Elucidation Of Resistance Mechanisms Research Articles

NUAK1-Mediated Phosphorylation of NADK Mitigates ROS Accumulation to Promote Osimertinib Resistance in Non-Small Cell Lung Carcinoma.

Osimertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor, is approved as a first-line therapy in advanced non-small cell lung carcinoma (NSCLC) patients with EGFR-activating mutations or the T790M resistance mutation. However, the efficacy of osimertinib is limited due to acquired resistance, highlighting the need to elucidate resistance mechanisms to facilitate the development of improved treatment strategies. Here, we screened for significantly upregulated genes encoding protein kinases in osimertinib-resistant NSCLC cells and identified NUAK1 as a pivotal regulator of osimertinib resistance. NUAK1 was highly expressed in osimertinib-resistant NSCLC and promoted the emergence of osimertinib resistance. Genetic or pharmacological blockade of NUAK1 restored the sensitivity of resistant NSCLC cells to osimertinib in vitro and in vivo. Mechanistically, NUAK1 directly interacted with and phosphorylated NADK at serine 64 (S64), which mitigated osimertinib-induced accumulation of reactive oxygen species (ROS) and contributed to the acquisition of osimertinib resistance in NSCLC. Furthermore, virtual drug screening identified T21195 as an inhibitor of NADK-S64 phosphorylation, and T21195 synergized with osimertinib to reverse acquired resistance by inducing ROS accumulation. Collectively, these findings highlight the role of the NUAK1-NADK axis in governing osimertinib resistance in NSCLC and indicate the potential of targeting this axis as a strategy for circumventing resistance.

Tumor-Immune Signatures of Treatment Resistance to Brentuximab Vedotin with Ipilimumab and/or Nivolumab in Hodgkin Lymphoma.

Identification of multi-omic immune markers from peripheral blood may help elucidate resistance mechanisms to checkpoint inhibitor and antibody-drug conjugate combinations with potential implications for treatment decisions in relapsed HL.

Evaluation of Co-production of Colistin Resistance and ESBL Genes among Gram-negative Clinical Isolates from Usmanu Danfodiyo University Teaching Hospital Sokoto, Nigeria

Study’s Excerpt/Novelty This study presents a comprehensive evaluation of colistin-resistant and extended-spectrum beta-lactamase (ESBL) gene co-production among Gram-negative clinical isolates from Usmanu Danfodiyo University Teaching Hospital in Sokoto. Notably, 13.9% of the isolates exhibited phenotypic co-production of colistin resistance and ESBL, with a significant presence of blaCTX-M and CTX-M 8 genes among ESBL producers, although no colistin resistance genes (mcr-1 and mcr-2) were detected via PCR. These findings highlight the necessity for integrated molecular and phenotypic investigations to fully elucidate resistance mechanisms in Gram-negative bacteria and underscore the need for further research to uncover alternative pathways contributing to observed resistance phenotypes. Full Abstract The emergence of antimicrobial resistance (AMR) is a major threat to global health. Its effects include high mortality and morbidity rates, treatment failure, and increased treatment costs. This study aimed to evaluate the co-production of colistin-resistant and extended-spectrum beta-lactamase (ESBL) genes among Gram-negative clinical isolates from Usmanu Danfodiyo University Teaching Hospital in Sokoto. Gram-negative bacteria were isolated from clinical specimens, including urine, feces, and wound aspirates. The Double-Disk Synergy Test and the Colistin Agar Test, respectively, were used to phenotypically validate the existence of colistin resistance and ESBL. Polymerase chain reaction (PCR) was used for molecular characterization. Primers were used to target genes linked to colistin resistance (mcr-1 and mcr-2) and ESBL genes (blaCTX-M, CTX-M 1, CTX-M 2, and CTX-M 8). The findings indicated that 13.9% of the isolates displayed co-production of Colistin and ESBL, and of these isolates, 60% had blaCTX-M genes, and 20% had CTX-M 8 linked to ESBL production. However, the presence of colistin resistance genes was not detected by PCR. Therefore, molecular analysis did not confirm the existence of the colistin resistance genes (mcr-1 and mcr-2) in these isolates. Consequently, the findings showed no molecular co-production of the ESBL and colistin resistance genes. This work emphasizes how crucial it is to look into molecular and phenotypic traits to completely comprehend how colistin resistance and ESBL genes coexist in Gram-negative isolates. More research is required to investigate other mechanisms behind the resistance phenotypes identified.

