Publications by authors named "David R Andes"

157 Publications

Evolution of the complex transcription network controlling biofilm formation in species.

Elife 2021 Apr 7;10. Epub 2021 Apr 7.

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States.

We examine how a complex transcription network composed of seven 'master' regulators and hundreds of target genes evolved over a span of approximately 70 million years. The network controls biofilm formation in several species, a group of fungi that are present in humans both as constituents of the microbiota and as opportunistic pathogens. Using a variety of approaches, we observed two major types of changes that have occurred in the biofilm network since the four extant species we examined last shared a common ancestor. Master regulator 'substitutions' occurred over relatively long evolutionary times, resulting in different species having overlapping, but different sets of master regulators of biofilm formation. Second, massive changes in the connections between the master regulators and their target genes occurred over much shorter timescales. We believe this analysis is the first detailed, empirical description of how a complex transcription network has evolved.
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http://dx.doi.org/10.7554/eLife.64682DOI Listing
April 2021

Specialized Metabolites Reveal Evolutionary History and Geographic Dispersion of a Multilateral Symbiosis.

ACS Cent Sci 2021 Feb 20;7(2):292-299. Epub 2021 Jan 20.

Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States.

Fungus-growing ants engage in a multilateral symbiosis: they cultivate a fungal garden as their primary food source and host symbiotic actinobacteria ( spp.) that provide chemical defenses. The bacterial symbionts produce small specialized metabolites that protect the fungal garden from specific fungal pathogens ( spp.), and in return, they are fed by the ant hosts. Multiple studies on the molecules underlying this symbiotic system have led to the discovery of a large number of structurally diverse antifungal molecules, but somewhat surprisingly no shared structural theme emerged from these studies. A large systematic study of Brazilian nests led to the discovery of the widespread production of a potent but overlooked antifungal agent, which we named attinimicin, by nearly two-thirds of all strains from multiple sites in Brazil. Here we report the structure of attinimicin, its putative biosynthetic gene cluster, and the evolutionary relationship between attinimicin and two related peptides, oxachelin A and cahuitamycin A. All three nonribosomal peptides are structural isomers with different primary peptide sequences. Attinimicin shows iron-dependent antifungal activity against specific environmental fungal parasites but no activity against the fungal cultivar. Attinimicin showed potent activity in a mouse infection model comparable to clinically used azole-containing antifungals. detection of attinimicin in both ant nests and on worker ants supports an ecological role for attinimicin in protecting the fungal cultivar from pathogens. The geographic spread of the attinimicin biosynthetic gene cluster in Brazilian spp. marks attinimicin as the first specialized metabolite from ant-associated bacteria with broad geographic distribution.
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http://dx.doi.org/10.1021/acscentsci.0c00978DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7908033PMC
February 2021

Continuous flow synthesis and antimicrobial evaluation of NHC* silver carboxylate derivatives of SBC3 in vitro and in vivo.

Metallomics 2021 02;13(2)

School of Chemistry, University College Dublin, Belfield, Stillorgan, Dublin 4, Republic of Ireland.

N-heterocyclic silver carbene compounds have been extensively studied and shown to be active agents against a host of pathogenic bacteria and fungi. By incorporating hypothesized virulence targeting substituents into NHC-silver systems via salt metathesis, an atom-efficient complexation process can be used to develop new complexes to target the passive and active systems of a microbial cell. The incorporation of fatty acids and an FtsZ inhibitor have been achieved, and creation of both the intermediate salt and subsequent silver complex has been streamlined into a continuous flow process. Biological evaluation was conducted with in vitro toxicology assays showing these novel complexes had excellent inhibition against Gram-negative strains E. coli, P. aeruginosa, and K. pneumoniae; further studies also confirmed the ability to inhibit biofilm formation in methicillin-resistant Staphylococcus aureus (MRSA) and C. Parapsilosis. In vivo testing using a murine thigh infection model showed promising inhibition of MRSA for the lead compound SBC3, which is derived from 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene (NHC*).
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http://dx.doi.org/10.1093/mtomcs/mfaa011DOI Listing
February 2021

Chemical Exchanges between Multilateral Symbionts.

Org Lett 2021 Mar 16;23(5):1648-1652. Epub 2021 Feb 16.

Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States.

Herein is a report on the molecular exchange occurring between multilateral symbiosis partners-a tit-for-tat exchange that led to the characterization of two new metabolites, conocandin B (fungal-derived) and dentigerumycin F (bacterial-derived). The structures were determined by NMR, mass spectrometry, genomic analysis, and chemical derivatizations. Conocandin B exhibits antimicrobial activity against both the bacterial symbionts of fungus-growing ant and human pathogenic strains by selectively inhibiting FabH, thus disrupting fatty acid biosynthesis.
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http://dx.doi.org/10.1021/acs.orglett.1c00068DOI Listing
March 2021

The protein kinase Ire1 impacts pathogenicity of Candida albicans by regulating homeostatic adaptation to endoplasmic reticulum stress.

Cell Microbiol 2021 May 26;23(5):e13307. Epub 2021 Jan 26.

Yeast Molecular Genetics Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.

