Dissemination of the transmissible quinolone-resistance gene qnrS1 by IncX plasmids in Nigeria

Transmissible antimicrobial resistance in Escherichia coli isolated from household drinking water in Ibadan, Nigeria

Contaminated household water in peri-urban communities is a reservoir for virulent Escherichia coli, but its role in the environmental transmission of antibiotic resistance genes (ARGs) remains poorly understood. This study characterized E. coli from household water and additionally aimed to investigate the transmissibility of ARGs from drug-resistant isolates. Twenty-five E. coli isolates from thirteen household well water sources were tested for resistance to 14 antibiotics by disc diffusion and whole-genome sequenced using the Illumina platform. The ARGs and plasmid replicon types were respectively predicted using ResFinder and PlasmidFinder. Multidrug-resistant strains carrying plasmid replicons found in unrelated strains were conjugated with nalidixic acid-resistant (NALR) E. coli C600 using the solid plate method. Fifteen isolates displayed a multi-drug resistance (MDR) phenotype, with 18 possessing ARGs that confer resistance to trimethoprim-sulfamethoxazole, macrolide, sulphonamide, aminoglycoside, chloramphenicol, β-lactams, and tetracycline. Fifteen of the 25 isolates belonged to sequence type detected more than once, and fourteen of these were multidrug resistant. Through solid plate mating, beta-lactam-resistant qnrS1-tet-dfrA14-positive strains bearing IncFI-, IncHI2, and IncHI2A successfully transferred ampicillin resistance to a nalidixic acid-resistant derivative of E. coli-C600. This research highlights the urgent need to safeguard household water sources against fecal contamination to curb the dissemination of ARGs among bacterial populations in this environment.

Genomic characterization of foodborne Salmonella enterica and Escherichia coli isolates from Saboba district and Bolgatanga Municipality Ghana

Salmonella enterica and Escherichia coli are well-known bacteria commonly associated with foodborne illnesses in humans and animals. Genomic characterization of these pathogens provides valuable insights into their evolution, virulence factors and resistance determinants. This study aimed to characterized previously isolated Salmonella (n = 14) and E. coli (n = 19) from milk, meat and its associated utensils in Ghana using whole-genome sequencing. Most of the Salmonella serovars (Fresno, Plymouth, Infantis, Give and Orleans) identified in this study are yet to be reported in Ghana. Most Salmonella isolates were pan-sensitive, but genes conferring resistance to fosfomycin (fosA7.2) and tetracycline (tet(A)) were detected in one and three isolates, respectively. Seven of the Salmonella isolates carried the IncI1-I(Gamma) plasmid replicon. Although antimicrobial resistance was not common among Salmonella strains, most (11/19) of the E. coli strains had at least one resistance gene, with nearly half (8/19) being multidrug resistant and carried plasmids. Three of the 19 E. coli strains belonged to serovars commonly associated with enteroaggregative E. coli (EAEC) pathotype. While strains belonging to virulence-associated lineages lacked key plasmid-encoded virulence plasmids, several plasmid replicons were detected in most of the E. coli (14/19) strains. Food contaminated with these pathogens can serve as a vehicle for disease transmission, posing a significant public health risk and necessitating stringent food safety and hygiene practices to prevent outbreaks. Hence, there is need for continuous surveillance and preventive measures to stop the spread of foodborne pathogens and reduce the risk of associated illnesses in Ghana.

Molecular characteristics of CTX-M β-lactamase-producing and quinolone-resistant Escherichia coli among deer in a popular tourist spot in Japan

