Plasmid-mediated Antibiotic Resistance Research Articles

Evolution and maintenance of a large multidrug-resistant plasmid in a Salmonella enterica Typhimurium host under differing antibiotic selection pressures.

The dissemination of antibiotic resistance genes (ARGs) through plasmids is a major mechanism for the development of bacterial antimicrobial resistance. The adaptation and evolution mechanisms of multidrug-resistant (MDR) plasmids with their hosts are not fully understood. Herein, we conducted experimental evolution of a 244 kb MDR plasmid (pJXP9) under various conditions including no antibiotics and mono- or combinational drug treatments of colistin (CS), cefotaxime (CTX), and ciprofloxacin (CIP). Our results showed that long-term with or without positive selections for pJXP9, spanning approximately 600 generations, led to modifications of the plasmid-encoded MDR and conjugative transfer regions. These modifications could mitigate the fitness cost of plasmid carriage and enhance plasmid maintenance. The extent of plasmid modifications and the evolution of plasmid-encoded antibiotic resistance depended on treatment type, particularly the drug class and duration of exposure. Interestingly, prolonged exposure to mono- and combinational drugs of CS and CIP resulted in a substantial loss of the plasmid-encoded MDR region and antibiotic resistance, comparable to the selection condition without antibiotic. By contrast, combinational treatment with CTX contributed to the maintenance of the MDR region over a long period of time. Furthermore, drug selection was able to maintain and even amplify the corresponding plasmid-encoded ARGs, with co-selection of ARGs in the adjacent regions. In addition, parallel mutations in chromosomal arcA were also found to be associated with pJXP9 plasmid carriage among endpoint-evolved clones from diverse treatments. Meanwhile, arcA deletion improved the persistence of pJXP9 plasmid without drugs. Overall, our findings indicated that plasmid-borne MDR region deletion and chromosomal arcA inactivation mutation jointly contributed to co-adaptation and co-evolution between MDR IncHI2 plasmid and Salmonella Typhimurium under different drug selection pressure.IMPORTANCEThe plasmid-mediated dissemination of antibiotic resistance genes has become a significant concern for human health, even though the carriage of multidrug-resistant (MDR) plasmids is frequently associated with fitness costs for the bacterial host. However, the mechanisms by which MDR plasmids and bacterial pairs evolve plasmid-mediated antibiotic resistance in the presence of antibiotic selections are not fully understood. Herein, we conducted an experimental evolution of a large multidrug-resistant plasmid in a Salmonella enterica Typhimurium host under single and combinatorial drug selection pressures. Our results show the adaptive evolution of plasmid-encoded antibiotic resistance through alterations of the MDR region in the plasmid, in particular substantial loss of the MDR region, in response to different positive selections, especially mono- and combinational drugs of colistin and ciprofloxacin. In addition, strong parallel mutations in chromosomal arcA were associated with pJXP9 carriage in Salmonella Typhimurium from diverse treatments. Our results thus highlight promoting the loss of the plasmid's MDR region could offer an alternative approach for combating plasmid-encoded antibiotic resistance.

Defense mechanisms of Salmonella against antibiotics: a review

Salmonella is a foodborne pathogenic bacterium that causes salmonellosis worldwide. Also, Salmonella is considered a serious problem for food safety and public health. Several antimicrobial classes including aminoglycosides, tetracyclines, phenols, and β-Lactams are used to treat Salmonella infections. Antibiotics have been prescribed for decades to treat infections caused by bacteria in human and animal healthcare. However, intensive use of antibiotics resulted in antibiotic resistance (AR) among several foodborne bacteria including Salmonella. Furthermore, multi-drug resistance (MDR) of Salmonella has increased dramatically. In addition to MDR Salmonella, extensively drug resistant (XDR) as well as pan drug resistant (PDR) Salmonella were reported globally. Therefore, increasing AR is becoming a serious universal public health crisis. Salmonella developed many mechanisms to ensure its survival against antimicrobials. The most prominent defense mechanisms against these antibiotics include enzymatic inactivation, expelling drugs from the cell through efflux pumps, altering the structure of drugs, and changing or protecting the targets of drugs. Additionally, the formation of biofilms and plasmid-mediated AR by Salmonella, enhancing its resistance to various antibiotics, making it a challenging pathogen in both healthcare and food industry settings. This review focuses exclusively on providing a detailed overview of the mechanisms of AR in Salmonella.

