AmpC hyperproduction in a Cedecea davisae implant-associated bone infection during treatment: a case report and therapeutic implications

Abstract Background Data on antimicrobial resistance mechanisms are scanty for Cedecea spp., with very variable antibiotic resistance patterns documented. Here we report the first in vivo resistance evolution of a C. davisae clinical isolate in a patient with a complex hand trauma and provide insight in the resistance mechanism, leading to therapeutic implications for this pathogen. Case presentation Cedecea davisae was isolated from a patient with hand trauma during a first surgical debridement. Six days after primary surgical treatment and under antimicrobial treatment with amoxicillin-clavulanic acid and later cefepime, follow up cultures yielded C. davisae which demonstrated a resistance development. The susceptible parental isolate and its resistant derivative were characterized by whole genome sequencing, ampC, ompC and ompF by RT- PCR. The resistant derivative demonstrated an A224G SNP in ampD, the transcriptional regulator of ampC, leading to a His75Arg change in the corresponding AmpD protein. AmpC transcription of the resistant derivative was 362-times higher than the susceptible isolate. Transcription levels of ompF and ompC were 8.5-fold and 1.3-fold lower, respectively, in the resistant derivative. Downregulation of OmpF putatively resulted from a mutation in the presumed promoter region upstream of the dusB-Fis operon, a proposed regulator for ompF. Conclusions This case demonstrates the in vivo resistance development of C. davisae within 7 days similar to that of the members of the Enterobacter cloacae complex. Our findings add valuable information for future therapeutic management of these opportunistic pathogens as they warrant the same empirical treatment as AmpC producers.

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Tigecycline-non-susceptible hypervirulent Klebsiella pneumoniae strains in Taiwan

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkz450 ◽

2019 ◽

Vol 75 (2) ◽

pp. 309-317 ◽

Cited By ~ 1

Author(s):

Yi-Hsiang Cheng ◽

Tzu-Wen Huang ◽

Chih-Han Juan ◽

Sheng-Hua Chou ◽

Yao-Yi Tseng ◽

...

Keyword(s):

Klebsiella Pneumoniae ◽

Resistance Mechanism ◽

Resistance Mechanisms ◽

Site Directed Mutagenesis ◽

Upstream Region ◽

Public Health Issue ◽

Directed Mutagenesis ◽

Resistance Development ◽

Invasive Diseases

Abstract Objectives Emergent antimicrobial-resistant hypervirulent Klebsiella pneumoniae (hvKp) is an important public health issue. We aimed to investigate resistance mechanisms and hypervirulent traits among tigecycline-non-susceptible (TNS) K. pneumoniae clinical strains, focusing on one hvKp strain with in vivo evolution of tigecycline resistance. Methods TNS K. pneumoniae strains causing invasive diseases in a medical centre in Taiwan between July 2015 and April 2018 were collected. Resistance mechanisms were determined and hvKp strains were defined as rmpA/rmpA2-carrying strains. Isogenic strains with and without tigecycline resistance were subjected to WGS and in vivo virulence testing. Further, site-directed mutagenesis was used to confirm the resistance mechanism. Results In total, 31 TNS K. pneumoniae strains were isolated, including six hypervirulent strains. Tigecycline resistance mechanisms were mostly caused by overexpression of AcrAB and OqxAB together with up-regulation of RamA or RarA, respectively. One TNS hypervirulent strain (KP1692; MIC=6 mg/L) derived from its tigecycline-susceptible counterpart (KP1677; MIC=0.75 mg/L) showed acrAB overexpression. WGS revealed four genetic variations between KP1677 and KP1692. In addition, using site-directed mutagenesis, we confirmed that a 1 bp insertion in the ramA upstream region (RamR-binding site), leading to ramA and acrAB overexpression in KP1692, was responsible for tigecycline resistance. The in vivo virulence experiment showed that the TNS hvKp strain KP1692 still retained its high virulence compared with KP1677. Conclusions hvKp strains accounted for 19.4% among TNS strains. We identified alterations in the ramA upstream region as a mechanism of in vivo tigecycline resistance development in an hvKp strain.

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Distribution and validation of genotypic and phenotypic glyphosate and PPO-nhibitor resistance in Palmer amaranth (Amaranthus palmeri) from southwestern Nebraska

Weed Technology ◽

10.1017/wet.2020.74 ◽

2020 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Maxwel C Oliveira ◽

Darci A Giacomini ◽

Nikola Arsenijevic ◽

Gustavo Vieira ◽

Patrick J Tranel ◽

...

