Plasmids and the spread of resistance

A strategy design based on antibiotic‑resistance and plasmid replicons genes of clinical Escherichia coli strains

Since antimicrobial resistance, especially β-lactam resistance genes were common in clinical Escherichia coli strains, this study had designed and developed multiplex amplification platform for rapid and accurate detection of such resistance genes in 542 clinical E. coli isolates. The obtained specimens were subjected to bacteriological examination, antimicrobial susceptibility testing, and detection of β-lactamase genes and plasmid replicons. The major virulence genes were detected by 7 groups of multiplex PCR and eight groups of multiplex PCR were designed to detect 8 different plasmid replicons including parA-parB, iteron, repA, and RNAI. It was found that most MDR isolates were co-resistant to penicillins (AMP) and fluoroquindones (LVX, CIP) and distribution of LVX and CIP resistance was significantly higher among female than male gender. RNAI (AY234375) showed the highest detection rate, followed by the iteron (J01724) and repA (M26308), indicating the relatively higher carriage rate of corresponding plasmids. Bla_OXA acquired the highest carriage rate, followed by group 2 bla_CTX-M and bla_SHV-1, indicating their prevalence among clinical E. coli. Among the β-lactamase genes, bla_OXA acquired the highest carriage rate, followed by group 2 bla_CTX-M and bla_SHV-1, indicating their prevalence among clinical E. coli. The RNAI (AY234375) showed the highest detection rate, followed by the iteron (J01724) and repA (M26308), indicating the relatively higher carriage rate of the corresponding plasmids by clinical E. coli isolates. It is shown that the developed multiplex amplification methodology is applicable to AMR detection, and such identification of plasmid replicons and β-lactamase genes may aid in the understanding of clinical E. coli isolate epidemiology.

Water bodies are potential hub for spatio-allotment of cell-free nucleic acid and pandemic: a pentadecadal (1969-2021) critical review on particulate cell-free DNA reservoirs in water nexus

BACKGROUND

In recent times, there had been report of diverse particulate nucleic acid-related infections and diseases which have been associated with endemic, sporadic, and pandemic reports spreading within water nexus. Some of such disease cases were seldom reported in earlier years of technological advancement and research based knowledge-scape. Although the usefulness of water, wastewater treatment systems, water regulatory organizations and water re-use policy in compliant regions remains sacrosanct, it has been implicated in diverse gene distribution.

MAIN BODY

A cosmopolitan bibliometric and critical assessment of cell-free DNA reservoir in water bodies was determined. This is done by analysing retrieved pentadecadal scientific publications in Scopus and Pubmed centre database, determining the twelve-monthly publication rates of related articles, and a content-review assessment of cell-free nucleic acids (cfNAs) in water environment. Our results revealed thirty-eight metric documents with sources as journals and books that conform to the inclusion criteria. The average reports/publication rate per year shows 16.7, while several single and collaborating authors are included with a collaboration index of 4.31. A zero average citation per document and citation per year indicate poor research interest and awareness.

SHORT CONCLUSION

It is important to note that a redirected interest to studies on cfNAs in water environments would encourage advancement of water treatment strategies to include specific approaches on the removal of cfNAs, membrane vesicles or DNA reservoirs, plasmids or extra-chromosomal DNA and other exogenous nucleic acids from water bodies. It may also lead to a generational development/improvement of water treatment strategies for the removals of cfNAs and its members from water bodies.

Distinct increase in antimicrobial resistance genes among Escherichia coli during 50 years of antimicrobial use in livestock production in China

Antimicrobial use in livestock production is linked to the emergence and spread of antimicrobial resistance (AMR), but large-scale studies on AMR changes in livestock isolates remain scarce. Here we applied whole-genome sequence analysis to 982 animal-derived Escherichia coli samples collected in China from the 1970s to 2019, finding that the number of AMR genes (ARGs) per isolate doubled-including those conferring resistance to critically important agents for both veterinary (florfenicol and norfloxacin) and human medicine (colistin, cephalosporins and meropenem). Plasmids of incompatibility groups IncC, IncHI2, IncK, IncI and IncX increased distinctly in the past 50 years, acting as highly effective vehicles for ARG spread. Using antimicrobials of the same class, or even unrelated classes, may co-select for mobile genetic elements carrying multiple co-existing ARGs. Prohibiting or strictly curtailing antimicrobial use in livestock is therefore urgently needed to reduce the growing threat from AMR.

Antimicrobial resistance in the globalized food chain: a One Health perspective applied to the poultry industry

Antimicrobial resistance (AMR) remains a major global public health crisis. The food animal industry will face escalating challenges to increase productivity while minimizing AMR, since the global demand for animal protein has been continuously increasing and food animals play a key role in the global food supply, particularly broiler chickens. As chicken products are sources of low-cost, high-quality protein, poultry production is an important economic driver for livelihood and survival in developed and developing regions. The globalization of the food supply, markedly in the poultry industry, is aligned to the globalization of the whole modern society, with an unprecedented exchange of goods and services, and transit of human populations among regions and countries. Considering the increasing threat posed by AMR, human civilization is faced with a complex, multifaceted problem compromising its future. Actions to mitigate antimicrobial resistance are needed in all sectors of the society at the human, animal, and environmental levels. This review discusses the problems associated with antimicrobial resistance in the globalized food chain, using the poultry sector as a model. We cover critical aspects of the emergence and dissemination of antimicrobial resistance in the poultry industry and their implications to public health in a global perspective. Finally, we provide current insights using the multidisciplinary One Health approach to mitigate AMR at the human-animal-environment interface.

Clinical Perspective of Antimicrobial Resistance in Bacteria

Antimicrobial resistance (AMR) has become a global clinical problem in recent years. With the discovery of antibiotics, infections were not a deadly problem for clinicians as they used to be. However, worldwide AMR comes with the overuse/misuse of antibiotics and the spread of resistance is deteriorated by a multitude of mobile genetic elements and relevant resistant genes. This review provides an overview of the current situation, mechanism, epidemiology, detection methods and clinical treatment for antimicrobial resistant genes in clinical important bacteria including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), penicillin-resistant Streptococcus pneumoniae (PRSP), extended-spectrum β-lactamase-producing Enterobacteriaceae, acquired AmpC β-lactamase-producing Enterobacteriaceae, carbapenemase-producing Enterobacteriaceae (CPE), multidrug-resistant (MDR) Acinetobacter baumannii and Pseudomonas aeruginosa.

Genetic Characterization of Antibiotic Resistant Enterobacteriaceae Isolates From Bovine Animals and the Environment in Nigeria

There is a link between antibiotic resistance in humans, livestock and the environment. This study was carried out to characterize antibiotic resistant bovine and environmental Enterobacteriaceae isolates from Edo state, Nigeria. A total of 109 consecutive isolates of Enterobacteriaceae were isolated from March–May 2015 from 150 fecal samples of healthy bovine animals from three farms at slaughter in Edo state Nigeria. Similarly, 43 Enterobacteriaceae isolates were also obtained from a total of 100 environmental samples from different sources. Isolates were recovered and identified from samples using standard microbiological techniques. Recovered isolates were pre-identified by the Microbact Gram-Negative identification system and confirmed with Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and ribosomal multilocus sequence typing (rMLST). Antibiotic susceptibility testing was carried out by Kirby-Bauer method for 14 antibiotics. Whole genome sequencing (WGS) was carried out for isolate characterization and identification of resistance determinants. Out of 109 animal and 43 environmental Enterobacteriaceae isolates, 18 (17%) and 8 (19%) isolates based on selection criteria showed antibiotic resistance and were further investigated by whole genome sequencing (WGS). Resistance genes were detected in all (100%) of the resistant bovine and environmental Enterobacteriaceae isolates. The resistance determinants included β-lactamase genes, aminoglycoside modifying enzymes, qnr genes, sulfonamide, tetracycline and trimethoprim resistance genes, respectively. Out of the 18 and 8 resistant animal and environmental isolates 3 (17%) and 2 (25%) were multidrug resistant (MDR) and had resistance determinants which included efflux genes, regulatory systems modulating antibiotic efflux and antibiotic target alteration genes. Our study shows the dissemination of antibiotic resistance especially MDR strains among Nigerian bovine and environmental Enterobacteriaceae isolates. The presence of these resistant strains in animals and the environment constitute a serious health concern indicated by the difficult treatment options of the infections caused by these organisms. To the best of our knowledge we report the first detailed genomic characterization of antibiotic resistance in bovine and environmental Enterobacteriaceae isolates for Nigeria.

The Use of Long-Read Sequencing Technologies in Infection Control: Horizontal Transfer of a blaCTX-M-27 Containing lncFII Plasmid in a Patient Screening Sample

Plasmid transfer is one important mechanism how antimicrobial resistance can spread between different species, contributing to the rise of multidrug resistant bacteria (MDRB) worldwide. Here were present whole genome sequencing (WGS) data of two MDRB isolates, an Escherichia coli and a Klebsiella quasipneumoniae, which were isolated from a single patient. Detailed analysis of long-read sequencing data identified an identical F2:A-:B- lncFII plasmid containing bla_CTX-M-27 in both isolates, suggesting horizontal plasmid exchange between the two species. As the plasmid of the E. coli strain carried multiple copies of the resistance cassette, the genomic data correlated with the increased antimicrobial resistance (AMR) detected for this isolate. Our case report demonstrates how long-read sequencing data of MDRB can be used to investigate the role of plasmid mediate resistance in the healthcare setting and explain resistance phenotypes.