Addressing the Challenges of PD-1 Targeted Immunotherapy in Cancer Treatment

Background: Immune checkpoint inhibitors targeting the programmed cell death protein 1 (PD-1)/PD-ligand 1 (PD-L1) axis have revolutionized cancer treatment, demonstrating remarkable clinical efficacy across multiple malignancies. However, their broader applicability and therapeutic potential remain constrained by several challenges. Objective: This review aims to provide a comprehensive overview of the current challenges associated with PD-1 targeted immunotherapy, encompassing resistance mechanisms, patient selection, toxicity management, and the development of novel combination strategies. Methods: A comprehensive literature search was conducted across PubMed, Embase, and Web of Science databases to identify and critically analyze studies investigating the challenges and limitations of PD-1 targeted immunotherapy in cancer treatment. Results: The primary challenges identified include: (1) Intrinsic and acquired resistance mechanisms, such as alterations in antigen presentation, tumor microenvironment factors, and immune cell dysfunction; (2) Lack of reliable predictive biomarkers for patient selection and response monitoring; (3) Immune-related adverse events and their effective management; (4) Optimization of combination regimens with other immunotherapies, targeted therapies, or conventional treatments; (5) Financial and accessibility barriers limiting the broader implementation of immunotherapy. Conclusion: PD-1 targeted immunotherapy has transformed cancer treatment, addressing the current challenges is imperative to maximize its therapeutic potential and broaden its applicability. Ongoing research efforts focused on elucidating resistance mechanisms, developing predictive biomarkers, managing toxicities, and exploring novel combination strategies hold promise for overcoming these limitations. Interdisciplinary collaborations and continued investment in immunotherapy research are essential to ensure that the benefits of these groundbreaking therapies are accessible to a wider patient population.

Differences in oxazolidinone resistance mechanisms and small colony variants emergence of Staphylococcus aureus induced in an in vitro resistance development model

ABSTRACT Invasive Staphylococcus aureus infections are associated with a high burden of disease, case fatality rate and healthcare costs. Oxazolidinones such as linezolid and tedizolid are considered potential treatment choices for conditions involving methicillin resistance or penicillin allergies. Additionally, they are being investigated as potential inhibitors of toxins in toxin-mediated diseases. In this study, linezolid and tedizolid were evaluated in an in vitro resistance development model for induction of resistance in S. aureus. Whole genome sequencing was conducted to elucidate resistance mechanisms through the identification of causal mutations. After inducing resistance to both linezolid and tedizolid, several partially novel single nucleotide variants (SNVs) were detected in the rplC gene, which encodes the 50S ribosome protein L3 in S. aureus. These SNVs were found to decrease the binding affinity, potentially serving as the underlying cause for oxazolidinone resistance. Furthermore, in opposite to linezolid we were able to induce phenotypically small colony variants of S. aureus after induction of resistance with tedizolid for the first time in literature. In summary, even if different antibiotic concentrations were required and SNVs were detected, the principal capacity of S. aureus to develop resistance to oxazolidinones seems to differ between linezolid and tedizolid in-vivo but not in vitro. Stepwise induction of resistance seems to be a time and cost-effective tool for assessing resistance evolution. Inducted-resistant strains should be examined and documented for epidemiological reasons, if MICs start to rise or oxazolidinone-resistant S. aureus outbreaks become more frequent.

CRISPR Interference-Based Inhibition of MAB_0055c Expression Alters Drug Sensitivity in Mycobacterium abscessus.

