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Chadwick BJ, Lin X. Effects of CO 2 in fungi. Curr Opin Microbiol 2024; 79:102488. [PMID: 38759247 PMCID: PMC11162916 DOI: 10.1016/j.mib.2024.102488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 04/21/2024] [Accepted: 04/25/2024] [Indexed: 05/19/2024]
Abstract
Carbon dioxide supplies carbon for photosynthetic species and is a major product of respiration for all life forms. Inside the human body where CO2 is a by-product of the tricarboxylic acid cycle, its level reaches 5% or higher. In the ambient atmosphere, ∼.04% of the air is CO2. Different organisms can tolerate different CO2 levels to various degrees, and experiencing higher CO2 is toxic and can lead to death. The fungal kingdom shows great variations in response to CO2 that has been documented by different researchers at different time periods. This literature review aims to connect these studies, highlight mechanisms underlying tolerance to high levels of CO2, and emphasize the effects of CO2 on fungal metabolism and morphogenesis.
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Affiliation(s)
| | - Xiaorong Lin
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA.
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McHale TC, Akampurira A, Gerlach ES, Mucunguzi A, Nicol MR, Williams DA, Nielsen K, Bicanic T, Fieberg A, Dai B, Meya DB, Boulware DR. 5-Flucytosine Longitudinal Antifungal Susceptibility Testing of Cryptococcus neoformans: A Substudy of the EnACT Trial Testing Oral Amphotericin. Open Forum Infect Dis 2023; 10:ofad596. [PMID: 38143852 PMCID: PMC10745249 DOI: 10.1093/ofid/ofad596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 11/21/2023] [Indexed: 12/26/2023] Open
Abstract
Background The EnACT trial was a phase 2 randomized clinical trial conducted in Uganda, which evaluated a novel orally delivered lipid nanocrystal (LNC) amphotericin B in combination with flucytosine for the treatment of cryptococcal meningitis. When flucytosine (5FC) is used as monotherapy in cryptococcosis, 5FC can induce resistant Cryptococcus mutants. Oral amphotericin B uses a novel drug delivery mechanism, and we assessed whether resistance to 5FC develops during oral LNC-amphotericin B therapy. Methods We enrolled Ugandans with HIV diagnosed with cryptococcal meningitis and who were randomized to receive 5FC and either standard intravenous (IV) amphotericin B or oral LNC-amphotericin B. We used broth microdilution to measure the minimum inhibitory concentration (MIC) of the first and last cryptococcal isolates in each participant. Breakpoints are inferred from 5FC in Candida albicans. We measured cerebral spinal fluid (CSF) 5FC concentrations by liquid chromatography and tandem mass spectrometry. Results Cryptococcus 5FC MIC50 was 4 µg/mL, and MIC90 was 8 µg/mL. After 2 weeks of therapy, there was no evidence of 5FC resistance developing, defined as a >4-fold change in susceptibility in any Cryptococcus isolate tested. The median CSF 5FC concentration to MIC ratio (interquartile range) was 3.0 (1.7-5.5) µg/mL. There was no association between 5FC/MIC ratio and early fungicidal activity of the quantitative rate of CSF yeast clearance (R2 = 0.004; P = .63). Conclusions There is no evidence of baseline resistance to 5FC or incident resistance during combination therapy with oral or IV amphotericin B in Uganda. Oral amphotericin B can safely be used in combination with 5FC.
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Affiliation(s)
- Thomas C McHale
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Elliot S Gerlach
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Melanie R Nicol
- Department of Experimental and Clinical Pharmacology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Darlisha A Williams
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
| | - Kirsten Nielsen
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Tihana Bicanic
- Institute of Infection and Immunity, St Georges, University of London, London, UK
| | - Ann Fieberg
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
| | - Biyue Dai
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
| | - David B Meya
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
- Infectious Diseases Institute, Makerere University, Kampala, Uganda
| | - David R Boulware
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
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