Characteristics in the whole-genome sequence of Klebsiella pneumoniae ST147 from Turkey

The study aimed to analyze antibiotic resistance determinants in a carbapenem-resistant Klebsiella pneumoniae by whole-genome sequencing (WGS). K. pneumoniae was isolated from a urine sample and it was characterized by 16S rDNA sequencing in Turkey. This strain was named as Kpn Rize-53-TR. Antimicrobial susceptibility testing was performed for seventeen antibiotics by VITEK-2 and the result was confirmed by MIC. The whole genome of isolate was sequenced by Illumina and was analysed by bioinformatic tools for MLST, replicon types, and antimicrobial resistance genes. The whole genome data was submitted to NCBI. The isolate was found to be resistant to all tested β-lactam antibiotics and the highest MIC values were found for piperacillin, piperacillin/tazobactam (≥128). No resistance to colistin and moderate susceptibility to amikacin and tetracycline was observed. The isolate carried 12 resistance genes belonging to 10 resistance classes; ere(A), fosA, oqxB, cmlA1, aac(a)-IIa, bla KPC-2, bla TEM-1A, bla SHV-67, bla CTX-M-15, bla OXA-1-2-9. Mutations were detected in gyrA (83Y) and parC (80I) genes. Clonal subtype of the isolate was ST147, and it had wzi420 and wzc38 alleles. Its serotype was O3/O3a. The bla KPC-2 was firstly found in both ST147 clonal group in Turkey and in serotype O3/O3a in the world. By plasmid replicon typing, five plasmids IncFII(K), Col(BS512), IncR, IncFIA(HI1) and IncFIB(pQil) were determined in Kpn Rize-53-TR and bla KPC-2 was located on IncFII(K) plasmid. The presence of bla KPC-2 on the plasmid with other resistance genes accelerates its own spread together with other resistance genes.

The Role of Antibiotic Resistance Genes in the Fitness Cost of Multiresistance Plasmids

By providing the bacterial cell with protection against several antibiotics at once, multiresistance plasmids have an evolutionary advantage in situations where antibiotic treatments are common, such as in hospital environments. However, resistance plasmids can also impose fitness costs on the bacterium in the absence of antibiotics, something that may limit their evolutionary success. The underlying mechanisms and the possible contribution of resistance genes to such costs are still largely not understood. Here, we have specifically investigated the contribution of plasmid-borne resistance genes to the reduced fitness of the bacterial cell. The pUUH239.2 plasmid carries 13 genes linked to antibiotic resistance and reduces bacterial fitness by 2.9% per generation. This cost is fully ameliorated by the removal of the resistance cassette. While most of the plasmid-borne resistance genes individually were cost-free, even when overexpressed, two specific gene clusters were responsible for the entire cost of the plasmid: the extended-spectrum-β-lactamase gene bla_CTX-M-15 and the tetracycline resistance determinants tetAR. The bla_CTX-M-15 cost was linked to the signal peptide that exports the β-lactamase into the periplasm, and replacement with an alternative signal peptide abolished the cost. Both the tetracycline pump TetA and its repressor TetR conferred a cost on the host cell, and the reciprocal expression of these genes is likely fine-tuned to balance the respective costs. These findings highlight that the cost of clinical multiresistance plasmids can be largely due to particular resistance genes and their interaction with other cellular systems, while other resistance genes and the plasmid backbone can be cost-free. IMPORTANCE Multiresistance plasmids are one of the main drivers of antibiotic resistance development and spread. Their evolutionary success through the accumulation and mobilization of resistance genes is central to resistance evolution. In this study, we find that the cost of the introduction of a multiresistance plasmid was completely attributable to resistance genes, while the rest of the plasmid backbone is cost-free. The majority of resistance genes on the plasmid had no appreciable cost to the host cell even when overexpressed, indicating that plasmid-borne resistance can be cost-free. In contrast, the widespread genes bla_CTX-M-15 and tetAR were found to confer the whole cost of the plasmid by affecting specific cellular functions. These findings highlight how the evolution of resistance on plasmids is dependent on the amelioration of associated fitness costs and point at a conundrum regarding the high cost of some of the most widespread β-lactamase genes.

Impact of a Regulation Restricting Critical Antimicrobial Usage on Prevalence of Antimicrobial Resistance in Escherichia coli Isolates From Fecal and Manure Pit Samples on Dairy Farms in Québec, Canada

To tackle antimicrobial resistance (AMR), one of the major health threats of this century, the World Health Organization (WHO) endorsed a global action plan in 2015. This plan calls countries to develop national actions to address AMR. The province of Québec, Canada, adopted a new regulation on the 25^th of February 2019, to limit the use in food animals of antimicrobials of very high importance in human medicine. We aimed to establish the impact of this regulation by comparing the AMR situation in dairy cattle in Québec ~2 years before and 2 years after its introduction. We sampled calves, cows, and the manure pit in 87 farms. Generic and putative ESBL/AmpC E. coli were tested for susceptibility to 20 antimicrobials. Logistic regression was used to investigate whether the probability of antimicrobial resistance differed between isolates obtained from the pre and post regulation periods by sample type (calves, cows, manure pit) and in general. To identify AMR genes dissemination mechanisms, we sequenced the whole genome of 15 generic isolates. In the generic collection, at the herd level, the proportion of multidrug resistant (MDR) isolates, decreased significantly from 83 to 71% (p = 0.05). Folate inhibitor and aminoglycoside resistances demonstrated a significant decrease. However, when analyzed by sample type (calves, cows, manure pit), we did not observe a significant AMR decrease in any of these categories. In the ESBL/AmpC collection, we did not detect any significant difference between the two periods. Also, the general resistance gene profile was similar pre and post regulation. We identified both clonal and plasmidic dissemination of resistance genes. In conclusion, as early as 2 years post regulation implementation, we observed a significant decrease in MDR in the dairy industry in Quebec in the generic E. coli collection with folate inhibitor and aminoglycoside resistances showing the most significant decrease. No other significant decreases were yet observed.

Clinically healthy household dogs and cats as carriers of multidrug-resistant Salmonella enterica with variable R plasmids

Introduction. Antimicrobial resistance (AMR) is a One Health issue concerning humans, animals and the environment and a unified One Health approach is required to contain this problematic issue. Dogs and cats are popular pet animals and are known to carry many bacterial pathogens that are of public health importance, including Salmonella . However, data on AMR in companion animals is limited.

Gap statement. Scant AMR data from bacteria originating from companion animals limits an accurate assessment of the impacts of pet-animal-related AMR on public health.

Purpose. This study aimed to phenotypically and genetically investigate AMR in Salmonella isolated from pet dogs and cats in Thailand.

Methodology. Salmonella enterica were isolated from pet dogs (n=159) and cats (n=19) in Thailand between 2016 and 2019. All isolates were serotyped. Phenotypic and genotypic antimicrobial resistance was examined. PCR-based replicon typing, replicon sequence typing and plasmid multilocus sequence typing were conducted to characterize plasmids.

Results. Seventy-seven serovars were identified, with serovars Weltevreden (9.6%) and Stockholm (9.0%) the most common. Most of the isolates (34.3%) were multidrug-resistant. The serovar Stockholm was an ESBL-producer and carried the β-lactamase genes bla TEM-1 and bla CTX-M-55. The plasmid-mediated quinolone resistance (PMQR) gene, qnrS, was also detected (10.1%). Class 1 integrons carrying the dfrA12-aadA2 cassette array were most frequent (45.9%). Five plasmid replicon types as IncA/C (0.6%), N (1.1%), IncFIIA (28.7%), IncHI1 (2.2%), and IncI1 (3.4%) were identified. Based on the pMLST typing scheme (n=9), plasmids were assigned into five different STs including IncA/C-ST6 (n=1), IncH1-ST16 (n=4), IncI1-ST3 (n=1), IncI1-ST60 (n=1) and IncI1-ST136 (n=1). The ST 16 of IncHI1 plasmid was a novel plasmid ST. Subtyping F-type plasmids using the RST scheme (n=9) revealed four different combinations of replicons including S1:A-:B- (n=4), S1:A-:B22 (n=2), S3:A-:B- (n=1) and S-:A-:B47 (n=1).

Conclusions. Our findings highlight the role of clinically healthy household dogs and cats as carriers of AMR Salmonella strains with different R plasmid. The implementation of AMR phenotypes instigation and genotypic monitoring and surveillance programmes in companion animals are imperative as integral components of the One Health framework.

Clinical Impact of Colistin Banning in Food Animal on mcr-1-Positive Enterobacteriaceae in Patients From Beijing, China, 2009-2019: A Long-Term Longitudinal Observational Study

The colistin resistance gene mcr-1 is emerging as a global public health concern, altering the regulation of colistin usage globally since 2017, especially in China. However, few studies have revealed the impact of policy change on the epidemiology of mcr-positive Enterobacteriaceae (MCRPE) in patients. Here, we describe a molecular epidemiological study to investigate the MCRPE in patients in China from 2009-2019. During the surveillance period, 26,080 non-duplicated Enterobacteriaceae isolates were collected in Beijing. Colistin-resistant isolates were screened by enrichment culture supplemented with colistin, and the presence of the mcr gene was determined by PCR amplification. MCRPE isolates were then analyzed by susceptibility testing, genotyping, and risk factor analysis. Of the 26,080 isolates, mcr-1 was detected in 171 (1.1%) of 15,742 Escherichia coli isolates and 7 (0.1%) of 10,338 Klebsiella pneumoniae isolates. The prevalence of mcr-1-positive E. coli (MCRPEC) showed an increasing trend from 2009 to 2016, while a decreasing trend was observed since 2017. Multi-locus sequence typing analysis showed that MCRPEC isolates had extremely diverse genetic backgrounds, and most of these isolates were non-clonal. The prevalence of MCRPE in China remained at a low level, and even showed a declining trend over the last 3 years after the banning of colistin usage as feed additive in food animal in 2017. However, colistin permission in clinical therapy could still increase the risk of MCRPE transmission and intractable infections, active surveillance and monitoring strategies of MCRPE are recommended to prolong the clinical longevity of colistin.

