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Phenotypic Variation Is Almost Entirely Independent of the Host-Pathogen Relationship in Clinical Isolates of S. aureus.

Land AD, Hogan P, Fritz S, Levin PA - PLoS ONE (2015)

Bottom Line: Biofilm formation, hemolysis and pigment formation have all been associated with virulence in mice.One exception was a small, but significant, correlation between an increased propensity for biofilm formation and isolation from skin and soft tissue infections (SSTIs).These data suggest the existence of significant evolutionary pressure on the S. aureus genome and highlight a role for host factors as a strong determinant of the host-pathogen relationship.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.

ABSTRACT

Background: A key feature of Staphylococcus aureus biology is its ability to switch from an apparently benign colonizer of ~30% of the population to a cutaneous pathogen, to a deadly invasive pathogen. Little is known about the mechanisms driving this transition or the propensity of different S. aureus strains to engender different types of host-pathogen interactions. At the same time, significant weight has been given to the role of specific in vitro phenotypes in S. aureus virulence. Biofilm formation, hemolysis and pigment formation have all been associated with virulence in mice.

Design: To determine if there is a correlation between in vitro phenotype and the three types of host-pathogen relationships commonly exhibited by S. aureus in the context of its natural human host, we assayed 300 clinical isolates for phenotypes implicated in virulence including hemolysis, sensitivity to autolysis, and biofilm formation. For comparative purposes, we also assayed phenotype in 9 domesticated S. aureus strains routinely used for analysis of virulence determinants in laboratory settings.

Results: Strikingly, the clinical strains exhibited significant phenotypic uniformity in each of the assays evaluated in this study. One exception was a small, but significant, correlation between an increased propensity for biofilm formation and isolation from skin and soft tissue infections (SSTIs). In contrast, we observed a high degree of phenotypic variation between common laboratory strains that exhibit virulence in mouse models. These data suggest the existence of significant evolutionary pressure on the S. aureus genome and highlight a role for host factors as a strong determinant of the host-pathogen relationship. In addition, the high degree of variation between laboratory strains emphasizes the need for caution when applying data obtained in one lab strain to the analysis of another.

No MeSH data available.


Related in: MedlinePlus

Hemolytic activity differs significantly between closely related laboratory, CA-MRSA and HA-MRSA strains.(A) Hemolytic activity was assessed by growing single colonies of S. aureus up to exponential phase in TSB, then back-diluted to an OD600 of ~0.05. Diluted cultures are then spotted on TSB agar plates supplemented with 5% sheep’s blood and incubated for 48hrs. Following incubation the “zones of hemolytic clearing” are measured and recorded. (B) Graphical representation of the “zones of hemolytic clearing” observed in reference strains. Data shown is average of 3 biological replicates. Error bars represent standard deviation.
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pone.0129670.g004: Hemolytic activity differs significantly between closely related laboratory, CA-MRSA and HA-MRSA strains.(A) Hemolytic activity was assessed by growing single colonies of S. aureus up to exponential phase in TSB, then back-diluted to an OD600 of ~0.05. Diluted cultures are then spotted on TSB agar plates supplemented with 5% sheep’s blood and incubated for 48hrs. Following incubation the “zones of hemolytic clearing” are measured and recorded. (B) Graphical representation of the “zones of hemolytic clearing” observed in reference strains. Data shown is average of 3 biological replicates. Error bars represent standard deviation.

Mentions: There was significant variation of hemolytic activity amongst the domesticated strains of S. aureus including the closely related strains, NCTC 8325 and SH1000. A large zone of hemolysis was observed for NCTC 8325 that was approximately three times the size of that observed for SH1000 (Fig 4B). Three strains, UAMS1, N315, and Mu50 showed no hemolytic activity in this assay. The three CA-MRSA strains also exhibited a wide range of variation with regard to hemolytic activity, with zones of clearing in TCH1516, FPR3757, and MW2 showed 9mm, 4mm and 1mm zones respectively, indicating a significant difference in each strain’s ability to lyse sheep red blood cells (Fig 4A and 4B).