Comparative analysis of three plasmids from Plesiomonas shigelloides strain MS-17-188 and their role in antimicrobial resistance.

Plesiomonas shigelloides strain MS-17-188 was isolated from a deceased catfish from East Mississippi and showed resistance to florfenicol, tetracyclines and a sulphonamide. WGS of strain MS-17-188 revealed three plasmids (pPSMS-171881, pPSMS-171882 and pPSMS-171883). To accurately determine the impact of three plasmids found in P. shigelloides strain MS-17-188 on the dissemination of antibiotic resistance genes and to provide insights into the molecular structure of these plasmids. The genetic features of these plasmids in terms of genes associated with antimicrobial resistance (AMR), virulence, transfer, maintenance and replication were identified using bioinformatic tools. Additionally, we investigated the in vitro mobilization and stability of plasmid-mediated resistance. The Comprehensive Antibiotic Resistance Database and Virulence Factors Database were used to detect the AMR genes and virulence genes of P. shigelloides plasmids. Moreover, plasmid mobility was evaluated by a filter-mating assay using strain MS-17-188 as a donor and azide-resistant Escherichia coli J53 as a recipient strain. A stability experiment was conducted to explore the persistence of plasmid-mediated antibiotic resistance in strain MS-17-188 in the absence and presence of selection. pPSMS-171881 harboured multidrug efflux complex (adeF) and two genes responsible for arsenic resistance (arsB and arsC). pPSMS-171882 had a region of 7085 bp encoding type IV secretion system proteins. pPSMS-171883 carried the tetracycline resistance genes tet(A) and tet(R), and a phenicol resistance gene (floR), which were flanked by two transposable elements and mobilization proteins, suggesting that there is a conjugative mechanism by which this plasmid can be mobilized. Results from the stability experiment indicated that pPSMS-171883 is lost over time in the absence of selective pressure. Moreover, pPSMS-171883 is more stable in P. shigelloides at growth temperatures of 30°C and 37°C compared with 40°C and 43°C. After intraperitoneal injection in catfish, P. shigelloides strain MS-17-188 resulted in no mortalities. This is the first study to report plasmid-mediated AMR in Plesiomonas isolated from cultured fish, which needs continued monitoring. This study will provide an understanding of the genetic mechanisms of AMR and virulence of P. shigelloides.

Plasmid Curing of Bacteria Isolated from Upper Respiratory Tract Infections among Patients Attending Specialist Hospital Sokoto

Study’s Novelty/Excerpt This study focuses on curing plasmid-mediated antibiotic resistance in bacteria associated with upper respiratory tract infections in patients at Specialist Hospital Sokoto, an area previously underexplored in this context. It uniquely demonstrates the successful reversal of antibiotic resistance in Staphylococcus aureus, Streptococcus pyogenes, and Pseudomonas aeruginosa through plasmid curing experiments, highlighting the significant role of plasmids in resistance mechanisms. Additionally, the study underscores the potential for plasmid-mediated resistance to be transferred among bacterial populations, presenting a critical concern for antimicrobial resistance management in the region. Full Abstract Presences of resistant plasmids (R-plasmids) in microorganisms make the cells avert the effect of antibiotics and complicates chemotherapy of infections. This study aimed to cure the plasmid of antibiotic-resistant bacteria associated with upper respiratory tract infections among patients attending Specialist Hospital Sokoto by reassessing their susceptibility to antibiotics that were previously resistant. One hundred (100) throat swab samples were collected and analysed. The isolates were isolated and identified using standard methods (Gram staining, biochemical and serological tests). The susceptibility of the isolates to various beta-lactam antibiotics was evaluated, and resistant bacteria were subjected to plasmid curing experiments followed by further susceptibility testing to reassess their susceptibility to the erstwhile resistance. Bacteria isolated were Staphylococcus aureus, Streptococcus pyogenes, and Pseudomonas aeruginosa, with the frequency of occurrence of 20 (57.2%), 9 (25.7%), and 6 (17.1%), respectively. The result of antibiotic susceptibility tests before plasmid curing showed that Staphylococcus aureus, Streptococcus pyogenes, and Pseudomonas aeruginosa resisted Cloxacilline, Cefuroxime, Cloxacillin and Augmentin. Susceptibility results after curing showed that almost all bacteria have reverted to sensitivity to all antibiotics except Cloxacillin and Augmentin. This research implies that the resistance possessed by the bacterial isolates is plasmid-mediated and may easily be transferred to other non-resistant bacteria, which may lead to an alarming rate of antimicrobial resistance in the study area.

