Carbapenemase-producing Salmonella enterica serotype Kentucky ST198, North Africa

A novel variant in Salmonella genomic island 1 of multidrug-resistant Salmonella enterica serovar Kentucky ST198

Salmonella enterica serovar Kentucky ST198 is a major health threat due to its resistance to ciprofloxacin and several other drugs, including third-generation cephalosporins. Many drug-resistant genes have been identified in the Salmonella genomic island 1 variant K (SGI1-K). In this study, we investigated the antimicrobial resistance (AMR) profile and genotypic relatedness of two isolates of ciprofloxacin-resistant (CIPR) S. Kentucky ST198 from poultry in Northeastern Thailand. We successfully assembled the complete genomes of both isolates, namely SSSE-01 and SSSE-03, using hybrid de novo assembly of both short- and long-read sequence data. The complete genomes revealed their highly similar genomic structures and a novel variant of SGI1-K underlying multidrug-resistant (MDR) patterns, including the presence of blaTEM-1b, which confers resistance to beta-lactams, including cephalosporins and lnu(F) which confers resistance to lincomycin and other lincosamides. In addition, the chromosomal mutations in the quinolone resistance-determining region (QRDR) were found at positions 83 (Ser83Phe) and 87 (Asp87Asn) of GyrA and at positions 57 (Thr57Ser) and 80 (Ser80Ile) of ParC suggesting high resistance to ciprofloxacin. We also compared SSSE-01 and SSSE-03 with publicly available complete genome data and revealed significant variations in SGI1-K genetic structures and variable relationships to antibiotic resistance. In comparison to the other isolates, SGI1-K of SSSE-01 and SSSE-03 had a relatively large deletion in the backbone, spanning from S011 (traG∆) to S027 (resG), and the inversion of the IS26-S044∆-yidY segment. Their MDR region was characterized by the inversion of a large segment, including the mer operon and the relocation of IntI1 and several resistance genes downstream of the IS26-S044∆-yidY segment. These structural changes were likely mediated by the recombination of IS26. The findings broaden our understanding of the possible evolution pathway of SGI1-K in fostering drug resistance, which may provide opportunities to control these MDR strains.IMPORTANCEThe emergence of ciprofloxacin-resistant (CIPR) Salmonella Kentucky ST198 globally has raised significant concerns. This study focuses on two poultry isolates from Thailand, revealing a distinct Salmonella genomic island 1 variant K (SGI1-K) genetic structure. Remarkably, multiple antibiotic resistance genes (ARGs) were identified within the SGI1-K as well as other locations in the chromosome, but not in plasmids. Comparing the SGI1-K genetic structures among global and even within-country isolates unveiled substantial variations. Intriguingly, certain isolates lacked ARGs within the SGI1-K, while others had ARGs relocated outside. The presence of chromosomal extended-spectrum β-lactamase (ESBL) genes and lincosamide resistance, lnu(F), gene, could potentially inform the choices of the treatment of CIPRS. Kentucky ST198 infections in humans. This study highlights the importance of understanding the diverse genetic structures of SGI1-K and emphasizes the role of animals and humans in the emergence of antimicrobial resistance.

Genomic characterization of multidrug-resistant Salmonella serovar Kentucky ST198 isolated in poultry flocks in Spain (2011-2017)

Salmonella Kentucky is commonly found in poultry and rarely associated with human disease. However, a multidrug-resistant (MDR) S. Kentucky clone [sequence type (ST)198] has been increasingly reported globally in humans and animals. Our aim here was to assess if the recently reported increase of S. Kentucky in poultry in Spain was associated with the ST198 clone and to characterize this MDR clone and its distribution in Spain. Sixty-six isolates retrieved from turkey, laying hen and broiler in 2011–2017 were subjected to whole-genome sequencing to assess their sequence type, genetic relatedness, and presence of antimicrobial resistance genes (ARGs), plasmid replicons and virulence factors. Thirteen strains were further analysed using long-read sequencing technologies to characterize the genetic background associated with ARGs. All isolates belonged to the ST198 clone and were grouped in three clades associated with the presence of a specific point mutation in the gyrA gene, their geographical origin and isolation year. All strains carried between one and 16 ARGs whose presence correlated with the resistance phenotype to between two and eight antimicrobials. The ARGs were located in the Salmonella genomic island (SGI-1) and in some cases (bla_SHV-12, catA1, cmlA1, dfrA and multiple aminoglycoside-resistance genes) in IncHI2/IncI1 plasmids, some of which were consistently detected in different years/farms in certain regions, suggesting they could persist over time. Our results indicate that the MDR S. Kentucky ST198 is present in all investigated poultry hosts in Spain, and that certain strains also carry additional plasmid-mediated ARGs, thus increasing its potential public health significance.