The unfolded protein response (UPR), crucial for the maintenance of endoplasmic reticulum (ER) homeostasis, is tied to the regulation of multiple cellular processes in pathogenic fungi. Here, we show that Candida albicans relies on an ER-resident protein, inositol-requiring enzyme 1 (Ire1) for sensing ER stress and activating the UPR. Compromised Ire1 function impacts cellular processes that are dependent on functional secretory homeostasis, as inferred from transcriptional profiling. Concordantly, an Ire1-mutant strain exhibits pleiotropic roles in ER stress response, antifungal tolerance, cell wall regulation and virulence-related traits. Hac1 is the downstream target of C. albicans Ire1 as it initiates the unconventional splicing of the 19 bp intron from HAC1 mRNA during tunicamycin-induced ER stress. Ire1 also activates the UPR in response to perturbations in cell wall integrity and cell membrane homeostasis in a manner that does not necessitate the splicing of HAC1 mRNA. Furthermore, the Ire1-mutant strain is severely defective in hyphal morphogenesis and biofilm formation as well as in establishing a successful infection in vivo. Together, these findings demonstrate that C. albicans Ire1 functions to regulate traits that are essential for virulence and suggest its importance in responding to multiple stresses, thus integrating various stress signals to maintain ER homeostasis.
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http://dx.doi.org/10.1111/cmi.13307DOI Listing
May 2021

A Label-Free Cellular Proteomics Approach to Decipher the Antifungal Action of DiMIQ, a Potent Indolo[2,3-]Quinoline Agent, against Biofilms.

Int J Mol Sci 2020 Dec 24;22(1). Epub 2020 Dec 24.

Department of Medicine, School of Medicine & Public Health, University of Wisconsin-Madison, Madison, WI 53706, USA.

forms extremely drug-resistant biofilms, which present a serious threat to public health globally. Biofilm-based infections are difficult to treat due to the lack of efficient antifungal therapeutics, resulting in an urgent demand for the development of novel antibiofilm strategies. In this study, the antibiofilm activity of DiMIQ (5,11-dimethyl-5-indolo[2,3-]quinoline) was evaluated against biofilms. DiMIQ is a synthetic derivative of indoquinoline alkaloid neocryptolepine isolated from a medicinal African plant, . Antifungal activity of DiMIQ was determined using the XTT assay, followed by cell wall and extracellular matrix profiling and cellular proteomes. Here, we demonstrated that DiMIQ inhibited biofilm formation and altered fungal cell walls and the extracellular matrix. Cellular proteomics revealed inhibitory action against numerous translation-involved ribosomal proteins, enzymes involved in general energy producing processes and select amino acid metabolic pathways including alanine, aspartate, glutamate, valine, leucine and isoleucine. DiMIQ also stimulated pathways of cellular oxidation, metabolism of carbohydrates, amino acids (glycine, serine, threonine, arginine, phenylalanine, tyrosine, tryptophan) and nucleic acids (aminoacyl-tRNA biosynthesis, RNA transport, nucleotide metabolism). Our findings suggest that DiMIQ inhibits biofilms by arresting translation and multidirectional pathway reshaping of cellular metabolism. Overall, this agent may provide a potent alternative to treating biofilm-associated infections.
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http://dx.doi.org/10.3390/ijms22010108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7795236PMC
December 2020

Turbinmicin inhibits Candida biofilm growth by disrupting fungal vesicle-mediated trafficking.

J Clin Invest 2021 Mar;131(5)

Department of Medicine, Medical Microbiology and Immunology.

The emergence of drug-resistant fungi has prompted an urgent threat alert from the US Centers for Disease Control (CDC). Biofilm assembly by these pathogens further impairs effective therapy. We recently identified an antifungal, turbinmicin, that inhibits the fungal vesicle-mediated trafficking pathway and demonstrates broad-spectrum activity against planktonically growing fungi. During biofilm growth, vesicles with unique features play a critical role in the delivery of biofilm extracellular matrix components. As these components are largely responsible for the drug resistance associated with biofilm growth, we explored the utility of turbinmicin in the biofilm setting. We found that turbinmicin disrupted extracellular vesicle (EV) delivery during biofilm growth and that this impaired the subsequent assembly of the biofilm matrix. We demonstrated that elimination of the extracellular matrix rendered the drug-resistant biofilm communities susceptible to fungal killing by turbinmicin. Furthermore, the addition of turbinmicin to otherwise ineffective antifungal therapy potentiated the activity of these drugs. The underlying role of vesicles explains this dramatic activity and was supported by phenotype reversal with the addition of exogenous biofilm EVs. This striking capacity to cripple biofilm assembly mechanisms reveals a new approach to eradicating biofilms and sheds light on turbinmicin as a promising anti-biofilm drug.
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http://dx.doi.org/10.1172/JCI145123DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7919718PMC
March 2021

An oxindole efflux inhibitor potentiates azoles and impairs virulence in the fungal pathogen Candida auris.

Nat Commun 2020 12 22;11(1):6429. Epub 2020 Dec 22.

Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.