Ubiquitous nanocolloids suppress the conjugative transfer of plasmid-mediated antibiotic resistance in aqueous environment

Nanocolloids (Nc) are widespread in natural water environment, whereas the potential effects of Nc on dissemination of antibiotic resistance remain largely unknown. In this study, Nc collected from the Yellow River in Henan province was tested for its ability to influence the conjugative transfer of resistant plasmid in aqueous environment. The results revealed that the conjugative transfer of RP4 plasmid between Escherichia coli was down-regulated by 52%–91% upon exposure to 1–10 mg/L Nc and the reduction became constant when the dose became higher (20−200 mg/L). Despite the exposure of Nc activated the anti-oxidation and SOS response in bacteria through up-regulating genes involved in glutathione biosynthesis and DNA recombination, the inhibition on the synthesis and secretion of extracellular polysaccharide induced the prevention of cell-cell contact, leading to the reduction of plasmid transfer. This was evidenced by the decreased bacterial adhesion and lowered levels of genes and metabolites relevant to transmembrane transport and D-glucose phosphorylation, as clarified in phenotypic, transcriptomics and metabolomics analysis of E. coli. The significant down-regulation of glycolysis/gluconeogenesis and TCA cycle was associated with the shortage of ATP induced by Nc. The up-regulation of global regulatory genes (korA and trbA) and the reduction of plasmid genes (trfAp, trbBp, and traG) expression also contributed to the suppressed conjugation of RP4 plasmid. The obtained findings remind that the role of ubiquitous colloidal particles is nonnegligible when practically and comprehensively assessing the risk of antibiotic resistance in the environment.

Nanoparticle-Mediated Plasmid Curing in Combating Antibiotic Resistance in Pathogenic Bacteria

Background: Nanotechnology has emerged as a pivotal domain in material science research with extensive applications across various sectors including biotechnology and medicine. Nanoparticles offer unique properties facilitating advancements in nanobiotechnology, particularly in nanomedicine, to combat bacterial infections and antibiotic resistance. This study aimed to determine the application of nanoparticles, specifically nano-TiO2, in treating plasmid-mediated antibiotic resistance in both Gram-negative and Gram-positive bacteria. Method: We evaluated antibiotic and nanomaterial sensitivity through disc diffusion and broth microdilution assays. Plasmid curing experiments were conducted using varying concentrations of nano-TiO2 and SDS as curing agents, followed by plasmid isolation and DNA extraction. The efficacy of nano-TiO2 in plasmid curing and DNA extraction was assessed, alongside the impact on bacterial growth and antibiotic resistance. Results: Results showed successful plasmid elimination with nano-TiO2 treatment, evidenced by the loss of plasmid DNA bands. Additionally, nano-TiO2 substantially enhanced DNA extraction efficiency and quality. The study indicated nano-TiO2's potential in combating antibiotic resistance by targeting plasmids, thereby presenting a novel approach in molecular biology techniques. Conclusion: In conclusion, this study underscores the promising role of nanoparticles in addressing bacterial infections and combating antibiotic resistance. Nano-TiO2 emerges as a valuable tool in DNA purification and plasmid curing, offering new avenues in molecular biology and antibiotic resistance research. However, further investigations are warranted to elucidate the broader implications of nanoparticles across diverse bacterial species and strains. These findings represent a significant step towards harnessing the potential of nanotechnology in combating antimicrobial resistance and advancing healthcare paradigms.

Graphene oxide influences transfer of plasmid-mediated antibiotic resistance genes into plants

