10 results on '"Nadav J. Mortman"'
Search Results
2. The Landscape of Phenotypic and Transcriptional Responses to Ciprofloxacin in Acinetobacter baumannii: Acquired Resistance Alleles Modulate Drug-Induced SOS Response and Prophage Replication
- Author
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Edward Geisinger, Germán Vargas-Cuebas, Nadav J. Mortman, Sapna Syal, Yunfei Dai, Elizabeth L. Wainwright, David Lazinski, Stephen Wood, Zeyu Zhu, Jon Anthony, Tim van Opijnen, and Ralph R. Isberg
- Subjects
Acinetobacter ,DNA gyrase ,fitness ,fluoroquinolone ,prophage ,antibiotic resistance ,Microbiology ,QR1-502 - Abstract
ABSTRACT The emergence of fluoroquinolone resistance in nosocomial pathogens has restricted the clinical efficacy of this antibiotic class. In Acinetobacter baumannii, the majority of clinical isolates now show high-level resistance due to mutations in gyrA (DNA gyrase) and parC (topoisomerase IV [topo IV]). To investigate the molecular basis for fluoroquinolone resistance, an exhaustive mutation analysis was performed in both drug-sensitive and -resistant strains to identify loci that alter ciprofloxacin sensitivity. To this end, parallel fitness tests of over 60,000 unique insertion mutations were performed in strains with various alleles in genes encoding the drug targets. The spectra of mutations that altered drug sensitivity were found to be similar in the drug-sensitive and gyrA parC double-mutant backgrounds, having resistance alleles in both genes. In contrast, the introduction of a single gyrA resistance allele, resulting in preferential poisoning of topo IV by ciprofloxacin, led to extreme alterations in the insertion mutation fitness landscape. The distinguishing feature of preferential topo IV poisoning was enhanced induction of DNA synthesis in the region of two endogenous prophages, with DNA synthesis associated with excision and circularization of the phages. Induction of the selective DNA synthesis in the gyrA background was also linked to heightened prophage gene transcription and enhanced activation of the mutagenic SOS response relative to that observed in either the wild-type (WT) or gyrA parC double mutant. Therefore, the accumulation of mutations that result in the stepwise evolution of high ciprofloxacin resistance is tightly connected to modulation of the SOS response and endogenous prophage DNA synthesis. IMPORTANCE Fluoroquinolones have been extremely successful antibiotics due to their ability to target multiple bacterial enzymes critical to DNA replication, the topoisomerases DNA gyrase and topo IV. Unfortunately, mutations lowering drug affinity for both enzymes are now widespread, rendering these drugs ineffective for many pathogens. To undermine this form of resistance, we examined how bacteria with target alterations differentially cope with fluoroquinolone exposures. We studied this problem in the nosocomial pathogen A. baumannii, which causes drug-resistant life-threatening infections. Employing genome-wide approaches, we uncovered numerous pathways that could be exploited to raise fluoroquinolone sensitivity independently of target alteration. Remarkably, fluoroquinolone targeting of topo IV in specific mutants caused dramatic hyperinduction of prophage replication and enhanced the mutagenic DNA damage response, but these responses were muted in strains with DNA gyrase as the primary target. This work demonstrates that resistance evolution via target modification can profoundly modulate the antibiotic stress response, revealing potential resistance-associated liabilities.