Introduction. Antimicrobial resistance (AMR) is a growing global concern. Clonal lineages of CTX-M β-lactamase-producing Escherichia coli (CTXE) and quinolone-resistant E. coli (QREC) were disseminated among the deer population in a famous tourist destination (Nara Park; NP) in Japan. Hypothesis/gap statement. The molecular characteristics of CTXE or QREC isolates, which could pose a threat to public health, have not been elucidated. Aim. This study aimed to characterize the genetic traits of CTXE and QREC isolates derived from NP deer and compare them with lineages prevalent worldwide. Methodology. Sixteen CTXE and three QREC isolates recovered from NP deer faeces between 2018 and 2020 were analysed using whole-genome sequencing (WGS). For endemic lineages, phylogenetic trees were constructed against the isolates registered in the EnteroBase database using the core genome SNP scheme. Results. The most prevalent lineage in NP deer was ST3580. Several pandemic lineages, such as sequence type (ST) 38, ST58 and ST117, were included. The QREC lineages prevalent among deer were designated as extra-intestinal pathogenic E. coli or uropathogenic E. coli (UPEC). Thirteen of the 24 antimicrobial resistance genes (ARGs) were considered high-risk ARG families. Chromosomal integration of bla CTX-M-15 was observed in all plasmid-negative isolates. Phylogenetic analysis suggested relationships between NP isolates and isolates sourced from the environment or poultry. Conclusion. ST3580 has a high potential for clonal dissemination. Furthermore, multiple clinically relevant lineages of CTXE and QREC are endemic in NP deer; however, they could be less virulent than isolates belonging to the same lineages, which could cause severe infectious diseases. Further studies are required to investigate the relationship between chromosomal integration of plasmid-encoded genes and the stable propagation of AMR bacteria in wildlife and the environment.

Quinolone-resistant Escherichia coli at the interface between humans, poultry and their shared environment- a potential public health risk

BACKGROUND

Commensal Escherichia coli residing in the guts of humans and animals are reservoirs of multidrug resistance (MDR) genes, including quinolone resistance genes, in humans and poultry. This study aimed to characterize quinolones resistance in E. coli recovered from poultry workers, chickens, and poultry farm/market environments in Abuja, Nigeria.

METHODS

This was a cross-sectional study conducted between December 2018 and April 2019 comprising poultry workers, chickens and their poultry farm/market environments. This study characterized E. coli isolates from stool, faecal and environmental samples using antimicrobial susceptibility testing and whole-genome sequencing methods. Core-genome multilocus sequences-based phylogeny was used to determine the relatedness between quinolone-resistant E. coli isolates. Data were analyzed using descriptive statistics.

RESULTS

Of 110 E. coli isolates, quinolone-resistant phenotypes were observed in 68.2% (n = 75) isolates. Whole-genome sequencing detected plasmid-mediated quinolone resistance (PMQR) genes in 63.6% (n = 70) isolates. The most prevalent PMQR gene detected in 56 of these 70 E. coli isolates was qnrS1, followed by qnrB19 in 14 isolates and aac(6')-lb-cr in two isolates. Fifteen ciprofloxacin and 19 nalidixic acid-resistant isolates respectively showed double mutations in the quinolone-resistance determining regions (QRDRs) of gyrA, with single or double mutations in parC, and a single mutation in parE. The most prevalent amino-acid substitutions observed were S83L + D87N in gyrA (46.5%, n = 20), S80I in parC (51.2%, n = 22) and S458A in parE (14%, n = 6). About 2.9% (2/70) of PMQR isolates were extended-spectrum beta-lactamase (ESBL) producers while 2.9% (2/70) had plasmid-mediated colistin resistance (PMCR) genes.

CONCLUSIONS

PMQR genes were prevalent in E. coli isolates recovered from healthy humans, chickens and poultry farm/market environments. PMCR genes (mcr-1.1) occurred in PMQR-positive isolates recovered from manure and drinking water originating from poultry farm/market environments. It was found that the gene encoding ESBL coexisted with qnrS-positive isolates of human and avian origin. Horizontal transfer of PMQR genes among E. coli isolates in the human-poultry-environment interface has public health implications for the spread of antimicrobial resistance. Relevant government agencies should enforce regulations to restrict the use of critically important antimicrobials in poultry production.