There is an unmet medical need for effective treatments against Mycobacterium abscessus infections. Although advanced molecular genetic tools to validate drug targets and resistance of M. abscessus exist, the practical design and construction of plasmids are relatively laborious and time-consuming. Thus, for this purpose, we used CRISPR interference (CRISPRi) combined with catalytically deactivated Cas9 to inhibit the gene expression of a predicted LysR-type transcriptional regulator gene, MAB_0055c, in M. abscessus and evaluated its contribution to the development of drug resistance. Our results showed that silencing the MAB_0055c gene lead to increased rifamycin susceptibility depending on the hydroquinone moiety. These results demonstrate that CRISPRi is an excellent approach for studying drug resistance in M. abscessus. IMPORTANCE In this study, we utilized CRISPR interference (CRISPRi) to specifically target the MAB_0055c gene in M. abscessus, a bacterium that causes difficult-to-treat infections. The study found that silencing the gene lead to increased rifabutin and rifalazil susceptibility. This study is the first to establish a link between the predicted LysR-type transcriptional regulator gene and antibiotic resistance in mycobacteria. These findings underscore the potential of using CRISPRi as a tool for elucidating resistance mechanisms, essential drug targets, and drug mechanisms of action, which could pave the way for more effective treatments for M. abscessus infections. The results of this study could have important implications for the development of new therapeutic options for this challenging-to-treat bacterial infection.

THE PERSPECTIVES OF WHOLE GENOME SEQUENCING IN STRENGTHENING THE OUTBREAK INVESTIGATIONS AND PUBLIC HEALTH SURVEILLANCE

The resistance of microorganisms to antimicrobial drugs has become a seriuos issue that have been studied by both researchers as well as worldwide. It is reliably known that bacterial resistance has covered most antimicrobial drug groups, including last-line options. The highest resistance rates have been registered among microbial strains circulating within healthcare settings, which typically affect immunocompromised individuals. Rapid and accurate diagnosis would greatly contribute to limiting the spread of antimicrobial resistance. Thus, whole-genome sequencing (WGS) based technology brings new possibilities for elucidating resistance mechanisms, generating valuable results that, together with epidemiological data, allow for determining the link between isolates and the respective sources of infection, facilitating effective prevention and control measures. The use of WGS technology has contributed to the containment of numerous outbreaks caused by various pathogens, including viruses and bacteria. In addition to the advantages and significant contribution to the microbiological diagnosis of infections, the widespread implementation of whole-genome sequencing in clinical and public health laboratories faces a series of challenges related to infrastructure, technical limitations, as well as financial and human resources.

The Role of Immunotherapy in Pancreatic Cancer.

Pancreatic adenocarcinoma remains one of the most lethal cancers globally, with a significant need for improved therapeutic options. While the recent breakthroughs of immunotherapy through checkpoint inhibitors have dramatically changed treatment paradigms in other malignancies based on considerable survival benefits, this is not so for pancreatic cancer. Chemotherapies with modest benefits are still the cornerstone of advanced pancreatic cancer treatment. Pancreatic cancers are inherently immune-cold tumors and have been largely refractory to immunotherapies in clinical trials. Understanding and overcoming the current failures of immunotherapy through elucidating resistance mechanisms and developing novel therapeutic approaches are essential to harnessing the potential durable benefits of immune-modulating therapy in pancreatic cancer patients.

Keystone Malaria Symposium 2022: a vibrant discussion of progress made and challenges ahead from drug discovery to treatment

Keystone Malaria Symposium 2022: a vibrant discussion of progress made and challenges ahead from drug discovery to treatment

Mutant KRAS-Associated Proteome Is Mainly Controlled by Exogenous Factors.

Understanding how mutant KRAS signaling is modulated by exogenous stimuli is of utmost importance to elucidate resistance mechanisms underlying pathway inhibition failure, and to uncover novel therapeutic targets for mutant KRAS patients. Hence, aiming at perceiving KRAS-autonomous versus -non autonomous mechanisms, we studied the response of two mutant KRAS colorectal cancer cell lines (HCT116 and LS174T) upon KRAS silencing and treatment with rhTGFβ1-activated fibroblasts secretome. A proteomic analysis revealed that rhTGFβ1-activated fibroblast-secreted factors triggered cell line-specific proteome alterations and that mutant KRAS governs 43% and 38% of these alterations in HCT116 and LS174T cells, respectively. These KRAS-dependent proteins were localized and displayed molecular functions that were common to both cell lines (e.g., extracellular exosome, RNA binding functions). Moreover, 67% and 78% of the KRAS-associated proteome of HCT116 and LS174T cells, respectively, was controlled in a KRAS-non-autonomous manner, being dependent on fibroblast-secreted factors. In HCT116 cells, KRAS-non-autonomously controlled proteins were mainly involved in proteoglycans in cancer, p53, and Rap1 signaling pathways; whereas in LS174T cells, they were associated with substrate adhesion-dependent cell-spreading and involved in metabolic processes. This work highlights the context-dependency of KRAS-associated signaling and reinforces the importance of integrating the tumor microenvironment in the study of KRAS-associated effects.