- Published
- 2019
- Full Text
- View/download PDF
3. Author Correction: Antibiotic susceptibility signatures identify potential antimicrobial targets in the Acinetobacter baumannii cell envelope
- Author
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Edward Geisinger, Nadav J. Mortman, Yunfei Dai, Murat Cokol, Sapna Syal, Andrew Farinha, Delaney G. Fisher, Amy Y. Tang, David W. Lazinski, Stephen Wood, Jon Anthony, Tim van Opijnen, and Ralph R. Isberg
- Subjects
Science - Abstract
A Correction to this paper has been published: https://doi.org/10.1038/s41467-020-20098-z
- Published
- 2020
- Full Text
- View/download PDF
4. Antibiotic susceptibility signatures identify potential antimicrobial targets in the Acinetobacter baumannii cell envelope
- Author
-
Nadav J. Mortman, Amy Y. Tang, Murat Cokol, Sapna Syal, Jon Anthony, Stephen Wood, Tim van Opijnen, Ralph R. Isberg, Delaney G. Fisher, Yunfei Dai, Andrew Farinha, Edward Geisinger, and David W. Lazinski
- Subjects
0301 basic medicine ,Science ,030106 microbiology ,Mutant ,General Physics and Astronomy ,Drug resistance ,DNA replication ,Biology ,medicine.disease_cause ,Article ,General Biochemistry, Genetics and Molecular Biology ,Bacterial genetics ,03 medical and health sciences ,polycyclic compounds ,medicine ,Cellular microbiology ,lcsh:Science ,Pathogen ,Gene ,Genetics ,Mutation ,Multidisciplinary ,Antimicrobials ,General Chemistry ,biochemical phenomena, metabolism, and nutrition ,bacterial infections and mycoses ,biology.organism_classification ,Acinetobacter baumannii ,030104 developmental biology ,bacteria ,lcsh:Q ,Cell envelope ,Microbial genetics - Abstract
A unique, protective cell envelope contributes to the broad drug resistance of the nosocomial pathogen Acinetobacter baumannii. Here we use transposon insertion sequencing to identify A. baumannii mutants displaying altered susceptibility to a panel of diverse antibiotics. By examining mutants with antibiotic susceptibility profiles that parallel mutations in characterized genes, we infer the function of multiple uncharacterized envelope proteins, some of which have roles in cell division or cell elongation. Remarkably, mutations affecting a predicted cell wall hydrolase lead to alterations in lipooligosaccharide synthesis. In addition, the analysis of altered susceptibility signatures and antibiotic-induced morphology patterns allows us to predict drug synergies; for example, certain beta-lactams appear to work cooperatively due to their preferential targeting of specific cell wall assembly machineries. Our results indicate that the pathogen may be effectively inhibited by the combined targeting of multiple pathways critical for envelope growth., A unique cell envelope contributes to the antibiotic resistance of the pathogen Acinetobacter baumannii. Here, Geisinger et al. identify A. baumannii mutants with altered antibiotic susceptibility, infer the function of uncharacterized proteins involved in envelope synthesis, and predict antibiotic synergies.
- Published
- 2020
5. Antibiotic hypersensitivity signatures identify targets for attack in the Acinetobacter baumannii cell envelope
- Author
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Amy Y. Tang, Ralph R. Isberg, Nadav J. Mortman, David W. Lazinski, Sapna Syal, Murat Cokol, Tim van Opijnen, Stephen Wood, Edward Geisinger, Andrew Farinha, Delaney G. Fisher, Yunfei Dai, and Jon Anthony
- Subjects
0303 health sciences ,030306 microbiology ,medicine.drug_class ,Antibiotics ,Mutant ,Drug action ,Computational biology ,Biology ,biology.organism_classification ,Acinetobacter baumannii ,Cell wall ,03 medical and health sciences ,medicine ,Cell envelope ,Pathogen ,Function (biology) ,030304 developmental biology - Abstract
Acinetobacter baumannii is an opportunistic pathogen that is a critical, high-priority target for new antibiotic development. Clearing of A. baumannii requires relatively high doses of antibiotics across the spectrum, primarily due to its protective cell envelope. Many of the proteins that support envelope integrity and modulate drug action are uncharacterized, largely because there is an absence of orthologs for several proteins that perform essential envelope-associated processes, impeding progress on this front. To identify targets that can synergize with current antibiotics, we performed an exhaustive analysis of A. baumannii mutants causing hypersensitivity to a multitude of antibiotic treatments. By examining mutants with antibiotic hypersensitivity profiles that parallel mutations in proteins of known function, we show that the function of poorly annotated proteins can be predicted and used to identify candidate missing link proteins in essential A. baumannii processes. Using this strategy, we uncovered multiple uncharacterized proteins with critical roles in cell division or cell elongation, and revealed that a predicted cell wall D,D-endopeptidase has an unappreciated function in lipooligosaccharide synthesis. Moreover, we provide a genetic strategy that uses hypersensitivity signatures to predict drug synergies, allowing the identification of β-lactams that work cooperatively based on the cell wall assembly machineries that they preferentially target. These data reveal multiple pathways critical for envelope growth in A. baumannii that can be targeted in combination strategies for attacking the pathogen.
