mechanisms of resistance to third generation cephalosporins

An increase in the number of Salmonella enterica serovar Saintpaul observed in Singapore in 2015-2016 in humans was accompanied by increased resistance to third generation cephalosporins. We aimed to understand the genetic mechanisms contributing to this resistance. Whole genome sequencing using MiSeq was performed on 49 S. Saintpaul isolates collected between 2014-2016. Nanopore sequencing was also performed in an attempt to obtain a full genome of the plasmids. All but one S. Saintpaul isolates sequenced belonged to a single sequence type based on an in silico 7-gene multi-locus sequence typing scheme suggesting a clonal lineage. In total 27/49 were resistant to third generation cephalosporins as confirmed by the broth microdilution method; the resistance was due to the presence of either bla_CTX-M-55 (n=23), bla_CTX-M-27 (n=1) or bla_CMY-2 (n=3) carried on a plasmid. Two isolates were also found to carry the mcr-1 gene on a different plasmid. Our study showed that all S. Saintpaul isolates resistant to third generation cephalosporins carried either bla_CTX-M-55, bla_CTX-M-27 or bla_CMY-2 on a plasmid. Continuous monitoring of Salmonella serovars is warranted to track the potential spread of these plasmids.

High Prevalence of Drug Resistance and Class 1 Integrons in Escherichia coli Isolated From River Yamuna, India: A Serious Public Health Risk

Globally, urban water bodies have emerged as an environmental reservoir of antimicrobial resistance (AMR) genes because resistant bacteria residing here might easily disseminate these traits to other waterborne pathogens. In the present study, we have investigated the AMR phenotypes, prevalent plasmid-mediated AMR genes, and integrons in commensal strains of Escherichia coli, the predominant fecal indicator bacteria isolated from a major urban river of northern India Yamuna. The genetic environment of bla_CTX–M–15 was also investigated. Our results indicated that 57.5% of the E. coli strains were resistant to at least two antibiotic classes and 20% strains were multidrug resistant, i.e., resistant to three or more antibiotic classes. The multiple antibiotic resistance index of about one-third of the E. coli strains was quite high (>0.2), reflecting high contamination of river Yamuna with antibiotics. With regard to plasmid-mediated AMR genes, bla_TEM–1 was present in 95% of the strains, followed by qnrS1 and armA (17% each), bla_CTX–M–15 (15%), strA-strB (12%), and tetA (7%). Contrary to the earlier reports where bla_CTX–M–15 was mostly associated with pathogenic phylogroup B2, our study revealed that the CTX-M-15 type extended-spectrum β-lactamases (ESBLs) were present in the commensal phylogroups A and B1, also. The genetic organization of bla_CTX–M–15 was similar to that reported for E. coli, isolated from other parts of the world; and ISEcp1 was present upstream of bla_CTX–M–15. The integrons of classes 2 and 3 were absent, but class 1 integron gene intI1 was present in 75% of the isolates, denoting its high prevalence in E. coli of river Yamuna. These evidences indicate that due to high prevalence of plasmid-mediated AMR genes and intI1, commensal E. coli can become vehicles for widespread dissemination of AMR in the environment. Thus, regular surveillance and management of urban rivers is necessary to curtail the spread of AMR and associated health risks.

Poultry and Wild Birds as a Reservoir of CMY-2 Producing Escherichia coli: The First Large-Scale Study in Greece

Resistance mediated by β-lactamases is a globally spread menace. The aim of the present study was to determine the occurrence of Escherichia coli producing plasmid-encoded AmpC β-lactamases (pAmpC) in animals. Fecal samples from chickens (n = 159), cattle (n = 104), pigs (n = 214), and various wild bird species (n = 168), collected from different Greek regions during 2018-2020, were screened for the presence of pAmpC-encoding genes. Thirteen E. coli displaying resistance to third-generation cephalosporins and a positive AmpC confirmation test were detected. bla_CMY-2 was the sole pAmpC gene identified in 12 chickens' and 1 wild bird (Eurasian magpie) isolates and was in all cases linked to an upstream ISEcp1-like element. The isolates were classified into five different sequence types: ST131, ST117, ST155, ST429, and ST1415. Four chickens' stains were assigned to ST131, while five chickens' strains and the one from the Eurasian magpie belonged to ST117. Seven pAmpC isolates co-harbored genes conferring resistance to tetracyclines (tetM, tetB, tetC, tetD), 3 carried sulfonamide resistance genes (sulI and sulII), and 10 displayed mutations in the quinolone resistance-determining regions of gyrA (S83L+D87N) and parC (S80I+E84V). This report provides evidence of pAmpC dissemination, describing for the first time the presence of CMY-2 in chickens and wild birds from Greece.

