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Spiga L, Jimenez AG, Santos RL, Winter SE. How microbiological tests reflect bacterial pathogenesis and host adaptation. Braz J Microbiol 2021; 52:1745-1753. [PMID: 34251610 PMCID: PMC8578236 DOI: 10.1007/s42770-021-00571-7] [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: 01/18/2021] [Accepted: 06/29/2021] [Indexed: 10/20/2022] Open
Abstract
Historically, clinical microbiological laboratories have often relied on isolation of pure cultures and phenotypic testing to identify microorganisms. These clinical tests are often based on specific biochemical reactions, growth characteristics, colony morphology, and other physiological aspects. The features used for identification in clinical laboratories are highly conserved and specific for a given group of microbes. We speculate that these features might be the result of evolutionary selection and thus may reflect aspects of the life cycle of the organism and pathogenesis. Indeed, several of the metabolic pathways targeted by diagnostic tests in some cases may represent mechanisms for host colonization or pathogenesis. Examples include, but are not restricted to, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella enterica, Shigella spp., and enteroinvasive Escherichia coli (EIEC). Here, we provide an overview of how some common tests reflect molecular mechanisms of bacterial pathogenesis.
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Affiliation(s)
- Luisella Spiga
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Angel G Jimenez
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Renato L Santos
- Departamento de Clínica E Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Sebastian E Winter
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Di Martino ML, Fioravanti R, Barbabella G, Prosseda G, Colonna B, Casalino M. Molecular evolution of the nicotinic acid requirement within the Shigella/EIEC pathotype. Int J Med Microbiol 2013; 303:651-61. [DOI: 10.1016/j.ijmm.2013.09.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/05/2013] [Accepted: 09/08/2013] [Indexed: 11/27/2022] Open
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Abstract
The emergence of new pathogens and the exploitation of novel pathogenic niches by bacteria typically require the horizontal transfer of virulence factors and subsequent adaptation--a "fine-tuning" process--for the successful incorporation of these factors into the microbe's genome. The function of newly acquired virulence factors may be hindered by the expression of genes already present in the bacterium. Occasionally, certain genes must be inactivated or deleted for full expression of the pathogen phenotype to occur. These genes are known as antivirulence genes (AVGs). Originally identified in Shigella, AVGs have improved our understanding of pathogen evolution and provided a novel approach to drug and vaccine development. In this review, we revisit the AVG definition and update the list of known AVGs, which now includes genes from pathogens such as Salmonella, Yersinia pestis, and the virulent Francisella tularensis subspecies. AVGs encompass a wide variety of different roles within the microbe, including genes involved in metabolism, biofilm synthesis, lipopolysaccharide modification, and host vasoconstriction. More recently, the use of one of these AVGs (lpxL) as a potential vaccine candidate highlights the practical application of studying AVG inactivation in microbial pathogens.
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Prunier AL, Schuch R, Fernández RE, Mumy KL, Kohler H, McCormick BA, Maurelli AT. nadA and nadB of Shigella flexneri 5a are antivirulence loci responsible for the synthesis of quinolinate, a small molecule inhibitor of Shigella pathogenicity. MICROBIOLOGY-SGM 2007; 153:2363-2372. [PMID: 17600080 DOI: 10.1099/mic.0.2007/006916-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The evolution of bacterial pathogens from commensal organisms involves virulence gene acquisition followed by pathoadaptation to the new host, including inactivation of antivirulence loci (AVL). AVL are core ancestral genes whose expression is incompatible with the pathogenic lifestyle. Previous studies identified cadA (encoding lysine decarboxylase) as an AVL of Shigella spp. In this study, AVL of Shigella were identified by examining a phenotypic difference from its non-pathogenic ancestor, Escherichia coli. Unlike most E. coli strains, Shigella spp. are nicotinic acid auxotrophs, the pathway for the de novo synthesis of NAD being uniformly defective. In Shigella flexneri, this defect is due to alterations in the nadA and/or nadB genes encoding the enzyme complex that converts L-aspartate to quinolinate, a precursor to NAD synthesis. Quinolinate was found to inhibit invasion and cell-to-cell spread of Sh. flexneri 5a and its ability to induce polymorphonuclear neutrophil transepithelial migration. Virulence of other Shigella species was also inhibited by quinolinate. Introduction of functional nadA and nadB genes from E. coli K-12 into Sh. flexneri 5a restored its ability to synthesize quinolinate but also resulted in strong attenuation of virulence in this strain. The results define nadA and nadB as AVL in Shigella and validate the concept of pathoadaptive evolution of bacteria from commensal ancestors by inactivation of AVL. They also suggest that studies focusing on this form of bacterial evolution can identify novel inhibitors of virulence in other bacterial pathogens.
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Affiliation(s)
- Anne-Laure Prunier
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, MD 20814-4799, USA
| | - Raymond Schuch
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, MD 20814-4799, USA
| | - Reinaldo E Fernández
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, MD 20814-4799, USA
| | - Karen L Mumy
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
- Mucosal Immunology Laboratory, Department of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Henrik Kohler
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
- Mucosal Immunology Laboratory, Department of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Beth A McCormick
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
- Mucosal Immunology Laboratory, Department of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Anthony T Maurelli
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, MD 20814-4799, USA
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Prunier AL, Schuch R, Fernández RE, Maurelli AT. Genetic structure of the nadA and nadB antivirulence loci in Shigella spp. J Bacteriol 2007; 189:6482-6. [PMID: 17586625 PMCID: PMC1951923 DOI: 10.1128/jb.00525-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Comparison of nadA and nadB in 14 Shigella strains and enteroinvasive Escherichia coli versus E. coli showed that at least one locus is altered in all strains. These observations explain the characteristic nicotinic acid auxotrophy of Shigella organisms and are consistent with the previously identified antivirulence nature of these genes for these pathogens.
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Affiliation(s)
- Anne-Laure Prunier
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, 4301 Jones Bridge Road, Bethesda, MD 20814-4799, USA
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