Candida auris is an emerging fungal pathogen that exhibits resistance to multiple drugs, including the most commonly prescribed antifungal, fluconazole. Here, we use a combinatorial screening approach to identify a bis-benzodioxolylindolinone (azoffluxin) that synergizes with fluconazole against C. auris. Azoffluxin enhances fluconazole activity through the inhibition of efflux pump Cdr1, thus increasing intracellular fluconazole levels. This activity is conserved across most C. auris clades, with the exception of clade III. Azoffluxin also inhibits efflux in highly azole-resistant strains of Candida albicans, another human fungal pathogen, increasing their susceptibility to fluconazole. Furthermore, azoffluxin enhances fluconazole activity in mice infected with C. auris, reducing fungal burden. Our findings suggest that pharmacologically targeting Cdr1 in combination with azoles may be an effective strategy to control infection caused by azole-resistant isolates of C. auris.
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http://dx.doi.org/10.1038/s41467-020-20183-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7755909PMC
December 2020

Biomineral armor in leaf-cutter ants.

Nat Commun 2020 11 24;11(1):5792. Epub 2020 Nov 24.

Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.

Although calcareous anatomical structures have evolved in diverse animal groups, such structures have been unknown in insects. Here, we report the discovery of high-magnesium calcite [CaMg(CO)] armor overlaying the exoskeletons of major workers of the leaf-cutter ant Acromyrmex echinatior. Live-rearing and in vitro synthesis experiments indicate that the biomineral layer accumulates rapidly as ant workers mature, that the layer is continuously distributed, covering nearly the entire integument, and that the ant epicuticle catalyzes biomineral nucleation and growth. In situ nanoindentation demonstrates that the biomineral layer significantly hardens the exoskeleton. Increased survival of ant workers with biomineralized exoskeletons during aggressive encounters with other ants and reduced infection by entomopathogenic fungi demonstrate the protective role of the biomineral layer. The discovery of biogenic high-magnesium calcite in the relatively well-studied leaf-cutting ants suggests that calcareous biominerals enriched in magnesium may be more common in metazoans than previously recognized.
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http://dx.doi.org/10.1038/s41467-020-19566-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7686325PMC
November 2020

A marine microbiome antifungal targets urgent-threat drug-resistant fungi.

Science 2020 11;370(6519):974-978

Pharmaceutical Sciences Division, University of Wisconsin-Madison, Madison, WI, USA.

New antifungal drugs are urgently needed to address the emergence and transcontinental spread of fungal infectious diseases, such as pandrug-resistant Leveraging the microbiomes of marine animals and cutting-edge metabolomics and genomic tools, we identified encouraging lead antifungal molecules with in vivo efficacy. The most promising lead, turbinmicin, displays potent in vitro and mouse-model efficacy toward multiple-drug-resistant fungal pathogens, exhibits a wide safety index, and functions through a fungal-specific mode of action, targeting Sec14 of the vesicular trafficking pathway. The efficacy, safety, and mode of action distinct from other antifungal drugs make turbinmicin a highly promising antifungal drug lead to help address devastating global fungal pathogens such as
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http://dx.doi.org/10.1126/science.abd6919DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7756952PMC
November 2020

Pharmacodynamic Evaluation of MRX-8, a Novel Polymyxin, in the Neutropenic Mouse Thigh and Lung Infection Models against Gram-Negative Pathogens.

Antimicrob Agents Chemother 2020 10 20;64(11). Epub 2020 Oct 20.

Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA

MRX-8 is a novel polymyxin analogue in development for the treatment of infections caused by Gram-negative pathogens, including those resistant to other antibiotic classes. In the present study, we examined the pharmacodynamic activity of MRX-8 against a variety of common Gram-negative pathogens in the neutropenic mouse thigh and lung models. Additionally, we examined polymyxin B (PMB) as a comparator. Plasma pharmacokinetics of MRX-8 and PMB were linear over a broad dosing range of 0.156 to 10 mg/kg of body weight and had similar AUC (area under the drug concentration-time curve from 0 h to infinity) exposures of MRX-8, 0.22 to 12.64 mg · h/liter, and PMB, 0.12 to 13.22 mg · h/liter. Dose fractionation was performed for MRX-8 using a single isolate, and the results demonstrated that both (maximum concentration of drug in serum)/MIC and AUC/MIC ratios were strongly associated with efficacy. In the thigh model, dose-ranging studies included strains of ( = 3), ( = 2), ( = 3), and ( = 1). Both MRX-8 and PMB exhibited increased effects with increasing doses. MRX-8 and PMB free AUC/MIC exposures for net stasis were similar for and at 20 to 30. Notably, for and , the free AUC/MIC ratio for stasis was numerically much smaller for MRX-8 at 6 to 8 than for PMB at 16 to 37. In the lung model, MRX-8 was also more effective than PMB when dosed to achieve similar free-drug AUC exposures over the study period. MRX-8 is a promising novel polymyxin analogue with activity against many different clinically relevant species in both the mouse thigh and lung models.
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http://dx.doi.org/10.1128/AAC.01517-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7577140PMC
October 2020

Core Recommendations for Antifungal Stewardship: A Statement of the Mycoses Study Group Education and Research Consortium.

J Infect Dis 2020 08;222(Suppl 3):S175-S198

Department of Infectious Diseases, Infection Control and Employee Health, MD Anderson Cancer Center, Houston, Texas, USA.