Identification and characterization of a spreadable IncI1 plasmid harbouring a blaCTX-M-15 gene in an Italian human isolate of Salmonella serovar Napoli

Salmonella enterica subsp. enterica serovar Napoli (S. Napoli) ranks among the top serovars causing human infections in Italy, although not common in other European countries. Isolates are generally pan-susceptible or resistant to aminoglycosides only, however data on antimicrobial resistance genes in strains of S. Napoli are limited. Recently an isolate encoding resistance to third generation cephalosporins was reported. This study aimed to characterize plasmid-encoded cephalosporin resistance due to the bla_CTX-M-15 gene in a human S. Napoli isolate in Italy, and to investigate plasmid stability over time. S. Napoli 16/174478 was confirmed to be ESBL-producing. The bla_CTX-M-15 gene was shown to be located on an IncI1α plasmid of 90,272 bp (50.03 GC%) encoding for 107 coding sequences (CDS). The plasmid was successfully transferred by conjugation to an E. coli 1816 recipient strain (conjugation frequency 3.9 × 10^-2 transconjugants per donor). Transconjugants were confirmed to carry the IncI1α plasmid, and to be ESBL-producing strains as well. Moreover, transconjugant colonies maintained the plasmid for up to 10 passages. The identification of S. Napoli isolates able to produce ESBLs is of great concern, as this pathogen is frequently associated with invasive infections and a higher risk of bacteraemia, and its reservoir has not yet been clearly identified.

Antibiotic resistance plasmid composition and architecture in Escherichia coli isolates from meat

Resistance plasmids play a crucial role in the transfer of antimicrobial resistance from the veterinary sector to human healthcare. In this study plasmids from foodborne Escherichia coli isolates with a known (ES)BL or tetracycline resistance were sequenced entirely with short- and long-read technologies to obtain insight into their composition and to identify driving factors for spreading. Resistant foodborne E. coli isolates often contained several plasmids coding for resistance to various antimicrobials. Most plasmids were large and contained multiple resistance genes in addition to the selected resistance gene. The majority of plasmids belonged to the IncI, IncF and IncX incompatibility groups. Conserved and variable regions could be distinguished in each of the plasmid groups. Clusters containing resistance genes were located in the variable regions. Tetracycline and (extended spectrum) beta-lactamase resistance genes were each situated in separate clusters, but sulphonamide, macrolide and aminoglycoside formed one cluster and lincosamide and aminoglycoside another. In most plasmids, addiction systems were found to maintain presence in the cell.

A framework for identifying the recent origins of mobile antibiotic resistance genes

Since the introduction of antibiotics as therapeutic agents, many bacterial pathogens have developed resistance to antibiotics. Mobile resistance genes, acquired through horizontal gene transfer, play an important role in this process. Understanding from which bacterial taxa these genes were mobilized, and whether their origin taxa share common traits, is critical for predicting which environments and conditions contribute to the emergence of novel resistance genes. This knowledge may prove valuable for limiting or delaying future transfer of novel resistance genes into pathogens. The literature on the origins of mobile resistance genes is scattered and based on evidence of variable quality. Here, we summarize, amend and scrutinize the evidence for 37 proposed origins of mobile resistance genes. Using state-of-the-art genomic analyses, we supplement and evaluate the evidence based on well-defined criteria. Nineteen percent of reported origins did not fulfill the criteria to confidently assign the respective origin. Of the curated origin taxa, >90% have been associated with infection in humans or domestic animals, some taxa being the origin of several different resistance genes. The clinical emergence of these resistance genes appears to be a consequence of antibiotic selection pressure on taxa that are permanently or transiently associated with the human/domestic animal microbiome.