Progress in Alternative Strategies to Combat Antimicrobial Resistance: Focus on Antibiotics

Antibiotic resistance, and, in a broader perspective, antimicrobial resistance (AMR), continues to evolve and spread beyond all boundaries. As a result, infectious diseases have become more challenging or even impossible to treat, leading to an increase in morbidity and mortality. Despite the failure of conventional, traditional antimicrobial therapy, in the past two decades, no novel class of antibiotics has been introduced. Consequently, several novel alternative strategies to combat these (multi-) drug-resistant infectious microorganisms have been identified. The purpose of this review is to gather and consider the strategies that are being applied or proposed as potential alternatives to traditional antibiotics. These strategies include combination therapy, techniques that target the enzymes or proteins responsible for antimicrobial resistance, resistant bacteria, drug delivery systems, physicochemical methods, and unconventional techniques, including the CRISPR-Cas system. These alternative strategies may have the potential to change the treatment of multi-drug-resistant pathogens in human clinical settings.

Playgrounds in City of Pushchino with Different Types of Coating as Reservoir of Antibiotic-Resistant Strains of Pseudomonas spp

In this study, we investigated antibiotic-resistant microorganisms isolated by the direct plating method from 6 playgrounds in the city of Pushchino, Moscow Region, with different types of coating: sand, soil with sand, grass and a modern playground coating made of pressed rubber crumb. According to the results of the study, sand is the cleanest type of coating, both in terms of the total count of cultivated microorganisms (8 × 10⁵/g of substrate) and in terms of the content of resistant strains. The most contaminated both in terms of the total count of cultivated microorganisms (1.2-1.9 × 10⁹/g of substrate) and in terms of the content of antibiotic-resistant strains was the coating of pressed rubber crumb. We isolated 65 antibiotic-resistant strains of fluorescent pseudomonads. Nine Pseudomonas strains were found to contain antibiotic resistance plasmids (one belongs to P-1 incompatibility group, seven to IncP-7 and one to unidentified incompatibility group). For the first time, we discovered a conjugative plasmid pD4A-46 conferring tetracycline resistance and belonging to the P-7 incompatibility group. Taking into account the results obtained under this study, it can be recommended to periodically treat the crumb rubber coating with non-toxic antiseptics, i.e. hydrogen peroxide or chlorhexidine.

Antibiotic Discovery and Resistance: The Chase and the Race

The history of antimicrobial resistance (AMR) evolution and the diversity of the environmental resistome indicate that AMR is an ancient natural phenomenon. Acquired resistance is a public health concern influenced by the anthropogenic use of antibiotics, leading to the selection of resistant genes. Data show that AMR is spreading globally at different rates, outpacing all efforts to mitigate this crisis. The search for new antibiotic classes is one of the key strategies in the fight against AMR. Since the 1980s, newly marketed antibiotics were either modifications or improvements of known molecules. The World Health Organization (WHO) describes the current pipeline as bleak, and warns about the scarcity of new leads. A quantitative and qualitative analysis of the pre-clinical and clinical pipeline indicates that few antibiotics may reach the market in a few years, predominantly not those that fit the innovative requirements to tackle the challenging spread of AMR. Diversity and innovation are the mainstays to cope with the rapid evolution of AMR. The discovery and development of antibiotics must address resistance to old and novel antibiotics. Here, we review the history and challenges of antibiotics discovery and describe different innovative new leads mechanisms expected to replenish the pipeline, while maintaining a promising possibility to shift the chase and the race between the spread of AMR, preserving antibiotic effectiveness, and meeting innovative leads requirements.

Rapid identification of mcr-1-positive Escherichia coli from patient urine using a novel lipid-based MALDI-TOF-MS assay

Mobilized colistin resistance (mcr) genes confer resistance to colistin, a last-resort antibiotic for multidrug-resistant Gram-negative infections. In this case report, we describe a novel lipid-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) diagnostic used to rapidly identify an mcr-1-positive Escherichia coli directly from a patient with a urinary tract infection without the need for ex vivo growth.

IncHI1A plasmids potentially facilitate a horizontal flow of antibiotic resistance genes to pathogens in microbial communities of urban residential sewage

Horizontal gene transfer via plasmids is important for the dissemination of antibiotic resistance genes among medically relevant pathogens. Specifically, the transfer of IncHI1A plasmids is believed to facilitate the spread of antibiotic resistance genes, such as carbapenemases, within the clinically important family Enterobacteriaceae. The microbial community of urban wastewater treatment plants has been shown to be highly permissive towards conjugal transfer of IncP1 plasmids. Here, we tracked the transfer of the P1 plasmid pB10 and the clinically relevant HI1A plasmid R27 in the microbial communities present in urban residential sewage entering full-scale wastewater treatment plants. We found that both plasmids readily transferred to these communities and that strains in the sewage were able to further disseminate them. Furthermore, that R27 has a broad potential host range, but a low host divergence. Interestingly, although the majority of R27 transfer events were to members of Enterobacteriaceae, we found a subset of transfer to other families, even other phyla. Indicating, that HI1A plasmids facilitate horizontal gene transfer both within Enterobacteriaceae, but also across families of especially Gammaproteobacteria, such as Moraxellaceae, Pseudomonadaceae and Shewanellaceae. pB10 displayed a similar potential host range as R27. In contrast to R27, pB10 had a high host divergence. By culture enrichment of the transconjugant communities, we show that sewage strains of Enterobacteriaceae and Aeromonadaceae can stably maintain R27 and pB10, respectively. Our results suggest that dissemination in the urban residual water system of HI1A plasmids may result in an accelerated acquisition of antibiotic resistance genes among pathogens.

A novel plasmid entry exclusion system in pKPC_UVA01, a promiscuous conjugative plasmid carrying the bla KPC carbapenemase gene

Conjugative plasmids are the principal mediator in the emergence and spread of antibiotic resistance genes in Enterobacterales. Plasmid entry exclusion (EEX) systems can restrict their transfer into the recipient bacteria carrying closely related plasmids. In this study, we identified and characterized a novel plasmid entry exclusion system in a carbapenem resistance plasmid pKPC_UVA01, which is responsible for widespread dissemination of the bla_KPC carbapenemase gene among Enterobacterales in the United States. The identified eex gene in the recipient strain of different Enterobacterales species inhibited the conjugation transfer of pKPC_UVA01 plasmids at a range of 200- to 400-fold, and this inhibition was found to be a dose-dependent function of the EEX protein in recipient cells. The C terminus truncated version of eex or eex with an early termination codon at the C terminus region alleviated the inhibition of conjugative transfer. Unlike the strict specificity of plasmid exclusion by the known EEX protein, the newly identified EEX in the recipient strain could inhibit the transfer of IncP and IncN plasmids. The eex gene from the plasmid pKPC_UVA01 was not required for conjugative transfer but was essential in the donor bacteria for entry exclusion of this plasmid. This was a novel function of a single protein that is essential in both donor and recipient bacteria for the entry exclusion of a plasmid. This eex gene is found to be distributed in multidrug resistance plasmids similar to pKPC_UVA01 in different Enterobacterales species and may contribute to the stability of this plasmid type by controlling its transfer.

Roles of Proteins Containing Immunoglobulin-Like Domains in the Conjugation of Bacterial Plasmids

Horizontal transfer of bacterial plasmids generates genetic variability and contributes to the dissemination of the genes that enable bacterial cells to develop antimicrobial resistance (AMR). Several aspects of the conjugative process have long been known, namely, those related to the proteins that participate in the establishment of cell-to-cell contact and to the enzymatic processes associated with the processing of plasmid DNA and its transfer to the recipient cell. In this work, we describe the roles of newly identified proteins that influence the conjugation of several plasmids. Genes encoding high-molecular-weight bacterial proteins that contain one or several immunoglobulin-like domains (Big) are located in the transfer regions of several plasmids that usually harbor AMR determinants. These Big proteins are exported to the external medium and target two extracellular organelles: the flagella and conjugative pili. The plasmid gene-encoded Big proteins facilitate conjugation by reducing cell motility and facilitating cell-to-cell contact by binding both to the flagella and to the conjugative pilus. They use the same export machinery as that used by the conjugative pilus components. In the examples characterized in this paper, these proteins influence conjugation at environmental temperatures (i.e., 25°C). This suggests that they may play relevant roles in the dissemination of plasmids in natural environments. Taking into account that they interact with outer surface organelles, they could be targeted to control the dissemination of different bacterial plasmids carrying AMR determinants.

IMPORTANCE Transmission of a plasmid from one bacterial cell to another, in several instances, underlies the dissemination of antimicrobial resistance (AMR) genes. The process requires well-characterized enzymatic machinery that facilitates cell-to-cell contact and the transfer of the plasmid. Our paper identifies novel plasmid gene-encoded high-molecular-weight proteins that contain an immunoglobulin-like domain and are required for plasmid transmission. They are encoded by genes on different groups of plasmids. These proteins are exported outside the cell. They bind to extracellular cell appendages such as the flagella and conjugative pili. Expression of these proteins reduces cell motility and increases the ability of the bacterial cells to transfer the plasmid. These proteins could be targeted with specific antibodies to combat infections caused by AMR microorganisms that harbor these plasmids.