Abstract 1284: The tumor scaffold protein SQSTM1 at the crossroads of DNA damage and immunotherapy responses in solid tumors

Abstract Introduction After the recent advent of Immune Checkpoint Inhibitors (ICIs), one of current challenge of clinical cancer trials is certainly to develop the optimal combinations of ICIs with DNA-Damaging Agents (chemotherapy and/or radiotherapy, named DDAs hereafter). Elucidating resistance mechanisms to these different treatments is pivotal to propose new predictive biomarkers and to develop therapeutic strategies to improve ICI efficiency. We hypothesized that resistance to DDA and ICIs is mediated in part by intrinsic tumor mechanisms, some of which may be shared. Methods To address this knowledge gap, we compared RNA expression signatures, antigen presentation, and PD-L1 expression from cohorts of cancer patients treated with radiotherapy, chemotherapy, and immunotherapy to identify shared molecular pathways that may mediate cross-resistance. Using a panel of lung cancer cell lines, we then confirmed that the tumor-cell-intrinsic expression of SQSTM1 is positively correlated with antigen presentation, and inversely with DNA damage repair and DDA/ICIs resistance gene signatures. This SQSTM1/HERV pathway was then supported in vitro using engineered silenced cell-lines (SQSTM1, MAVS, and STING ShRNA) treated with FDA-approved DDA (cisplatin, oxaliplatin, doxorubicin, and ionizing radiations) or synthetic double-stranded RNA (5’ppp dsRNAs and poly IC). Results Through three complementary approaches (in silico, ex vivo on patient cohorts, and in vitro), we identify the p62/SQSTM1 scaffold protein as a key molecular mediator able of predicting and controlling sensitivity for DDA and ICIs. Mechanistically, in response to DNA damage, we found that SQSTM1 is essential for the inhibition of DNA repair and the reactivation of human endogenous retroviruses (hERV). Analogous to a “viral alarm”, the hERV are sensed and activate IFN responses that drive the expression of MHC-I and PD-L1, leading to tumor immune evasion. Targeting the hERV pathways in SQSTM1-depleted tumor cells by poly(I:C)/Lyovec, or docetaxel treatment can rescue the hERV, IFN, and MHC pathway, providing a promising therapeutic avenue turning a “cold” into a “hot” tumor in non-responders cancer patients. Conclusion Depending on its levels, we thus propose SQSTM1 as a predictive biomarker for guiding treatment decisions from i) ICI alone, ii) ICI combined with cisplatin, or; iii) ICI combined with poly(I:C)/Lyovec or docetaxel, with the aim to increase immunotherapy efficacy. Citation Format: Iris Grosjean, Grégoire D’Andréa, Nathalie Yazbeck, Amine Belaid, Barnabé Roméo, Marie Angela Domdom, Nicolas Guillot, Eric Gilson, Emmanuel Chamorey, Gérard Milano, Véronique Hofman, Marius Ilié, Isabelle Benard-Thiery, Simon Heeke, Patrick Brest, François Ghiringhelli, Paul Hofman, Baharia Mograbi. The tumor scaffold protein SQSTM1 at the crossroads of DNA damage and immunotherapy responses in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1284.

The H92R substitution in PSST is a reliable diagnostic biomarker for predicting resistance to mitochondrial electron transport inhibitors of complex I in European populations of Tetranychus urticae.