- Published
- 2020
6. The Landscape of Phenotypic and Transcriptional Responses to Ciprofloxacin in Acinetobacter baumannii: Acquired Resistance Alleles Modulate Drug-Induced SOS Response and Prophage Replication
- Author
-
Zeyu Zhu, Elizabeth L. Wainwright, Tim van Opijnen, Ralph R. Isberg, Nadav J. Mortman, Germán Vargas-Cuebas, Stephen Wood, David W. Lazinski, Jon Anthony, Yunfei Dai, Sapna Syal, and Edward Geisinger
- Subjects
Acinetobacter baumannii ,DNA Topoisomerase IV ,antibiotic resistance ,prophage ,DNA damage ,Topoisomerase IV ,Prophages ,Microbial Sensitivity Tests ,Biology ,Virus Replication ,fluoroquinolone ,DNA gyrase ,Microbiology ,03 medical and health sciences ,Antibiotic resistance ,ciprofloxacin ,Virology ,Drug Resistance, Bacterial ,topoisomerase IV ,SOS response ,SOS Response, Genetics ,Prophage ,Alleles ,030304 developmental biology ,Genetics ,0303 health sciences ,Whole Genome Sequencing ,Acinetobacter ,030306 microbiology ,Topoisomerase ,Gene Expression Profiling ,Therapeutics and Prevention ,biology.organism_classification ,Editor's Pick ,QR1-502 ,3. Good health ,Anti-Bacterial Agents ,fitness ,Phenotype ,Mutation ,biology.protein ,DNA Damage ,Research Article - Abstract
Fluoroquinolones have been extremely successful antibiotics due to their ability to target multiple bacterial enzymes critical to DNA replication, the topoisomerases DNA gyrase and topo IV. Unfortunately, mutations lowering drug affinity for both enzymes are now widespread, rendering these drugs ineffective for many pathogens. To undermine this form of resistance, we examined how bacteria with target alterations differentially cope with fluoroquinolone exposures. We studied this problem in the nosocomial pathogen A. baumannii, which causes drug-resistant life-threatening infections. Employing genome-wide approaches, we uncovered numerous pathways that could be exploited to raise fluoroquinolone sensitivity independently of target alteration. Remarkably, fluoroquinolone targeting of topo IV in specific mutants caused dramatic hyperinduction of prophage replication and enhanced the mutagenic DNA damage response, but these responses were muted in strains with DNA gyrase as the primary target. This work demonstrates that resistance evolution via target modification can profoundly modulate the antibiotic stress response, revealing potential resistance-associated liabilities., The emergence of fluoroquinolone resistance in nosocomial pathogens has restricted the clinical efficacy of this antibiotic class. In Acinetobacter baumannii, the majority of clinical isolates now show high-level resistance due to mutations in gyrA (DNA gyrase) and parC (topoisomerase IV [topo IV]). To investigate the molecular basis for fluoroquinolone resistance, an exhaustive mutation analysis was performed in both drug-sensitive and -resistant strains to identify loci that alter ciprofloxacin sensitivity. To this end, parallel fitness tests of over 60,000 unique insertion mutations were performed in strains with various alleles in genes encoding the drug targets. The spectra of mutations that altered drug sensitivity were found to be similar in the drug-sensitive and gyrA parC double-mutant backgrounds, having resistance alleles in both genes. In contrast, the introduction of a single gyrA resistance allele, resulting in preferential poisoning of topo IV by ciprofloxacin, led to extreme alterations in the insertion mutation fitness landscape. The distinguishing feature of preferential topo IV poisoning was enhanced induction of DNA synthesis in the region of two endogenous prophages, with DNA synthesis associated with excision and circularization of the phages. Induction of the selective DNA synthesis in the gyrA background was also linked to heightened prophage gene transcription and enhanced activation of the mutagenic SOS response relative to that observed in either the wild-type (WT) or gyrA parC double mutant. Therefore, the accumulation of mutations that result in the stepwise evolution of high ciprofloxacin resistance is tightly connected to modulation of the SOS response and endogenous prophage DNA synthesis.