Whole-Genome Sequencing of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli From Human Infections in Finland Revealed Isolates Belonging to Internationally Successful ST131-C1-M27 Subclade but Distinct From Non-human Sources

Antimicrobial resistance (AMR) is a growing concern in public health, particularly for the clinically relevant extended-spectrum beta-lactamase (ESBL) and AmpC-producing Enterobacteriaceae. Studies describing ESBL-producing Escherichia coli clinical samples from Finland to the genomic level and investigation of possible zoonotic transmission routes are scarce. This study characterizes ESBL-producing E. coli from clinical samples in Finland using whole genome sequencing (WGS). Comparison is made between animal, food, and environmental sources in Finland to gain insight into potential zoonotic transmission routes and to recognize successful AMR genes, bacterial sequence types (STs), and plasmids. ESBL-producing E. coli isolates (n = 30) obtained from the Eastern Finland healthcare district between 2018 and 2020 underwent WGS and were compared to sequences from non-human and healthy human sources (n = 67) isolated in Finland between 2012 and 2018. A majority of the clinical isolates belonged to ST131 (n = 21; 70%), of which 19 represented O25:H4 and fimH30 allele, and 2 O16:H5 and fimH41 allele. Multidrug resistance was common, and the most common bla gene identified was bla CTX-M-27 (n = 14; 47%) followed by bla CTX-M-15 (n = 10; 33%). bla CTX-M-27 was identified in 13 out of 21 isolates representing ST131, with 12 isolates belonging to a recently discovered international E. coli ST131 C1-M27 subclade. Isolates were found to be genetically distinct from non-human sources with core genome multilocus sequence typing based analysis. Most isolates (n = 26; 87%) possessed multiple replicons, with IncF family plasmids appearing in 27 (90%) and IncI1 in 5 (17%) isolates. IncF[F1:A2:B20] replicon was identified in 11, and IncF[F-:A2:B20] in 4 isolates. The results indicate the ST131-C1-M27 clade gaining prevalence in Europe and provide further evidence of the concerning spread of this globally successful pathogenic clonal group. This study is the first to describe ESBL-producing E. coli in human infections with WGS in Finland and provides important information on global level of the spread of ESBL-producing E. coli belonging to the C1-M27 subclade. The results will help guide public health actions and guide future research.

Higher abundance of core antimicrobial resistant genes in effluent from wastewater treatment plants

Wastewater treatment plants (WWTPs) receive sewage water from a variety of sources, including livestock farms, hospitals, industries, and households, that contain antimicrobial resistant bacteria (ARB) and antimicrobial resistant genes (ARGs). Current treatment technologies are unable to completely remove ARB and ARGs, which are eventually released into the aquatic environment. This study focused on the core resistome of urban WWTPs that are persistent through wastewater treatment processes. We adopted the Hiseq-based metagenomic sequencing approach to identify the core resistome, their genetic context, and pathogenic potential of core ARGs in the influent (IN) and effluent (EF) samples of 12 urban WWTPs in South Korea. In this study, the abundance of ARGs ranged from 0.32 to 3.5 copies of ARGs per copy of the 16S rRNA gene, where the IN samples were relatively higher than the EF samples, especially for the macrolide-lincosamide-streptogramin (MLS)- and tetracycline- resistant genes. On the other hand, there were 43 core ARGs sharing up to 90% of the total, among which the relative abundance of sul1, APH(3'')-lb, and RbpA was higher in EF than in IN (p < 0.05). Moreover, tetracycline and sulfonamide-related core ARGs in both EF and IN were significantly more abundant on plasmids than on chromosomes (p < 0.05). We also found that the majority of core ARGs were carried by opportunistic pathogens such as Acinetobacter baumannii, Enterobacter cloacae, and Pseudomonas aeruginosa in both IN and EF. In addition, phages were the only mobile elements whose abundance correlated with that of core ARGs in EF, suggesting that transduction may play a major role in disseminating ARGs in the receiving water environment of the urban WWTP. The persistent release of core ARGs with pathogenic potential into environmental water is of immediate concern. The mobility of ARGs and ARBs in the environment is a major public health concern. These results should be taken into consideration when developing policy to mitigate environmental dissemination of ARG by WWTPs.

GraphPlas: Refined Classification of Plasmid Sequences Using Assembly Graphs

Plasmids are extra-chromosomal genetic materials with important markers that affect the function and behaviour of the microorganisms supporting their environmental adaptations. Hence the identification and recovery of such plasmid sequences from assemblies is a crucial task in metagenomics analysis. In the past, machine learning approaches have been developed to separate chromosomes and plasmids. However, there is always a compromise between precision and recall in the existing classification approaches. The similarity of compositions between chromosomes and their plasmids makes it difficult to separate plasmids and chromosomes with high accuracy. However, high confidence classifications are accurate with a significant compromise of recall, and vice versa. Hence, the requirement exists to have more sophisticated approaches to separate plasmids and chromosomes accurately while retaining an acceptable trade-off between precision and recall. We present GraphPlas, a novel approach for plasmid recovery using coverage, composition and assembly graph topology. We evaluated GraphPlas on simulated and real short read assemblies with varying compositions of plasmids and chromosomes. Our experiments show that GraphPlas is able to significantly improve accuracy in detecting plasmid and chromosomal contigs on top of popular state-of-the-art plasmid detection tools. The source code is freely available at: https://github.com/anuradhawick/GraphPlas.

Detecting genes associated with antimicrobial resistance and pathogen virulence in three New Zealand rivers

The emergence of clinically significant antimicrobial resistance (AMR) in bacteria is frequently attributed to the use of antimicrobials in humans and livestock and is often found concurrently with human and animal pathogens. However, the incidence and natural drivers of antimicrobial resistance and pathogenic virulence in the environment, including waterways and ground water, are poorly understood. Freshwater monitoring for microbial pollution relies on culturing bacterial species indicative of faecal pollution, but detection of genes linked to antimicrobial resistance and/or those linked to virulence is a potentially superior alternative. We collected water and sediment samples in the autumn and spring from three rivers in Canterbury, New Zealand; sites were above and below reaches draining intensive dairy farming. Samples were tested for loci associated with the AMR-related group 1 CTX-M enzyme production (bla_CTX-M) and Shiga toxin producing Escherichia coli (STEC). The bla_CTX-M locus was only detected during spring and was more prevalent downstream of intensive dairy farms. Loci associated with STEC were detected in both the autumn and spring, again predominantly downstream of intensive dairying. This cross-sectional study suggests that targeted testing of environmental DNA is a useful tool for monitoring waterways. Further studies are now needed to extend our observations across seasons and to examine the relationship between the presence of these genetic elements and the incidence of disease in humans.

A nationwide genomic study of clinical Klebsiella pneumoniae in Norway 2001-15: introduction and spread of ESBLs facilitated by clonal groups CG15 and CG307

Objectives

To use the nationwide Norwegian surveillance programme on resistant microbes in humans (NORM) to address longitudinal changes in the population structure of Klebsiella pneumoniae isolates from 2001–15, focusing on the emergence and dissemination of ESBL-producing K. pneumoniae in Norway.

Methods

Among blood (n = 6124) and urinary tract (n = 5496) surveillance isolates from 2001–15, we used Illumina technology to whole genome sequence 201 ESBL-producing isolates from blood (n = 130) and urine (n = 71), and 667 non-ESBL isolates from blood. Complete genomes for four isolates were resolved with Oxford Nanopore sequencing.

Results

In a highly diverse collection, Klebsiella variicola ssp. variicola caused 24.5% of Klebsiella pneumoniae species complex (KpSC) bacteraemias. ESBL production was limited to K. pneumoniae sensu stricto (98.5%). A diverse ESBL population of 57 clonal groups (CGs) were dominated by MDR CG307 (17%), CG15 (12%), CG70 (6%), CG258 (5%) and CG45 (5%) carrying bla_CTX-M-15. Yersiniabactin was significantly more common in ESBL-positive (37.8%) compared with non-ESBL K. pneumoniae sensu stricto isolates (12.7%), indicating convergence of virulence and resistance determinants. Moreover, we found a significantly lower prevalence of yersiniabactin (3.0%, 37.8% and 17.3%), IncFIB (58.7%, 87.9% and 79.4%) and IncFII plasmid replicons (40.5%, 82.8% and 54.2%) in K. variicola ssp. variicola compared with ESBL- and non-ESBL K. pneumoniae sensu stricto isolates, respectively.

Conclusions

The increase in Norwegian ESBL-producing KpSC during 2010–15 was driven by CG307 and CG15 carrying bla_CTX-M-15. K. variicola ssp. variicola was a frequent cause of invasive KpSC infection, but rarely carried ESBLs.

Long-Read Sequencing Reveals Evolution and Acquisition of Antimicrobial Resistance and Virulence Genes in Salmonella enterica

Salmonella enterica is a significant and phylogenetically diverse zoonotic pathogen. To understand its genomic heterogeneity and antimicrobial resistance, we performed long-read sequencing on Salmonella isolated from retail meats and food animals. A collection of 134 multidrug-resistant isolates belonging to 33 serotypes were subjected to PacBio sequencing. One major locus of diversity among these isolates was the presence and orientation of Salmonella pathogenic islands (SPI), which varied across different serotypes but were largely conserved within individual serotypes. We also identified insertion of an IncQ resistance plasmid into the chromosome of fourteen strains of serotype I 4,[5],12:i:- and the Salmonella genomic island 1 (SGI-1) in five serotypes. The presence of various SPIs, SGI-1 and integrated plasmids contributed significantly to the genomic variability and resulted in chromosomal resistance in 55.2% (74/134) of the study isolates. A total of 93.3% (125/134) of isolates carried at least one plasmid, with isolates carrying up to seven plasmids. We closed 233 plasmid sequences of thirteen replicon types, along with twelve hybrid plasmids. Some associations between Salmonella isolate source, serotype, and plasmid type were seen. For instance, IncX plasmids were more common in serotype Kentucky from retail chicken. Plasmids IncC and IncHI had on average more than five antimicrobial resistance genes, whereas in IncX, it was less than one per plasmid. Overall, 60% of multidrug resistance (MDR) strains that carried >3 AMR genes also carried >3 heavy metal resistance genes, raising the possibility of co-selection of antimicrobial resistance in the presence of heavy metals. We also found nine isolates representing four serotypes that carried virulence plasmids with the spv operon. Together, these data demonstrate the power of long-read sequencing to reveal genomic arrangements and integrated plasmids with a high level of resolution for tracking and comparing resistant strains from different sources. Additionally, the findings from this study will help expand the reference set of closed Salmonella genomes that can be used to improve genome assembly from short-read data commonly used in One Health antimicrobial resistance surveillance.

