scholarly journals Pathogen clonal expansion underlies multiorgan dissemination and organ-specific outcomes during murine systemic infection

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Karthik Hullahalli ◽  
Matthew K Waldor
Keyword(s):  
Population Biology ◽  
Cell Envelope ◽  
Systemic Infection ◽  
Clonal Expansion ◽  
Inoculum Size ◽  
Pathogen Population ◽  
Infection Dynamics ◽  
Specific Pathogen ◽  
Organ Specific ◽  
Bacterial Replication

The dissemination of pathogens through blood and their establishment within organs lead to severe clinical outcomes. However, the within-host dynamics that underly pathogen spread to and clearance from systemic organs remain largely uncharacterized. In animal models of infection, the observed pathogen population results from the combined contributions of bacterial replication, persistence, death, and dissemination, each of which can vary across organs. Quantifying the contribution of each these processes is required to interpret and understand experimental phenotypes. Here, we leveraged STAMPR, a new barcoding framework, to investigate the population dynamics of extraintestinal pathogenic E. coli, a common cause of bacteremia, during murine systemic infection. We show that while bacteria are largely cleared by most organs, organ-specific clearance failures are pervasive and result from dramatic expansions of clones representing less than 0.0001% of the inoculum. Clonal expansion underlies the variability in bacterial burden between animals, and stochastic dissemination of clones profoundly alters the pathogen population structure within organs. Despite variable pathogen expansion events, host bottlenecks are consistent yet highly sensitive to infection variables, including inoculum size and macrophage depletion. We adapted our barcoding methodology to facilitate multiplexed validation of bacterial fitness determinants identified with transposon mutagenesis and confirmed the importance of bacterial hexose metabolism and cell envelope homeostasis pathways for organ-specific pathogen survival. Collectively our findings provide a comprehensive map of the population biology that underlies bacterial systemic infection and a framework for barcode-based high-resolution mapping of infection dynamics.

scholarly journals Pathogen clonal expansion underlies multiorgan dissemination and organ-specific outcomes during systemic infection

2021 ◽  
Author(s):  
Karthik Hullahalli ◽  
Matthew K Waldor
Keyword(s):  
Genetic Factors ◽  
Systemic Infection ◽  
Clonal Expansion ◽  
Inoculum Size ◽  
Pathogen Population ◽  
E Coli ◽  
Highly Sensitive ◽  
Organ Specific ◽  
Bacterial Genetic ◽  
Pathogen Populations

The dissemination of pathogens through blood and their establishment within organs lead to severe clinical outcomes. However, the within-host dynamics that underly pathogen spread to and clearance from systemic organs remain largely uncharacterized. Here, we investigate the population dynamics of extraintestinal pathogenic E. coli, a common cause of bacteremia, during systemic infection. We show that while bacteria are largely cleared by most organs, organ-specific clearance failures are pervasive and result from dramatic expansions of clones representing less than 0.0001% of the inoculum. Clonal expansion underlies the variability in bacterial burden between animals, and stochastic dissemination of clones profoundly alters the pathogen population structure within organs. Despite variable pathogen expansion events, host bottlenecks are consistent yet highly sensitive to infection variables, including inoculum size and macrophage depletion. Finally, we identify organ-specific bacterial genetic factors that distinguish between establishment of within-organ pathogen populations and subsequent survival or expansion.

scholarly journals Salmonella typhimurium Persists within Macrophages in the Mesenteric Lymph Nodes of Chronically Infected Nramp1+/+ Mice and Can Be Reactivated by IFNγ Neutralization

2004 ◽  
Vol 199 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Denise M. Monack ◽  
Donna M. Bouley ◽  
Stanley Falkow
Keyword(s):  
Lymph Nodes ◽  
Persistent Infection ◽  
Systemic Disease ◽  
Systemic Infection ◽  
Neutralizing Antibody ◽  
Interferon Γ ◽  
Mesenteric Lymph Nodes ◽  
Fecal Shedding ◽  
Mesenteric Lymph ◽  
Bacterial Replication

Host-adapted strains of Salmonella are capable of establishing a persistent infection in their host often in the absence of clinical disease. The mouse model of Salmonella infection has primarily been used as a model for the acute systemic disease. Therefore, the sites of long-term S. typhimurium persistence in the mouse are not known nor are the mechanisms of persistent infection clearly understood. Here, we show that S. typhimurium can persist for as long as 1 yr in the mesenteric lymph nodes (MLNs) of 129sv Nramp1+/+ (Slc11a1+/+) mice despite the presence of high levels of anti–S. typhimurium antibody. Tissues from 129sv mice colonized for 60 d contain numerous inflammatory foci and lesions with features resembling S. typhi granulomas. Tissues from mice infected for 365 d have very few organized inflammatory lesions, but the bacteria continue to persist within macrophages in the MLN and the animals generally remain disease-free. Finally, chronically infected mice treated with an interferon-γ neutralizing antibody exhibited symptoms of acute systemic infection, with evidence of high levels of bacterial replication in most tissues and high levels of fecal shedding. Thus, interferon-γ, which may affect the level of macrophage activation, plays an essential role in the control of the persistent S. typhimurium infection in mice.

