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Han J, Aljahdali N, Zhao S, Tang H, Harbottle H, Hoffmann M, Frye JG, Foley SL. Infection biology of Salmonella enterica. EcoSal Plus 2024:eesp00012023. [PMID: 38415623 DOI: 10.1128/ecosalplus.esp-0001-2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 07/31/2023] [Indexed: 02/29/2024]
Abstract
Salmonella enterica is the leading cause of bacterial foodborne illness in the USA, with an estimated 95% of salmonellosis cases due to the consumption of contaminated food products. Salmonella can cause several different disease syndromes, with the most common being gastroenteritis, followed by bacteremia and typhoid fever. Among the over 2,600 currently identified serotypes/serovars, some are mostly host-restricted and host-adapted, while the majority of serotypes can infect a broader range of host species and are associated with causing both livestock and human disease. Salmonella serotypes and strains within serovars can vary considerably in the severity of disease that may result from infection, with some serovars that are more highly associated with invasive disease in humans, while others predominantly cause mild gastroenteritis. These observed clinical differences may be caused by the genetic make-up and diversity of the serovars. Salmonella virulence systems are very complex containing several virulence-associated genes with different functions that contribute to its pathogenicity. The different clinical syndromes are associated with unique groups of virulence genes, and strains often differ in the array of virulence traits they display. On the chromosome, virulence genes are often clustered in regions known as Salmonella pathogenicity islands (SPIs), which are scattered throughout different Salmonella genomes and encode factors essential for adhesion, invasion, survival, and replication within the host. Plasmids can also carry various genes that contribute to Salmonella pathogenicity. For example, strains from several serovars associated with significant human disease, including Choleraesuis, Dublin, Enteritidis, Newport, and Typhimurium, can carry virulence plasmids with genes contributing to attachment, immune system evasion, and other roles. The goal of this comprehensive review is to provide key information on the Salmonella virulence, including the contributions of genes encoded in SPIs and plasmids during Salmonella pathogenesis.
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Affiliation(s)
- Jing Han
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Nesreen Aljahdali
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
- Biological Science Department, College of Science, King Abdul-Aziz University, Jeddah, Saudi Arabia
| | - Shaohua Zhao
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, Maryland, USA
| | - Hailin Tang
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
| | - Heather Harbottle
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, Maryland, USA
| | - Maria Hoffmann
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, Maryland, USA
| | - Jonathan G Frye
- Agricutlutral Research Service, U.S. Department of Agriculture, Athens, Georgia, USA
| | - Steven L Foley
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas, USA
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2
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Li F, Ye K, Li X, Ye L, Guo L, Wang L, Yang J. Genetic characterization of Carbapenem-Resistant Escherichia coli from China, 2015-2017. BMC Microbiol 2021; 21:248. [PMID: 34535075 PMCID: PMC8449468 DOI: 10.1186/s12866-021-02307-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 08/31/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The molecular characteristics of carbapenem-resistant Escherichia coli (CREco) remain unclear. METHODS We conducted a multi-center bacterial resistance monitoring project from 2015 to 2017.The minimum inhibitory concentrations ofCREco were determined bybroth microdilution method. The genome sequencing of CREcoisolates was performed, and single-nucleotide polymorphism (SNP) was analyzed. RESULTS A total of 144CREcoisolatescollected from 10 cities in China were involved in this study. ST167 (n = 43) is the most popular type, followed by ST410(n = 14), ST131(n = 9). There were 102 (70.83%) CREco isolates that produced various NDMs, including NDM-1 (n = 16), NDM-4(n = 1), NDM-5(n = 79), NDM-6(n = 2) and NDM-9(n = 4). In addition, 15 isolates produced KPC-2, three isolates wereIMP-4 positive, and three isolates produced OXA-48. Genetic relatedness and phylogenetic analysis showed that isolates with the same ST had a high degree of homology. Some STs (including ST167, ST410, ST131, ST46, ST405 and ST617) exhibited a trend of outbreak. CONCLUSIONS The majority of CREco belonged to ST167, followed by ST410 and ST131, and most of them carried various NDM-coding genes. The spread of high-risk clones of CREco has occurred in different regions of China.
