Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive Phenotypes
Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) regulates resistance to β-lactams via preferential production of an alternative penicillin-binding protein (PBP), PBP2a. PBP2a binds many β-lactam antibiotics with less affinity than PBPs which are predominant in methicillin-susce...
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| Format: | Article |
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MDPI AG
2022-03-01
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| Series: | Antibiotics |
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| Online Access: | https://www.mdpi.com/2079-6382/11/4/462 |
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| author | Selvi C. Ersoy Liana C. Chan Michael R. Yeaman Henry F. Chambers Richard A. Proctor Kevin C. Ludwig Tanja Schneider Adhar C. Manna Ambrose Cheung Arnold S. Bayer |
| author_facet | Selvi C. Ersoy Liana C. Chan Michael R. Yeaman Henry F. Chambers Richard A. Proctor Kevin C. Ludwig Tanja Schneider Adhar C. Manna Ambrose Cheung Arnold S. Bayer |
| author_sort | Selvi C. Ersoy |
| collection | DOAJ |
| description | Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) regulates resistance to β-lactams via preferential production of an alternative penicillin-binding protein (PBP), PBP2a. PBP2a binds many β-lactam antibiotics with less affinity than PBPs which are predominant in methicillin-susceptible (MSSA) strains. A novel, rather frequent in vitro phenotype was recently identified among clinical MRSA bloodstream isolates, termed “NaHCO<sub>3</sub>-responsiveness”. This phenotype features β-lactam susceptibility of certain MRSA strains only in the presence of NaHCO<sub>3</sub>. Two distinct PBP2a variants, 246G and 246E, have been linked to the NaHCO<sub>3</sub>-responsive and NaHCO<sub>3</sub>-non-responsive MRSA phenotypes, respectively. To determine the mechanistic impact of PBP2a variants on β-lactam susceptibility, binding profiles of a fluorescent penicillin probe (Bocillin-FL) to each purified PBP2a variant were assessed and compared to whole-cell binding profiles characterized by flow cytometry in the presence vs. absence of NaHCO<sub>3</sub>. These investigations revealed that NaHCO<sub>3</sub> differentially influenced the binding of the fluorescent penicillin, Bocillin-FL, to the PBP2a variants, with binding intensity and rate of binding significantly enhanced in the 246G compared to the 246E variant. Of note, the NaHCO<sub>3</sub>-β-lactam (oxacillin)-responsive JE2 strain, which natively harbors the 246G variant, had enhanced Bocillin-FL whole-cell binding following exposure to NaHCO<sub>3</sub>. This NaHCO<sub>3</sub>-mediated increase in whole-cell Bocillin-FL binding was not observed in the NaHCO<sub>3</sub>-non-responsive parental strain, COL, which contains the 246E PBP2a variant. Surprisingly, genetic swaps of the <i>mecA</i> coding sites between JE2 and COL did not alter the NaHCO<sub>3</sub>-enhanced binding seen in JE2 vs. COL. These data suggest that the non-coding regions of <i>mecA</i> may be involved in NaHCO<sub>3</sub>-responsiveness. This investigation also provides strong evidence that the NaHCO<sub>3</sub>-responsive phenotype in MRSA may involve NaHCO<sub>3</sub>-mediated increases in both initial cell surface β-lactam binding, as well as ultimate PBP2a binding of β-lactams. |
| first_indexed | 2024-03-09T11:14:43Z |
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| id | doaj.art-329a3c32a6454aac89e76ce5f344b0ce |
| institution | Directory Open Access Journal |
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| language | English |
| last_indexed | 2024-03-09T11:14:43Z |
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| series | Antibiotics |
