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Fortney KR, Brothwell JA, Batteiger TA, Duplantier R, Katz BP, Spinola SM. A Haemophilus ducreyi strain lacking the yfeABCD iron transport system is virulent in human volunteers. Infect Immun 2024; 92:e0005824. [PMID: 38780215 DOI: 10.1128/iai.00058-24] [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: 02/02/2024] [Accepted: 05/08/2024] [Indexed: 05/25/2024] Open
Abstract
Haemophilus ducreyi causes the genital ulcer disease chancroid and painful cutaneous ulcers in children who live in the tropics. To acquire heme from the host, H. ducreyi expresses a TonB-dependent hemoglobin receptor, HgbA, which is necessary and sufficient for H. ducreyi to progress to the pustular stage of disease in a controlled human infection model. HgbA transports hemoglobin across the outer membrane; how heme is transported across the cytoplasmic membrane is unclear. In previous studies, transcripts encoding the YfeABCD heme transporter were upregulated in experimental lesions caused by H. ducreyi in human volunteers, suggesting the latter may have a role in virulence. Here we constructed a double deletion mutant, 35000HPΔyfeABΔyfeCD, which exhibited growth defects relative to its parent 35000HP in media containing human hemoglobin as an iron source. Five human volunteers were inoculated at three sites on the skin overlying the deltoid with each strain. The results of the trial showed that papules formed at 100% (95% CI, 71.5, 100) at both 35000HP and 35000HPΔyfeABΔyfeCD-inoculated sites (P = 1.0). Pustules formed at 60% (95% CI, 25.9, 94.1) at parent-inoculated sites and 53% (95% CI, 18.3, 88.4) at mutant-inoculated sites (P = 0.79). Thus, the ABC transporter encoded by yfeAB and yfeCD was dispensable for H. ducreyi virulence in humans. In the absence of YfeABCD, H. ducreyi likely utilizes other periplasmic binding proteins and ABC-transporters such as HbpA, SapABCDF, and DppBCDF to shuttle heme from the periplasm into the cytoplasm, underscoring the importance of redundancy of such systems in gram-negative pathogens.
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Affiliation(s)
- Kate R Fortney
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Julie A Brothwell
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Teresa A Batteiger
- Department of Medicine, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Rory Duplantier
- Department of Medicine, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Barry P Katz
- Department of Biostatistics and Health Data Science, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Stanley M Spinola
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
- Department of Medicine, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, USA
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Brothwell JA, Fortney KR, Williams JS, Batteiger TA, Duplantier R, Grounds D, Jannasch AS, Katz BP, Spinola SM. Formate production is dispensable for Haemophilus ducreyi virulence in human volunteers. Infect Immun 2023; 91:e0017623. [PMID: 37594273 PMCID: PMC10501210 DOI: 10.1128/iai.00176-23] [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: 05/05/2023] [Accepted: 06/29/2023] [Indexed: 08/19/2023] Open
Abstract
Haemophilus ducreyi is a causative agent of cutaneous ulcers in children who live in the tropics and of the genital ulcer disease chancroid in sexually active persons. In the anaerobic environment of abscesses and ulcers, anaerobic respiration and mixed acid fermentation (MAF) can be used to provide cellular energy. In Escherichia coli, MAF produces formate, acetate, lactate, succinate, and ethanol; however, MAF has not been studied in H. ducreyi. In human challenge experiments with H. ducreyi 35000HP, transcripts of the formate transporter FocA and pyruvate formate lyase (PflB) were upregulated in pustules compared to the inocula. We made single and double mutants of focA and pflB in 35000HP. Growth of 35000HPΔfocA was similar to 35000HP, but 35000HPΔpflB and 35000HPΔfocA-pflB had growth defects during both aerobic and anaerobic growth. Mutants lacking pflB did not secrete formate into the media. However, formate was secreted into the media by 35000HPΔfocA, indicating that H. ducreyi has alternative formate transporters. The pH of the media during anaerobic growth decreased for 35000HP and 35000HPΔfocA, but not for 35000HPΔpflB or 35000HPΔfocA-pflB, indicating that pflB is the main contributor to media acidification during anaerobic growth. We tested whether formate production and transport were required for virulence in seven human volunteers in a mutant versus parent trial between 35000HPΔfocA-pflB and 35000HP. The pustule formation rate was similar for 35000HP (42.9%)- and 35000HPΔfocA-pflB (62%)-inoculated sites. Although formate production occurs during in vitro growth and focA-pflB transcripts are upregulated during human infection, focA and pflB are not required for virulence in humans.
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Affiliation(s)
- Julie A. Brothwell
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Kate R. Fortney
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Jalan S. Williams
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Teresa A. Batteiger
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Rory Duplantier
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Danielle Grounds
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Amber S. Jannasch
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, USA
| | - Barry P. Katz
- Department of Biostatistics and Health Data Sciences, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Stanley M. Spinola
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
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Brothwell JA, Fortney KR, Batteiger T, Katz BP, Spinola SM. Dispensability of Ascorbic Acid Uptake and Utilization Encoded by ulaABCD for the Virulence of Haemophilus ducreyi in Humans. J Infect Dis 2023; 227:317-321. [PMID: 35876728 PMCID: PMC10169391 DOI: 10.1093/infdis/jiac314] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/13/2022] [Accepted: 07/21/2022] [Indexed: 02/04/2023] Open
Abstract
Compared with wounded skin, ascorbic acid is enriched in pustules of humans experimentally infected with Haemophilus ducreyi. Compared with the broth-grown inocula, transcription of the H. ducreyi ulaABCD operon, which encodes genes for ascorbic acid uptake, is increased in pustules. We hypothesized that ascorbic acid uptake plays a role in H. ducreyi virulence. Five volunteers were infected with both H. ducreyi strain 35000HP and its isogenic ulaABCD deletion mutant at multiple sites; the papule and pustule formation rates of the mutant and parent strains were similar. Thus, ascorbic acid uptake is not essential for H. ducreyi virulence in humans.
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Affiliation(s)
- Julie A Brothwell
- Departments of Microbiology and Immunology, Indiana University, Indianapolis, Indiana, USA
| | - Kate R Fortney
- Departments of Microbiology and Immunology, Indiana University, Indianapolis, Indiana, USA
| | - Teresa Batteiger
- Department of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Barry P Katz
- Department of Biostatistics and Health Data Science, Indiana University, Indianapolis, Indiana, USA
| | - Stanley M Spinola
- Departments of Microbiology and Immunology, Indiana University, Indianapolis, Indiana, USA.,Department of Medicine, Indiana University, Indianapolis, Indiana, USA.,Department of Pathology and Laboratory Medicine, Indiana University, Indianapolis, Indiana, USA
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