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Affiliation(s)
- Fengtian Li
- Laboratory Medicine Department, First Medical Center of Chinese PLA General Hospital, Beijing, 100853, China
| | - Kun Ye
- Laboratory Medicine Department, First Medical Center of Chinese PLA General Hospital, Beijing, 100853, China
| | - Xin Li
- Laboratory Medicine Department, First Medical Center of Chinese PLA General Hospital, Beijing, 100853, China
| | - Liyan Ye
- Laboratory Medicine Department, First Medical Center of Chinese PLA General Hospital, Beijing, 100853, China
| | - Ling Guo
- Laboratory Medicine Department, First Medical Center of Chinese PLA General Hospital, Beijing, 100853, China
| | - Lifeng Wang
- Laboratory Medicine Department, First Medical Center of Chinese PLA General Hospital, Beijing, 100853, China
| | - Jiyong Yang
- Laboratory Medicine Department, First Medical Center of Chinese PLA General Hospital, Beijing, 100853, China.
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3
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Mejía L, Medina JL, Bayas R, Salazar CS, Villavicencio F, Zapata S, Matheu J, Wagenaar JA, González-Candelas F, Vinueza-Burgos C. Genomic Epidemiology of Salmonella Infantis in Ecuador: From Poultry Farms to Human Infections. Front Vet Sci 2020; 7:547891. [PMID: 33134346 PMCID: PMC7550756 DOI: 10.3389/fvets.2020.547891] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 08/20/2020] [Indexed: 11/13/2022] Open
Abstract
Salmonella enterica is one of the most important foodborne pathogens around the world. In the last years, S. enterica serovar Infantis has become an important emerging pathogen in many countries, often as multidrug resistant clones. To understand the importance of S. enterica in the broiler industry in Ecuador, we performed a study based on phenotypic and WGS data of isolates from poultry farms, chicken carcasses and humans. We showed a high prevalence of S. enterica in poultry farms (41.4%) and chicken carcasses (55.5%), but a low prevalence (1.98%) in human samples. S. Infantis was shown to be the most prevalent serovar with a 98.2, 97.8, and 50% in farms, foods, and humans, respectively, presenting multidrug resistant patterns. All sequenced S. Infantis isolates belonged to ST32. For the first time, a pESI-related megaplasmid was identified in Ecuadorian samples. This plasmid contains genes of antimicrobial resistance, virulence factors, and environmental stress tolerance. Genomic analysis showed a low divergence of S. Infantis strains in the three analyzed components. The results from this study provide important information about genetic elements that may help understand the molecular epidemiology of S. Infantis in Ecuador.
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Affiliation(s)
- Lorena Mejía
- Instituto de Microbiología, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Quito, Ecuador.,Institute for Integrative Systems Biology, University of Valencia, Valencia, Spain
| | - José Luis Medina
- Unidad de Investigación de Enfermedades Transmitidas por Alimentos y Resistencia a los Antimicrobianos (UNIETAR), Facultad de Medicina Veterinaria, Universidad Central del Ecuador, Quito, Ecuador
| | - Rosa Bayas
- Instituto de Microbiología, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Quito, Ecuador
| | - Carolina Satan Salazar
- Centro de Referencia Nacional de Resistencia a los Antimicrobianos, Instituto Nacional de Investigación en Salud Pública "Leopoldo Izquieta Pérez", Quito, Ecuador
| | - Fernando Villavicencio
- Centro de Referencia Nacional de Resistencia a los Antimicrobianos, Instituto Nacional de Investigación en Salud Pública "Leopoldo Izquieta Pérez", Quito, Ecuador
| | - Sonia Zapata
- Instituto de Microbiología, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Quito, Ecuador
| | - Jorge Matheu
- Department of Food Safety and Zoonoses, World Health Organization (WHO), Geneva, Switzerland