In recent years, the global public health community has increasingly recognized the importance of antimicrobial stewardship (AMS) in the fight to improve outcomes, decrease costs, and curb increases in antimicrobial resistance around the world. However, the subject of antifungal stewardship (AFS) has received less attention. While the principles of AMS guidelines likely apply to stewarding of antifungal agents, there are additional considerations unique to AFS and the complex field of fungal infections that require specific recommendations. In this article, we review the literature on AMS best practices and discuss AFS through the lens of the global core elements of AMS. We offer recommendations for best practices in AFS based on a synthesis of this evidence by an interdisciplinary expert panel of members of the Mycoses Study Group Education and Research Consortium. We also discuss research directions in this rapidly evolving field. AFS is an emerging and important component of AMS, yet requires special considerations in certain areas such as expertise, education, interventions to optimize utilization, therapeutic drug monitoring, and data analysis and reporting.
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http://dx.doi.org/10.1093/infdis/jiaa394DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7403757PMC
August 2020

Achievement of clinical isavuconazole blood concentrations in transplant recipients with isavuconazonium sulphate capsules administered via enteral feeding tube.

J Antimicrob Chemother 2020 10;75(10):3023-3028

Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.

Background: Isavuconazole is a triazole antifungal available in IV and capsule formulation. Prescribing information states that capsules should not be chewed, crushed, dissolved or opened because the drug was not studied in this manner. However, considering the pharmacokinetics of the capsules, we theorized opening and sprinkling the contents into an enteral feeding tube (EFT) would result in adequate absorption and systemic concentrations of isavuconazole.

Objectives: To determine whether patients receiving isavuconazonium sulphate capsules via EFT would achieve clinical blood concentrations of isavuconazole.

Methods: Nineteen solid organ and HCT recipients receiving isavuconazole via EFT for prevention or treatment of invasive fungal infection (IFI) were prospectively identified at four academic medical centres in the USA. Patients were included in this evaluation if they received isavuconazole via EFT for at least 5 days and therapeutic drug monitoring (TDM) was performed.

Results: TDM was performed after a median of 7 days (range 6-17) following EFT administration and 15 days (range 7-174) of isavuconazole therapy overall. Median isavuconazole concentration was 1.8 μg/mL (range 0.3-5.2). Median isavuconazole concentrations in patients with or without prior IV administration were 1.8 μg/mL (range 0.3-5.2) and 2.2 μg/mL (range 0.8-3.6; P = 0.896), respectively. Concentrations achieved with the EFT route were similar to or greater than the corresponding concentrations via the IV route in six patients who had TDM performed during both routes of administration.

Conclusions: It is reasonable to consider opening isavuconazonium sulphate capsules and administering the contents enterally for prevention and treatment of IFI.
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http://dx.doi.org/10.1093/jac/dkaa274DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7778376PMC
October 2020

Old In Vitro Antimicrobial Breakpoints Are Misleading Stewardship Efforts, Delaying Adoption of Innovative Therapies, and Harming Patients.

Open Forum Infect Dis 2020 Jul 13;7(7):ofaa084. Epub 2020 Mar 13.

JMI Laboratories, North Liberty, Iowa, USA.

The current antimicrobial market and old (pre-2000) in vitro antimicrobial susceptibility test interpretative criteria (STIC) are not working properly. Malfunctioning susceptibility breakpoints and antimicrobial markets have serious implications for both patients (ie, from a safety and efficacy perspective) and antibiotic-focused pharmaceutical and biotechnology company economic viability. Poorly functioning STIC fail both patients and clinicians since they do not discriminate between likely effective and ineffective antimicrobial regimens. Poor economic viability fails patients and clinicians as it decreases the industry's ability to develop antimicrobial agents that clinicians and patients urgently require now and in the future. Herein, we review how STIC for older antimicrobial agents were determined and how their correction can impact the perceived utility of old relative to new antimicrobial agents. Moreover, we describe the data and analysis needs to systematically reevaluate older STIC values. We call for professional infectious diseases societies, government agencies, and other consensus bodies interested in the appropriate use of antimicrobial agents to join an effort to systematically evaluate and, where warranted, correct STIC for all relevant antimicrobial agents. This effort will amplify the effects of other measures designed to increase appropriate antimicrobial use (ie, good antimicrobial stewardship), development, and regulation.
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http://dx.doi.org/10.1093/ofid/ofaa084DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7336562PMC
July 2020

Contributions of the Biofilm Matrix to Pathogenesis.

J Fungi (Basel) 2020 Feb 3;6(1). Epub 2020 Feb 3.

Departments of Medicine and Medical Microbiology & Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA.

In healthcare settings, spp. cause invasive disease with high mortality. The overwhelming majority of cases are associated with the use of critically-needed medical devices, such as vascular catheters. On the surface of these indwelling materials, forms resilient, adherent biofilm communities. A hallmark characteristic of this process is the production of an extracellular matrix, which promotes fungal adhesion and provides protection from external threats. In this review, we highlight the medical relevance of device-associated biofilms and draw attention to the process of -biofilm-matrix production. We provide an update on the current understanding of how biofilm extracellular matrix contributes to pathogenicity, particularly through its roles in the promoting antifungal drug tolerance and immune evasion.
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http://dx.doi.org/10.3390/jof6010021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7151000PMC
February 2020

Polymyxin Susceptibility Testing and Interpretive Breakpoints: Recommendations from the United States Committee on Antimicrobial Susceptibility Testing (USCAST).