Keyword(s):

Cluster Analysis ◽

Gene Amplification ◽

Cropping Systems ◽

Resistance Mechanism ◽

Geographic Area ◽

Glyphosate Resistance ◽

Resistance Mechanisms ◽

Palmer Amaranth ◽

Resistance Evolution ◽

Inhibitor Resistance

Abstract Failure to control Palmer amaranth with glyphosate and protoporphyrinogen IX oxidase (PPO)-inhibitor herbicides was reported across southwestern Nebraska in 2017. The objectives of this study were to 1) confirm and 2) validate glyphosate and PPO-inhibitor (fomesafen and lactofen) resistance in 51 Palmer amaranth accessions from southwestern Nebraska using genotypic and whole-plant phenotypic assay correlations and cluster analysis, and 3) determine which agronomic practices might be influencing glyphosate resistance in Palmer amaranth accessions in that location. Based on genotypic assay, 88% of 51 accessions contained at least one individual with amplification (>2 copies) of the 5-enolypyruvyl-shikimate-3-phosphate synthase (EPSPS) gene, which confers glyphosate resistance; and/or a mutation in the PPX2 gene, either ΔG210 or R128G, which endows PPO-inhibitor resistance in Palmer amaranth. Cluster analysis and high correlation (0.83) between genotypic and phenotypic assays demonstrated that EPSPS gene amplification is the main glyphosate resistance mechanism in Palmer amaranth accessions from southwestern Nebraska. In contrast, there was poor association between genotypic and phenotypic responses for PPO-inhibitor resistance, which was attributed to segregation for PPO-inhibitor resistance within these accessions and/or the methodology that was adopted herein. Genotypic assays can expedite the process of confirming known glyphosate and PPO-inhibitor resistance mechanisms in Palmer amaranth from southwestern Nebraska and other locations. Phenotypic assays are also a robust method for confirming glyphosate resistance but not necessarily PPO-inhibitor resistance in Palmer amaranth. Moreover, random forest analysis of glyphosate resistance in Palmer amaranth indicated that EPSPS gene amplification, county, and current and previous crops are the main factors influencing glyphosate resistance within that geographic area. Most glyphosate-susceptible Palmer amaranth accessions were found in a few counties in areas with high crop diversity. Results presented here confirm the spread of glyphosate resistance and PPO-inhibitor resistance in Palmer amaranth accessions from southwestern Nebraska and demonstrate that less diverse cropping systems are an important driver of herbicide resistance evolution in Palmer amaranth.

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Advanced Resistance Studies Identify Two Discrete Mechanisms in Staphylococcus aureus to Overcome Antibacterial Compounds that Target Biotin Protein Ligase

Antibiotics ◽

10.3390/antibiotics9040165 ◽

2020 ◽

Vol 9 (4) ◽

pp. 165 ◽

Cited By ~ 1

Author(s):

Andrew J. Hayes ◽

Jiulia Satiaputra ◽

Louise M. Sternicki ◽

Ashleigh S. Paparella ◽

Zikai Feng ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Transcriptional Repression ◽

Molecular Mechanisms ◽

Resistance Mechanism ◽

Resistance Mechanisms ◽

Resistance Rate ◽

Biotin Protein Ligase ◽

Essential Enzyme

Biotin protein ligase (BPL) inhibitors are a novel class of antibacterial that target clinically important methicillin-resistant Staphylococcus aureus (S. aureus). In S. aureus, BPL is a bifunctional protein responsible for enzymatic biotinylation of two biotin-dependent enzymes, as well as serving as a transcriptional repressor that controls biotin synthesis and import. In this report, we investigate the mechanisms of action and resistance for a potent anti-BPL, an antibacterial compound, biotinyl-acylsulfamide adenosine (BASA). We show that BASA acts by both inhibiting the enzymatic activity of BPL in vitro, as well as functioning as a transcription co-repressor. A low spontaneous resistance rate was measured for the compound (<10−9) and whole-genome sequencing of strains evolved during serial passaging in the presence of BASA identified two discrete resistance mechanisms. In the first, deletion of the biotin-dependent enzyme pyruvate carboxylase is proposed to prioritize the utilization of bioavailable biotin for the essential enzyme acetyl-CoA carboxylase. In the second, a D200E missense mutation in BPL reduced DNA binding in vitro and transcriptional repression in vivo. We propose that this second resistance mechanism promotes bioavailability of biotin by derepressing its synthesis and import, such that free biotin may outcompete the inhibitor for binding BPL. This study provides new insights into the molecular mechanisms governing antibacterial activity and resistance of BPL inhibitors in S. aureus.