Proteus mirabilis isolated from untreated hospital wastewater, Ibadan, Southwestern Nigeria showed low-level resistance to fluoroquinolone and carried qnrD3 on Col3M plasmids

Untreated wastewater emanating from healthcare facilities are risk factors for the spread of antimicrobial resistance (AMR) at the human-environment interface. In this study, we investigated the determinants of resistance in three multidrug resistant strains of Proteus mirabilis isolated from untreated wastewater collected from three government owned hospitals in Ibadan, Nigeria. Despite showing low-level resistance to ciprofloxacin, whole genome sequencing revealed the transferable mechanism of quinolone resistance (TMQR) gene qnrD3 carried on Col3M plasmids in all the isolates. Core genome phylogenetic analysis showed the isolates are closely related differing from each other by ≤ 23 single nucleotide polymorphisms (SNP). Further, they shared the closest evolutionary relationship with isolates from China. Similarly, the Col3M plasmids is most closely related to p3M-2A found in P. vulgaris 3 M isolated from the intestine of shrimps in China. This to the best of our knowledge is the first report of Col3M plasmids carrying qnrD3 in environmental bacterial isolates. Our results indicate a possible silent spread of this important plasmid associated with the dissemination of qnrD3 in Nigeria, and further highlights the important role played by untreated wastewater from healthcare facilities in the spread of AMR in low- and middle-income countries.

A large self-transmissible resistance plasmid from Nigeria contains genes that ameliorate a carrying cost

Antimicrobial resistance is rapidly expanding, in a large part due to mobile genetic elements. We screened 94 fecal fluoroquinolone-resistant Escherichia coli isolates from Nigeria for six plasmid-mediated quinolone resistance (PMQR) genes. Sixteen isolates harbored at least one of the PMQR genes and four were positive for aac-6-Ib-cr. In one strain, aac-6-Ib-cr was mapped to a 125 Kb self-transmissible IncFII plasmid, pMB2, which also bears bla_CTX-M-15, seven other functional resistance genes and multiple resistance pseudogenes. Laboratory strains carrying pMB2 grew faster than isogenic strains lacking the plasmid in both rich and minimal media. We excised a 32 Kb fragment containing transporter genes and several open-reading frames of unknown function. The resulting 93 Kb mini-plasmid conferred slower growth rates and lower fitness than wildtype pMB2. Trans-complementing the deletion with the cloned sitABCD genes confirmed that they accounted for the growth advantage conferred by pMB2 in iron-depleted media. pMB2 is a large plasmid with a flexible resistance region that contains loci that can account for evolutionary success in the absence of antimicrobials. Ancillary functions conferred by resistance plasmids can mediate their retention and transmissibility, worsening the trajectory for antimicrobial resistance and potentially circumventing efforts to contain resistance through restricted use.

Multidrug-resistant Citrobacter freundii ST139 co-producing NDM-1 and CMY-152 from China

The emergence of carbapenemase-producing Citrobacter freundii poses a significant threat to public health worldwide. Here, we reported a C. freundii strain CWH001 which was resistant to all tested antimicrobials except tetracycline. Whole genome sequencing and analysis were performed. The strain, which belonged to a new sequence type ST139, showed close relationship with other foreign C. freundii strains through phylogenetic analysis. A novel variant of the intrinsic bla_CMY gene located on the chromosome was identified and designated as bla_CMY-152. Coexistence of bla_NDM-1 with qnrS1 was found on a conjugative IncN plasmid, which had a backbone appearing in various plasmids. Other class A ESBL genes (bla_VEB-3 and bla_TEM-1) were also detected on two different novel plasmids. The emergence of multidrug-resistant C. freundii is of major concern, causing great challenges to the treatment of clinical infections. Great efforts need to be taken for the specific surveillance of this opportunistic pathogen.