Antimicrob Agents Chemother 2020 01 27;64(2). Epub 2020 Jan 27.

ICPD, Schenectady, New York, USA.

The polymyxins are important agents for carbapenem-resistant Gram-negative bacilli. The United States Committee on Antimicrobial Susceptibility Testing breakpoint recommendations for colistin and polymyxin B are that isolates of , , and are considered susceptible at MIC values of ≤2 mg/liter. These recommendations are contingent upon dosing and testing strategies that are described in this commentary. Importantly, these recommendations are not applicable to lower respiratory tract infections, for which we recommend no breakpoints. Furthermore, there is no breakpoint recommendation for polymyxin B for lower urinary tract infections.
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http://dx.doi.org/10.1128/AAC.01495-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6985752PMC
January 2020

Pharmacodynamic Evaluation of Omadacycline against Staphylococcus aureus in the Neutropenic Mouse Pneumonia Model.

Antimicrob Agents Chemother 2020 01 27;64(2). Epub 2020 Jan 27.

Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA

Omadacycline is an effective therapy for community-acquired bacterial pneumonia (CABP). Given its potent activity against methicillin-susceptible (MSSA) and methicillin-resistant (MRSA), we sought to determine the pharmacodynamic activity and target pharmacokinetic/pharmacodynamic (PK/PD) exposures associated with a therapeutic effect in the neutropenic mouse pneumonia model against 10 MSSA/MRSA strains. The area under the concentration-time curve (AUC)/MIC associated with 1-log kill was noted at 24-h epithelial lining fluid (ELF) and plasma AUC/MIC exposures of ∼2 (ELF range, <0.93 to 19; plasma range, <1.06 to 17) and 2-log kill was noted at 24-h ELF and plasma AUC/MIC exposures of ∼12 (ELF range, 2.5 to 130; plasma range, 3.5 to 151).
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http://dx.doi.org/10.1128/AAC.02058-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6985749PMC
January 2020

WCK 5222 (Cefepime/Zidebactam) Pharmacodynamic Target Analysis against Metallo-β-lactamase producing in the Neutropenic Mouse Pneumonia Model.

Antimicrob Agents Chemother 2019 Oct 7. Epub 2019 Oct 7.

Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA

WCK 5222 is a combination of cefepime and the novel β-lactam enhancer (BLE) zidebactam. Zidebactam has a dual mechanism of action involving high-affinity penicillin binding protein (PBP) 2 binding as well as inhibition of Ambler class A, and C, enzymes. In the current study, we evaluated the effect of zidebactam on the cefepime pharmacodynamic target time above MIC (T>MIC) exposure required for efficacy against a diverse group of carbapenem-resistant (CRE) secondary to MBL-production. Plasma and ELF pharmacokinetic (PK) studies were performed for both cefepime (6.25, 25, and 100 mg/kg) and zidebactam (3.125, 12.5, and 50 mg/kg) after subcutaneous administration to mice. Only total drug was considered as protein binding is <10%. Both drugs exhibited similar PK exposures including terminal elimination half-life (cefepime ∼0.4 h, zidebactam 0.3-0.5 h). The penetration into ELF was concentration dependent for both drugs, reaching 50% and 70% for cefepime and zidebactam, respectively. Dose ranging studies were performed in lung-infected mice with one of eight MBL-producing clinical strains. WCK 5222 was administered in Q4- and Q8-hourly regimens to vary exposures from 0-100% T>MIC. The results were modelled to evaluate the relationship between cefepime T>MIC, when zidebactam was co-administered, and therapeutic effect. The results revealed a strong association between T>MIC and effect (R 0.82). Net stasis in organism burden occurred at cefepime T>MIC exposures of only 18%. A 1-log kill endpoint was demonstrated for the group of organisms at approximately 31% T>MIC. These target exposures for stasis and 1-log kill are much lower than previously observed cephalosporin monotherapy PK/PD targets.
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http://dx.doi.org/10.1128/AAC.01648-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6879221PMC
October 2019

Determination of Pharmacodynamic Target Exposures for Rezafungin against Candida tropicalis and Candida dubliniensis in the Neutropenic Mouse Disseminated Candidiasis Model.

Antimicrob Agents Chemother 2019 11 22;63(11). Epub 2019 Oct 22.

Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA

Rezafungin (CD101) is a novel echinocandin under development for once-weekly intravenous (i.v.) dosing. We evaluated the pharmacodynamics (PD) of rezafungin against 4 and 4 strains, using the neutropenic mouse invasive candidiasis model. The area under the concentration-time curve (AUC)/MIC was a robust predictor of efficacy ( = 0.93 and 0.72, respectively). The stasis free-drug 24-h AUC/MIC target exposure for the group ranged from 3 to 25, whereas the 1-log-kill free-drug 24-h AUC/MIC target exposure ranged from 4.3 to 62. These values are similar to those found in previous rezafungin PD studies with other spp. Based on recent surveillance susceptibility data, AUC/MIC targets are likely to be exceeded for >99% of and isolates with the previously studied human dose of 400 mg i.v. once weekly.
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http://dx.doi.org/10.1128/AAC.01556-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6811416PMC
November 2019

Characterization of an Uncinocarpus reesii-expressed recombinant tube precipitin antigen of Coccidioides posadasii for serodiagnosis.