As an emerging contaminant, antibiotic resistance genes (ARGs) are raising concerns about its significant threat to public health. Meanwhile, graphene oxide (GO), which also has a potential ecological damage with increasingly entering the environment, has a great influence on the transfer of ARGs. However, little is known about the effects mechanisms of GO on the migration of antibiotic resistance genes (ARGs) from bacteria into plants. In this study, we investigated the influence of GO on the transfer of ARGs carried by RP4 plasmids from Bacillus subtilis into rice plants. Our results showed that the presence of GO at concentrations ranging from 0 to 400 mg L−1 significantly reduced the transfer of ARGs into rice roots by 13–71 %. Moreover, the migration of RP4 from the roots to aboveground parts was significantly impaired by GO. These effects may be attributed to several factors. First, higher GO concentrations led to low pH in the culture solution, resulting in a substantial decrease in the number of antibiotic-resistant bacteria. Second, GO induced oxidative stress in rice, as indicated by enhanced Evans blue dye staining, and elevated levels of malondialdehyde, nitric oxide, and phenylalanine ammonia-lyase activity. The oxidative stress negatively affected plant growth, as demonstrated by the reduced fresh weight and altered lignin content in the rice. Microscopic observations confirmed the entry of GO into root cells but not leaf mesophyll cells. Furthermore, potential recipients of RP4 plasmid strains in rice after co-cultivation experiments were identified, including Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus cereus. These findings clarify the influence of GO on ARGs in the bacteria–plant system and emphasize the need to consider its potential ecological risks.

Characterisation and mobilisation of IncA/C plasmid-mediated antibiotic resistance in Edwardsiella ictaluri

Edwardsiella ictaluri is an important pathogen in farmed raised catfish. Recently, we showed that resistance to tetracycline and florfenicol in the E. ictaluri MS-17-156 strain isolated from channel catfish was facilitated by acquisition of a 135 kb plasmid (named pEIMS-171561). We described the genetic structure of pEIMS-171561. Plasmid copy number and stability within E. ictaluri strain MS-17-156 was determined. We also investigated the in vitro and in vivo transferability of pEIMS-171561 using catfish as a model for in vivo transfer. pEIMS-171561 belonged to the IncA/C group and contained florfenicol efflux major facilitator superfamily (MFS) (floR), sulfonamides (sul2), and tetracycline efflux MFS (tetD) genes. The plasmid contained two conjugative transfer-associated regions and encoded six transposases and insertion sequences. In vitro conjugation experiments demonstrated that the IncA/C plasmid can transfer from E. ictaluri to Escherichia coli. The plasmid was stable in E. ictaluri without selection pressure for 33 days. We showed that pEIMS-171561 did not transfer from E. ictaluri MS-17-156 to endogenous microbiota in catfish. Moreover, we could not detect in vivo conjugal transfer of pEIMS-171561 from E. ictaluri to E. coli. Results from real-time PCR revealed upregulation of the floR gene in the intestines of catfish receiving florfenicol-medicated feed, compared with that in catfish receiving unmedicated feed. This study demonstrated that pEIMS-171561 did not disseminate from E. ictaluri to gut microbiota under selective pressure. This result suggests a limited role of the fish microbiota as a reservoir for this plasmid and for the spread of resistance.

Factors associated with plasmid antibiotic resistance gene carriage revealed using large-scale multivariable analysis

Plasmids are major vectors of bacterial antibiotic resistance, but understanding of factors associated with plasmid antibiotic resistance gene (ARG) carriage is limited. We curated > 14,000 publicly available plasmid genomes and associated metadata. Duplicate and replicate plasmids were excluded; where possible, sample metadata was validated externally (BacDive database). Using Generalised Additive Models (GAMs) we assessed the influence of 12 biotic/abiotic factors (e.g. plasmid genetic factors, isolation source, collection date) on ARG carriage, modelled as a binary outcome. Separate GAMs were built for 10 major ARG types. Multivariable analysis indicated that plasmid ARG carriage patterns across time (collection years), isolation sources (human/livestock) and host bacterial taxa were consistent with antibiotic selection pressure as a driver of plasmid-mediated antibiotic resistance. Only 0.42% livestock plasmids carried carbapenem resistance (compared with 12% human plasmids); conversely, tetracycline resistance was enriched in livestock vs human plasmids, reflecting known prescribing practices. Interpreting results using a timeline of ARG type acquisition (determined by literature review) yielded additional novel insights. More recently acquired ARG types (e.g. colistin and carbapenem) showed increases in plasmid carriage during the date range analysed (1994–2019), potentially reflecting recent onset of selection pressure; they also co-occurred less commonly with ARGs of other types, and virulence genes. Overall, this suggests that following acquisition, plasmid ARGs tend to accumulate under antibiotic selection pressure and co-associate with other adaptive genes (other ARG types, virulence genes), potentially re-enforcing plasmid ARG carriage through co-selection.