scholarly journals Galleria mellonellaas an infection model for the multi-host pathogenStreptococcus agalactiaereflects hypervirulence of ST283

2018 ◽  
Author(s):  
Anne Six ◽  
Sakranmanee Kranjangwong ◽  
Margaret Crumlish ◽  
Ruth Zadoks ◽  
Daniel Walker
Keyword(s):  
Low Cost ◽  
Group B Streptococcus ◽  
Systemic Infection ◽  
Invasive Disease ◽  
Larval Survival ◽  
Infection Model ◽  
Virulence Determinants ◽  
Bacterial Replication ◽  
Group B ◽  
Dose Dependent

AbstractStreptococcus agalactiae, or group B streptococcus (GBS), infects diverse hosts including humans, economically important livestock and fishes. In the context of human health, GBS is a major cause of neonatal infections and an emerging cause of invasive disease in adults. Here we show that GBS is able to establish a systemic infection inG. mellonellalarvae that is associated with extensive bacterial replication and dose dependent larval survival. This infection model is suitable for use with GBS isolates from both homeothermic and poikilothermic hosts and a hypervirulent sequence type (ST) associated with invasive human disease, ST283, shows increased virulence in this model, indicating it may be useful in studying GBS virulence determinants. In addition, we demonstrate that larval survival can be afforded by antibiotic treatment and so the model may also be useful in the development of novel anti-GBS strategies. The use ofG. mellonellain GBS research has the potential to provide a low cost infection model that could reduce the number of vertebrates used in the study of GBS infection.

scholarly journals YraP Contributes to Cell Envelope Integrity and Virulence ofSalmonella entericaSerovar Typhimurium

2018 ◽  
Vol 86 (11) ◽  
Author(s):  
Faye C. Morris ◽  
Timothy J. Wells ◽  
Jack A. Bryant ◽  
Anna E. Schager ◽  
Yanina R. Sevastsyanovich ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Cell Envelope ◽  
Systemic Infection ◽  
Eukaryotic Cell ◽  
Infection Model ◽  
Content Type ◽  
Protein Levels ◽  
K 12

ABSTRACTMutations in σE-regulated lipoproteins have previously been shown to impact bacterial viability under conditions of stress and duringin vivoinfection. YraP is conserved across a number of Gram-negative pathogens, includingNeisseria meningitidis, where the homolog is a component of the Bexsero meningococcal group B vaccine. Investigations using laboratory-adaptedEscherichia coliK-12 have shown thatyraPmutants have elevated sensitivity to a range of compounds, including detergents and normally ineffective antibiotics. In this study, we investigate the role of the outer membrane lipoprotein YraP in the pathogenesis ofSalmonella entericaserovar Typhimurium. We show that mutations inS. TyphimuriumyraPresult in a defective outer membrane barrier with elevated sensitivity to a range of compounds. This defect is associated with attenuated virulence in an oral infection model and during the early stages of systemic infection. We show that this attenuation is not a result of defects in lipopolysaccharide and O-antigen synthesis, changes in outer membrane protein levels, or the ability to adhere to and invade eukaryotic cell linesin vitro.

scholarly journals The Sisal Virome: Uncovering the Viral Diversity of Agave Varieties Reveals New and Organ-Specific Viruses

2021 ◽  
Vol 9 (8) ◽  
pp. 1704
Author(s):  
Gabriel Quintanilha-Peixoto ◽  
Paula Luize Camargos Fonseca ◽  
Fábio Trigo Raya ◽  
Marina Pupke Marone ◽  
Dener Eduardo Bortolini ◽  
...  
Keyword(s):  
Economic Value ◽  
Systemic Infection ◽  
Lower Number ◽  
Taxa Richness ◽  
Fiber Extraction ◽  
Organ Specific ◽  
Plant Microbiota ◽  
Natural Leaf ◽  
Agave Sisalana ◽  
Rna And Dna

Sisal is a common name for different plant varieties in the genus Agave (especially Agave sisalana) used for high-quality natural leaf fiber extraction. Despite the economic value of these plants, we still lack information about the diversity of viruses (virome) in non-tequilana species from the genus Agave. In this work, by associating RNA and DNA deep sequencing we were able to identify 25 putative viral species infecting A. sisalana, A. fourcroydes, and Agave hybrid 11648, including one strain of Cowpea Mild Mottle Virus (CPMMV) and 24 elements likely representing new viruses. Phylogenetic analysis indicated they belong to at least six viral families: Alphaflexiviridae, Betaflexiviridae, Botourmiaviridae, Closteroviridae, Partitiviridae, Virgaviridae, and three distinct unclassified groups. We observed higher viral taxa richness in roots when compared to leaves and stems. Furthermore, leaves and stems are very similar diversity-wise, with a lower number of taxa and dominance of a single viral species. Finally, approximately 50% of the identified viruses were found in all Agave organs investigated, which suggests that they likely produce a systemic infection. This is the first metatranscriptomics study focused on viral identification in species from the genus Agave. Despite having analyzed symptomless individuals, we identified several viruses supposedly infecting Agave species, including organ-specific and systemic species. Surprisingly, some of these putative viruses are probably infecting microorganisms composing the plant microbiota. Altogether, our results reinforce the importance of unbiased strategies for the identification and monitoring of viruses in plant species, including those with asymptomatic phenotypes.

