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Tiwari S, Nizet O, Dillon N. Development of a high-throughput minimum inhibitory concentration (HT-MIC) testing workflow. Front Microbiol 2023; 14:1079033. [PMID: 37303796 PMCID: PMC10249070 DOI: 10.3389/fmicb.2023.1079033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 04/24/2023] [Indexed: 06/13/2023] Open
Abstract
The roots of the minimum inhibitory concentration (MIC) determination go back to the early 1900s. Since then, the test has undergone modifications and advancements in an effort to increase its dependability and accuracy. Although biological investigations use an ever-increasing number of samples, complicated processes and human error sometimes result in poor data quality, which makes it challenging to replicate scientific conclusions. Automating manual steps using protocols decipherable by machine can ease procedural difficulties. Originally relying on manual pipetting and human vision to determine the results, modern broth dilution MIC testing procedures have incorporated microplate readers to enhance sample analysis. However, current MIC testing procedures are unable to simultaneously evaluate a large number of samples efficiently. Here, we have created a proof-of-concept workflow using the Opentrons OT-2 robot to enable high-throughput MIC testing. We have further optimized the analysis by incorporating Python programming for MIC assignment to streamline the automation. In this workflow, we performed MIC tests on four different strains, three replicates per strain, and analyzed a total of 1,152 wells. Comparing our workflow to a conventional plate MIC procedure, we find that the HT-MIC method is 800% faster while simultaneously boasting a 100% accuracy. Our high-throughput MIC workflow can be adapted in both academic and clinical settings since it is faster, more efficient, and as accurate than many conventional methods.
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Affiliation(s)
- Suman Tiwari
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX, United States
| | - Oliver Nizet
- La Jolla Country Day School, La Jolla, CA, United States
| | - Nicholas Dillon
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX, United States
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Davis K, Greenstein T, Viau Colindres R, Aldridge BB. Leveraging laboratory and clinical studies to design effective antibiotic combination therapy. Curr Opin Microbiol 2021; 64:68-75. [PMID: 34628295 PMCID: PMC8671129 DOI: 10.1016/j.mib.2021.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 07/28/2021] [Accepted: 09/16/2021] [Indexed: 01/21/2023]
Abstract
Interest in antibiotic combination therapy is increasing due to antimicrobial resistance and a slowing antibiotic pipeline. However, aside from specific indications, combination therapy in the clinic is often not administered systematically; instead, it is used at the physician's discretion as a bet-hedging mechanism to increase the chances of appropriately targeting a pathogen(s) with an unknown antibiotic resistance profile. Some recent clinical trials have been unable to demonstrate superior efficacy of combination therapy over monotherapy. Other trials have shown a benefit of combination therapy in defined circumstances consistent with recent studies indicating that factors including species, strain, resistance profile, and microenvironment affect drug combination efficacy and drug interactions. In this review, we discuss how a careful study design that takes these factors into account, along with the different drug interaction and potency metrics for assessing combination performance, may provide the necessary insight to understand the best clinical use-cases for combination therapy.
