Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>

ABSTRACT Antimicrobial susceptibility testing standards driving clinical decision-making have centered around the use of cation-adjusted Mueller-Hinton broth (CA-MHB) as the medium with the notion of supporting bacterial growth, without consideration of recapitulating the in vivo environment. Howeve...

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Autores principales:	Michael J. Salazar, Henrique Machado, Nicholas A. Dillon, Hannah Tsunemoto, Richard Szubin, Samira Dahesh, Joseph Pogliano, George Sakoulas, Bernhard O. Palsson, Victor Nizet, Adam M. Feist
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Staphylococcus aureus antibiotic resistance nafcillin USA300 adaptive laboratory evolution drug resistance mechanisms Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/87e85fc604b34bc8ba13b69e385db06f
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spelling	oai:doaj.org-article:87e85fc604b34bc8ba13b69e385db06f2021-12-02T18:15:46ZGenetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>10.1128/mSystems.00828-192379-5077https://doaj.org/article/87e85fc604b34bc8ba13b69e385db06f2020-04-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSystems.00828-19https://doaj.org/toc/2379-5077ABSTRACT Antimicrobial susceptibility testing standards driving clinical decision-making have centered around the use of cation-adjusted Mueller-Hinton broth (CA-MHB) as the medium with the notion of supporting bacterial growth, without consideration of recapitulating the in vivo environment. However, it is increasingly recognized that various medium conditions have tremendous influence on antimicrobial activity, which in turn may have major implications on the ability of in vitro susceptibility assays to predict antibiotic activity in vivo. To elucidate differential growth optimization and antibiotic resistance mechanisms, adaptive laboratory evolution was performed in the presence or absence of the antibiotic nafcillin with methicillin-resistant Staphylococcus aureus (MRSA) TCH1516 in either (i) CA-MHB, a traditional bacteriological nutritionally rich medium, or (ii) Roswell Park Memorial Institute (RPMI), a medium more reflective of the in vivo host environment. Medium adaptation analysis showed an increase in growth rate in RPMI, but not CA-MHB, with mutations in apt, adenine phosphoribosyltransferase, and the manganese transporter subunit, mntA, occurring reproducibly in parallel replicate evolutions. The medium-adapted strains showed no virulence attenuation. Continuous exposure of medium-adapted strains to increasing concentrations of nafcillin led to medium-specific evolutionary strategies. Key reproducibly occurring mutations were specific for nafcillin adaptation in each medium type and did not confer resistance in the other medium environment. Only the vraRST operon, a regulator of membrane- and cell wall-related genes, showed mutations in both CA-MHB- and RPMI-evolved strains. Collectively, these results demonstrate the medium-specific genetic adaptive responses of MRSA and establish adaptive laboratory evolution as a platform to study clinically relevant resistance mechanisms. IMPORTANCE The ability of pathogens such as Staphylococcus aureus to evolve resistance to antibiotics used in the treatment of infections has been an important concern in the last decades. Resistant acquisition usually translates into treatment failure and puts patients at risk of unfavorable outcomes. Furthermore, the laboratory testing of antibiotic resistance does not account for the different environment the bacteria experiences within the human body, leading to results that do not translate into the clinic. In this study, we forced methicillin-resistant S. aureus to develop nafcillin resistance in two different environments, a laboratory environment and a physiologically more relevant environment. This allowed us to identify genetic changes that led to nafcillin resistance under both conditions. We concluded that not only does the environment dictate the evolutionary strategy of S. aureus to nafcillin but also that the evolutionary strategy is specific to that given environment.Michael J. SalazarHenrique MachadoNicholas A. DillonHannah TsunemotoRichard SzubinSamira DaheshJoseph PoglianoGeorge SakoulasBernhard O. PalssonVictor NizetAdam M. FeistAmerican Society for MicrobiologyarticleStaphylococcus aureusantibiotic resistancenafcillinUSA300adaptive laboratory evolutiondrug resistance mechanismsMicrobiologyQR1-502ENmSystems, Vol 5, Iss 2 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Staphylococcus aureus antibiotic resistance nafcillin USA300 adaptive laboratory evolution drug resistance mechanisms Microbiology QR1-502