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Influence of High Mutation Rates on the Mechanisms and Dynamics of In Vitro and In Vivo Resistance Development to Single or Combined Antipseudomonal Agents

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00174-07 ◽

2007 ◽

Vol 51 (7) ◽

pp. 2574-2581 ◽

Cited By ~ 28

Author(s):

V. Plasencia ◽

N. Borrell ◽

M. D. Maciá ◽

B. Moya ◽

J. L. Pérez ◽

...

Keyword(s):

Combined Therapy ◽

Bacterial Load ◽

Resistance Mechanism ◽

Resistant Mutant ◽

Mutation Rates ◽

Aminoglycoside Resistance ◽

Resistance Development ◽

Mutant Cells

ABSTRACT We studied the mechanisms and dynamics of the development of resistance to ceftazidime (CAZ) alone or combined with tobramycin (TOB) or ciprofloxacin (CIP) in vitro and in vivo (using a mouse model of lung infection with human antibiotic regimens). Pseudomonas aeruginosa strain PAO1 and its hypermutable derivative PAOΔmutS were used, and the results were compared with those previously obtained with CIP, TOB, and CIP plus TOB (CIP-TOB) under the same conditions. An important (200-fold) amplification of the number of resistant mutant cells was documented for PAOΔmutS-infected mice that were under CAZ treatment compared to the number for mice that received placebo, whereas the median number of resistant mutant cells was below the detection limits for mice infected by PAO1. These results were intermediate between the high amplification with CIP (50,000-fold) and the low amplification with TOB (10-fold). All CAZ-resistant single mutant cells selected in vitro or in vivo hyperproduced AmpC. On the other hand, the three combinations studied were found to be highly effective in the prevention of in vivo resistance development in mice infected with PAOΔmutS, although the highest therapeutic efficacy (in terms of mortality and total bacterial load reduction) compared to those of the individual regimens was obtained with CIP-TOB and the lowest was with CAZ-CIP. Nevertheless, mutant cells that were resistant to the three combinations tested were readily selected in vitro for PAOΔmutS (mutation rates from 1.2 × 10−9 to 5.8 × 10−11) but not for PAO1, highlighting the potential risk for antimicrobial resistance development associated with the presence of hypermutable strains, even when combined therapy was used. All five independent CAZ-TOB-resistant PAOΔmutS double mutants studied presented the same resistance mechanism (AmpC hyperproduction plus an aminoglycoside resistance mechanism not related to MexXY), whereas four different combinations of resistance mechanisms were documented for the five CAZ-CIP-resistant double mutants.

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Development and Persistence of Antimicrobial Resistance in Pseudomonas aeruginosa: a Longitudinal Observation in Mechanically Ventilated Patients

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01278-06 ◽

2007 ◽

Vol 51 (4) ◽

pp. 1341-1350 ◽

Cited By ~ 47

Author(s):

Anita Reinhardt ◽

Thilo Köhler ◽

Paul Wood ◽

Peter Rohner ◽

Jean-Luc Dumas ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Antimicrobial Resistance ◽

Selective Pressure ◽

Resistance Mechanism ◽

Resistance Mechanisms ◽

Antimicrobial Treatment ◽

Aminoglycoside Resistance ◽

Prolonged Intubation ◽

Treatment Regimens ◽

Underlying Mechanisms

ABSTRACT Intubated patients frequently become colonized by Pseudomonas aeruginosa, which is subsequently responsible for ventilator-associated pneumonia. This pathogen readily acquires resistance against available antimicrobials. Depending on the resistance mechanism selected for, resistance might either be lost or persist after removal of the selective pressure. We investigated the rapidity of selection, as well as the persistence, of antimicrobial resistance and determined the underlying mechanisms. We selected 109 prospectively collected P. aeruginosa tracheal isolates from two patients based on their prolonged intubation and colonization periods, during which they had received carbapenem, fluoroquinolone (FQ), or combined β-lactam-aminoglycoside therapies. We determined antimicrobial resistance phenotypes by susceptibility testing and used quantitative real-time PCR to measure the expression of resistance determinants. Within 10 days after the initiation of therapy, all treatment regimens selected resistant isolates. Resistance to β-lactam and FQ was correlated with ampC and mexC gene expression levels, respectively, whereas imipenem resistance was attributable to decreased oprD expression. Combined β-lactam-aminoglycoside resistance was associated with the appearance of small-colony variants. Imipenem and FQ resistance persisted for prolonged times once the selecting antimicrobial treatment had been discontinued. In contrast, resistance to β-lactams disappeared rapidly after removal of the selective pressure, to reappear promptly upon renewed exposure. Our results suggest that resistant P. aeruginosa is selected in less than 10 days independently of the antimicrobial class. Different resistance mechanisms lead to the loss or persistence of resistance after the removal of the selecting agent. Even if resistant isolates are not evident upon culture, they may persist in the lung and can be rapidly reselected.

