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Bhushan G, Castano V, Wong Fok Lung T, Chandler C, McConville TH, Ernst RK, Prince AS, Ahn D. Lipid A modification of colistin-resistant Klebsiella pneumoniae does not alter innate immune response in a mouse model of pneumonia. Infect Immun 2024; 92:e0001624. [PMID: 38771050 DOI: 10.1128/iai.00016-24] [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: 01/26/2024] [Accepted: 04/26/2024] [Indexed: 05/22/2024] Open
Abstract
Polymyxin resistance in carbapenem-resistant Klebsiella pneumoniae bacteria is associated with high morbidity and mortality in vulnerable populations throughout the world. Ineffective antimicrobial activity by these last resort therapeutics can occur by transfer of mcr-1, a plasmid-mediated resistance gene, causing modification of the lipid A portion of lipopolysaccharide (LPS) and disruption of the interactions between polymyxins and lipid A. Whether this modification alters the innate host immune response or carries a high fitness cost in the bacteria is not well established. To investigate this, we studied infection with K. pneumoniae (KP) ATCC 13883 harboring either the mcr-1 plasmid (pmcr-1) or the vector control (pBCSK) ATCC 13883. Bacterial fitness characteristics of mcr-1 acquisition were evaluated. Differentiated human monocytes (THP-1s) were stimulated with KP bacterial strains or purified LPS from both parent isolates and isolates harboring mcr-1. Cell culture supernatants were analyzed for cytokine production. A bacterial pneumonia model in WT C57/BL6J mice was used to monitor immune cell recruitment, cytokine induction, and bacterial clearance in the bronchoalveolar lavage fluid (BALF). Isolates harboring mcr-1 had increased colistin MIC compared to the parent isolates but did not alter bacterial fitness. Few differences in cytokines were observed with purified LPS from mcr-1 expressing bacteria in vitro. However, in a mouse pneumonia model, no bacterial clearance defect was observed between pmcr-1-harboring KP and parent isolates. Consistently, no differences in cytokine production or immune cell recruitment in the BALF were observed, suggesting that other mechanisms outweigh the effect of these lipid A mutations in LPS.
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Affiliation(s)
- Gitanjali Bhushan
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Victor Castano
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Tania Wong Fok Lung
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Courtney Chandler
- Department of Microbial Pathogenesis, University of Maryland, School of Dentistry, Baltimore, Maryland, USA
| | - Thomas H McConville
- Department of Medicine, Columbia University Irving Medical Center, New York, New York, USA
| | - Robert K Ernst
- Department of Microbial Pathogenesis, University of Maryland, School of Dentistry, Baltimore, Maryland, USA
| | - Alice S Prince
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Danielle Ahn
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
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Pérez-Ortega J, van Harten RM, Haagsman HP, Tommassen J. Physiological consequences of inactivation of lgmB and lpxL1, two genes involved in lipid A synthesis in Bordetella bronchiseptica. Res Microbiol 2023; 174:104049. [PMID: 36871896 DOI: 10.1016/j.resmic.2023.104049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 02/16/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023]
Abstract
To develop a Bordetella bronchiseptica vaccine with reduced endotoxicity, we previously inactivated lpxL1, the gene encoding the enzyme that incorporates a secondary 2-hydroxy-laurate in lipid A. The mutant showed a myriad of phenotypes. Structural analysis showed the expected loss of the acyl chain but also of glucosamine (GlcN) substituents, which decorate the phosphates in lipid A. To determine which structural change causes the various phenotypes, we inactivated here lgmB, which encodes the GlcN transferase, and lpxL1 in an isogenic background and compared the phenotypes. Like the lpxL1 mutation, the lgmB mutation resulted in reduced potency to activate human TLR4 and to infect macrophages and in increased susceptibility to polymyxin B. These phenotypes are therefore related to the loss of GlcN decorations. The lpxL1 mutation had a stronger effect on hTLR4 activation and additionally resulted in reduced murine TLR4 activation, surface hydrophobicity, and biofilm formation, and in a fortified outer membrane as evidenced by increased resistance to several antimicrobials. These phenotypes, therefore, appear to be related to the loss of the acyl chain. Moreover, we determined the virulence of the mutants in the Galleria mellonella infection model and observed reduced virulence of the lpxL1 mutant but not of the lgmB mutant.
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Affiliation(s)
- Jesús Pérez-Ortega
- Section Molecular Microbiology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands; Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands.
| | - Roel M van Harten
- Section of Molecular Host Defense, Division of Infectious Diseases and Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, the Netherlands.
| | - Henk P Haagsman
- Section of Molecular Host Defense, Division of Infectious Diseases and Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, the Netherlands.
| | - Jan Tommassen
- Section Molecular Microbiology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands; Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands.
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