Environmentally relevant concentrations of mercury facilitate the horizontal transfer of plasmid-mediated antibiotic resistance genes

Abundant antibiotic resistance genes (ARGs) are typically found in mercury (Hg)-contaminated aquatic environments. This phenomenon is partly attributed to the co-resistance, cross-resistance, and shared regulatory responses to Hg and antibiotics. However, it remains unclear whether and how Hg influences the conjugative transfer of ARGs mediated by mobilizable plasmids. In the present study, we found that Hg2+ at the environmentally relevant concentrations (0.001–0.5 mg L−1) facilitated the conjugative transfer of ARGs through the mobilizable plasmid RP4 from the donor Escherichia coli HB101 to the recipient E. coli K12. Exposure to Hg2+ significantly increases the formation of reactive oxygen species, malondialdehyde production, antioxidant enzyme activities, and cell membrane permeability, while decreasing the concentration of glutathione. Scanning electron microscopy and transmission electron microscopy showed that the cell membrane suffered from oxidative damage, which is beneficial for conjugative transfer. The expression of global regulatory genes (korA, korB, and trbA) negatively regulating conjugative transfer was restrained by Hg2+, while promoting the expression of positive regulatory genes involved in the mating pair formation system (trbBp and traF) and the DNA transfer and replication systems (trfAp and traJ). Although a high Hg2+ concentration (1.0 mg L−1) suppressed ARGs conjugative transfer, our results suggest that Hg2+ facilitates the dissemination of ARGs in aquatic environments at environmentally relevant concentrations. This study improves our understanding of ARGs dissemination in Hg-contaminated aquatic environments.

Non-Darwinian Selection of Plasmid-Mediated Antibiotic Resistance

Resistance of bacteria to antibiotics is an inevitable consequence of long-term exposure to sub lethal drug concentrations, and the problem has been greatly exacerbated by inappropriate use. Resistance can be conferred by chromosomal mutations that are passed on in normal cell division (vertical gene transfer) or by horizontal gene transfer processes such as conjugation. Darwinian natural selection implies that individual organisms possessing a survival advantage over their peers will represent an increasing proportion of the total population in subsequent generations. Using the techniques of evolutionary dynamics, we have modelled the selection of antibiotic resistant strains of bacteria resulting from either vertical or horizontal gene transfer, and the consequences of these events for drug sensitivity. Our model suggests that the dynamics of horizontal gene transfer are such that plasmid-bearing bacteria may dominate a population despite having a growth disadvantage compared to the same bacteria that do not carry the plasmid. Horizontal gene transfer than by vertical transfer propagates antibiotic resistance more rapidly. These findings have implications for the design of combination drug regimens for treatment of bacterial infections.

Effect of sulfamethazine on the horizontal transfer of plasmid-mediated antibiotic resistance genes and its mechanism of action

As a new type of environmental pollutant, antibiotic resistance genes (ARGs) pose a huge challenge to global health. Horizontal gene transfer (HGT) represents an important route for the spread of ARGs. The widespread use of sulfamethazine (SM2) as a broad-spectrum bacteriostatic agent leads to high residual levels in the environment, thereby increasing the spread of ARGs. Therefore, we chose to study the effect of SM2 on the HGT of ARGs mediated by plasmid RP4 from Escherichia coli (E. coli) HB101 to E. coli NK5449 as well as its mechanism of action. The results showed that compared with the control group, SM2 at concentrations of 10 mg/L and 200 mg/L promoted the HGT of ARGs, but transfer frequency decreased at concentrations of 100 mg/L and 500 mg/L. The transfer frequency at 200 mg/L was 3.04 × 10−5, which was 1.34-fold of the control group. The mechanism of SM2 improving conjugation transfer is via enhancement of the mRNA expression of conjugation genes (trbBP, trfAP) and oxidative stress genes, inhibition of the mRNA expression of vertical transfer genes, up regulation of the outer membrane protein genes (ompC, ompA), promotion of the formation of cell pores, and improvement of the permeability of cell membrane to promote the conjugation transfer of plasmid RP4. The results of this study provide theoretical support for studying the spread of ARGs in the environment.