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Affiliation(s)
- Kathleen Davis
- Department of Molecular Biology & Microbiology, Tufts University School of Medicine, United States; Stuart B. Levy Center for Integrated Management of Antimicrobial Resistance, United States
| | - Talia Greenstein
- Stuart B. Levy Center for Integrated Management of Antimicrobial Resistance, United States; Graduate School of Biomedical Sciences, Tufts University School of Medicine, United States
| | - Roberto Viau Colindres
- Stuart B. Levy Center for Integrated Management of Antimicrobial Resistance, United States; Department of Geographic Medicine and Infectious Diseases, Tufts Medical Center, United States
| | - Bree B Aldridge
- Department of Molecular Biology & Microbiology, Tufts University School of Medicine, United States; Stuart B. Levy Center for Integrated Management of Antimicrobial Resistance, United States; Graduate School of Biomedical Sciences, Tufts University School of Medicine, United States
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Villapún VM, Balacco DL, Webber MA, Hall T, Lowther M, Addison O, Kuehne SA, Grover LM, Cox SC. Repeated exposure of nosocomial pathogens to silver does not select for silver resistance but does impact ciprofloxacin susceptibility. Acta Biomater 2021; 134:760-773. [PMID: 34329788 DOI: 10.1016/j.actbio.2021.07.056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 07/16/2021] [Accepted: 07/22/2021] [Indexed: 12/25/2022]
Abstract
The rise of antimicrobial resistant bacteria coupled with a void in antibiotic development marks Antimicrobial Resistance as one of the biggest current threats to modern medicine. Antimicrobial metals are being developed and used as alternative anti-infectives, however, the existence of known resistance mechanisms and limited data regarding bacterial responses to long-term metal exposure are barriers to widespread implementation. In this study, a panel of reference and clinical strains of major nosocomial pathogens were subjected to serial dosage cycles of silver and ciprofloxacin. Populations exposed to silver initially showed no change in sensitivity, however, increasingly susceptibility was observed after the 25th cycle. A control experiment with ciprofloxacin revealed a selection for resistance over time, with silver treated bacteria showing faster adaptation. Morphological analysis revealed filamentation in Gram negative species suggesting membrane perturbation, while sequencing of isolated strains identified mutations in numerous genes. These included those encoding for efflux systems, chemosensory systems, stress responses, biofilm formation and respiratory chain processes, although no consistent locus was identified that correlated with silver sensitivity. These results suggest that de novo silver resistance is hard to select in a range of nosocomial pathogens, although silver exposure may detrimentally impact sensitivity to antibiotics in the long term. STATEMENT OF SIGNIFICANCE: The adaptability of microbial life continuously calls for the development of novel antibiotic molecules, however, the cost and risk associated with their discovery have led to a drying up in the pipeline, causing antimicrobial resistance (AMR) to be a major threat to healthcare. From all available strategies, antimicrobial metals and, more specifically, silver showcase large bactericidal spectrum and limited toxic effect which coupled with a large range of processes available for their delivery made these materials as a clear candidate to tackle AMR. Previous reports have shown the ability of this metal to enact a synergistic effect with other antimicrobial therapies, nevertheless, the discovery of Ag resistance mechanisms since the early 70s and limited knowledge on the long term influence of silver on AMR poses a threat to their applicability. The present study provides quantitative data on the influence of silver based therapies on AMR development for a panel of reference and clinical strains of major nosocomial pathogens, revealing that prolonged silver exposure may detrimentally impact sensitivity to antibiotics.
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Affiliation(s)
- Victor M Villapún
- School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
| | - Dario L Balacco
- School of Dentistry, University of Birmingham, Edgbaston B15 2TT, United Kingdom
| | - Mark A Webber
- Quadram Institute Bioscience, Norwich Research Park, NR4 7UQ, United Kingdom; Norwich Medical School, University of East Anglia. Norwich Research Park, NR4 7TJ, United Kingdom
| | - Thomas Hall
- School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT, United Kingdom
| | - Morgan Lowther
- School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT, United Kingdom
| | - Owen Addison
- Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, SE1 9RT, United Kingdom
| | - Sarah A Kuehne
- School of Dentistry, University of Birmingham, Edgbaston B15 2TT, United Kingdom
| | - Liam M Grover
- School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT, United Kingdom
| | - Sophie C Cox
- School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
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Environmental conditions dictate differential evolution of vancomycin resistance in Staphylococcus aureus. Commun Biol 2021; 4:793. [PMID: 34172889 PMCID: PMC8233327 DOI: 10.1038/s42003-021-02339-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 06/09/2021] [Indexed: 02/06/2023] Open
Abstract
While microbiological resistance to vancomycin in Staphylococcus aureus is rare, clinical vancomycin treatment failures are common, and methicillin-resistant S. aureus (MRSA) strains isolated from patients after prolonged vancomycin treatment failure remain susceptible. Adaptive laboratory evolution was utilized to uncover mutational mechanisms associated with MRSA vancomycin resistance in a physiological medium as well as a bacteriological medium used in clinical susceptibility testing. Sequencing of resistant clones revealed shared and media-specific mutational outcomes, with an overlap in cell wall regulons (walKRyycHI, vraSRT). Evolved strains displayed similar properties to resistant clinical isolates in their genetic and phenotypic traits. Importantly, resistant phenotypes that developed in physiological media did not translate into resistance in bacteriological media. Further, a bacteriological media-specific mechanism for vancomycin resistance associated with a mutated mprF was confirmed. This study bridges the gap between the understanding of clinical and microbiological vancomycin resistance in S. aureus and expands the number of allelic variants (18 ± 4 mutations for the top 5 mutated genes) that result in vancomycin resistance phenotypes.