Ebmeyer and colleagues developed a genomic framework for identification and scrutiny of the origins of antibiotic resistance genes. Using data scoured from the literature and publicly available genomes, their results indicate that only 81% of previously reported origins are valid, and that the majority of resistance genes of which the origin is known to date emerged in taxa that have been associated with infection in humans and domesticated animals.

In vitro synergistic activity of fosfomycin in combination with other antimicrobial agents against carbapenem-resistant Klebsiella pneumoniae isolated from patients in a hospital in Thailand

INTRODUCTION

Carbapenem-resistant Klebsiella pneumoniae (CRKP) causes high morbidity and mortality worldwide. The purpose of the study was to assess the synergistic activity of fosfomycin in combination with other antimicrobial agents against CRKP isolated from patients in Songklanagarind Hospital, Thailand.

METHODS

A total of 35 K. pneumoniae isolates were obtained from patients in Songklanagarind Hospital. The MICs of imipenem and meropenem were determined in all isolates by broth microdilution. In all CRKP isolates, the presence of carbapenemase and extended-spectrum β-lactamase (ESBL) genes was investigated by PCR, while the production of these enzymes was determined by combined disk test. In the carbapenemase-genes-negative CRKP isolates, the porin loss and efflux pump were characterized by SDS-PAGE and broth microdilution, respectively. Finally, the synergistic effects of fosfomycin and other antimicrobial agents were evaluated by checkerboard analysis.

RESULTS

Twenty-one of 35 K. pneumoniae isolates were classified as CRKP. Most of CRKP isolates carried bla_NDM-1 (n = 18), bla_SHV (n = 21), bla_CTX-M (n = 21), and bla_TEM (n = 16). In fosfomycin-based combination, the result showed that the highest synergistic activity in this study was observed in the combination of fosfomycin and gentamicin (61.9%).

CONCLUSION

These findings suggested that the fosfomycin and gentamicin combination might be useful as a possible treatment option for CRKP infection.

Snapshot Study of Whole Genome Sequences of Escherichia coli from Healthy Companion Animals, Livestock, Wildlife, Humans and Food in Italy

Animals, humans and food are all interconnected sources of antimicrobial resistance (AMR), allowing extensive and rapid exchange of AMR bacteria and genes. Whole genome sequencing (WGS) was used to characterize 279 Escherichia coli isolates obtained from animals (livestock, companion animals, wildlife), food and humans in Italy. E. coli predominantly belonged to commensal phylogroups B1 (46.6%) and A (29%) using the original Clermont criteria. One hundred and thirty-six sequence types (STs) were observed, including different pandemic (ST69, ST95, ST131) and emerging (ST10, ST23, ST58, ST117, ST405, ST648) extraintestinal pathogenic Escherichia coli (ExPEC) lineages. Eight antimicrobial resistance genes (ARGs) and five chromosomal mutations conferring resistance to highest priority critically important antimicrobials (HP-CIAs) were identified (qnrS1, qnrB19, mcr-1, bla_CTX-M1,15,55, bla_CMY-2, gyrA/parC/parE, ampC and pmrB). Twenty-two class 1 integron arrangements in 34 strains were characterized and 11 ARGs were designated as intI1 related gene cassettes (aadA1, aadA2, aadA5, aad23, ant2_Ia, dfrA1, dfrA7, dfrA14, dfrA12, dfrA17, cmlA1). Notably, most intI1 positive strains belonged to rabbit (38%) and poultry (24%) sources. Three rabbit samples carried the mcr-1 colistin resistance gene in association with IS6 family insertion elements. Poultry meat harbored some of the most prominent ExPEC STs, including ST131, ST69, ST10, ST23, and ST117. Wildlife showed a high average number of virulence-associated genes (VAGs) (mean = 10), mostly associated with an ExPEC pathotype and some predominant ExPEC lineages (ST23, ST117, ST648) were identified.