Mitochondrial Electron Transport Inhibitors of complex I (METI-I), such as tebufenpyrad and fenpyroximate, are acaricides that have been used extensively to control Tetranychus urticae Koch (Acari: Tetranychidae) for more than 20 years. Because of the ability of this spider mite to rapidly develop acaricide resistance, field (cross-) resistance monitoring and elucidation of resistance mechanisms are extremely important for resistance management (RM). In the present study, 42 European T. urticae field populations were screened for tebufenpyrad and fenpyroximate resistance, and the correlation between resistance and the H92R substitution in PSST was investigated. According to the calculated lethal concentration values that kill 90% of the population (LC90 ), tebufenpyrad and fenpyroximate would fail to control many of the collected populations at recommended field rates. Six populations exhibited high to very high resistance levels (200- to over 1950-fold) to both METI-Is. Analysis based on the LC50 values displayed a clear correlation between tebufenpyrad and fenpyroximate resistance, further supporting cross-resistance, which is of great operational importance in acaricide RM. The previously uncovered METI-I target-site mutation H92R in the PSST homologue of complex I (NADH:ubiquinone oxidoreductase) was found with high allele frequencies in populations resistant to tebufenpyrad and fenpyroximate. Synergist assays showed this mutation is not the only factor involved in METI-I resistance and additive or synergistic effects of multiple mechanisms most likely determine the phenotypic strength. The predictive value of resistance by H92R is very high in European populations and offers great potential to be used as a molecular diagnostic marker for METI-I resistance. © 2022 Society of Chemical Industry.

Biomarkers for Cyclin-Dependent Kinase 4/6 Inhibitors in the Treatment of Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative Advanced/Metastatic Breast Cancer: Translation to Clinical Practice.

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors have emerged as effective treatments for patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced/metastatic breast cancer (mBC). Dedicated research efforts have been undertaken to find predictive biomarkers of response or resistance to these therapies although no molecular biomarkers for mBC have reached the clinic so far. This review aims to summarize and evaluate the performance of biomarkers in predicting progression-free survival in phase II and III clinical trials of CDK4/6 inhibitors in HR+/HER2- mBC. For this narrative review, a structured literature search of PubMed, Embase, and the Cochrane library (CENTRAL) was performed. Phase II or III clinical trials of a CDK4/6 inhibitor in patients with HR+/HER2- mBC reporting on at least one molecular biomarker analysis of progression-free survival were included. Publications and selected conference abstracts were included up until November 2021. Twenty-two articles reporting biomarker results of 12 clinical trials were included. Retinoblastoma protein status and cyclin E1 mRNA expression were promising baseline biomarkers, whereas PIK3CA circulating tumor DNA ratio on treatment relative to baseline, change in plasma thymidine kinase activity, and circulating tumor cell count were potential dynamic biomarkers of response. A number of biomarkers were unsuccessful, despite a strong mechanistic rationale, and others are still being explored. Our review of clinical trials showed that there are a number of promising biomarkers at baseline and several dynamic biomarkers that might predict response to CDK4/6 inhibitors. Validation of these findings and assessment of clinical utility are crucial to make the final translation to clinical practice. Better understanding of disease heterogeneity and further elucidation of resistance mechanisms could inform future studies of rationally selected biomarkers.

Triticale Improvement: Mining of Genes Related to Yellow Rust Resistance in Triticale Based on Transcriptome Sequencing.

Yellow (stripe) rust caused by Puccinia striiformis f. sp. tritici (Pst) is a major destructive fungal disease of small grain cereals, leading to large yield losses. The breeding of resistant varieties is an effective, sustainable way to control yellow rust. Elucidation of resistance mechanisms against yellow rust and identification of candidate genes associated with rust resistance are thus crucial. In this study, seedlings of two Triticosecale Wittmack cultivars, highly resistant Gannong No. 2 and susceptible Shida No. 1, were inoculated with Pst race CYR34. Transcriptome sequencing (RNA-seq) was then used to investigate their transcriptional responses against pathogen infection before and after the appearance of symptoms—10 and 20 days after inoculation, respectively. According to the RNA-seq data, the number of upregulated and downregulated differentially expressed genes (DEGs) in the resistant cultivar was greater than in the susceptible cultivar. A total of 2,560 DEGs commonly expressed in the two cultivars on two sampling dates were subjected to pathway analysis, which revealed that most DEGs were closely associated with defense and metabolic activities. Transcription factor enrichment analysis indicated that the expressions of NAC, WRKY, and FAR1 families were also significantly changed. Further in-depth analysis of resistance genes revealed that almost all serine/threonine-protein kinases were upregulated in the resistant cultivar. Other genes related to disease resistance, such as those encoding disease-resistance- and pathogenesis-related proteins were differentially regulated in the two cultivars. Our findings can serve as a resource for gene discovery and facilitate elucidation of the complex defense mechanisms involved in triticale resistance to Pst.

Novel Dormancy Mechanism of Castration Resistance in Bone Metastatic Prostate Cancer Organoids.