Evolution of ColE1-like plasmids across γ-Proteobacteria: From bacteriocin production to antimicrobial resistance

Antimicrobial resistance is one of the major threats to Public Health worldwide. Understanding the transfer and maintenance of antimicrobial resistance genes mediated by mobile genetic elements is thus urgent. In this work, we focus on the ColE1-like plasmid family, whose distinctive replication and multicopy nature has given rise to key discoveries and tools in molecular biology. Despite being massively used, the hosts, functions, and evolutionary history of these plasmids remain poorly known. Here, we built specific Hidden Markov Model (HMM) profiles to search ColE1 replicons within genomes. We identified 1,035 ColE1 plasmids in five Orders of γ-Proteobacteria, several of which are described here for the first time. The phylogenetic analysis of these replicons and their characteristic MOB_P5/HEN relaxases suggest that ColE1 plasmids have diverged apart, with little transfer across orders, but frequent transfer across families. Additionally, ColE1 plasmids show a functional shift over the last decades, losing their characteristic bacteriocin production while gaining several antimicrobial resistance genes, mainly enzymatic determinants and including several extended-spectrum betalactamases and carbapenemases. Furthermore, ColE1 plasmids facilitate the intragenomic mobilization of these determinants, as various replicons were identified co-integrated with large non-ColE1 plasmids, mostly via transposases. These results illustrate how families of plasmids evolve and adapt their gene repertoires to bacterial adaptive requirements.

The extraordinary adaptability of bacteria and the massive prevalence of mobile genetic elements within populations has turned antimicrobial resistance into a growing threat to Public Health. Among all the mobile genetic elements, plasmids have been the focus of attention as these extrachromosomal molecules of DNA are able to mobilize several antimicrobial resistance genes at once through conjugation. However, although small mobilizable and non-conjugative replicons have been traditionally overlooked when analyzing plasmid-mediated antimicrobial resistance, they have recently been described as important carriers of AMR genes. In this work, we have analyzed the ColE1-like plasmid family, whose study has been neglected even if they are one of the main groups of small plasmids in natural populations of Proteobacteria. We observed that these plasmids have evolved for a long time within γ-Proteobacteria acquiring different genetic features in specific hosts, being major players in the spread of antimicrobial resistance determinants.

Bacterial toxin-antitoxin modules: classification, functions, and association with persistence

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Ubiquitously present bacterial Toxin-Antitoxin (TA) modules consist of stable toxin associated with labile antitoxin.

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Classification of TAs modules based on inhibition of toxin through antitoxin in 8 different classes.

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Variety of specific toxin targets and the abundance of TA modules in various deadly pathogens.

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Specific role of TAs modules in conservation of the resistant genes, emergence of persistence & biofilm formation.

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Proposed antibacterial strategies involving TA modules for elimination of multi-drug resistance.

Toxin-antitoxin (TA) modules are ubiquitous gene loci among bacteria and are comprised of a toxin part and its cognate antitoxin part. Under normal physiological conditions, antitoxin counteracts the toxicity of the toxin whereas, during stress conditions, TA modules play a crucial role in bacterial physiology through involvement in the post-segregational killing, abortive infection, biofilms, and persister cell formation. Most of the toxins are proteinaceous that affect translation or DNA replication, although some other intracellular molecular targets have also been described. While antitoxins may be a protein or RNA, that generally neutralizes its cognate toxin by direct interaction or with the help of other signaling elements and thus helps in the TA module regulation. In this review, we have discussed the current state of the multifaceted TA (type I–VIII) modules by highlighting their classification and specific targets. We have also discussed the presence of TA modules in the various pathogens and their role in antibiotic persistence development as well as biofilm formation, by influencing the different cellular processes. In the end, assembling knowledge about ubiquitous TA systems from pathogenic bacteria facilitated us to propose multiple novel antibacterial strategies involving artificial activation of TA modules.

Impact of Escherichia coli probiotic strains ED1a and Nissle 1917 on the excretion and gut carriage of extended-spectrum beta-lactamase-producing E. coli in pigs

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The inoculated cefotaxime-resistant E. coli was a good pig gut colonizer.

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Probiotics could not reduce faecal excretion of resistant E. coli in inoculated pigs.

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Resistant E. coli titers were lower in digestive tracts of the probiotic-treated pigs.

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No transfer of the bla_CTX−M-1 gene was detected.

We evaluated the impact of the administration of two Escherichia coli probiotic strains (ED1a and Nissle 1917) to pigs on the gut carriage or shedding of extended-spectrum beta-lactamase-producing E. coli. The probiotics were given to four sows from 12 days before farrowing to the weaning day, and to the 23 piglets (infected treated group (IPro)) from birth to the age of 49 days. Four other sows and their 24 piglets (infected non-treated group (INT)) did not receive the probiotics. IPro and INT piglets (n = 47) were orally inoculated with the strain E. coli 17–348F-RifR carrying the bla_CTX−M-1 gene and resistant to rifampicin. Cefotaxime-resistant (CTX^R) E. coli and rifampicin-resistant (Rif^R) E. coli were cultured and excretion of probiotics was studied using PCR on individual faecal and post-mortem samples, and from manure collected after the challenge with resistant E. coli. CTX^R and Rif^RE^.coli isolates were characterized to detect transfer of the bla_CTX−M-1 to other strains_.. Overall, there was no significant reduction in faecal excretion of CTX^R and Rif^RE. coli in IPro pigs compared with INT pigs, although the CTX^R and Rif^RE. coli titres were slightly, but significantly lower in the colon, caecum and rectum at post mortem. Excretion of the probiotics decreased with age, but Nissle 1917 was detected in most pigs at post-mortem. No transfer of the bla_CTX−M-1 gene to probiotic and other E. coli strains was detected. In conclusion, in our experimental conditions, the used probiotics did not reduce shedding of the challenge strain.

Structural Diversity, Fitness Cost, and Stability of a BlaNDM-1-Bearing Cointegrate Plasmid in Klebsiella pneumoniae and Escherichia coli

Cointegrate/hybrid plasmids combine the genetic elements of two or more plasmids and generally carry abundant antimicrobial resistance determinants. Hence, the spread of cointegrate plasmids will accelerate the transmission of AMR genes. To evaluate the transmission risk caused by cointegrate plasmids, we investigated the structural diversity, fitness cost, and stability of a cointegrate plasmid in Klebsiella pneumoniae YZ6 and Escherichia coli EC600. The cointegrate plasmid pSL131_IncA/C_IncX3 was from a clinical Salmonella Lomita strain. After transferring the plasmid into E. coli EC600 by conjugation, we observed plasmids with different structures, including a full-length original plasmid and two truncated versions. By contrast, DNA fragment deletion and bla_CTX-M-14 gene insertion in the plasmid were detected in a transconjugant derived from K. pneumoniae YZ6. These results suggest that the structure of the plasmid was unstable during conjugation. Furthermore, both the full-length plasmid in EC600 and the structurally reorganized plasmid in YZ6 imposed a fitness cost on the bacterial host and enhanced biofilm formation ability. Serial passaging in antibiotic-free medium resulted in a rapid decline of the plasmid in YZ6. However, the stability of the structurally reorganized plasmid in YZ6 was improved via serial passaging in antibiotic-containing medium. SNP calling revealed that mutations of the outer membrane porin may play an essential role in this process. These findings indicate that structural versatility could contribute to the dissemination of cointegrate plasmids. Although the plasmid incurred a fitness cost in other Enterobacteriaceae species, positive selection could alleviate the adverse effects.

Chicken gut microbiome members limit the spread of an antimicrobial resistance plasmid in Escherichia coli

Plasmid-mediated antimicrobial resistance is a major contributor to the spread of resistance genes within bacterial communities. Successful plasmid spread depends upon a balance between plasmid fitness effects on the host and rates of horizontal transmission. While these key parameters are readily quantified in vitro, the influence of interactions with other microbiome members is largely unknown. Here, we investigated the influence of three genera of lactic acid bacteria (LAB) derived from the chicken gastrointestinal microbiome on the spread of an epidemic narrow-range ESBL resistance plasmid, IncI1 carrying blaCTX-M-1, in mixed cultures of isogenic Escherichia coli strains. Secreted products of LAB decreased E. coli growth rates in a genus-specific manner but did not affect plasmid transfer rates. Importantly, we quantified plasmid transfer rates by controlling for density-dependent mating opportunities. Parametrization of a mathematical model with our in vitro estimates illustrated that small fitness costs of plasmid carriage may tip the balance towards plasmid loss under growth conditions in the gastrointestinal tract. This work shows that microbial interactions can influence plasmid success and provides an experimental-theoretical framework for further study of plasmid transfer in a microbiome context.

Mathematical Models of Plasmid Population Dynamics

With plasmid-mediated antibiotic resistance thriving and threatening to become a serious public health problem, it is paramount to increase our understanding of the forces that enable the spread and maintenance of drug resistance genes encoded in mobile genetic elements. The relevance of plasmids as vehicles for the dissemination of antibiotic resistance genes, in addition to the extensive use of plasmid-derived vectors for biotechnological and industrial purposes, has promoted the in-depth study of the molecular mechanisms controlling multiple aspects of a plasmids' life cycle. This body of experimental work has been paralleled by the development of a wealth of mathematical models aimed at understanding the interplay between transmission, replication, and segregation, as well as their consequences in the ecological and evolutionary dynamics of plasmid-bearing bacterial populations. In this review, we discuss theoretical models of plasmid dynamics that span from the molecular mechanisms of plasmid partition and copy-number control occurring at a cellular level, to their consequences in the population dynamics of complex microbial communities. We conclude by discussing future directions for this exciting research topic.