Beneficial Chromosomal Integration of the Genes for CTX-M Extended-Spectrum β-Lactamase in Klebsiella pneumoniae for Stable Propagation

Dominant F-type plasmids harboring the gene have been pointed out to be responsible for the dissemination of the CTX-M extended-spectrum-β-lactamase (ESBL)-producing K. pneumoniae. Recently, the emergence of K. pneumoniae isolates with the bla_CTX-M gene in their chromosomes has been reported occasionally worldwide. Such a chromosomal location of the resistance gene could be beneficial for stable propagation, as was the Acinetobacter baumannii ST191 harboring chromosomal bla_OXA-23 that is endemic to South Korea. Through the present study, particular clones were identified as having built-in resistance genes in their chromosomes, and the chromosomal integration events were tracked by assessing their genomes. The cefotaxime-resistant K. pneumoniae clones of this study were particularized as results of the fastidiousness for plasmids to acquire the bla_CTX-M gene for securing the diversity and of the chromosomal addiction of the bla_CTX-M gene for ensuring propagation.

The acquired CTX-M-type extended-spectrum-β-lactamase (ESBL)-producing Enterobacterales are of great concern in clinical settings because they limit therapeutic options for patients infected by the pathogens. An intriguing clonality of CTX-M ESBL-producing Klebsiella pneumoniae blood isolates was observed from a national cohort study, and comparative genomics were assessed for the 115 K. pneumoniae blood isolates carrying the bla_CTX-M gene. The plasmid preference of particular clones of a sequence type (ST) was assessed by liquid mating. A quarter of the bla_CTX-M gene-carrying K. pneumoniae blood isolates harbor the gene in their chromosome, and most of those with the built-in bla_CTX-M gene belonged either to ST307 or ST48. Notably, all 16 K. pneumoniae ST48 isolates harbored two copies of the bla_CTX-M-15 gene in the chromosome. The chromosomal integration of the bla_CTX-M-15 gene was mostly derived from the ISEcp1-targeting 5-bp AT-rich locus in the chromosome. The IS26-mediated chromosomal integration occurred when the upstream ISEcp1 from the bla_CTX-M gene was truncated, targeting the anchor IS26 copy in the chromosome. Higher transfer efficiency of the bla_CTX-M-15 gene-carrying FIA:R plasmid was observed in ST17 than that of the bla_CTX-M-14 gene-carrying FIB:FII plasmid. The transfer efficiency of the plasmid differed by isolate among the ST307 members. The K. pneumoniae clones ST307 and ST48 harboring the bla_CTX-M-15 gene in the chromosome were able to disseminate stably in clinical settings regardless of the environmental pressure, and the current population of K. pneumoniae blood isolates was constructed. Further follow-up is needed for the epidemiology of this antimicrobial resistance.

IMPORTANCE Dominant F-type plasmids harboring the gene have been pointed out to be responsible for the dissemination of the CTX-M extended-spectrum-β-lactamase (ESBL)-producing K. pneumoniae. Recently, the emergence of K. pneumoniae isolates with the bla_CTX-M gene in their chromosomes has been reported occasionally worldwide. Such a chromosomal location of the resistance gene could be beneficial for stable propagation, as was the Acinetobacter baumannii ST191 harboring chromosomal bla_OXA-23 that is endemic to South Korea. Through the present study, particular clones were identified as having built-in resistance genes in their chromosomes, and the chromosomal integration events were tracked by assessing their genomes. The cefotaxime-resistant K. pneumoniae clones of this study were particularized as results of the fastidiousness for plasmids to acquire the bla_CTX-M gene for securing the diversity and of the chromosomal addiction of the bla_CTX-M gene for ensuring propagation.

Resistance Profiling and Molecular Characterization of Extended-Spectrum/Plasmid-Mediated AmpC β-Lactamase-Producing Escherichia coli Isolated from Healthy Broiler Chickens in South Korea