| | - Jaap A Wagenaar
- Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands.,Wageningen Bioveterinary Research (WBVR), Lelystad, Netherlands
| | - Fernando González-Candelas
- Institute for Integrative Systems Biology, University of Valencia, Valencia, Spain.,Joint Research Unit "Infection and Public Health" FISABIO-University of Valencia, Valencia, Spain.,CIBER (Centro de Investigación Biomédica en Red) in Epidemiology and Public Health, Valencia, Spain
| | - Christian Vinueza-Burgos
- Unidad de Investigación de Enfermedades Transmitidas por Alimentos y Resistencia a los Antimicrobianos (UNIETAR), Facultad de Medicina Veterinaria, Universidad Central del Ecuador, Quito, Ecuador
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4
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Staes I, Passaris I, Cambré A, Aertsen A. Population heterogeneity tactics as driving force in Salmonella virulence and survival. Food Res Int 2019; 125:108560. [DOI: 10.1016/j.foodres.2019.108560] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 07/05/2019] [Accepted: 07/12/2019] [Indexed: 01/28/2023]
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5
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Müller J, Spriewald S, Stecher B, Stadler E, Fuchs TM. Evolutionary Stability of Salmonella Competition with the Gut Microbiota: How the Environment Fosters Heterogeneity in Exploitative and Interference Competition. J Mol Biol 2019; 431:4732-4748. [PMID: 31260689 DOI: 10.1016/j.jmb.2019.06.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 06/19/2019] [Accepted: 06/19/2019] [Indexed: 11/27/2022]
Abstract
Following ingestion, gastrointestinal pathogens compete against the gastrointestinal microbiota and overcome host immune defenses in order to cause infections. Besides employing direct killing mechanisms, the commensal microbiota occupies metabolic niches to outcompete invading pathogens. Salmonella enterica serovar Typhimurium (S. Typhimurium) uses several strategies to successfully colonize the gut and establish infection, of which an increasing number is based on phenotypic heterogeneity within the S. Typhimurium population. The utilization of myo-inositol (MI) and the production of colicin confer a selective advantage over the microbiota in terms of exploitative and interference competition, respectively. In this review, we summarize the genetic basis underlying bistability of MI catabolism and colicin production. As demonstrated by single-cell analyses, a stochastic switch in the expression of the genes responsible for colicin production and MI degradation constitutes the heterogeneity of the two phenotypes. Both genetic systems are tightly regulated to avoid their expression under non-appropriate conditions and possible detrimental effects on bacterial fitness. Moreover, evolutionary mechanisms underlying formation and stability of these phenotypes in S. Typhimurium are discussed. We propose that both MI catabolism and colicin production create a bet-hedging strategy, which provides an adaptive benefit for S. Typhimurium in the fluctuating environment of the mammalian gut.
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Affiliation(s)
- Johannes Müller
- Technische Universität München, Centre for Mathematical Sciences, Boltzmannstr. 3, 85747 Garching, Germany; Institute for Computational Biology, Helmholtz Center Munich, 85764 Neuherberg, Germany
| | - Stefanie Spriewald
- Max von Pettenkofer-Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany
| | - Bärbel Stecher
- Max von Pettenkofer-Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany
| | - Eva Stadler
- Technische Universität München, Centre for Mathematical Sciences, Boltzmannstr. 3, 85747 Garching, Germany
| | - Thilo M Fuchs
- Friedrich-Loeffler-Institut, Institut für Molekulare Pathogenese, Naumburger Str. 96a, 07743 Jena, Germany.