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Target-Site Resistances to ALS and PPO Inhibitors Are Linked in Waterhemp (Amaranthus tuberculatus)

Weed Science ◽

10.1614/ws-d-16-00090.1 ◽

2016 ◽

Vol 65 (1) ◽

pp. 4-8 ◽

Cited By ~ 4

Author(s):

Patrick J. Tranel ◽

Chenxi Wu ◽

Ahmed Sadeque

Keyword(s):

Resistance Mechanism ◽

Acetolactate Synthase ◽

Resistance Mechanisms ◽

Target Site ◽

Recurrent Parent ◽

Common Waterhemp ◽

Independent Assortment ◽

Resistance Evolution ◽

Amaranthus Tuberculatus ◽

Molecular Marker Analysis

It is generally expected that, in the case of multiple herbicide resistance, different resistance mechanisms within a weed will follow Mendel’s law of independent assortment. Research was conducted to investigate anecdotal observations suggesting that target site–based resistances to inhibitors of acetolactate synthase (ALS) and protoporphyrinogen oxidase (PPO) did not follow independent assortment in common waterhemp. Cosegregation of the two resistances was observed in backcross lines (population sensitive to both herbicides as recurrent parent). Specifically, whereas 52% of backcross plants were resistant to a PPO inhibitor, this percentage increased to 92% when the backcross plants were preselected for resistance to an ALS inhibitor. Molecular marker analysis confirmed that the corresponding genes (ALSandPPX2) were genetically linked. When data from all plants analyzed were pooled, the genetic distance between the two genes was calculated to be 7.5 cM. The two genes were found to be about 195 kb apart in the recently published grain amaranth genome, explaining the observed genetic linkage. There is likely enough recombination that occurs between the linked genes to prevent the linkage from having significant implications in terms of resistance evolution. Nevertheless, documentation of the happenstance linkage between target-site genes for resistance to ALS and PPO inhibitors in waterhemp is a reminder that one should not assume distinct resistance mechanism will independently assort.

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Resistance pathways of human immunodeficiency virus type 1 against the combination of zidovudine and lamivudine

Journal of General Virology ◽

10.1099/vir.0.022657-0 ◽

2010 ◽

Vol 91 (8) ◽

pp. 1898-1908 ◽

Cited By ~ 12

Author(s):

K. Theys ◽

K. Deforche ◽

P. Libin ◽

R. J. Camacho ◽

K. Van Laethem ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Bayesian Network ◽

Human Immunodeficiency Virus Type ◽

Selective Pressure ◽

Novel Mutations ◽

Resistance Development ◽

Resistance Evolution ◽

Immunodeficiency Virus

A better understanding of human immunodeficiency virus type 1 drug-resistance evolution under the selective pressure of combination treatment is important for the design of long-term effective treatment strategies. We applied Bayesian network learning to sequences from patients treated with the reverse transcriptase inhibitor combination of zidovudine (AZT) and lamivudine (3TC) to identify the role of many treatment-selected mutations in the development of resistance. Based on the Bayesian network structure, an in vivo fitness landscape was built, reflecting the necessary selective pressure under treatment, to evolve naive sequences to sequences obtained from patients treated with the combination. This landscape, combined with an evolutionary model, was used to predict resistance evolution in longitudinal sequence pairs. In our analysis, mutations 41L, 70R, 184V and 215F/Y were identified as major resistance mutations to the combination of AZT and 3TC, as they were associated directly with treatment experience. The network also suggested a possible role in resistance development for a number of novel mutations. Estimated fitness, using the landscape, correlated significantly with in vitro resistance phenotype in genotype–phenotype pairs (R 2=0.70). Variation in predicted evolution under selective pressure correlated significantly with observed in vivo evolution during AZT plus 3CT treatment. In conclusion, we confirmed current knowledge on resistance development to the combination of AZT and 3CT, but additional novel mutations were identified. Moreover, a model to predict resistance evolution during AZT and 3CT treatment has been built and validated.