We aimed to identify and characterize extended-spectrum β-lactamase (ESBL)-and/or plasmid-mediated AmpC β-lactamase (pAmpC)-producing Escherichia coli isolated from healthy broiler chickens slaughtered for human consumption in Korea. A total of 332 E. coli isolates were identified from 339 cloacal swabs in 2019. More than 90% of the isolates were resistant to multiple antimicrobials. ESBL/pAmpC-production was noted in 14% (46/332) of the isolates. Six of the CTX-M-β-lactamase-producing isolates were found to co-harbor at least one plasmid-mediated quinolone resistance gene. We observed the co-existence of blaCMY-2 and mcr-1 genes in the same isolate for the first time in Korea. Phylogenetic analysis demonstrated that the majority of blaCMY-2-carrying isolates belonged to subgroup D. Conjugation confirmed the transferability of blaCTX-M and blaCMY-2 genes, as well as non-β-lactam resistance traits from 60.9% (28/46) of the ESBL/pAmpC-producing isolates to a recipient E. coli J53. The ISECP, IS903, and orf477 elements were detected in the upstream or downstream regions. The blaCTX-M and blaCMY-2 genes mainly belonged to the IncI1, IncHI2, and/or IncFII plasmids. Additionally, the majority of ESBL/pAmpC-producing isolates exhibited heterogeneous PFGE profiles. This study showed that healthy chickens act as reservoirs of ESBL/pAmpC-producing E. coli that can potentially be transmitted to humans.

Horizontal Plasmid Transfer among Klebsiella pneumoniae Isolates Is the Key Factor for Dissemination of Extended-Spectrum β-Lactamases among Children in Tanzania

Horizontal spread of plasmids carrying multiple resistance genes is considered an important mechanism behind the global health problem caused by multidrug-resistant bacteria. Nevertheless, knowledge about spread of plasmids in a community is limited. Our detailed molecular analyses of K. pneumoniae isolated from hospitalized and healthy children in Tanzania disclosed an epidemic spread of a resistance plasmid. In this study population, we revealed horizontal plasmid transfer among K. pneumoniae as the key factor for dissemination of ESBLs. Traditional outbreak investigation and surveillance focus on the spread of bacterial clones, and short-read sequencing can result in erroneous plasmid composition. Our approach using long-read sequencing reveals horizontal gene transfer of antimicrobial resistance, and therefore has a potential impact on outbreak investigations and approaches to limit spread of AMR.

Increased knowledge about the role of horizontal gene transfer is key to improve our understanding of the spread of antimicrobial resistance (AMR) in human populations. We therefore studied the dissemination of the bla_CTX-M-15 extended-spectrum-β-lactamase (ESBL) gene in Klebsiella pneumoniae isolates obtained from stool samples from hospitalized children and healthy controls below 2 years of age in Dar es Salaam, Tanzania, from August 2010 to July 2011. We performed Illumina whole-genome sequencing (WGS) to characterize resistance genes, multilocus sequence type (MLST), plasmid incompatibility group (Inc), and plasmid MLST of 128 isolates of K. pneumoniae with bla_CTX-M-15 recovered from both healthy and hospitalized children. We assessed the phylogenetic relationship using single nucleotide polymorphism (SNP)-based analysis and resolved the sequences of five reference plasmids by Oxford Nanopore technology to investigate plasmid dissemination. The WGS analyses revealed the presence of a bla_CTX-M-15-positive IncFII_K5/IncR plasmid with a highly conserved backbone in 70% (90/128) of the isolates. This plasmid, harboring genes encoding resistance to most β-lactams, aminoglycosides, trimethoprim-sulfamethoxazole, and chloramphenicol, was present in phylogenetically very diverse K. pneumoniae strains (48 different MLSTs) carried by both hospitalized and healthy children. Our data strongly suggest widespread horizontal transfer of this ESBL-carrying plasmid both in hospitals and in the general population.

IMPORTANCE Horizontal spread of plasmids carrying multiple resistance genes is considered an important mechanism behind the global health problem caused by multidrug-resistant bacteria. Nevertheless, knowledge about spread of plasmids in a community is limited. Our detailed molecular analyses of K. pneumoniae isolated from hospitalized and healthy children in Tanzania disclosed an epidemic spread of a resistance plasmid. In this study population, we revealed horizontal plasmid transfer among K. pneumoniae as the key factor for dissemination of ESBLs. Traditional outbreak investigation and surveillance focus on the spread of bacterial clones, and short-read sequencing can result in erroneous plasmid composition. Our approach using long-read sequencing reveals horizontal gene transfer of antimicrobial resistance, and therefore has a potential impact on outbreak investigations and approaches to limit spread of AMR.