Advanced prostate cancer (PCa) patients with bone metastases are treated with androgen pathway directed therapy (APDT). However, this treatment invariably fails and the cancer becomes castration resistant. To elucidate resistance mechanisms and to provide a more predictive pre-clinical research platform reflecting tumor heterogeneity, we established organoids from a patient-derived xenograft (PDX) model of bone metastatic prostate cancer, PCSD1. APDT-resistant PDX-derived organoids (PDOs) emerged when cultured without androgen or with the anti-androgen, enzalutamide. Transcriptomics revealed up-regulation of neurogenic and steroidogenic genes and down-regulation of DNA repair, cell cycle, circadian pathways and the severe acute respiratory syndrome (SARS)-CoV-2 host viral entry factors, ACE2 and TMPRSS2. Time course analysis of the cell cycle in live cells revealed that enzalutamide induced a gradual transition into a reversible dormant state as shown here for the first time at the single cell level in the context of multi-cellular, 3D living organoids using the Fucci2BL fluorescent live cell cycle tracker system. We show here a new mechanism of castration resistance in which enzalutamide induced dormancy and novel basal-luminal-like cells in bone metastatic prostate cancer organoids. These PDX organoids can be used to develop therapies targeting dormant APDT-resistant cells and host factors required for SARS-CoV-2 viral entry.

Basal-Luminal Hybrid Cells Emerge as a New Dormant, Androgen Pathway Directed Therapy-Resistant Population in Patient-Derived Prostate Cancer Organoids

Advanced prostate cancer (PCa) patients with bone metastases are treated standardly with Androgen Pathway Directed Therapy (APDT), however, they invariably become APDT-resistant. To elucidate resistance mechanisms and to provide more predictive pre-clinical research platforms reflecting tumor heterogeneity, w e established organoids from patient-derived xenograft (PDX) models of bone metastatic prostate cancer. APDT-resistant PDX-derived organoids (PDOs) emerged when cultured without androgen or with the anti-androgen, enzalutamide. Transcriptomics revealed up-regulation of neurogenic and steroidogenic genes and down-regulation of DNA repair, cell cycle, circadian pathways and the severe acute respiratory syndrome (SARS)-CoV-2 host viral entry factors, ACE2 and TMPRSS2. These experiments demonstrated that PDOs can be used to develop therapies targeting dormant APDT-resistant cells and host factors required for SARS-CoV-2 viral entry. Enzalutamide treatment decreased androgen receptor (AR) protein and induced dormant, hybrid basal-luminal cells as shown here for the first time in live organoids using the Fucci2BL fluorescent cell cycle tracker system.

Antibiotic Production and Antibiotic Resistance: The Two Sides of AbrB1/B2, a Two-Component System of Streptomyces coelicolor.

Antibiotic resistance currently presents one of the biggest threats to humans. The development and implementation of strategies against the spread of superbugs is a priority for public health. In addition to raising social awareness, approaches such as the discovery of new antibiotic molecules and the elucidation of resistance mechanisms are common measures. Accordingly, the two-component system (TCS) of Streptomyces coelicolor AbrB1/B2, offer amenable ways to study both antibiotic production and resistance. Global transcriptomic comparisons between the wild-type strain S. coelicolor M145 and the mutant ΔabrB, using RNA-Seq, showed that the AbrB1/B2 TCS is implicated in the regulation of different biological processes associated with stress responses, primary and secondary metabolism, and development and differentiation. The ΔabrB mutant showed the up-regulation of antibiotic biosynthetic gene clusters and the down-regulation of the vancomycin resistance gene cluster, according to the phenotypic observations of increased antibiotic production of actinorhodin and undecylprodigiosin, and greater susceptibility to vancomycin. The role of AbrB1/B2 in vancomycin resistance has also been shown by an in silico analysis, which strongly indicates that AbrB1/B2 is a homolog of VraR/S from Staphylococcus aureus and LiaR/S from Enterococcus faecium/Enterococcus faecalis, both of which are implied in vancomycin resistance in these pathogenic organisms that present a serious threat to public health. The results obtained are interesting from a biotechnological perspective since, on one hand, this TCS is a negative regulator of antibiotic production and its high degree of conservation throughout Streptomyces spp. makes it a valuable tool for improving antibiotic production and the discovery of cryptic metabolites with antibiotic action. On the other hand, AbrB1/B2 contributes to vancomycin resistance and is a homolog of VraR/S and LiaR/S, important regulators in clinically relevant antibiotic-resistant bacteria. Therefore, the study of AbrB1/B2 could provide new insight into the mechanism of this type of resistance.