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6
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García-Pastor L, Sánchez-Romero MA, Gutiérrez G, Puerta-Fernández E, Casadesús J. Formation of phenotypic lineages in Salmonella enterica by a pleiotropic fimbrial switch. PLoS Genet 2018; 14:e1007677. [PMID: 30252837 PMCID: PMC6173445 DOI: 10.1371/journal.pgen.1007677] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 10/05/2018] [Accepted: 09/05/2018] [Indexed: 11/29/2022] Open
Abstract
The std locus of Salmonella enterica, an operon acquired by horizontal transfer, encodes fimbriae that permit adhesion to epithelial cells in the large intestine. Expression of the std operon is bistable, yielding a major subpopulation of StdOFF cells (99.7%) and a minor subpopulation of StdON cells (0.3%). In addition to fimbrial proteins, the std operon encodes two proteins, StdE and StdF, that have DNA binding capacity and control transcription of loci involved in flagellar synthesis, chemotaxis, virulence, conjugal transfer, biofilm formation, and other cellular functions. As a consequence of StdEF pleiotropic transcriptional control, StdON and StdOFF subpopulations may differ not only in the presence or absence of Std fimbriae but also in additional phenotypic traits. Separation of StdOFF and StdON lineages by cell sorting confirms the occurrence of lineage-specific features. Formation of StdOFF and StdON lineages may thus be viewed as a rudimentary bacterial differentiation program. We show that the std fimbrial operon of Salmonella enterica undergoes bistable expression, a trait far from exceptional among loci that encode components of the bacterial envelope. However, an unsuspected trait of the std operon is the presence of two genes that encode pleiotropic regulators of gene expression. Indeed, StdE and StdF are DNA-binding proteins that control transcription of hundreds of genes. As a consequence, StdEF govern multiple phenotypic traits, and the fimbriated and non-fimbriated Salmonella lineages may differ in motility, virulence, conjugal transfer, biofilm formation, and potentially in other phenotypic features. We hypothesize that pleiotropic control of gene expression by StdEF may contribute to adapt the non-fimbriated lineage to acute infection and the fimbriated lineage to chronic infection.
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Affiliation(s)
- Lucía García-Pastor
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | | | - Gabriel Gutiérrez
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Elena Puerta-Fernández
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Sevilla, Spain
- * E-mail: (EPF); (JC)
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
- * E-mail: (EPF); (JC)
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7
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Tanner JR, Kingsley RA. Evolution of Salmonella within Hosts. Trends Microbiol 2018; 26:986-998. [PMID: 29954653 PMCID: PMC6249985 DOI: 10.1016/j.tim.2018.06.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 05/22/2018] [Accepted: 06/01/2018] [Indexed: 11/18/2022]
Abstract
Within-host evolution has resulted in thousands of variants of Salmonella that exhibit remarkable diversity in host range and disease outcome, from broad host range to exquisite host restriction, causing gastroenteritis to disseminated disease such as typhoid fever. Within-host evolution is a continuing process driven by genomic variation that occurs during each infection, potentiating adaptation to a new niche resulting from changes in animal husbandry, the use of antimicrobials, and emergence of immune compromised populations. We discuss key advances in our understanding of the evolution of Salmonella within the host, inferred from (i) the process of host adaptation of Salmonella pathovars in the past, and (ii) direct observation of the generation of variation and selection of beneficial traits during single infections. Salmonella is a bacterial pathogen with remarkable diversity in its host range and pathogenicity due to past within-host evolution in vertebrate species that modified ancestral mechanisms of pathogenesis. Variation arising during infection includes point mutations, new genes acquired through horizontal gene transfer (HGT), deletions, and genomic rearrangements. Beneficial mutations increase in frequency within the host and, if they retain the ability to be transmitted to subsequent hosts, may become fixed in the population. Whole-genome sequencing of sequential isolates from clinical infections reveals within-host HGT and point mutations that impact therapy and clinical management. HGT is the primary mechanism for evolution in prokaryotes and is synergised by complex networks of transfer involving the microbiome. Within-host evolution of Salmonella, resulting in new pathovars, can proceed in the absence of HGT.
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Affiliation(s)
- Jennifer R Tanner
- Quadram Institute Bioscience, Norwich Research Park, Colney, Norwich, UK
| | - Robert A Kingsley
- Quadram Institute Bioscience, Norwich Research Park, Colney, Norwich, UK.
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8
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García-Pastor L, Puerta-Fernández E, Casadesús J. Bistability and phase variation in Salmonella enterica. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1862:752-758. [PMID: 29369799 DOI: 10.1016/j.bbagrm.2018.01.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Accepted: 01/09/2018] [Indexed: 11/18/2022]
Abstract
Cell-to-cell differences in bacterial gene expression can merely reflect the occurrence of noise. In certain cases, however, heterogeneous gene expression is a programmed event that results in bistable expression. If bistability is heritable, bacterial lineages are formed. When programmed bistability is reversible, the phenomenon is known as phase variation. In certain cases, bistability is controlled by genetic mechanisms (e. g., DNA rearrangement). In other cases, bistability has epigenetic origin. A robust epigenetic mechanism for the formation of bacterial lineages is the formation of heritable DNA methylation patterns. However, bistability can also arise upon propagation of gene expression patterns by feedback loops that are stable upon cell division. This review describes examples of bistability and phase variation in Salmonella enterica and discusses their adaptive value, sometimes in a speculative manner.