spellingShingle	Staphylococcus aureus antibiotic resistance nafcillin USA300 adaptive laboratory evolution drug resistance mechanisms Microbiology QR1-502 Michael J. Salazar Henrique Machado Nicholas A. Dillon Hannah Tsunemoto Richard Szubin Samira Dahesh Joseph Pogliano George Sakoulas Bernhard O. Palsson Victor Nizet Adam M. Feist Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>
description	ABSTRACT Antimicrobial susceptibility testing standards driving clinical decision-making have centered around the use of cation-adjusted Mueller-Hinton broth (CA-MHB) as the medium with the notion of supporting bacterial growth, without consideration of recapitulating the in vivo environment. However, it is increasingly recognized that various medium conditions have tremendous influence on antimicrobial activity, which in turn may have major implications on the ability of in vitro susceptibility assays to predict antibiotic activity in vivo. To elucidate differential growth optimization and antibiotic resistance mechanisms, adaptive laboratory evolution was performed in the presence or absence of the antibiotic nafcillin with methicillin-resistant Staphylococcus aureus (MRSA) TCH1516 in either (i) CA-MHB, a traditional bacteriological nutritionally rich medium, or (ii) Roswell Park Memorial Institute (RPMI), a medium more reflective of the in vivo host environment. Medium adaptation analysis showed an increase in growth rate in RPMI, but not CA-MHB, with mutations in apt, adenine phosphoribosyltransferase, and the manganese transporter subunit, mntA, occurring reproducibly in parallel replicate evolutions. The medium-adapted strains showed no virulence attenuation. Continuous exposure of medium-adapted strains to increasing concentrations of nafcillin led to medium-specific evolutionary strategies. Key reproducibly occurring mutations were specific for nafcillin adaptation in each medium type and did not confer resistance in the other medium environment. Only the vraRST operon, a regulator of membrane- and cell wall-related genes, showed mutations in both CA-MHB- and RPMI-evolved strains. Collectively, these results demonstrate the medium-specific genetic adaptive responses of MRSA and establish adaptive laboratory evolution as a platform to study clinically relevant resistance mechanisms. IMPORTANCE The ability of pathogens such as Staphylococcus aureus to evolve resistance to antibiotics used in the treatment of infections has been an important concern in the last decades. Resistant acquisition usually translates into treatment failure and puts patients at risk of unfavorable outcomes. Furthermore, the laboratory testing of antibiotic resistance does not account for the different environment the bacteria experiences within the human body, leading to results that do not translate into the clinic. In this study, we forced methicillin-resistant S. aureus to develop nafcillin resistance in two different environments, a laboratory environment and a physiologically more relevant environment. This allowed us to identify genetic changes that led to nafcillin resistance under both conditions. We concluded that not only does the environment dictate the evolutionary strategy of S. aureus to nafcillin but also that the evolutionary strategy is specific to that given environment.
format	article
author	Michael J. Salazar Henrique Machado Nicholas A. Dillon Hannah Tsunemoto Richard Szubin Samira Dahesh Joseph Pogliano George Sakoulas Bernhard O. Palsson Victor Nizet Adam M. Feist
author_facet	Michael J. Salazar Henrique Machado Nicholas A. Dillon Hannah Tsunemoto Richard Szubin Samira Dahesh Joseph Pogliano George Sakoulas Bernhard O. Palsson Victor Nizet Adam M. Feist
author_sort	Michael J. Salazar
title	Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>
title_short	Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>
title_full	Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>
title_fullStr	Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>
title_full_unstemmed	Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>
title_sort	genetic determinants enabling medium-dependent adaptation to nafcillin in methicillin-resistant <named-content content-type="genus-species">staphylococcus aureus</named-content>
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/87e85fc604b34bc8ba13b69e385db06f
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Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant <named-content content-type="genus-species">Staphylococcus aureus</named-content>

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