Genomic epidemiology of emerging ESBL-producing Salmonella Kentucky bla CTX-M-14b in Europe

Global dissemination of ciprofloxacin-resistant Salmonella Kentucky has been observed over the past decades. In recent years, there have been reports of extended-spectrum β-lactamase (ESBL) producing S. Kentucky. Routine surveillance at the European Centre for Disease Prevention and Control (ECDC) detected cases with a ciprofloxacin-resistant S. Kentucky with the ESBL-gene bla_CTX-M-14b. Ensuing research identified 78 cases in 2013–2018 in eight European countries. Compared to other S. Kentucky and non-typhoidal Salmonella infections, reported to the European Surveillance System, these cases were more likely to be elderly and to present urinary-tract infections. Bayesian time-scaled phylogeny on whole genome sequences of isolates from these cases and supplementary isolates from public sequence databases was used to infer the origin and spread of this clone. We dated the origin of the bla_CTX-M-14b clone to approximately 2005 in Northern Africa, most likely in Egypt. The geographic origin predicted by the phylogenetic analysis is consistent with the patients’ travel history. Next to multiple introductions of the clone to Europe from Egypt, our analysis suggests that in some parts of Europe the clone might have formed a stable population, from which further spread has occurred. Comparative genomics indicated that the bla_CTX-M-14b gene is present on the bacterial chromosome, within the type VI secretion system region. The bla_CTX-M-14b gene is integrated downstream of the hcp1 gene, on a 2854 bp plasmid fragment containing also ISEcp1. This is the first report of a chromosomally integrated CTX-M gene in Salmonella spp. in Europe, previous studies having identified similar genes only on plasmids.

Carbapenemase Producing Gram-Negative Bacteria in Tunisia: History of Thirteen Years of Challenge

The wide spread of multidrug-resistant bacteria, particularly carbapenem-resistant Gram-negative bacteria (CR-GNB), constitutes a major public health threat worldwide, owing to the limited therapeutic options. This review will describe and uncover the Tunisian experience in the challenge against carbapenem resistance. Indeed, we illuminate on the dissemination of CR-GNB in different hospitals, animals, and other natural environments in this country. We resumed the different carbapenemase variants detected from various bacterial species and mapped their regional distribution, basing on Tunisian published data during a period extended from 2006, the date of its first description in Tunisia, to February 2019. We also resumed the different mobile genetic elements implicated in their dissemination. This review shows that the majority of the research reports focused in the north and the coastal cities in spite of the fact that KPC and IMP carbapenemases were uncommonly detected in our country. However, VIM, NDM-1, and OXA-48 enzymes were usually reported with the predominance of OXA-48 among Enterobacteriaceae. Furthermore, OXA-23, OXA-51, and OXA-58 carbapenemases constituted the main mechanism conferring carbapenem resistance among Acinetobacter baumannii in Tunisia. Collaborative efforts and raising awareness of the threat of antibiotic resistance are required in order to minimize the spread of multidrug-resistant bacteria.

Replication of the Salmonella Genomic Island 1 (SGI1) triggered by helper IncC conjugative plasmids promotes incompatibility and plasmid loss

The mobilizable resistance island Salmonella genomic island 1 (SGI1) is specifically mobilized by IncA and IncC conjugative plasmids. SGI1, its variants and IncC plasmids propagate multidrug resistance in pathogenic enterobacteria such as Salmonella enterica serovars and Proteus mirabilis. SGI1 modifies and uses the conjugation apparatus encoded by the helper IncC plasmid, thus enhancing its own propagation. Remarkably, although SGI1 needs a coresident IncC plasmid to excise from the chromosome and transfer to a new host, these elements have been reported to be incompatible. Here, the stability of SGI1 and its helper IncC plasmid, each expressing a different fluorescent reporter protein, was monitored using fluorescence-activated cell sorting (FACS). Without selective pressure, 95% of the cells segregated into two subpopulations containing either SGI1 or the helper plasmid. Furthermore, FACS analysis revealed a high level of SGI1-specific fluorescence in IncC⁺ cells, suggesting that SGI1 undergoes active replication in the presence of the helper plasmid. SGI1 replication was confirmed by quantitative PCR assays, and extraction and restriction of its plasmid form. Deletion of genes involved in SGI1 excision from the chromosome allowed a stable coexistence of SGI1 with its helper plasmid without selective pressure. In addition, deletion of S003 (rep) or of a downstream putative iteron-based origin of replication, while allowing SGI1 excision, abolished its replication, alleviated the incompatibility with the helper plasmid and enabled its cotransfer to a new host. Like SGI1 excision functions, rep expression was found to be controlled by AcaCD, the master activator of IncC plasmid transfer. Transient SGI1 replication seems to be a key feature of the life cycle of this family of genomic islands. Sequence database analysis revealed that SGI1 variants encode either a replication initiator protein with a RepA_C domain, or an alternative replication protein with N-terminal replicase and primase C terminal 1 domains.