PLoS One 2019 14;14(8):e0221228. Epub 2019 Aug 14.

South Texas Center for Emerging Infectious Disease and Department of Biology, University of Texas at San Antonio, San Antonio, Texas, United States of America.

Early and accurate diagnosis of coccidioidomycosis, also known as Valley fever, is critical for appropriate disease treatment and management. Current serodiagnosis is based on the detection of patient serum antibodies that react with tube precipitin (TP) and complement fixation (CF) antigens of Coccidioides. IgM is the first class of antibodies produced by hosts in response to coccidioidal insults. The highly glycosylated β-glucosidase 2 (BGL2) is a major active component of the TP antigen that stimulates IgM antibody responses during early Coccidioides infection. The predominant IgM epitope on BGL2 is a unique 3-O-methyl-mannose moiety that is not produced by commonly used protein expression systems. We genetically engineered and expressed a recombinant BGL2 (rBGL2ur), derived from Coccidioides, in non-pathogenic Uncinocarpus reesii, a fungus phylogenetically related to the Coccidioides pathogen. The rBGL2ur protein was purified from the culture medium of transformed U. reesii by nickel affinity chromatography, and the presence of 3-O-methyl mannose was demonstrated by gas chromatography. Seroreactivity of the purified rBGL2ur protein was tested by enzyme-linked immunosorbent assays using sera from 90 patients with coccidioidomycosis and 134 control individuals. The sensitivity and specificity of the assay with rBGL2ur were 78.8% and 87.3%, respectively. These results were comparable to those obtained using a proprietary MiraVista Diagnostic (MVD) IgM (63.3% sensitivity; 96.3% specificity), but significantly better than the ID-TP assay using non-concentrated patient sera (33.3% sensitivity; 100% specificity). Expression of rBGL2ur in U. reesii retains its antigenicity for coccidioidomycosis serodiagnosis and greatly reduces biosafety concerns for antigen production, as Coccidioides spp. are biological safety level 3 agents.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0221228PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6693751PMC
March 2020

The Candida albicans biofilm gene circuit modulated at the chromatin level by a recent molecular histone innovation.

PLoS Biol 2019 08 9;17(8):e3000422. Epub 2019 Aug 9.

Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India.

Histone H3 and its variants regulate gene expression but the latter are absent in most ascomycetous fungi. Here, we report the identification of a variant histone H3, which we have designated H3VCTG because of its exclusive presence in the CTG clade of ascomycetes, including Candida albicans, a human pathogen. C. albicans grows both as single yeast cells and hyphal filaments in the planktonic mode of growth. It also forms a three-dimensional biofilm structure in the host as well as on human catheter materials under suitable conditions. H3VCTG null (hht1/hht1) cells of C. albicans are viable but produce more robust biofilms than wild-type cells in both in vitro and in vivo conditions. Indeed, a comparative transcriptome analysis of planktonic and biofilm cells reveals that the biofilm circuitry is significantly altered in H3VCTG null cells. H3VCTG binds more efficiently to the promoters of many biofilm-related genes in the planktonic cells than during biofilm growth, whereas the binding of the core canonical histone H3 on the corresponding promoters largely remains unchanged. Furthermore, biofilm defects associated with master regulators, namely, biofilm and cell wall regulator 1 (Bcr1), transposon enhancement control 1 (Tec1), and non-dityrosine 80 (Ndt80), are significantly rescued in cells lacking H3VCTG. The occupancy of the transcription factor Bcr1 at its cognate promoter binding sites was found to be enhanced in the absence of H3VCTG in the planktonic form of growth resulting in enhanced transcription of biofilm-specific genes. Further, we demonstrate that co-occurrence of valine and serine at the 31st and 32nd positions in H3VCTG, respectively, is essential for its function. Taken together, we show that even in a unicellular organism, differential gene expression patterns are modulated by the relative occupancy of the specific histone H3 type at the chromatin level.
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http://dx.doi.org/10.1371/journal.pbio.3000422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6703697PMC
August 2019

A targeted fungal prophylaxis protocol with static dosed fluconazole significantly reduces invasive fungal infection after liver transplantation.

Transpl Infect Dis 2019 Oct 23;21(5):e13156. Epub 2019 Aug 23.

Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA.

Background: Invasive fungal infection (IFI) after liver transplant (LTx) is associated with extensive morbidity and mortality. Targeted prophylaxis reduces risk, but qualifying criteria, drug of choice and regimen are unclear and compliance is inconsistent.

Objective: Assess the impact of a risk factor-based fungal prophylaxis protocol (FPP) after LTx on fungal infection rates, fungal epidemiology, and transplant outcomes.