- Published
- 2019
7. Author Correction: Antibiotic susceptibility signatures identify potential antimicrobial targets in the Acinetobacter baumannii cell envelope
- Author
-
Andrew Farinha, Nadav J. Mortman, Tim van Opijnen, Stephen Wood, David W. Lazinski, Amy Y. Tang, Murat Cokol, Edward Geisinger, Sapna Syal, Delaney G. Fisher, Yunfei Dai, Ralph R. Isberg, and Jon Anthony
- Subjects
Acinetobacter baumannii ,DNA, Bacterial ,medicine.drug_class ,Science ,DNA Mutational Analysis ,Antibiotics ,Cellular microbiology ,General Physics and Astronomy ,Microbial Sensitivity Tests ,DNA replication ,General Biochemistry, Genetics and Molecular Biology ,Microbiology ,Bacterial Proteins ,Cell Wall ,Drug Resistance, Multiple, Bacterial ,medicine ,Humans ,Author Correction ,Cross Infection ,Multidisciplinary ,biology ,Antimicrobials ,Drug Synergism ,General Chemistry ,Antimicrobial ,biology.organism_classification ,Anti-Bacterial Agents ,Mutation ,DNA Transposable Elements ,Microbial genetics ,Cell envelope ,Acinetobacter Infections - Abstract
A unique, protective cell envelope contributes to the broad drug resistance of the nosocomial pathogen Acinetobacter baumannii. Here we use transposon insertion sequencing to identify A. baumannii mutants displaying altered susceptibility to a panel of diverse antibiotics. By examining mutants with antibiotic susceptibility profiles that parallel mutations in characterized genes, we infer the function of multiple uncharacterized envelope proteins, some of which have roles in cell division or cell elongation. Remarkably, mutations affecting a predicted cell wall hydrolase lead to alterations in lipooligosaccharide synthesis. In addition, the analysis of altered susceptibility signatures and antibiotic-induced morphology patterns allows us to predict drug synergies; for example, certain beta-lactams appear to work cooperatively due to their preferential targeting of specific cell wall assembly machineries. Our results indicate that the pathogen may be effectively inhibited by the combined targeting of multiple pathways critical for envelope growth.
- Published
- 2020
8. The landscape of intrinsic and evolved fluoroquinolone resistance inAcinetobacter baumanniiincludes suppression of drug-induced prophage replication
- Author
-
Ralph R. Isberg, Elizabeth L. Wainwright, Nadav J. Mortman, Zeyu Zhu, Stephen Wood, Sapna Syal, David W. Lazinski, Jon Anthony, Germán Vargas-Cuebas, Edward Geisinger, and Tim van Opijnen
- Subjects
Genetics ,0303 health sciences ,030306 microbiology ,Topoisomerase ,Mutant ,Biology ,biology.organism_classification ,DNA gyrase ,3. Good health ,Acinetobacter baumannii ,03 medical and health sciences ,biology.protein ,Insertion ,SOS response ,Gene ,Prophage ,030304 developmental biology - Abstract
The emergence of fluoroquinolone resistance in nosocomial pathogens has restricted the clinical efficacy of this antibiotic class. InAcinetobacter baumannii, the majority of clinical isolates now show high-level resistance due to mutations ingyrA(DNA gyrase) andparC(Topo IV). To investigate the molecular basis for fluoroquinolone resistance, an exhaustive mutation analysis was performed in both drug sensitive and resistant strains to identify loci that alter the sensitivity of the organism to ciprofloxacin. To this end, parallel fitness tests of over 60,000 unique insertion mutations were performed in strains with various alleles in genes encoding the drug targets. The spectrum of mutations that altered drug sensitivity was found to be similar in the drug sensitive and double mutantgyrAparCbackground having resistance alleles in both genes. In contrast, introduction of a singlegyrAresistance allele, resulting in preferential poisoning of Topo IV by ciprofloxacin, led to extreme alterations in the insertion mutation fitness landscape. The distinguishing feature of preferential Topo IV poisoning was induction of DNA synthesis in the region of two endogenous prophages, which appeared to occurin situ. Induction of the selective DNA synthesis