Geographical resistome profiling in the honeybee microbiome reveals resistance gene transfer conferred by mobilizable plasmids

BackgroundThe spread of antibiotic resistance genes (ARGs) has been of global concern as one of the greatest environmental threats. The gut microbiome of animals has been found to be a large reservoir of ARGs, which is also an indicator of the environmental antibiotic spectrum. The conserved microbiota makes the honeybee a tractable and confined ecosystem for studying the maintenance and transfer of ARGs across gut bacteria. Although it has been found that honeybee gut bacteria harbor diverse sets of ARGs, the influences of environmental variables and the mechanism driving their distribution remain unclear.ResultsWe characterized the gut resistome of two closely related honeybee species, Apis cerana and Apis mellifera, domesticated in 14 geographic locations across China. The composition of the ARGs was more associated with host species rather than with geographical distribution, and A. mellifera had a higher content of ARGs in the gut. There was a moderate geographic pattern of resistome distribution, and several core ARG groups were found to be prevalent among A. cerana samples. These shared genes were mainly carried by the honeybee-specific gut members Gilliamella and Snodgrassella. Transferrable ARGs were frequently detected in honeybee guts, and the load was much higher in A. mellifera samples. Genomic loci of the bee gut symbionts containing a streptomycin resistance gene cluster were nearly identical to those of the broad-host-range IncQ plasmid, a proficient DNA delivery system in the environment. By in vitro conjugation experiments, we confirmed that the mobilizable plasmids could be transferred between honeybee gut symbionts by conjugation. Moreover, “satellite plasmids” with fragmented genes were identified in the integrated regions of different symbionts from multiple areas.ConclusionsOur study illustrates that the gut microbiota of different honeybee hosts varied in their antibiotic resistance structure, highlighting the role of the bee microbiome as a potential bioindicator and disseminator of antibiotic resistance. The difference in domestication history is highly influential in the structuring of the bee gut resistome. Notably, the evolution of plasmid-mediated antibiotic resistance is likely to promote the probability of its persistence and dissemination.Aghy2aoGk5W_8F1dgySKf9Video

Uncovering antimicrobial resistance in three agricultural biogas plants using plant-based substrates

Antimicrobial resistance (AMR) is becoming an increasing global concern and the anaerobic digestion (AD) process represents a potential transmission route when digestates are used as fertilizing agents. AMR contaminants, e.g. antibiotic-resistant bacteria (ARB) and plasmid-mediated antibiotic resistance genes (ARGs) have been found in different substrates and AD systems, but not yet been investigated in plant-based substrates. AMR transfer from soils to vegetable microbiomes has been observed, and thus crop material potentially represents a so far neglected AMR load in agricultural AD processes, contributing to AMR spread. In order to test this hypothesis, this study examined the AMR situation throughout the process of three biogas plants using plant-based substrates only, or a mixture of plant-based and manure substrates. The evaluation included a combination of culture-independent and –dependent methods, i.e., identification of ARGs, plasmids, and pathogenic bacteria by DNA arrays, and phylogenetic classification of bacterial isolates and their phenotypic resistance pattern. To our knowledge, this is the first study on AMR in plant-based substrates and the corresponding biogas plant. The results showed that the bacterial community isolated from the investigated substrates and the AD processing facilities were mainly Gram-positive Bacillus spp. Apart from Pantoea agglomerans, no other Gram-negative species were found, either by bacteria culturing or by DNA typing array. In contrast, the presence of ARGs and plasmids clearly indicated the existence of Gram-negative pathogenic bacteria, in both substrate and AD process. Compared with substrates, digestates had lower levels of ARGs, plasmids, and culturable ARB. Thus, digestate could pose a lower risk of spreading AMR than substrates per se. In conclusion, plant-based substrates are associated with AMR, including culturable Gram-positive ARB and Gram-negative pathogenic bacteria-associated ARGs and plasmids. Thus, the AMR load from plant-based substrates should be taken into consideration in agricultural biogas processing.

Environmentally Relevant Concentrations of Mercury Facilitate the Horizontal Transfer of Plasmid-Mediated Antibiotic Resistance Genes

Environmentally Relevant Concentrations of Mercury Facilitate the Horizontal Transfer of Plasmid-Mediated Antibiotic Resistance Genes

Paclitaxel and its derivative facilitate the transmission of plasmid-mediated antibiotic resistance genes through conjugative transfer