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Affiliation(s)
- Lucía García-Pastor
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado 1095, 41080 Sevilla, Spain
| | - Elena Puerta-Fernández
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado 1095, 41080 Sevilla, Spain
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado 1095, 41080 Sevilla, Spain.
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9
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Abstract
Some host-adapted bacterial pathogens are capable of causing persistent infections in humans. For example, Helicobacter pylori inhabits the human gastric mucosa and persistence can be lifelong. Salmonella enterica serovar Typhi causes systemic infections that involve colonization of the reticuloendothelial system and some individuals become lifelong carriers. In this review, I compare and contrast the different lifestyles of Helicobacter and Salmonella within the host and the strategies they have evolved to persist in mammalian hosts. Persistently infected carriers serve as the reservoirs for these pathogens, and the carrier state is an essential feature that is required for survival of the bacteria within a restricted host population. Therefore, investigating the chronic carrier state should provide insight into bacterial survival strategies, as well as new therapeutic approaches for treatments.
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Affiliation(s)
- Denise M Monack
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305
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10
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Monack DM. Salmonella persistence and transmission strategies. Curr Opin Microbiol 2012; 15:100-7. [DOI: 10.1016/j.mib.2011.10.013] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 10/27/2011] [Accepted: 10/27/2011] [Indexed: 12/24/2022]
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11
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Cronin M, Ventura M, Fitzgerald GF, van Sinderen D. Progress in genomics, metabolism and biotechnology of bifidobacteria. Int J Food Microbiol 2011; 149:4-18. [PMID: 21320731 DOI: 10.1016/j.ijfoodmicro.2011.01.019] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 01/06/2011] [Accepted: 01/10/2011] [Indexed: 12/16/2022]
Abstract
Members of the genus Bifidobacterium were first described over a century ago and were quickly associated with a healthy intestinal tract due to their numerical dominance in breast-fed babies as compared to bottle-fed infants. Health benefits elicited by bifidobacteria to its host, as supported by clinical trials, have led to their wide application as probiotic components of health-promoting foods, especially in fermented dairy products. However, the relative paucity of genetic tools available for bifidobacteria has impeded development of a comprehensive molecular understanding of this genus. In this review we present a summary of current knowledge on bifidobacterial metabolism, classification, physiology and genetics and outline the currently available methods for genetically accessing and manipulating the genus.
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Affiliation(s)
- Michelle Cronin
- Cork Cancer Research Centre, Mercy University Hospital and Leslie C. Quick Jnr. Laboratory, University College Cork, Cork, Ireland
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12
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Abstract
Fimbria-mediated interaction with the host elicits both innate and adaptive immune responses, and thus their expression may not always be beneficial in vivo. Furthermore, the metabolic drain of producing fimbriae is significant. It is not surprising, therefore, to find that fimbrial production in Escherichia coli and Salmonella enterica is under extensive environmental regulation. In many instances, fimbrial expression is regulated by phase variation, in which individual cells are capable of switching between fimbriate and afimbriate states to produce a mixed population. Mechanisms of phase variation vary considerably between different fimbriae and involve both genetic and epigenetic processes. Notwithstanding this, fimbrial expression is also sometimes controlled at the posttranscriptional level. In this chapter, we review key features of the regulation of fimbrial gene expression in E. coli and Salmonella. The occurrence and distribution of fimbrial operons vary significantly among E. coli pathovars and even among the many Salmonella serovars. Therefore, general principles are presented on the basis of detailed discussion of paradigms that have been extensively studied, including Pap, type 1 fimbriae, and curli. The roles of operon specific regulators like FimB or CsgD and of global regulatory proteins like Lrp, CpxR, and the histone-like proteins H-NS and IHF are reviewed as are the roles of sRNAs and of signalling nucleotide cyclic-di-GMP. Individual examples are discussed in detail to illustrate how the regulatory factors cooperate to allow tight control of expression of single operons. Molecular networks that allow coordinated expression between multiple fimbrial operons and with flagella in a single isolate are also presented. This chapter illustrates how adhesin expression is controlled, and the model systems also illustrate general regulatory principles germane to our overall understanding of bacterial gene regulation.