Prevalence and Characterization of ESBL/AmpC Producing Escherichia coli from Fresh Meat in Portugal

The present study aimed to characterize the extended-spectrum β-lactamases and plasmid-mediated AmpC β-lactamases (ESBL/PMAβ) among Escherichia coli producers isolated from beef, pork, and poultry meat collected at retail, in Portugal. A total of 638 meat samples were collected and inoculated on selective medium for the search of E. coli resistant to 3rd generation cephalosporins. Isolates were characterized by antimicrobial susceptibility testing, molecular assays targeting ESBL/AmpC, plasmid-mediated quinolone resistance (PMQR), and plasmid-mediated colistin resistance (PMCR) encoding genes. The highest frequency of E. coli non-wild type to 3rd generation cephalosporins and fluoroquinolones was observed in broiler meat (30.3% and 93.3%, respectively). Overall, a diversity of acquired resistance mechanisms, were detected: bla_ESBL [bla_CTX-M-1 (n = 19), bla_CTX-M-15 (n = 4), bla_CTX-M-32 (n = 12), bla_CTX-M-55 (n = 8), bla_CTX-M-65 (n = 4), bla_CTX-M-27 (n = 2), bla_CTX-M-9 (n = 1), bla_CTX-M-14 (n = 11), bla_SHV-12 (n = 27), bla_TEM-52 (n = 1)], bla_PMAβ [bla_CMY-2 (n = 8)], PMQR [qnrB (n = 27), qnrS (n = 21) and aac(6')-Ib-type (n = 4)] and PMCR [mcr-1 (n = 8)]. Our study highlights that consumers may be exposed through the food chain to multidrug-resistant E. coli carrying diverse plasmid-mediated antimicrobial resistance genes, posing a great hazard to food safety and a public health risk.

BioF is a novel B2 metallo-β-lactamase from Pseudomonas sp. isolated from an on-farm biopurification system

Antimicrobial resistance represents a major global health concern and environmental bacteria are considered a source of resistance genes. Carbapenems are often used as the last antibiotic option to treat multidrug-resistant bacteria. Metallo-β-lactamases (MBLs) are able to render resistance to almost all β-lactam antibiotics, including carbapenems. Unfortunately, there are no inhibitors against MBLs for clinical use. Subclass B2 MBLs are the only enzymes working as strict carbapenemases, under-represented, encoded in chromosome genes and only functional as mono-zinc enzymes. Despite current efforts in MBLs inhibitor development, B2 carbapenemase activity is especially difficult to suppress, even in vitro. In this study we characterized BioF, a novel subclass B2 MBL identified in a new environmental Pseudomonas sp. strain isolated from an on-farm biopurification system (BPS). Although bla_BioF is most likely a chromosomal gene, it is found in a genomic island and may represent a step previous to the horizontal transmission of B2 genes. The new B2 MBL is active as a mono-zinc enzyme and is a potent carbapenemase with incipient activity against some cephalosporins. BioF activity is not affected by excess zinc and is only inhibited at high metal chelator concentrations. The discovery and characterization of B2 MBL BioF as a potent carbapenemase in a BPS bacterial isolate emphasizes the importance of exploring antibiotic resistances existing in the environmental microbiota under the influence of human activities before they could emerge clinically.

Molecular Epidemiology and Characteristics of CTX-M-55 Extended-Spectrum β-Lactamase-Producing Escherichia coli From Guangzhou, China

In recent years, the CTX-M-55 extended-spectrum β-lactamase (ESBL)-positive rate has gradually increased in the clinic. To identify the molecular epidemiology and characteristics of bla _{CTX-M -55}-positive isolates, a total of 374 non-repetitive ESBL-producing Escherichia coli strains were collected from patients in two hospitals in Guangzhou, and 89 bla _{CTX-M -55}-positive isolates were selected by CTX-M-1-group PCR amplification and confirmed by DNA sequencing. Whole-genome sequencing was used to analyze the resistance phenotype, plasmid types, phylogenetic relationships and genetic environment of the bla _{CTX-M -55} gene. Conjugation experiments and PCR were performed to confirm whether the plasmid harboring bla _CTX-M-55 gene could be transferred. The results showed that all bla _CTX-M-55-positive isolates were resistant to ceftriaxone, and 88.76 and 76.40% were resistant to ceftazidime and cefepime, respectively. The resistance rates to levofloxacin and sulfamethoxazole were 66.29 and 59.55%, respectively. However, the sensitivity rate of piperacillin/tazobactam, amoxicillin/clavulanate, and amikacin exceeded 90%. All bla _CTX-M-55-positive isolates were sensitive to carbapenems. Thirty-two STs were detected in the bla _CTX-M-55-positive isolates, among which the detection rate of ST1193 was relatively high (19.10%, 17/89), and other ST types were scattered. It remains to be seen whether ST1193 carrying the bla _{CTX-M -55} gene can become a popular clone strain in this region in the future. The plasmid types carrying the bla _{CTX-M -55} gene included IncI1, IncFII, IncFIC, IncFIB, IncHI2, IncI2, and IncX/Y, among which the IncI1 and IncFII plasmids were the main plasmids, accounting for 37.80 and 28.09%, respectively. Among them, 11 strains of the IncI1 plasmid existed in ST1193 strains. The bla _{CTX-M -55} gene was found on chromosomes of 13 isolates, and seemed to be increasing annually. Up to five distinct types of genetic environments surrounding the bla _{CTX-M -55} gene were analyzed. The most common structure was type II "ISEcp1-bla _{CTX-M -55}-ORF477." In conclusion, whether ST1193, which carries bla _{CTX-M -55} gene, will be an epidemic clone of this region in the future remains to be concerned. The plasmids IncI1 and IncFII, and mobile elements such as ISEcp1 and IS26 may be the main factors leading to the spread and prevalence of CTX-M-55 genotypes.

Third generation cephalosporin resistance in clinical non-typhoidal Salmonella enterica in Germany and emergence of bla CTX-M-harbouring pESI plasmids

Non-typhoidal Salmonella enterica is an important gastrointestinal pathogen causing a considerable burden of disease. Resistance to third generation cephalosporins poses a serious threat for treatment of severe infections. In this study occurrence, phylogenetic relationship, and mechanisms of third generation cephalosporin resistance were investigated for clinical non-typhoidal S. enterica isolates in Germany. From 2017 to 2019, we detected 168 unique clinical S. enterica isolates with phenotypic resistance to third generation cephalosporins in a nation-wide surveillance. Compared to previous years, we observed a significant (P=0.0002) and consistent increase in resistant isolates from 0.41 % in 2005 to 1.71 % in 2019. In total, 34 different serovars were identified, most often S. Infantis (n=41; 24.4 %), S. Typhimurium (n=27; 16.1 %), S. Kentucky (n=21; 12.5 %), and S. Derby (n=17; 10.1 %). Whole genome analyses revealed extended-spectrum β-lactamase (ESBL) genes as main cause for third generation cephalosporin resistance, and most prevalent were bla_CTX-M-1 (n=55), bla_CTX-M-14 (n=25), and bla_CTX-M-65 (n=23). There was no strict correlation between serovar, phylogenetic lineage, and ESBL type but some serovar/ESBL gene combinations were detected frequently, such as bla_CTX-M-1 and bla_CTX-M-65 in S. Infantis or bla_CTX-M-14b in S. Kentucky. The ESBL genes were mainly located on plasmids, including IncI, IncA/C variants, emerging pESI variants, and a novel bla_CTX-M-1harbouring plasmid. We conclude that third generation cephalosporin resistance is on the rise among clinical S. enterica isolates in Germany, and occurrence in various S. enterica serovars is most probably due to multiple acquisition events of plasmids.

Genomic Comparison of Conjugative Plasmids from Salmonella enterica and Escherichia coli Encoding Beta-Lactamases and Capable of Mobilizing Kanamycin Resistance Col-like Plasmids

Salmonella enterica and Escherichia coli are important human pathogens that frequently contain plasmids, both large and small, carrying antibiotic resistance genes. Large conjugative plasmids are known to mobilize small Col plasmids, but less is known about the specificity of mobilization. In the current study, six S. enterica and four E. coli strains containing large plasmids were tested for their ability to mobilize three different kanamycin resistance Col plasmids (KanR plasmids). Large conjugative plasmids from five isolates, four S. enterica and one E. coli, were able to mobilize KanR plasmids of various types. Plasmids capable of mobilizing the KanR plasmids were either IncI1 or IncX, while IncI1 and IncX plasmids with no evidence of conjugation had disrupted transfer regions. Conjugative plasmids of similar types mobilized similar KanR plasmids, but not all conjugative plasmid types were capable of mobilizing all of the KanR plasmids. These data describe some of the complexities and specificities of individual small plasmid mobilization.

A transferrable IncL/M plasmid harboring a gene encoding IMP-1 metallo-β-lactamase in clinical isolates of Enterobacteriaceae

BACKGROUND

The worldwide spread of carbapenemase-producing Enterobacteriaceae (CPE) has reduced the clinical utility of carbapenems. Plasmids often play an important role in the spread of genes encoding drug-resistance factors, especially in the horizontal transfer of these genes among species of Enterobacteriaceae. This study describes a patient infected with three species of CPE carrying an identical transferrable IncL/M plasmid.

METHODS

Clinical isolates of CPE were collected at St. Luke's International Hospital, Tokyo, Japan, from 2015 to 2019. Three species of CPE isolates, Enterobacter cloacae, Klebsiella aerogenes and Serratia marcescens, were isolated from a patient who developed severe gallstone pancreatitis associated with bloodstream infection, with all three isolates producing IMP-1 metallo-β-lactamase. The complete sequences of the plasmids of the three isolates were determined by both MiSeq and MinION. The medical chart of this patient was retrospectively reviewed conducted to obtain relevant clinical information.