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Antimicrobial treatment of Mycoplasma hyopneumoniae infections.

Mycoplasmas in swine ◽

10.1079/9781789249941.0181 ◽

2021 ◽

pp. 181-205

Author(s):

Anne V. Gautier-Bouchardon

Keyword(s):

Mycoplasma Hyopneumoniae ◽

Resistance Mechanisms ◽

Antimicrobial Treatment ◽

Antimicrobial Treatments

Abstract This chapter reviews the antimicrobials and antimicrobial treatments used to control M. hyopneumoniae infections. It also gives an overview of in vitro and in vivo activities of these antimicrobials and of resistance mechanisms described for M. hyopneumoniae towards these antimicrobials.

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Cancer Stem Cells: Powerful Targets to Improve Current Anticancer Therapeutics

Stem Cells International ◽

10.1155/2019/9618065 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15 ◽

Cited By ~ 11

Author(s):

Rayana L. Bighetti-Trevisan ◽

Lucas O. Sousa ◽

Rogerio M. Castilho ◽

Luciana O. Almeida

Keyword(s):

Stem Cells ◽

Cancer Stem Cells ◽

Cancer Cells ◽

Resistance Mechanisms ◽

In Vivo Studies ◽

Tumor Resistance ◽

Therapeutic Implications ◽

Anticancer Therapeutics

A frequent observation in several malignancies is the development of resistance to therapy that results in frequent tumor relapse and metastasis. Much of the tumor resistance phenotype comes from its heterogeneity that halts the ability of therapeutic agents to eliminate all cancer cells effectively. Tumor heterogeneity is, in part, controlled by cancer stem cells (CSC). CSC may be considered the reservoir of cancer cells as they exhibit properties of self-renewal and plasticity and the capability of reestablishing a heterogeneous tumor cell population. The endowed resistance mechanisms of CSC are mainly attributed to several factors including cellular quiescence, accumulation of ABC transporters, disruption of apoptosis, epigenetic reprogramming, and metabolism. There is a current need to develop new therapeutic drugs capable of targeting CSC to overcome tumor resistance. Emerging in vitro and in vivo studies strongly support the potential benefits of combination therapies capable of targeting cancer stem cell-targeting agents. Clinical trials are still underway to address the pharmacokinetics, safety, and efficacy of combination treatment. This review will address the main characteristics, therapeutic implications, and perspectives of targeting CSC to improve current anticancer therapeutics.

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Nanoparticles for Cancer Therapy: Current Progress and Challenges

10.20944/preprints202108.0218.v1 ◽

2021 ◽

Author(s):

Shreelaxmi Gavas ◽

Sameer Quazi ◽

Tomasz Karpiński

Keyword(s):

Multidrug Resistance ◽

Cancer Treatment ◽

Resistance Mechanisms ◽

Multi Drug Resistance ◽

Cancer Therapies ◽

Therapeutic Implications ◽

Current Perspective ◽

Reduced Toxicity

Cancer is one of the leading causes of death and morbidity with a complex pathophysiology. Traditional cancer therapies include chemotherapy, radiation therapy, targeted therapy, and immunotherapy. However, limitations such as lack of specificity, cytotoxicity, and multi-drug resistance pose a substantial challenge for favorable cancer treatment. The advent of nanotechnology has revolutionized the arena of cancer diagnosis and treatment. Nanoparticles (1-100nm) can be used in the treatment of cancer owing to their specific advantages such as biocompatibility, reduced toxicity, more excellent stability, enhanced permeability and retention effect, and precise targeting. Nanoparticles are classified into several main categories. The nanoparticle drug delivery system is particular and utilizes tumor and tumor environment characteristics. Nanoparticles not only solve the limitations of conventional cancer treatment but also overcome multidrug resistance. Additionally, as new multidrug resistance mechanisms are unraveled and studied, nanoparticles are being investigated more vigorously. Various therapeutic implications of nano-formulations have created brand new perspectives for cancer treatment. However, a majority of the research is limited to in vivo and in vitro studies, and the number of nano-drugs that are approved has not much amplified over the years. In this review, we discuss numerous types of nanoparticles, targeting mechanisms along with approved nanotherapeutics for oncological implications in cancer treatment. Further, we also summarize the current perspective, advantages, and challenges in clinical translation.

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