Tetracycline use in the community may promote decreased susceptibility to quinolones in Escherichia coli isolates

We previously found that the hospital use of tetracyclines is associated with quinolone resistance in hospital isolates of Enterobacteriaceae. Tetracyclines are heavily used in the community. Our aim was to assess whether their use in the community favors quinolone resistance in community isolates of Escherichia coli. Monthly data of community antibiotics use and E. coli quinolone resistance in a 1.3 million inhabitant French area were obtained from 2009 to 2014, and were analyzed with autoregressive integrated moving average (ARIMA) models. Quinolone use decreased from 10.1% of the total antibiotic use in 2009 to 9.3% in 2014 (trend, - 0.016; p-value < 0.0001), while tetracycline use increased from 16.5% in 2009 to 17.1% in 2014 (trend, 0.016; p < 0.0001). The mean (95% confidence interval) monthly proportions of isolates that were non-susceptible to nalidixic acid and ciprofloxacin were 14.8% (14.2%-15.5%) and 9.5% (8.8%-10.1%), respectively, with no significant temporal trend. After adjusting on quinolone use, tetracycline use in the preceding month was significantly associated with nalidixic acid non-susceptibility (estimate [SD], 0.01 [0.007]; p-value, 0.04), but not with ciprofloxacin non-susceptibility (estimate [SD], 0.01 [0.009]; p-value, 0.23). Tetracycline use in the community may promote quinolone non-susceptibility in E. coli. Decreasing both tetracycline and quinolone use may be necessary to fight against the worldwide growth of quinolone resistance.

IncX2 and IncX1-X2 Hybrid Plasmids Coexisting in a FosA6-Producing Escherichia coli Strain

IncX plasmids are receiving much attention as vehicles of carbapenem and colistin resistance genes, such as bla_NDM, bla_KPC, and mcr-1 Among them, IncX2 subgroup plasmids remain rare. Here, we characterized IncX2 and IncX1-X2 hybrid plasmids coexisting in a FosA6-producing Escherichia coli strain that were possibly generated as a consequence of recombination events between an R6K-like IncX2 plasmid and a pLN126_33-like IncX1 plasmid. Variable multidrug resistance mosaic regions were observed in these plasmids, indicating their potential to serve as flexible carriers of resistance genes. The diversity of IncX group plasmid backbones and accessory genes and the evolution of hybrid IncX plasmids pose a challenge in detecting and classifying them.

Carriage of type II toxin-antitoxin systems by the growing group of IncX plasmids

The stable maintenance of certain plasmids in bacterial populations has contributed significantly to the current worldwide antibiotic resistance (AbR) emergency. IncX plasmids, long underestimated in this regard, have achieved recent notoriety for their roles in transmission of resistance to carbapenem and colistin, the last-line antibiotics for Gram-negative infections. Toxin-antitoxin (TA) systems contribute to stable maintenance of many AbR plasmids, and a few TA systems have been previously described in the IncX plasmids. Here we present an updated overview of the IncX plasmid family and an in silico analysis of the type II TA systems carried in 153 completely sequenced IncX plasmids that are readily available in public databases at time of writing. The greatest number is in the IncX1 subgroup, followed by IncX3 and IncX4, with only a few representatives of IncX2, IncX5 and IncX6. Toxins from the RelE/ParE superfamily are abundant within IncX1 and IncX4 subgroups, and are associated with a variety of antitoxins. By contrast, the HicBA system is almost exclusively encoded by IncX4 plasmids. Toxins from the superfamily CcdB/MazF were also identified, as were less common systems such as PIN-like and GNAT toxins, and plasmids encoding more than one TA system are probably not unusual. Our results highlight the importance of the IncX plasmid group and update previous much smaller studies, and we present for the first time a detailed analysis of type II TA systems in these plasmids.

Prevalence of Quinolone Resistance in Enterobacteriaceae from Sierra Leone and the Detection of qnrB Pseudogenes and Modified LexA Binding Sites

A collection of 74 Enterobacteriaceae isolates found in Bo, Sierra Leone, were tested for quinolone antibiotic susceptibility and resistance mechanisms. The majority of isolates (62%) were resistant to quinolones, and 61% harbored chromosomal gyrA and/or parC mutations. Plasmid-mediated quinolone resistance genes were ubiquitous, with qnrB and aac(6')-Ib-cr being the most prevalent. Mutated LexA binding sites were found in all qnrB1 genes, and truncated qnrB pseudogenes were found in the majority of Citrobacter isolates.