in thegyrAbackground was also linked to enhanced activation of SOS response and heightened transcription of prophage genes relative to that observed in either the WT orgyrAparCdouble mutants. Therefore, the accumulation of mutations that result in the stepwise evolution of high ciprofloxacin resistance is tightly connected to suppression of hyperactivation of the SOS response and endogenous prophage DNA synthesis.ImportanceFluoroquinolones have been extremely successful antibiotics. Their clinical efficacy derives from the ability to target multiple bacterial enzymes critical to DNA replication, the topoisomerases DNA gyrase and Topo IV. Unfortunately, mutations lowering drug affinity for both enzymes are now widespread, rendering these drugs ineffective for many pathogens. To undermine this form of resistance, we sought to understand how bacteria with target alterations differentially cope with fluoroquinolone exposures. We studied this problem in the nosocomial pathogenA. baumannii, which causes resistant, life-threating infections. Employing genome-wide approaches, we uncovered numerous pathways that could be exploited to lower fluoroquinolone resistance independently of target alteration. Remarkably, fluoroquinolone targeting of Topo IV in specific mutants caused dramatic prophage hyperinduction, a response that was muted in strains with DNA gyrase as the primary target. This work demonstrates that resistance evolution via target modification can profoundly modulate the antibiotic stress response, revealing potential resistance-associated liabilities.
- Published
- 2018
9. A global regulatory system links virulence and antibiotic resistance to envelope homeostasis in Acinetobacter baumannii
- Author
-
Nadav J. Mortman, Ralph R. Isberg, Albert K. Tai, Edward Geisinger, and Germán Vargas-Cuebas
- Subjects
Acinetobacter baumannii ,0301 basic medicine ,Polymers ,Gene Expression ,Drug resistance ,Transcriptome ,Mice ,Antibiotics ,Drug Resistance, Multiple, Bacterial ,Medicine and Health Sciences ,Transcriptional regulation ,Homeostasis ,Cell Cycle and Cell Division ,lcsh:QH301-705.5 ,Regulation of gene expression ,Virulence ,Antimicrobials ,Drugs ,Anti-Bacterial Agents ,Chemistry ,Macromolecules ,Lytic cycle ,Cell Processes ,Physical Sciences ,Female ,Cellular Structures and Organelles ,Research Article ,Acinetobacter Infections ,Signal Transduction ,lcsh:Immunologic diseases. Allergy ,Materials by Structure ,DNA transcription ,Materials Science ,030106 microbiology ,Immunology ,Microbial Sensitivity Tests ,Biology ,Microbiology ,beta-Lactam Resistance ,beta-Lactamases ,03 medical and health sciences ,Cell Walls ,Antibiotic resistance ,Bacterial Proteins ,Microbial Control ,Virology ,Drug Resistance, Bacterial ,Hypersensitivity ,Genetics ,Animals ,Molecular Biology ,Alleles ,Pharmacology ,Biology and Life Sciences ,Cell Biology ,Gene Expression Regulation, Bacterial ,Peptidoglycans ,Polymer Chemistry ,biology.organism_classification ,Mice, Inbred C57BL ,lcsh:Biology (General) ,Antibiotic Resistance ,Biofilms ,Clinical Immunology ,Parasitology ,Antimicrobial Resistance ,Clinical Medicine ,lcsh:RC581-607 - Abstract
The nosocomial pathogen Acinetobacter baumannii is a significant threat due to its ability to cause infections refractory to a broad range of antibiotic treatments. We show here that a highly conserved sensory-transduction system, BfmRS, mediates the coordinate development of both enhanced virulence and resistance in this microorganism. Hyperactive alleles of BfmRS conferred increased protection from serum complement killing and allowed lethal systemic disease in mice. BfmRS also augmented resistance and tolerance against an expansive set of antibiotics, including dramatic protection from β-lactam toxicity. Through transcriptome profiling, we showed that BfmRS governs these phenotypes through global transcriptional regulation of a post-exponential-phase-like program of gene expression, a key feature of which is modulation of envelope biogenesis and defense pathways. BfmRS