| spelling | doaj.art-329a3c32a6454aac89e76ce5f344b0ce2023-12-01T00:32:14ZengMDPI AGAntibiotics2079-63822022-03-0111446210.3390/antibiotics11040462Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive PhenotypesSelvi C. Ersoy0Liana C. Chan1Michael R. Yeaman2Henry F. Chambers3Richard A. Proctor4Kevin C. Ludwig5Tanja Schneider6Adhar C. Manna7Ambrose Cheung8Arnold S. Bayer9The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, CA 90502, USAThe Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, CA 90502, USAThe Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, CA 90502, USASchool of Medicine, University of California-San Francisco (UCSF), San Francisco, CA 94143, USADepartments of Medicine and Medical Microbiology/Immunology, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53715, USAInstitute for Pharmaceutical Microbiology, University Hospital Bonn, University of Bonn, D-53113 Bonn, GermanyInstitute for Pharmaceutical Microbiology, University Hospital Bonn, University of Bonn, D-53113 Bonn, GermanyDepartment of Microbiology & Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USADepartment of Microbiology & Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USAThe Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, CA 90502, USAMethicillin-resistant <i>Staphylococcus aureus</i> (MRSA) regulates resistance to β-lactams via preferential production of an alternative penicillin-binding protein (PBP), PBP2a. PBP2a binds many β-lactam antibiotics with less affinity than PBPs which are predominant in methicillin-susceptible (MSSA) strains. A novel, rather frequent in vitro phenotype was recently identified among clinical MRSA bloodstream isolates, termed “NaHCO<sub>3</sub>-responsiveness”. This phenotype features β-lactam susceptibility of certain MRSA strains only in the presence of NaHCO<sub>3</sub>. Two distinct PBP2a variants, 246G and 246E, have been linked to the NaHCO<sub>3</sub>-responsive and NaHCO<sub>3</sub>-non-responsive MRSA phenotypes, respectively. To determine the mechanistic impact of PBP2a variants on β-lactam susceptibility, binding profiles of a fluorescent penicillin probe (Bocillin-FL) to each purified PBP2a variant were assessed and compared to whole-cell binding profiles characterized by flow cytometry in the presence vs. absence of NaHCO<sub>3</sub>. These investigations revealed that NaHCO<sub>3</sub> differentially influenced the binding of the fluorescent penicillin, Bocillin-FL, to the PBP2a variants, with binding intensity and rate of binding significantly enhanced in the 246G compared to the 246E variant. Of note, the NaHCO<sub>3</sub>-β-lactam (oxacillin)-responsive JE2 strain, which natively harbors the 246G variant, had enhanced Bocillin-FL whole-cell binding following exposure to NaHCO<sub>3</sub>. This NaHCO<sub>3</sub>-mediated increase in whole-cell Bocillin-FL binding was not observed in the NaHCO<sub>3</sub>-non-responsive parental strain, COL, which contains the 246E PBP2a variant. Surprisingly, genetic swaps of the <i>mecA</i> coding sites between JE2 and COL did not alter the NaHCO<sub>3</sub>-enhanced binding seen in JE2 vs. COL. These data suggest that the non-coding regions of <i>mecA</i> may be involved in NaHCO<sub>3</sub>-responsiveness. This investigation also provides strong evidence that the NaHCO<sub>3</sub>-responsive phenotype in MRSA may involve NaHCO<sub>3</sub>-mediated increases in both initial cell surface β-lactam binding, as well as ultimate PBP2a binding of β-lactams.https://www.mdpi.com/2079-6382/11/4/462penicillin-binding proteinssodium bicarbonateβ-lactamsmethicillin-resistant <i>Staphylococcus aureus</i> |
| spellingShingle | Selvi C. Ersoy Liana C. Chan Michael R. Yeaman Henry F. Chambers Richard A. Proctor Kevin C. Ludwig Tanja Schneider Adhar C. Manna Ambrose Cheung Arnold S. Bayer Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive Phenotypes Antibiotics penicillin-binding proteins sodium bicarbonate β-lactams methicillin-resistant <i>Staphylococcus aureus</i> |
| title | Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive Phenotypes |
| title_full | Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive Phenotypes |
| title_fullStr | Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive Phenotypes |
| title_full_unstemmed | Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive Phenotypes |
| title_short | Impacts of NaHCO<sub>3</sub> on β-Lactam Binding to PBP2a Protein Variants Associated with the NaHCO<sub>3</sub>-Responsive versus NaHCO<sub>3</sub>-Non-Responsive Phenotypes |
| title_sort | impacts of nahco sub 3 sub on β lactam binding to pbp2a protein variants associated with the nahco sub 3 sub responsive versus nahco sub 3 sub non responsive phenotypes |
| topic | penicillin-binding proteins sodium bicarbonate β-lactams methicillin-resistant <i>Staphylococcus aureus</i> |
| url | https://www.mdpi.com/2079-6382/11/4/462 |
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