Methods: Observational cohort study of adult LTx recipients between July 1, 2009, and June 30, 2017. Patients in the FPP group were given a set dose of 400 mg fluconazole without renal adjustment on POD 1-14 via pharmacist delegation protocol.

Results: One hundred and eighty-nine patients met inclusion criteria; 50 in the FPP and 139 in the pre-implementation comparator group. Of those who would be considered high-risk, 22.3% received antifungal prophylaxis prior to FPP implementation vs 92% after implementation (P < .0001). There were significantly fewer fungal infections in the FPP group at 1 year (12.5% vs 26.6%, P = .03). IFI in the pre-implementation control group was due to Candida species in 95% of cases; 30% were species with reduced fluconazole susceptibility. IFI in the FPP group was due to Candida species in all cases, and no isolates had reduced fluconazole susceptibility. Aspergillus did not account for any IFI between the groups. One-year patient and graft survival were similar between groups. In a multivariable model accounting for patient and donor age, donor type, MELD, and cold ischemic time, FPP was protective against fungal infection (HR 0.3, P = .015). FPP did not significantly impact graft survival (HR 0.4, P = .14), but trended toward improved patient survival. (HR 0.18, P = .06).

Conclusion: Implementation of a targeted FPP utilizing static dosing of fluconazole 400 mg × 14 days to those that meet high-risk criteria significantly reduces invasive fungal infection after liver transplant. Use of this protocol did not adversely affect fungal epidemiology and may have a positive impact on allograft and patient survival. Future large prospective studies are needed to better evaluate survival impact.
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http://dx.doi.org/10.1111/tid.13156DOI Listing
October 2019

Pharmacodynamic Target Determination for Delafloxacin against Klebsiella pneumoniae and Pseudomonas aeruginosa in the Neutropenic Murine Pneumonia Model.

Antimicrob Agents Chemother 2019 10 23;63(10). Epub 2019 Sep 23.

Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA

Delafloxacin is a broad-spectrum anionic fluoroquinolone that has completed a phase 3 study for community-acquired bacterial pneumonia. We investigated the pharmacodynamic target for delafloxacin against 12 and 5 strains in the neutropenic murine lung infection model. The median 24-h free-drug area under the curve (AUC)/MIC values associated with net stasis and 1-log kill were 28.6 and 64.1 for , respectively. The 24-h AUC/MIC values associated with net stasis and 1-log kill for were 5.66 and 14.3, respectively.
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http://dx.doi.org/10.1128/AAC.01131-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6761510PMC
October 2019

Impact of Triazole Therapeutic Drug Monitoring Availability and Timing.

Antimicrob Agents Chemother 2019 10 23;63(10). Epub 2019 Sep 23.

Department of Medicine, Division of Infectious Diseases, University of Wisconsin, Madison, Wisconsin, USA

Therapeutic drug monitoring (TDM) is an established strategy to optimize antifungal therapy with certain triazoles. While established relationships exist between concentration and safety or efficacy, the impact of TDM timing on outcomes is unknown. We report clinical outcomes, including antifungal exposure and mortality, in patients receiving institutional versus reference laboratory TDM. The availability of in-house triazole assays reduced the time to drug concentration result (12 versus 68 h; < 0.001) and time to achieve therapeutic serum concentrations (10 versus 31 days; < 0.001). Subtherapeutic concentrations were associated with higher patient mortality (32% versus 13.3%; = 0.036).
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http://dx.doi.org/10.1128/AAC.01245-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6761504PMC
October 2019

Small-Molecule Morphogenesis Modulators Enhance the Ability of 14-Helical β-Peptides To Prevent Candida albicans Biofilm Formation.

Antimicrob Agents Chemother 2019 09 23;63(9). Epub 2019 Aug 23.

Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA

is an opportunistic fungal pathogen responsible for mucosal candidiasis and systemic candidemia in humans. Often, these infections are associated with the formation of drug-resistant biofilms on the surfaces of tissues or medical devices. Increased incidence of resistance to current antifungals has heightened the need for new strategies to prevent or eliminate biofilm-related fungal infections. In prior studies, we designed 14-helical β-peptides to mimic the structural properties of natural antimicrobial α-peptides (AMPs) in an effort to develop active and selective antifungal compounds. These amphiphilic, cationic, helical β-peptides exhibited antifungal activity against planktonic cells and inhibited biofilm formation and Recent studies have suggested the use of antivirulence agents in combination with antifungals. In this study, we investigated the use of compounds that target polymorphism, such as 1-dodecanol, isoamyl alcohol, and farnesol, to attempt to improve β-peptide efficacy for preventing biofilms. Isoamyl alcohol, which prevents hyphal formation, reduced the minimum biofilm prevention concentrations (MBPCs) of β-peptides by up to 128-fold. Combinations of isoamyl alcohol and antifungal β-peptides resulted in less than 10% hemolysis at the antifungal MBPCs. Overall, our results suggest potential benefits of combination therapies comprised of morphogenesis modulators and antifungal AMP peptidomimetics for preventing biofilm formation.
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http://dx.doi.org/10.1128/AAC.02653-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6709471PMC
September 2019

Pharmacokinetic/Pharmacodynamic Evaluation of Solithromycin against Streptococcus pneumoniae Using Data from a Neutropenic Murine Lung Infection Model.