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13
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Abstract
The gastrointestinal tract represents the largest mucosal membrane surface in the human body. The immune system in the gut is the first line of host defense against mucosal microbial pathogens and it plays a crucial role in maintaining mucosal homeostasis. Membranous or microfold cells, commonly referred to as microfold cells, are specialized epithelial cells of the gut-associated lymphoid tissues (GALT) and they play a sentinel role for the intestinal immune system by delivering luminal antigens through the follicle-associated epithelium to the underlying immune cells. M cells sample and uptake antigens at their apical membrane, encase them in vesicles to transport them to the basolateral membrane of M cells, and from there deliver antigens to the nearby lymphocytes. On the flip side, some intestinal pathogens exploit M cells as their portal of entry to invade the host and cause infections. In this article, we briefly review our current knowledge on the morphology, development, and function of M cells, with an emphasis on their dual role in the pathogenesis of gut infection and in the development of host mucosal immunity.
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Ledeboer NA, Frye JG, McClelland M, Jones BD. Salmonella enterica serovar Typhimurium requires the Lpf, Pef, and Tafi fimbriae for biofilm formation on HEp-2 tissue culture cells and chicken intestinal epithelium. Infect Immun 2006; 74:3156-69. [PMID: 16714543 PMCID: PMC1479237 DOI: 10.1128/iai.01428-05] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Revised: 01/03/2006] [Accepted: 02/22/2006] [Indexed: 01/08/2023] Open
Abstract
Recent work has demonstrated that Salmonella enterica serovar Typhimurium forms biofilms on HEp-2 tissue culture cells in a type 1 fimbria-dependent manner. To investigate how biofilm growth of HEp-2 tissue culture cells affects gene expression in Salmonella, we compared global gene expression during planktonic growth and biofilm growth. Microarray results indicated that the transcription of approximately 100 genes was substantially altered by growth in a biofilm. These genes encode proteins with a wide range of functions, including antibiotic resistance, central metabolism, conjugation, intracellular survival, membrane transport, regulation, and fimbrial biosynthesis. The identification of five fimbrial gene clusters was of particular interest, as we have demonstrated that type 1 fimbriae are required for biofilm formation on HEp-2 cells and murine intestinal epithelium. Mutations in each of these fimbriae were constructed in S. enterica serovar Typhimurium strain BJ2710, and the mutants were found to have various biofilm phenotypes on plastic, HEp-2 cells, and chicken intestinal tissue. The pef and csg mutants were defective for biofilm formation on each of the three surfaces tested, while the lpf mutant exhibited a complete loss of the ability to form a biofilm on chicken intestinal tissue but only an intermediate loss of the ability to form a biofilm on tissue culture cells and plastic surfaces. The bcf mutant displayed increased biofilm formation on both HEp-2 cells and chicken intestinal epithelium, while the sth mutant had no detectable biofilm defects. In all instances, the mutants could be restored to a wild-type phenotype by a plasmid carrying the functional genes. This is the first work to identify the genomic responses of Salmonella to biofilm formation on host cells, and this work highlights the importance of fimbriae in adhering to and adapting to a eukaryotic cell surface. An understanding of these interactions is likely to provide new insights for intervention strategies in Salmonella colonization and infection.
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Affiliation(s)
- Nathan A Ledeboer
- Department of Microbiology, Roy J. and Lucille A. Carver School of Medicine, University of Iowa, Iowa City, IA 52242-1109.