scholarly journals Importance of Bacterial Replication and Alveolar Macrophage-Independent Clearance Mechanisms during Early Lung Infection with Streptococcus pneumoniae

2015 ◽  
Vol 83 (3) ◽  
pp. 1181-1189 ◽  
Author(s):  
Emilie Camberlein ◽  
Jonathan M. Cohen ◽  
Ricardo José ◽  
Catherine J. Hyams ◽  
Robin Callard ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Alveolar Macrophage ◽  
Half Life ◽  
Doubling Time ◽  
Lung Infection ◽  
Inoculum Size ◽  
High Dose ◽  
Content Type ◽  
Bacterial Replication ◽  
Doubling Times

Although the importance of alveolar macrophages for host immunity during earlyStreptococcus pneumoniaelung infection is well established, the contribution and relative importance of other innate immunity mechanisms and of bacterial factors are less clear. We have used a murine model ofS. pneumoniaeearly lung infection with wild-type, unencapsulated, andpara-amino benzoic acid auxotroph mutant TIGR4 strains to assess the effects of inoculum size, bacterial replication, capsule, and alveolar macrophage-dependent and -independent clearance mechanisms on bacterial persistence within the lungs. Alveolar macrophage-dependent and -independent (calculated indirectly) clearance half-lives and bacterial replication doubling times were estimated using a mathematical model. In this model, after infection with a high-dose inoculum of encapsulatedS. pneumoniae, alveolar macrophage-independent clearance mechanisms were dominant, with a clearance half-life of 24 min compared to 135 min for alveolar macrophage-dependent clearance. In addition, after a high-dose inoculum, successful lung infection required rapid bacterial replication, with an estimatedS. pneumoniaedoubling time of 16 min. The capsule had wide effects on early lung clearance mechanisms, with reduced half-lives of 14 min for alveolar macrophage-independent and 31 min for alveolar macrophage-dependent clearance of unencapsulated bacteria. In contrast, with a lower-dose inoculum, the bacterial doubling time increased to 56 min and theS. pneumoniaealveolar macrophage-dependent clearance half-life improved to 42 min and was largely unaffected by the capsule. These data demonstrate the large effects of bacterial factors (inoculum size, the capsule, and rapid replication) and alveolar macrophage-independent clearance mechanisms during early lung infection withS. pneumoniae.

scholarly journals Branched chain fatty acid synthesis drives tissue-specific innate immune response and  infection dynamics of  Staphylococcus aureus

2021 ◽  
Vol 17 (9) ◽  
pp. e1009930
Author(s):  
Xi Chen ◽  
Wei Ping Teoh ◽  
Madison R. Stock ◽  
Zachary J. Resko ◽  
Francis Alonzo
Keyword(s):  
Fatty Acids ◽  
Staphylococcus Aureus ◽  
Fatty Acid ◽  
Membrane Fluidity ◽  
Unsaturated Fatty Acids ◽  
Cell Envelope ◽  
Acyl Chain ◽  
Dependent Manner ◽  
Infection Dynamics ◽  
Branched Chain

Fatty acid-derived acyl chains of phospholipids and lipoproteins are central to bacterial membrane fluidity and lipoprotein function. Though it can incorporate exogenous unsaturated fatty acids (UFA), Staphylococcus aureus synthesizes branched chain fatty acids (BCFA), not UFA, to modulate or increase membrane fluidity. However, both endogenous BCFA and exogenous UFA can be attached to bacterial lipoproteins. Furthermore, S. aureus membrane lipid content varies based upon the amount of exogenous lipid in the environment. Thus far, the relevance of acyl chain diversity within the S. aureus cell envelope is limited to the observation that attachment of UFA to lipoproteins enhances cytokine secretion by cell lines in a TLR2-dependent manner. Here, we leveraged a BCFA auxotroph of S. aureus and determined that driving UFA incorporation disrupted infection dynamics and increased cytokine production in the liver during systemic infection of mice. In contrast, infection of TLR2-deficient mice restored inflammatory cytokines and bacterial burden to wildtype levels, linking the shift in acyl chain composition toward UFA to detrimental immune activation in vivo. In in vitro studies, bacterial lipoproteins isolated from UFA-supplemented cultures were resistant to lipase-mediated ester hydrolysis and exhibited heightened TLR2-dependent innate cell activation, whereas lipoproteins with BCFA esters were completely inactivated after lipase treatment. These results suggest that de novo synthesis of BCFA reduces lipoprotein-mediated TLR2 activation and improves lipase-mediated hydrolysis making it an important determinant of innate immunity. Overall, this study highlights the potential relevance of cell envelope acyl chain repertoire in infection dynamics of bacterial pathogens.

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