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Sanchez-Rosario Y, Johnson MDL. Media Matters, Examining Historical and Modern Streptococcus pneumoniae Growth Media and the Experiments They Affect. Front Cell Infect Microbiol 2021; 11:613623. [PMID: 33834003 PMCID: PMC8021847 DOI: 10.3389/fcimb.2021.613623] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 03/02/2021] [Indexed: 12/18/2022] Open
Abstract
While some bacteria can thrive for generations in minerals and salts, many require lavish nutrition and specific chemicals to survive to the point where they can be observed and researched. Although researchers once boiled and rendered animal flesh and bones to obtain a media that facilitated bacterial growth, we now have a plethora of formulations and manufacturers to provide dehydrated flavors of historical, modified, and modern media. The purpose of media has evolved from simple isolation to more measured study. However, in some instances, media formulated to aid the metabolic, nutritional, or physical properties of microbes may not be best suited for studying pathogen behavior or resilience as a function of host interactions. While there have been comparative studies on handfuls of these media in Streptococcus pneumoniae, this review focuses on describing both the historical and modern composition of common complex (Todd Hewitt and M17), semi-defined (Adams and Roe), and defined pneumococcal media (RPMI and Van de Rijn and Kessler), key components discovered/needed for cultivation/growth enhancement, and effects these different media have on bacterial phenotypes and experimental outcomes. While many researchers find the best conditions to grow and experiment on their bacteria of choice, the reasons for some researchers to use a specific medium is at best, not discussed, and at worst, arbitrary. As such, the goal of this review is to highlight the differences in pneumococcal media to encourage investigators to challenge their decisions on why they use a given medium, discuss the recipe, and explain their reasoning.
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Affiliation(s)
| | - Michael D L Johnson
- Department of Immunobiology, University of Arizona, Tucson, AZ, United States.,BIO5 Institute, University of Arizona, Tucson, AZ, United States.,Valley Fever Center for Excellence, University of Arizona, Tucson, AZ, United States
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Deimmunized Lysostaphin Synergizes with Small-Molecule Chemotherapies and Resensitizes Methicillin-Resistant Staphylococcus aureus to β-Lactam Antibiotics. Antimicrob Agents Chemother 2021; 65:AAC.01707-20. [PMID: 33318001 DOI: 10.1128/aac.01707-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 12/06/2020] [Indexed: 12/25/2022] Open
Abstract
There is an urgent need for novel agents to treat drug-resistant bacterial infections, such as multidrug-resistant Staphylococcus aureus (MRSA). Desirable properties for new antibiotics include high potency, narrow species selectivity, low propensity to elicit new resistance phenotypes, and synergy with standard-of-care (SOC) chemotherapies. Here, we describe analysis of the antibacterial potential exhibited by F12, an innovative anti-MRSA lysin that has been genetically engineered to evade detrimental antidrug immune responses in human patients. F12 possesses high potency and rapid onset of action, it has narrow selectivity against pathogenic staphylococci, and it manifests synergy with numerous SOC antibiotics. Additionally, resistance to F12 and β-lactam antibiotics appears mutually exclusive, and, importantly, we provide evidence that F12 resensitizes normally resistant MRSA strains to β-lactams both in vitro and in vivo These results suggest that combinations of F12 and SOC antibiotics are a promising new approach to treating refractory S. aureus infections.
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