Antimicrob Agents Chemother 2019 08 25;63(8). Epub 2019 Jul 25.

Department of Medicine, Section of Infectious Diseases, University of Wisconsin School of Medicine, Madison, Wisconsin, USA.

Solithromycin (CEM-101) is a novel fluoroketolide antimicrobial agent with activity against typical and atypical pathogens associated with community-acquired bacterial pneumonia. Using a neutropenic murine lung infection model, the objectives of this study were to identify the pharmacokinetic/pharmacodynamic (PK/PD) index most closely associated with efficacy and the magnitude of such indices associated with solithromycin efficacy against Plasma and epithelial lining fluid (ELF) samples for pharmacokinetics (PK) were collected serially over 24 hours from healthy mice administered single doses of solithromycin (0.625 to 40 mg/kg). Neutropenic CD-1 mice infected with 10 CFUs of one of five isolates were administered solithromycin (0.156 to 160 mg/kg/day) via oral gavage. Doses were administered in a fractionated manner for mice infected with one isolate, while mice infected with the remaining four isolates received solithromycin as either a regimen every 6 hours or every 12 hours. A three-compartment model best described solithromycin PK in the plasma and ELF (r = 0.935 and 0.831, respectively). The ratio of total-drug ELF to free-drug plasma area under the concentration-time curve (AUC) from time 0 to 24 hours was 2.7. Free-drug plasma and total-drug ELF AUC to minimum inhibitory concentration ratios (AUC/MIC ratios) were most predictive of efficacy (r = 0.851 and 0.850, respectively). The magnitude of free-drug plasma/total-drug ELF AUC/MIC ratios associated with net bacterial stasis and a 1- and 2-log CFU reduction from baseline was 1.65/1.26, 6.31/15.1, and 12.8/59.8, respectively. These data provided dose selection support for solithromycin for clinical trials in patients with community-acquired bacterial pneumonia.
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http://dx.doi.org/10.1128/AAC.02606-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6658793PMC
August 2019

Pharmacodynamics of Omadacycline against Staphylococcus aureus in the Neutropenic Murine Thigh Infection Model.

Antimicrob Agents Chemother 2019 07 24;63(7). Epub 2019 Jun 24.

Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA

Omadacycline is a novel aminomethylcycline antibiotic with potent activity against , including methicillin-susceptible (MSSA) and methicillin-resistant (MRSA). We investigated the pharmacodynamic activity of omadacycline against 10 MSSA/MRSA strains in a neutropenic murine thigh model. The median 24-h area under the concentration-time curve (AUC)/MIC values associated with net stasis and 1-log kill were 21.9 and 57.7, respectively.
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http://dx.doi.org/10.1128/AAC.00624-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6591633PMC
July 2019

Bacterial Infections in the Stem Cell Transplant Recipient and Hematologic Malignancy Patient.

Infect Dis Clin North Am 2019 06;33(2):399-445

Department of Medicine, Division of Infectious Disease, University of Wisconsin School of Medicine and Public Health, 1685 Highland Drive, Centennial Building, 5th Floor, Madison, WI 53705, USA.

Bacteremia (bloodstream infection) is frequent (20%-30% incidence) in the stem cell transplant and hematologic malignancy population and often occurs in the early post-transplant engraftment period. In most studies, Gram-positive bacteria occur at greater frequency than gram-negative bacteria, although some centers report that rates of gram-negative bloodstream infections have recently increased. In many centers, resistance rates among Enterococci and gram-negative bacteria, especially the Enterobacteriaceae, are extensive and associated with increased mortality. Better prediction tools, enhanced infection control, and new anti-infective agents hold promise for the treatment of highly resistant pathogens in this population.
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http://dx.doi.org/10.1016/j.idc.2019.02.011DOI Listing
June 2019

The antimicrobial potential of Streptomyces from insect microbiomes.

Nat Commun 2019 01 31;10(1):516. Epub 2019 Jan 31.

Department of Bacteriology, University of Wisconsin-Madison, Madison, 53706, WI, USA.

Antimicrobial resistance is a global health crisis and few novel antimicrobials have been discovered in recent decades. Natural products, particularly from Streptomyces, are the source of most antimicrobials, yet discovery campaigns focusing on Streptomyces from the soil largely rediscover known compounds. Investigation of understudied and symbiotic sources has seen some success, yet no studies have systematically explored microbiomes for antimicrobials. Here we assess the distinct evolutionary lineages of Streptomyces from insect microbiomes as a source of new antimicrobials through large-scale isolations, bioactivity assays, genomics, metabolomics, and in vivo infection models. Insect-associated Streptomyces inhibit antimicrobial-resistant pathogens more than soil Streptomyces. Genomics and metabolomics reveal their diverse biosynthetic capabilities. Further, we describe cyphomycin, a new molecule active against multidrug resistant fungal pathogens. The evolutionary trajectories of Streptomyces from the insect microbiome influence their biosynthetic potential and ability to inhibit resistant pathogens, supporting the promise of this source in augmenting future antimicrobial discovery.
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http://dx.doi.org/10.1038/s41467-019-08438-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6355912PMC
January 2019