RESULTS

The three CPE species carried an IncL/M plasmid, pSL264, which was 81,133 bp in size and harbored bla_IMP-1. The genetic environment surrounding bla_IMP-1 consisted of int1-bla_IMP-1-aac(6')-IIc-qacL-qacEdelta1-sul1-istB-IS21. Conjugation experiments showed that S. marcescens could transmit the plasmid to E. cloacae and K. aerogenes. In contrast, pSL264 could not transfer from E. cloacae or K. aerogenes to S. marcescens.

CONCLUSION

The IncL/M plasmid pSL264 harboring bla_IMP-1 was able to transfer among different species of Enterobacteriaceae in a patient receiving long-term antimicrobial treatment. The worldwide emergence and spread of IncL/M plasmids harboring carbapenemase-encoding genes among species of Enterobacteriaceae is becoming a serious public health hazard.

Multidrug-Resistant Lineage of Enterotoxigenic Escherichia coli ST182 With Serotype O169:H41 in Airline Waste

Enterotoxigenic Escherichia coli (ETEC) is the primary aetiologic agent of traveller’s diarrhoea and a significant cause of diarrhoeal disease and death in developing countries. ETEC O169:H41 strains are known to cause both traveller’s diarrhoea and foodborne outbreaks in developed countries and are cause for concern. Here, whole-genome sequencing (WGS) was used to assemble 46 O169:H41 (ST182) E. coli draft genomes derived from two airplane waste samples sourced from a German international airport. The ST182 genomes were compared with all 84 publicly available, geographically diverse ST182 genomes to construct a core genome-based phylogenetic tree. ST182 isolates were all phylogroup E, the majority serotype O169:H41 (n = 121, 93%) and formed five major clades. The airplane waste isolates differed by an average of 15 core SNPs (range 0–45) but their accessory genome content was diverse. While uncommon in other ST182 genomes, all airplane-derived ST182 isolates carried: (i) extended-spectrum β-lactamase gene bla_CTX–M–15 notably lacking the typical adjacent ISEcp1; (ii) qnrS1 and the S83L mutation in gyrA, both conferring resistance to fluoroquinolones; and (iii) a class 1 integron structure (IS26-intI1_Δ648-dfrA17-aadA5-qacEΔ1-sul1-ORF-srpC-padR-IS6100-mphR-mrx-mphA-IS26) identified previously in major extraintestinal pathogenic E. coli STs but not in ETEC. ST182 isolates carried ETEC-specific virulence factors STp + CS6. Adhesin/invasin tia was identified in 89% of aircraft ST182 isolates (vs 23%) and was located on a putative genomic island within a hotspot region for various insertions including PAI I₅₃₆ and plasmid-associated transposons. The most common plasmid replicons in this collection were IncFII (100%; F2:A-:B-) and IncB/O/K/Z (89%). Our data suggest that potentially through travel, E. coli ST182 are evolving a multidrug-resistant profile through the acquisition of class 1 integrons and different plasmids.

Genetic Analysis of mcr-1-Carrying Plasmids From Gram-Negative Bacteria in a Dutch Tertiary Care Hospital: Evidence for Intrapatient and Interspecies Transmission Events

The role of plasmids in the complex pandemic of antimicrobial resistance is increasingly being recognized. In this respect, multiple mobile colistin resistance (mcr) gene-carrying plasmids have been described. However, the characteristics and epidemiology of these plasmids within local healthcare settings are largely unknown. We retrospectively characterized the genetic composition and epidemiology of plasmids from mcr-1-positive bacterial isolates identified from patients from a large academic hospital in the Netherlands. Clinical Gram-negative bacteria with an MIC > 2 μg/mL for colistin, obtained from patients hospitalized at the Erasmus MC University Medical Center Rotterdam during the years 2010-2018, were screened for presence of the mcr-1 gene. Extracted plasmids from mcr-1-positive isolates were sequenced using a combination of short- and long-read sequencing platforms, characterized by incompatibility type and genetic composition and compared to publicly available mcr-1-carrying plasmid sequences. In 21 isolates from 14 patients, mcr-1 was located on a plasmid. These plasmids were of diverse genetic background involving Inc types IncX4, IncI2(delta), IncHI2, as well as double Inc types IncHI2/IncN and IncHI2/IncQ. mcr-1-carrying plasmids were found in Escherichia coli, Klebsiella pneumoniae, and Kluyvera georgiana, and within the chromosome of an ST147 K. pneumoniae isolate. In depth analysis indicated intrapatient, interpatient, and interspecies transmission events of mcr-1-carrying plasmids. In addition, our results show that the mcr-1 gene resides in a rich environment full of other (mcr-1 negative) plasmids and of many different Inc types, enabling interplasmidal transfer events and facilitating widespread dissemination of the mcr-1 gene. Multiple mcr-1-carrying plasmid transmission events had likely occurred among isolates from hospitalized patients. Recognition and identification of plasmid transmission events within hospitals is necessary in order to design and implement effective infection control measures.

The dilution effect limits plasmid horizontal transmission in multispecies bacterial communities

By transferring ecologically important traits between species, plasmids drive genomic divergence and evolutionary innovation in their bacterial hosts. Bacterial communities are often diverse and contain multiple coexisting plasmids, but the dynamics of plasmids in multi-species communities are poorly understood. Here, we show, using experimental multi-species communities containing two plasmids, that bacterial diversity limits the horizontal transmission of plasmids due to the ‘dilution effect’; this is an epidemiological phenomenon whereby living alongside less proficient host species reduces the expected infection risk for a focal host species. In addition, plasmid horizontal transmission was also affected by plasmid diversity, such that the rate of plasmid conjugation was reduced from co-infected host cells carrying both plasmids. In diverse microbial communities, plasmid spread may be limited by the dilution effect and plasmid–plasmid interactions, reducing the rate of horizontal transmission.

Benzydamine Reverses TMexCD-TOprJ-Mediated High-Level Tigecycline Resistance in Gram-Negative Bacteria

Recently, a novel efflux pump gene cluster called tmexCD1-toprJ1 and its variants have been identified, which undermine the antibacterial activity of tigecycline, one of the last remaining options effective against multidrug-resistant (MDR) Gram-negative bacteria. Herein, we report the potent synergistic effect of the non-steroidal anti-inflammatory drug benzydamine in combination with tigecycline at sub-inhibitory concentrations against various temxCD-toprJ-positive Gram-negative pathogens. The combination of benzydamine and tigecycline killed all drug-resistant pathogens during 24 h of incubation. In addition, the evolution of tigecycline resistance was significantly suppressed in the presence of benzydamine. Studies on the mechanisms of synergism showed that benzydamine disrupted the bacterial proton motive force and the functionality of this kind of novel plasmid-encoded resistance-nodulation-division efflux pump, thereby promoting the intracellular accumulation of tigecycline. Most importantly, the combination therapy of benzydamine and tigecycline effectively improved the survival of Galleria mellonella larvae compared to tigecycline monotherapy. Our findings provide a promising drug combination therapeutic strategy for combating superbugs carrying the tmexCD-toprJ gene.

Prevalence of IncFIB Plasmids Found among Salmonella enterica Serovar Schwarzengrund Isolates from Animal Sources in Taiwan Using Whole-Genome Sequencing

Salmonella enterica serovar Schwarzengrund is one of the most frequently isolated Salmonella serotypes responsible for human and poultry infections in Taiwan, and it has raised public health concerns. To better facilitate the understanding of transmission patterns and the dynamics of epidemics, sharing molecular data on pathogen profiles is urgently needed. The objectives of the current study were to determine and establish baseline data of S. enterica serovar Schwarzengrund isolates from 23 epidemiologically unrelated sources from year 2000 to 2018 and examine their phenotypic and genotypic characteristics. Genomic DNA of the Salmonella isolates was extracted and subjected to whole-genome sequencing using an Illumina platform. Results showed that all selected isolates exhibited multidrug resistance, and six of those were resistant to ciprofloxacin phenotypically. Genotypically, these isolates carried genes resistant to aminoglycoside (100%), phenicol (91.3%), β-lactams (69.5%), folate pathway antagonist (100%), tetracycline (82.6%), and fluoroquinolone (4.3%). Moreover, these isolates harbor integrons with five different gene cassettes identified for the first time, which are associated with resistance to trimethoprim, streptomycin, tetracycline, sulfonamide, chloramphenicol, and gentamicin. Furthermore, prevalence of IncFIB plasmid was found among studied isolates, which may increase its ability to colonize the chicken cecum and cause extra-intestinal disease. Salmonella pathogenicity islands SPI-1 to SPI-5, SPI-13, and SPI-14, as well as C63PI locus, were also detected in all isolates. This study demonstrated that a considerable high antimicrobial resistance with high virulence levels of Salmonella were found from animal sources. Sharing data on these pathogen profiles can not only help increase the reproducibility and accessibility of genomic analysis but can also support surveillance and epidemiological investigations for salmonellosis in the region.

Aetiology and severity of childhood pneumonia in primary care in Malawi: a cohort study

OBJECTIVE

To determine the aetiology of community acquired pneumonia in children presenting to primary care in Northern Malawi, and to ascertain predictors for identification of children requiring hospitalisation.

DESIGN

The BIOmarkers TO diagnose PnEumonia study was a prospective cohort study conducted from March to June 2016.

SETTING

Primary care in Northern Malawi.

PATIENTS

494 children aged 2 -59 months with WHO defined pneumonia.

MAIN OUTCOMES AND MEASURES

Number of children with bacterial infection identified and the sensitivity/specificity of WHO markers of severity for need for hospitalisation.

RESULTS

13 (2.6%) children had a bacterium consistent with pneumonia identified. A virus consistent with pneumonia was identified in in 448 (90.7%) of children. 56 children were admitted to hospital and two children died within 30 days. 442 (89.5%) received antibiotic therapy. Eleven children (2.6%) had HIV. WHO severity markers at baseline demonstrated poor sensitivity for the need for hospitalisation with a sensitivity of 0.303 (95% CI 0.188 to 0.441) and a specificity 0.9 (95% CI 0.868 to 0.926). A prediction rule to indicate the need for hospitalisation was developed.