The rapid dissemination of antibiotic resistance by horizontal gene transfer (HGT) renders the global resistance crisis more tense and urgent as few effective antimicrobials are available to combat multidrug-resistant (MDR) pathogens at present. Conjugation is one of the most dominant and representative pathways of HGT. Antibiotic residue in environment is recognized as an important accelerator for conjugal transfer, whereas the roles of non-antibiotic pharmaceuticals in this process are not fully understood. Here we found that environmentally relevant concentrations of paclitaxel as well as its derivative docetaxel, two commonly used anticancer drugs, remarkably facilitated the conjugative transfer of resistance plasmids carrying multiple antibiotic resistance genes (ARGs). The underlying mechanisms accounting for the enhanced conjugation were investigated by detecting the activity of RpoS regulon, membrane permeability, SOS response and gene expression of conjugative transfer systems. Our results showed that paclitaxel induced a series of cellular responses, including up-regulation of rpoS expression, activated SOS response, increased cell membrane permeability, enhanced plasmid replication and mating pilus formation. Collectively, our data provide new insight on the roles of paclitaxel and its derivative in promoting the conjugal transfer of ARGs, highlighting the importance of good antimicrobial stewardship.

Melatonin prevents conjugative transfer of plasmid-mediated antibiotic resistance genes by disrupting proton motive force

The widespread dissemination of antibiotic resistance genes (ARGs) is a serious problem and constitutes a threat for public health. Plasmid-mediated conjugative transfer of ARGs is recognized as one of the most important pathways accounting for this global crisis. Inhibiting the conjugative transfer of resistant gene-bearing plasmids provides a feasible strategy to prevent the spread of antibiotic resistance. Here we found that melatonin, a neurohormone secreted from pineal gland, substantially inhibited the horizontal transfer of RP4–7 plasmid in a dose-dependent manner. Furthermore, melatonin could also suppress the conjugal frequency of different types of clinical plasmids that carrying colistin resistance gene mcr-1 rather than blaNDM or tet(X) genes. Next, we investigated the mechanisms underlying the inhibitory effect of melatonin on conjugation. As a result, we showed that the addition of melatonin markedly reduced bacterial membrane permeability and inhibited the oxidative stress. In line with these observations, the conjugative transfer-related genes were regulated accordingly. Most importantly, we uncovered that melatonin disrupted bacterial proton motive force (PMF), which is an essential bacterial energy metabolism substance and is important for conjugative process. Collectively, these results provide implications that some non-antibiotics such as melatonin are effective inhibitors of transmission of ARGs and raise a promising strategy to confront the increasing resistant infections.

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.

An optimal control problem applied to plasmid-mediated antibiotic resistance

An optimal control problem applied to plasmid-mediated antibiotic resistance

Plasmid-Mediated Antibiotic Resistant Escherichia coli in Sarawak Rivers and Aquaculture Farms, Northwest of Borneo.

Background: The emergence of plasmid-mediated antibiotic resistance in Escherichia coli in water resources could pose a serious threat to public health. The study aims to investigate the dispersion of plasmid-mediated antibiotic-resistant E. coli from six rivers in Sarawak and two aquaculture farms in Borneo. Methods: A total of 74 water samples were collected for the determination of their bacteria colony count. An IMViC test identified 31 E. coli isolates and tested their susceptibility against twelve clinically important antibiotics. The extraction of plasmid DNA was done using alkali lysis SDS procedures. Characteristics, including plasmid copy number, molecular weight size, resistance rate and multiple antibiotic resistance (MAR), were assessed. Results: Our findings revealed that bacterial counts in rivers and aquaculture farms ranged from log 2.00 to 3.68 CFU/mL and log 1.70 to 5.48 cfu/mL, respectively. Resistance to piperacillin (100%) was observed in all E. coli; resistance to amoxicillin (100%) and ampicillin (100%) was observed in E. coli found in aquaculture farms; resistance to streptomycin (93%) was observed in E. coli found in rivers. All E. coli were resistant to ≥2 antibiotics and formed 26 MAR profiles, ranging from an index of 0.17 to 0.83, indicating that there are high risks of contamination. Some (48.4%) of the E. coli were detected with plasmids (1.2 to >10 kb), whereas 51.6% of the E. coli did not harbor any plasmids. The plasmid copy numbers reported were one plasmid (n = 7), two plasmids (n = 4), ≥ two plasmids (4). E. coli isolated from the Muara Tuang River showed the highest-molecular-weight plasmids. A statistical analysis revealed that there is no significant correlation (r = 0.21, p = 0.253) between the number of plasmids and the MAR index of the tested isolates. Conclusion: The distribution of MAR in E. coli from rivers is higher compared to the aquaculture environment. Our study suggests that MAR in isolates could be chromosome-mediated. Our results suggest that riverbed sediments could serve as reservoirs for MAR bacteria, including pathogens, under different climatic conditions, and their analysis could provide information for public health concerns.