A Phylogenetic and Phenotypic Analysis of Salmonella enterica Serovar Weltevreden, an Emerging Agent of Diarrheal Disease in Tropical Regions

Salmonella enterica serovar Weltevreden (S. Weltevreden) is an emerging cause of diarrheal and invasive disease in humans residing in tropical regions. Despite the regional and international emergence of this Salmonella serovar, relatively little is known about its genetic diversity, genomics or virulence potential in model systems. Here we used whole genome sequencing and bioinformatics analyses to define the phylogenetic structure of a diverse global selection of S. Weltevreden. Phylogenetic analysis of more than 100 isolates demonstrated that the population of S. Weltevreden can be segregated into two main phylogenetic clusters, one associated predominantly with continental Southeast Asia and the other more internationally dispersed. Subcluster analysis suggested the local evolution of S. Weltevreden within specific geographical regions. Four of the isolates were sequenced using long read sequencing to produce high quality reference genomes. Phenotypic analysis in Hep-2 cells and in a murine infection model indicated that S. Weltevreden were significantly attenuated in these models compared to the classical S. Typhimurium reference strain SL1344. Our work outlines novel insights into this important emerging pathogen and provides a baseline understanding for future research studies.

Organisms belonging to the species Salmonella enterica are a major cause of infection globally. Such infections can be zoonotic in origin or transmitted between humans. One of the most notable features of the genus Salmonella is that the dominant serovars that cause human infections change over time, with new threats periodically emerging. These trends often go unnoticed and are underreported in low-income locations. There is good evidence that Salmonella Weltevreden is emerging (particularly in low-income countries in the tropics) as a significant cause of diarrhea and sometimes invasive bacterial disease in humans. However, little is known about the phylogenetic structure or virulence potential of this unstudied serovar. Here, we provide a detailed phylogenetic analysis of S. Weltevreden through whole genome sequencing and bioinformatics tools. We identify that specific phylogenetic clusters are associated with geographical regions, providing novel data regarding the global distribution of different clades and high quality reference genomes to facilitate future work. We additionally show that S. Weltevreden has a distinct virulence-associated phenotype in conventional laboratory Salmonella pathogenicity assays that will guide future investigations on this serovar.

Genetic characterization of three qnrS1-harbouring multidrug-resistance plasmids and qnrS1-containing transposons circulating in Ho Chi Minh City, Vietnam

Plasmid-mediated quinolone resistance (PMQR) refers to a family of closely related genes that confer decreased susceptibility to fluoroquinolones. PMQR genes are generally associated with integrons and/or plasmids that carry additional antimicrobial resistance genes active against a range of antimicrobials. In Ho Chi Minh City (HCMC), Vietnam, we have previously shown a high frequency of PMQR genes within commensal Enterobacteriaceae. However, there are limited available sequence data detailing the genetic context in which the PMQR genes reside, and a lack of understanding of how these genes spread across the Enterobacteriaceae. Here, we aimed to determine the genetic background facilitating the spread and maintenance of qnrS1, the dominant PMQR gene circulating in HCMC. We sequenced three qnrS1-carrying plasmids in their entirety to understand the genetic context of these qnrS1-embedded plasmids and also the association of qnrS1-mediated quinolone resistance with other antimicrobial resistance phenotypes. Annotation of the three qnrS1-containing plasmids revealed a qnrS1-containing transposon with a closely related structure. We screened 112 qnrS1-positive commensal Enterobacteriaceae isolated in the community and in a hospital in HCMC to detect the common transposon structure. We found the same transposon structure to be present in 71.4 % (45/63) of qnrS1-positive hospital isolates and in 36.7 % (18/49) of qnrS1-positive isolates from the community. The resulting sequence analysis of the qnrS1 environment suggested that qnrS1 genes are widely distributed and are mobilized on elements with a common genetic background. Our data add additional insight into mechanisms that facilitate resistance to multiple antimicrobials in Gram-negative bacteria in Vietnam.