CONCLUSIONS AND RELEVANCE

The low rate of bacterial infection and high use of antibiotics in the setting of high immunisation rates highlights the changing profile of childhood pneumonia. Similarly, the markers of need for hospitalisation may have changed in the setting of extended immunisation. Further studies are required to examine this.

High-risk clones of extended-spectrum β-lactamase-producing Klebsiella pneumoniae isolated from the University Hospital Establishment of Oran, Algeria (2011-2012)

The purpose of the study was to characterize the resistome, virulome, mobilome and Clustered Regularly Interspaced Short Palindromic Repeats-associated (CRISPR-Cas) system of extended-spectrum β-lactamase producing Klebsiella pneumoniae (ESBL-KP) clinical isolates and to determine their phylogenetic relatedness. The isolates were from Algeria, isolated at the University Hospital Establishment of Oran, between 2011 and 2012. ESBL-KP isolates (n = 193) were screened for several antibiotic resistance genes (ARGs) using qPCR followed by Pulsed-Field Gel Electrophoresis (PFGE). Representative isolates were selected from PFGE clusters and subjected to whole-genome sequencing (WGS). Genomic characterization of the WGS data by studying prophages, CRISPR-Cas systems, Multi-Locus Sequence Typing (MLST), serotype, ARGs, virulence genes, plasmid replicons, and their pMLST. Phylogenetic and comparative genomic were done using core genome MLST and SNP-Based analysis. Generally, the ESBL-KP isolates were polyclonal. The whole genome sequences of nineteen isolates were taken of main PFGE clusters. Sixteen sequence types (ST) were found including high-risk clones ST14, ST23, ST37, and ST147. Serotypes K1 (n = 1), K2 (n = 2), K3 (n = 1), K31 (n = 1), K62 (n = 1), and K151 (n = 1) are associated with hyper-virulence. CRISPR-Cas system was found in 47.4%, typed I-E and I-E*. About ARGs, from 193 ESBL-KP, the majority of strains were multidrug-resistant, the CTX-M-1 enzyme was predominant (99%) and the prevalence of plasmid-mediated quinolone resistance (PMQR) genes was high with aac(6')-lb-cr (72.5%) and qnr's (65.8%). From 19 sequenced isolates we identified ESBL, AmpC, and carbapenemase genes: blaCTX-M-15 (n = 19), blaOXA-48 (n = 1), blaCMY-2 (n = 2), and blaCMY-16 (n = 2), as well as non-ESBL genes: qnrB1 (n = 12), qnrS1 (n = 1) and armA (n = 2). We found IncF, IncN, IncL/M, IncA/C2, and Col replicon types, at least once per isolate. This study is the first to report qnrS in ESBL-KP in Algeria. Our analysis shows the concerning co-existence of virulence and resistance genes and would support that genomic surveillance should be a high priority in the hospital environment.

Temperature and Nutrient Limitations Decrease Transfer of Conjugative IncP-1 Plasmid pKJK5 to Wild Escherichia coli Strains

Plasmid-mediated dissemination of antibiotic resistance among fecal Enterobacteriaceae in natural ecosystems may contribute to the persistence of antibiotic resistance genes in anthropogenically impacted environments. Plasmid transfer frequencies measured under laboratory conditions might lead to overestimation of plasmid transfer potential in natural ecosystems. This study assessed differences in the conjugative transfer of an IncP-1 (pKJK5) plasmid to three natural Escherichia coli strains carrying extended-spectrum beta-lactamases, by filter mating. Matings were performed under optimal laboratory conditions (rich LB medium and 37°C) and environmentally relevant temperatures (25, 15 and 9°C) or nutrient regimes mimicking environmental conditions and limitations (synthetic wastewater and soil extract). Under optimal nutrient conditions and temperature, two recipients yielded high transfer frequencies (5 × 10-1) while the conjugation frequency of the third strain was 1000-fold lower. Decreasing mating temperatures to psychrophilic ranges led to lower transfer frequencies, albeit all three strains conjugated under all the tested temperatures. Low nutritive media caused significant decreases in transconjugants (-3 logs for synthetic wastewater; -6 logs for soil extract), where only one of the strains was able to produce detectable transconjugants. Collectively, this study highlights that despite less-than-optimal conditions, fecal organisms may transfer plasmids in the environment, but the transfer of pKJK5 between microorganisms is limited mainly by low nutrient conditions.

Molecular epidemiology of cefotaxime-resistant but ceftazidime-susceptible Enterobacterales and evaluation of the in vitro bactericidal activity of ceftazidime and cefepime

Extended-spectrum β-lactamases' (ESBLs) production is the main resistance mechanism to third-generation cephalosporins (TGCs) in gram-negative bacilli. In Argentina, there is a high prevalence of cefotaximase-type ESBLs (CTX-M). For this reason, dissociated resistance phenotype (DRP) displaying a profile of resistance to cefotaxime (CTX) and susceptibility to ceftazidime (CAZ) might be detected. The aims of this study were to determine the prevalence of DRP in Enterobacterales clinical isolates, to characterize the mechanisms responsible for this phenotype and to evaluate the in vitro behaviour against different antibiotics. Sixty Enterobacterales resistant to any TGC were studied, and among them, 25% displayed a DRP. The β-lactamases associated with DRP were 5/11 CTX-M-2, 4/11 CTX-M-14, 1/11 CTX-M-15 and 1/11 CMY-2 in E. coli, 2/3 CTX-M-2 and 1/3 CMY-2 in P. mirabilis and 1/1 CTX-M-14 in K. pneumoniae. Furthermore, CTX-M-2 and CTX-M-14 were related with DRP in both wild-type isolates and the corresponding transconjugants. Time-kill experiments showed CAZ bactericidal activity on CTX-M-2-and CTX-M-14-producing strains and bacterial regrowth in those CMY-2 producers. An opposite behaviour was evident when cefepime (FEP) was used. However, CAZ and gentamicin combination showed a synergistic effect against the CMY-2 producers. We concluded that Enterobacterales with DRP responded differently to CAZ or FEP depending on the type of β-lactamase they possess, suggesting that these cephalosporins could be a therapeutic option. Therefore, the characterization of the involved resistance mechanism might contribute to define the appropriate antibiotic treatment.

Metallo-β-lactamases in the Age of Multidrug Resistance: From Structure and Mechanism to Evolution, Dissemination, and Inhibitor Design

Antimicrobial resistance is one of the major problems in current practical medicine. The spread of genes coding for resistance determinants among bacteria challenges the use of approved antibiotics, narrowing the options for treatment. Resistance to carbapenems, last resort antibiotics, is a major concern. Metallo-β-lactamases (MBLs) hydrolyze carbapenems, penicillins, and cephalosporins, becoming central to this problem. These enzymes diverge with respect to serine-β-lactamases by exhibiting a different fold, active site, and catalytic features. Elucidating their catalytic mechanism has been a big challenge in the field that has limited the development of useful inhibitors. This review covers exhaustively the details of the active-site chemistries, the diversity of MBL alleles, the catalytic mechanism against different substrates, and how this information has helped developing inhibitors. We also discuss here different aspects critical to understand the success of MBLs in conferring resistance: the molecular determinants of their dissemination, their cell physiology, from the biogenesis to the processing involved in the transit to the periplasm, and the uptake of the Zn(II) ions upon metal starvation conditions, such as those encountered during an infection. In this regard, the chemical, biochemical and microbiological aspects provide an integrative view of the current knowledge of MBLs.

Detection of unprecedented level of antibiotic resistance and identification of antibiotic resistance factors, including QRDR mutations in Escherichia coli isolated from commercial chickens from North India

AIM

This study aimed to investigate the occurrence of antibiotic resistance phenotype and simultaneously understand its genetic basis in Escherichia coli isolated from the cloacal swabs of commercial chickens from north India.

METHODS AND RESULTS

Escherichia coli isolates were assessed for susceptibility to 14 different antibiotics using the disc-diffusion technique and were screened for the presence of 22 antibiotic resistance genes (ARGs) by employing PCR. Isolates were found to be highly resistant to fluoroquinolones (nalidixic acid 91%, norfloxacin 73% and ciprofloxacin 66%), tetracycline (71%), beta-lactams (ampicillin 49% and amoxicillin/clavulanic acid 37%), co-trimoxazole (48%), streptomycin (31%) and chloramphenicol (28%); and comparatively less resistant to cefazolin (13%), amikacin (10%), aztreonam (4%), gentamicin (4%) and ceftriaxone (3%). Sixty-three percent of isolates were resistant to more than four different drugs. Abundance of plasmid-borne ARGs like tetA (83%), sul3 (44%), aadA1 (44%), strA (43%), strB (41%), qnrS (38%), sul2 (28%) and aac(6)-Ib-cr (15%) was observed among the isolates. Forty-five percent of isolates possessed more than five different ARGs. Quinolone resistance-determining region (QRDR) mutations within gyrA and parC genes were found to be the major determiners of quinolone resistance. QRDR mutations included leu83, asn87 and gly87 within gyrase-A polypeptide and ile80 and lys84 within topoisomerase IV (encoded by parC).

CONCLUSIONS

Our findings suggest the abuse of antibiotics as feed additives and prophylactic drugs in Indian poultry sector. It also projects this industry as an active hotspot for the replication and selection of ARGs.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our findings would provide evidence to the authorities for formulating effective strategies for restricting antibiotic usage as non-therapeutic agents in food animals. Occurrence of both plasmid-borne and chromosome-borne resistance towards quinolones can drive movement of resistance phenotype across bacterial species and vertical movement of resistance along the bacterial generations, respectively, which can pose mitigation challenges.