activity defended against cell-wall lesions through both β-lactamase-dependent and -independent mechanisms, with the latter being connected to control of lytic transglycosylase production and proper coordination of morphogenesis and division. In addition, hypersensitivity of bfmRS knockouts could be suppressed by unlinked mutations restoring a short, rod cell morphology, indicating that regulation of drug resistance, pathogenicity, and envelope morphogenesis are intimately linked by this central regulatory system in A. baumannii. This work demonstrates that BfmRS controls a global regulatory network coupling cellular physiology to the ability to cause invasive, drug-resistant infections., Author summary Infections with the hospital-acquired bacterium Acinetobacter baumannii are highly difficult to treat. The pathogen has evolved multiple lines of defense against antimicrobial stress, including a barrier-forming cell envelope as well as control systems that respond to antimicrobial stresses by enhancing antibiotic resistance and virulence. Here, we uncovered the role of a key stress-response system, BfmRS, in controlling the transition of A. baumannii to a state of heightened resistance and virulence. We show that BfmRS enhances pathogenicity in mammalian hosts, and augments the ability to grow in the presence of diverse antibiotics and tolerate transient, high-level antibiotic exposures. Connected to these effects is the ability of BfmRS to globally reprogram gene expression and control multiple pathways that build, protect, and shape the cell envelope. Moreover, we determined that resistance-enhancing mutations bypassing the need for BfmRS also modulate envelope- and morphology-associated pathways, further linking control of physiology with resistance in A. baumannii. This work uncovers a global control circuit that shifts cellular physiology in ways that promote hospital-associated disease, and points to inhibition of this circuit as a potential strategy for disarming the pathogen.
- Published
- 2018
10. A global regulatory system links virulence and antibiotic resistance to envelope homeostasis in Acinetobacter baumannii.
- Author
-
Edward Geisinger, Nadav J Mortman, Germán Vargas-Cuebas, Albert K Tai, and Ralph R Isberg
- Subjects
Immunologic diseases. Allergy ,RC581-607 ,Biology (General) ,QH301-705.5 - Abstract
The nosocomial pathogen Acinetobacter baumannii is a significant threat due to its ability to cause infections refractory to a broad range of antibiotic treatments. We show here that a highly conserved sensory-transduction system, BfmRS, mediates the coordinate development of both enhanced virulence and resistance in this microorganism. Hyperactive alleles of BfmRS conferred increased protection from serum complement killing and allowed lethal systemic disease in mice. BfmRS also augmented resistance and tolerance against an expansive set of antibiotics, including dramatic protection from β-lactam toxicity. Through transcriptome profiling, we showed that BfmRS governs these phenotypes through global transcriptional regulation of a post-exponential-phase-like program of gene expression, a key feature of which is modulation of envelope biogenesis and defense pathways. BfmRS activity defended against cell-wall lesions through both β-lactamase-dependent and -independent mechanisms, with the latter being connected to control of lytic transglycosylase production and proper coordination of morphogenesis and division. In addition, hypersensitivity of bfmRS knockouts could be suppressed by unlinked mutations restoring a short, rod cell morphology, indicating that regulation of drug resistance, pathogenicity, and envelope morphogenesis are intimately linked by this central regulatory system in A. baumannii. This work demonstrates that BfmRS controls a global regulatory network coupling cellular physiology to the ability to cause invasive, drug-resistant infections.
- Published
- 2018
- Full Text
- View/download PDF
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