Near-isogenic soybean lines carrying Asian soybean rust resistance genes for practical pathogenicity validation

Asian soybean rust caused by the fungal pathogen Phakopsora pachyrhizi is the most devastating disease of soybean. The host cultivar specificity of the pathogen shows considerable differentiation depending on the area and season of its emergence. Although resistance genes for P. pachyrhizi (Rpp) have been reported in several soybean varieties, the genetic background of these varieties is highly differentiated. Furthermore, some of the varieties harbor unknown genetic factors in addition to Rpp that could influence resistance reactions against the pathogen. In order to gain a comprehensive understanding of Rpp–P. pachyrhizi interactions, homogenous plant material harboring Rpp genes is necessary. In this study, we bred Rpp-near isogenic lines (Rpp-NILs), which retained identical plant characters originating from a single genetic background, and accordingly showed low-variant compatible/incompatible reactions against the pathogen. These Rpp-NILs can be used as genetic resources for studying P. pachyrhizi epidemiology and elucidating resistance mechanisms. Compatible/incompatible relationships between the soybean rust resistance gene Rpp and isolates of the pathogen P. pachyrhizi are clearly distinguishable using the Rpp-NILs bred in this study.

Molecular mechanisms associated with quinolone resistance in Enterobacteriaceae: review and update.

Quinolones are broad-spectrum antibiotics, which are used for the treatment of different infectious diseases associated with Enterobacteriaceae. During recent decades, the wide use as well as overuse of quinolones against diverse infections has led to the emergence of quinolone-resistant bacterial strains. Herein, we present the development of quinolone antibiotics, their function and also the different quinolone resistance mechanisms in Enterobacteriaceae by reviewing recent literature. All data were extracted from Google Scholar search engine and PubMed site, using keywords; quinolone resistance, Enterobacteriaceae, plasmid-mediated quinolone resistance, etc. The acquisition of resistance to quinolones is a complex and multifactorial process. The main resistance mechanisms consist of one or a combination of target-site gene mutations altering the drug-binding affinity of target enzymes. Other mechanisms of quinolone resistance are overexpression of AcrAB-tolC multidrug-resistant efflux pumps and downexpression of porins as well as plasmid-encoded resistance proteins including Qnr protection proteins, aminoglycoside acetyltransferase (AAC(6')-Ib-cr) and plasmid-encoded active efflux pumps such as OqxAB and QepA. The elucidation of resistance mechanisms will help researchers to explore new drugs against the resistant strains.

Resistance risk assessment of the novel complex II inhibitor pyflubumide in the polyphagous pest Tetranychus urticae

Pyflubumide is a novel selective carboxanilide acaricide that inhibits mitochondrial complex II of spider mite species such as Tetranychus urticae. We explored the baseline toxicity and potential cross-resistance risk of pyflubumide in a reference panel of T. urticae strains resistant to various acaricides with different modes of action. A cyenopyrafen-resistant strain (JPR) was identified as the only strain with low-to-moderate level of cross-resistance to pyflubumide (LC50 = 49.07 mg/L). In a resistance risk assessment approach, JPR was subsequently selected which led to two highly resistant strains JPR-R1 (RR = 466.7) and JPR-R2 (RR = 614.8). Interestingly, compared to adult females, resistance was much less pronounced in adult males and eggs of the two JPR-R strains. In order to elucidate resistance mechanisms, we first sequenced the complex II subunits in susceptible and resistant strains, but target-site insensitivity could not be detected. In contrast, synergism/antagonism experiments strongly suggested that cytochrome P450 monooxygenases are involved in pyflubumide resistance. We therefore conducted genome-wide gene expression experiments to investigate constitutive and induced expression patterns and documented the overexpression of five cytochrome P450 and four carboxyl/choline esterase genes in the JPR-R strains after pyflubumide exposure. Together, we provide a first resistance risk assessment of a novel complex II inhibitor and provide first evidence for metabolic resistance mediated by cytochrome P450s in T. urticae.