The Salmonella genomic island 1 (SGI1) and its variants propagate multidrug resistance in several species of human and animal pathogens with the help of IncA and IncC conjugative plasmids that are absolutely required for SGI1 dissemination. These helper plasmids are known to trigger the excision of SGI1 from the chromosome. Here, we found that IncC plasmids also trigger the replication of the excised, circular form of SGI1 by enabling the expression of an SGI1-borne replication initiator gene. In return, high-copy replication of SGI1 interferes with the persistence of the IncC plasmid and prevents its cotransfer into a recipient cell, thereby allowing integration and stabilization of SGI1 into the chromosome of the new host. This finding is important to better understand the complex interactions between SGI1-like elements and their helper plasmids that lead to widespread and highly efficient propagation of multidrug resistance genes to a broad range of human and animal pathogens.

High occurrence of β-lactamase-producing Salmonella Heidelberg from poultry origin

Salmonella Heidelberg is commonly reported in foodborne outbreaks around the world, and chickens and poultry products are known as important source of these pathogen. Multidrug-resistant S. Heidelberg strains are disseminated into poultry production chair, which can lead to severe clinical infections in humans and of difficult to treat. This study aimed at evaluating the β-lactam susceptibility and genotypic relatedness of Salmonella Heidelberg at Brazilian poultry production chain. Sixty-two S. Heidelberg strains from poultry production chain (poultry, poultry meat and poultry farm) were used. All strains were evaluated to antimicrobial susceptibility by diffusion disk test, as well as β-lactam resistance genes. Genotypic relatedness was assessed by Pulsed-Field Gel Eletrophoresis, using Xba1 restriction enzyme. Forty-one strains were characterized as multidrug-resistant according to phenotype characterization. The resistance susceptibility revealed 31 distinct profiles, with higher prevalence of streptomycin (61/62), nalidixic acid (50/62), tetracycline (43/62) and β-lactam drugs (37/62). blaCMY-2 was the more frequent β-lactamase gene found (38/62); other resistance genes found were blaCTX-M (2/62), blaSHV (3/62) and blaTEM-1 (38/62). No carbapenemase genes was found. The Pulsed-Field Gel Electrophoresis showed 58 different profiles. Strains with a larger number of antimicrobial resistance were grouped into ten major clusters apart from others. The spread of resistance by ampC continues to rise, thereby turning concern to public health, since the β-lactam antimicrobials are used as a therapeutic treatment in humans.

The European Union Summary Report on Antimicrobial Resistance in zoonotic and indicator bacteria from humans, animals and food in 2017/2018

Data on antimicrobial resistance (AMR) in zoonotic and indicator bacteria from humans, animals and food are collected annually by the EU Member States (MSs), jointly analysed by EFSA and ECDC and reported in a yearly EU Summary Report. The annual monitoring of AMR in animals and food within the EU is targeted at selected animal species corresponding to the reporting year. The 2017 monitoring specifically focussed on pigs and calves under 1 year of age, as well as their derived carcases/meat, while the monitoring performed in 2018 specifically focussed on poultry and their derived carcases/meat. Monitoring and reporting of AMR in 2017/2018 included data regarding Salmonella, Campylobacter and indicator Escherichia coli isolates, as well as data obtained from the specific monitoring of ESBL-/AmpC-/carbapenemase-producing E. coli isolates. Additionally, some MSs reported voluntary data on the occurrence of meticillin-resistant Staphylococcus aureus in animals and food, with some countries also providing data on antimicrobial susceptibility. This report provides, for the first time, an overview of the main findings of the 2017/2018 harmonised AMR monitoring in the main food-producing animal populations monitored, in related carcase/meat samples and in humans. Where available, data monitoring obtained from pigs, calves/cattle, broilers, laying hens and turkeys, as well as from carcase/meat samples and humans were combined and compared at the EU level, with particular emphasis on multiple drug resistance, complete susceptibility and combined resistance patterns to critically important antimicrobials, as well as Salmonella and E. coli isolates exhibiting presumptive ESBL-/AmpC-/carbapenemase-producing phenotypes. The outcome indicators for AMR in food-producing animals, such as complete susceptibility to the harmonised panel of antimicrobials in E. coli and the prevalence of ESBL-/AmpC-producing E. coli have been also specifically analysed over the period 2014-2018.

A toxin antitoxin system promotes the maintenance of the IncA/C-mobilizable Salmonella Genomic Island 1

The multidrug resistance Salmonella Genomic Island 1 (SGI1) is an integrative mobilizable element identified in several enterobacterial pathogens. This chromosomal island requires a conjugative IncA/C plasmid to be excised as a circular extrachromosomal form and conjugally mobilized in trans. Preliminary observations suggest stable maintenance of SGI1 in the host chromosome but paradoxically also incompatibility between SGI1 and IncA/C plasmids. Here, using a Salmonella enterica serovar Agona clonal bacterial population as model, we demonstrate that a Toxin-Antitoxin (TA) system encoded by SGI1 plays a critical role in its stable host maintenance when an IncA/C plasmid is concomitantly present. This system, designated sgiAT for Salmonella genomic island 1 Antitoxin and Toxin respectively, thus seems to play a stabilizing role in a situation where SGI1 is susceptible to be lost through plasmid IncA/C-mediated excision. Moreover and for the first time, the incompatibility between SGI1 and IncA/C plasmids was experimentally confirmed.