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15
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Weening EH, Barker JD, Laarakker MC, Humphries AD, Tsolis RM, Bäumler AJ. The Salmonella enterica serotype Typhimurium lpf, bcf, stb, stc, std, and sth fimbrial operons are required for intestinal persistence in mice. Infect Immun 2005; 73:3358-66. [PMID: 15908362 PMCID: PMC1111867 DOI: 10.1128/iai.73.6.3358-3366.2005] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Revised: 12/16/2004] [Accepted: 02/15/2005] [Indexed: 12/22/2022] Open
Abstract
Salmonella enterica serotype Typhimurium causes human infections that can frequently be traced back through the food chain to healthy livestock whose intestine is colonized by the pathogen. Little is known about the genes important for intestinal carriage of S. enterica serotype Typhimurium in vertebrate animals. Here we characterized the role of 10 fimbrial operons, agf, fim, lpf, pef, bcf, stb, stc, std, stf, and sth, using competitive infection experiments performed in genetically susceptible (BALB/c) and resistant (CBA) mice. Deletion of agfAB, fimAICDHF, lpfABCDE, pefABCDI, bcfABCDEFG, stbABCD, stcABCD, stdAB, stfACDEFG, or sthABCDE did not reduce the ability of S. enterica serotype Typhimurium to colonize the spleen and cecum of BALB/c mice 5 days after infection. Similarly, deletion of agfAB, fimAICDHF, pefABCDI, and stfACDEFG did not result in reduced recovery of S. enterica serotype Typhimurium from fecal samples collected from infected CBA mice over a 30-day time period. However, S. enterica serotype Typhimurium strains carrying deletions in lpfABCDE, bcfABCDEFG, stbABCD, stcABCD, stdAB, or sthABCDE were recovered at significantly reduced numbers from the feces of CBA mice. There was a good correlation (R(2) = 0.9626) between competitive indices in the cecum and fecal samples of CBA mice at 30 days after infection, suggesting that the recovery of S. enterica serotype Typhimurium from fecal samples closely reflected its ability to colonize the cecum. Collectively, these data show that six fimbrial operons (lpf, bcf, stb, stc, std, and sth) contribute to long-term intestinal carriage of S. enterica serotype Typhimurium in genetically resistant mice.
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Affiliation(s)
- Eric H Weening
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, One Shields Ave., Davis, CA 95616-8645, USA
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Humphries AD, Raffatellu M, Winter S, Weening EH, Kingsley RA, Droleskey R, Zhang S, Figueiredo J, Khare S, Nunes J, Adams LG, Tsolis RM, Bäumler AJ. The use of flow cytometry to detect expression of subunits encoded by 11 Salmonella enterica serotype Typhimurium fimbrial operons. Mol Microbiol 2003; 48:1357-76. [PMID: 12787362 DOI: 10.1046/j.1365-2958.2003.03507.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Salmonella enterica serotype Typhimurium (S. Typhimurium) genome contains 13 putative fimbrial operons termed agf (csg), fim, pef, lpf, bcf, saf, stb, stc, std, stf, sth, sti and stj. Evidence for in vitro expression of fimbrial proteins encoded by these operons is currently only available for agf, fim and pef. We raised antisera against putative major fimbrial subunits of S. Typhimurium, including AgfA, FimA, PefA, LpfA, BcfA, StbA, StcA, StdA, StfA, SthA and StiA. Elaboration of StcA on the bacterial surface could be detected by flow cytometry and immunoelectron microscopy after expression of the cloned stcABCD operon from a heterologous T7 promoter in Escherichia coli. To study the expression of fimbrial antigens in S. Typhimurium by flow cytometry, we constructed strains carrying deletions of agfAB, pefBACDI, lpfABCDE, bcfABCDEFG, stbABCD, stcABC, stdAB, stfACDEFG, sthABCDE or stiABCDE. Using these deletion mutants for gating, expression of fimbrial antigens was measured by flow cytometry in cultures grown in vitro or in samples recovered 8 h after infection of bovine ligated ileal loops with S. Typhimurium. FimA was the only fimbrial antigen expressed by S. Typhimurium after static growth in Luria-Bertani (LB) broth. Injection of static LB broth cultures of S. Typhimurium into bovine ligated ileal loops resulted in the expression of BcfA, FimA, LpfA, PefA, StbA, StcA, StdA, StfA and StiA. These data show that in vivo growth conditions drastically alter the repertoire of fimbrial antigens expressed in S. Typhimurium.
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Affiliation(s)
- Andrea D Humphries
- Department of Medical Microbiology and Immunology, College of Medicine, Texas A and M University System Health Science Center, 407 Reynolds Medical Building, College Station 77843-1114, USA
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