Phenotypic Variation Is Almost Entirely Independent of the Host-Pathogen Relationship in Clinical Isolates of S. aureus.

Land AD, Hogan P, Fritz S, Levin PA - PLoS ONE (2015)

Hemolytic activity differs significantly between closely related laboratory, CA-MRSA and HA-MRSA strains.(A) Hemolytic activity was assessed by growing single colonies of S. aureus up to exponential phase in TSB, then back-diluted to an OD600 of ~0.05. Diluted cultures are then spotted on TSB agar plates supplemented with 5% sheep’s blood and incubated for 48hrs. Following incubation the “zones of hemolytic clearing” are measured and recorded. (B) Graphical representation of the “zones of hemolytic clearing” observed in reference strains. Data shown is average of 3 biological replicates. Error bars represent standard deviation.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4476556&req=5

pone.0129670.g004: Hemolytic activity differs significantly between closely related laboratory, CA-MRSA and HA-MRSA strains.(A) Hemolytic activity was assessed by growing single colonies of S. aureus up to exponential phase in TSB, then back-diluted to an OD600 of ~0.05. Diluted cultures are then spotted on TSB agar plates supplemented with 5% sheep’s blood and incubated for 48hrs. Following incubation the “zones of hemolytic clearing” are measured and recorded. (B) Graphical representation of the “zones of hemolytic clearing” observed in reference strains. Data shown is average of 3 biological replicates. Error bars represent standard deviation.
Mentions: There was significant variation of hemolytic activity amongst the domesticated strains of S. aureus including the closely related strains, NCTC 8325 and SH1000. A large zone of hemolysis was observed for NCTC 8325 that was approximately three times the size of that observed for SH1000 (Fig 4B). Three strains, UAMS1, N315, and Mu50 showed no hemolytic activity in this assay. The three CA-MRSA strains also exhibited a wide range of variation with regard to hemolytic activity, with zones of clearing in TCH1516, FPR3757, and MW2 showed 9mm, 4mm and 1mm zones respectively, indicating a significant difference in each strain’s ability to lyse sheep red blood cells (Fig 4A and 4B).

Bottom Line: Biofilm formation, hemolysis and pigment formation have all been associated with virulence in mice.One exception was a small, but significant, correlation between an increased propensity for biofilm formation and isolation from skin and soft tissue infections (SSTIs).These data suggest the existence of significant evolutionary pressure on the S. aureus genome and highlight a role for host factors as a strong determinant of the host-pathogen relationship.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Washington University in Saint Louis, Saint Louis, Missouri, United States of America.

ABSTRACT

Background: A key feature of Staphylococcus aureus biology is its ability to switch from an apparently benign colonizer of ~30% of the population to a cutaneous pathogen, to a deadly invasive pathogen. Little is known about the mechanisms driving this transition or the propensity of different S. aureus strains to engender different types of host-pathogen interactions. At the same time, significant weight has been given to the role of specific in vitro phenotypes in S. aureus virulence. Biofilm formation, hemolysis and pigment formation have all been associated with virulence in mice.

Design: To determine if there is a correlation between in vitro phenotype and the three types of host-pathogen relationships commonly exhibited by S. aureus in the context of its natural human host, we assayed 300 clinical isolates for phenotypes implicated in virulence including hemolysis, sensitivity to autolysis, and biofilm formation. For comparative purposes, we also assayed phenotype in 9 domesticated S. aureus strains routinely used for analysis of virulence determinants in laboratory settings.

Results: Strikingly, the clinical strains exhibited significant phenotypic uniformity in each of the assays evaluated in this study. One exception was a small, but significant, correlation between an increased propensity for biofilm formation and isolation from skin and soft tissue infections (SSTIs). In contrast, we observed a high degree of phenotypic variation between common laboratory strains that exhibit virulence in mouse models. These data suggest the existence of significant evolutionary pressure on the S. aureus genome and highlight a role for host factors as a strong determinant of the host-pathogen relationship. In addition, the high degree of variation between laboratory strains emphasizes the need for caution when applying data obtained in one lab strain to the analysis of another.

No MeSH data available.


Related in: MedlinePlus