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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

Laboratory strains Newman and UAMS1, together with slow growing HA and CA-MRSA strains exhibit poor biofilm formation.To determine the relative ability of S. aureus to form biofilms we used a standard 96-well plate assay on each of our staphylococcal strains [70,71]. (A) Single colonies of S. aureus were grown overnight in TSB + glucose. Cultures were backdiluted to an OD600 of 0.005 in TSB + glucose and 100ul aliquots of each strain are plated in triplicate in 96 well microtiter plates. Microtiter plates were grown statically at 37°C for 24hrs. Unattached cells are discarded and the remaining attached cells are then stained with crystal violet. Results depicted here represent the mean and standard deviation of 12 replicates of each reference strain type (B) Representative image of the crystal violet staining of microtiter plates for each reference strain. Images are taken from above.
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pone.0129670.g003: Laboratory strains Newman and UAMS1, together with slow growing HA and CA-MRSA strains exhibit poor biofilm formation.To determine the relative ability of S. aureus to form biofilms we used a standard 96-well plate assay on each of our staphylococcal strains [70,71]. (A) Single colonies of S. aureus were grown overnight in TSB + glucose. Cultures were backdiluted to an OD600 of 0.005 in TSB + glucose and 100ul aliquots of each strain are plated in triplicate in 96 well microtiter plates. Microtiter plates were grown statically at 37°C for 24hrs. Unattached cells are discarded and the remaining attached cells are then stained with crystal violet. Results depicted here represent the mean and standard deviation of 12 replicates of each reference strain type (B) Representative image of the crystal violet staining of microtiter plates for each reference strain. Images are taken from above.

Mentions: To determine the relative ability of the domesticated S. aureus strains to form biofilms we used a standard 96-well plate assay on each of our staphylococcal strains (Materials and Methods). Single colonies of S. aureus were grown overnight in TSB + glucose. Cultures were backdiluted to an OD600 of 0.005 in TSB + glucose and 100ul aliquots of each strain are plated in triplicate in 96 well microtiter plates. Microtiter plates were grown statically at 37°C for 24hrs. The domesticated strains tested in the biofilm assays exhibited a high degree of variation (Fig 3).


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)

Laboratory strains Newman and UAMS1, together with slow growing HA and CA-MRSA strains exhibit poor biofilm formation.To determine the relative ability of S. aureus to form biofilms we used a standard 96-well plate assay on each of our staphylococcal strains [70,71]. (A) Single colonies of S. aureus were grown overnight in TSB + glucose. Cultures were backdiluted to an OD600 of 0.005 in TSB + glucose and 100ul aliquots of each strain are plated in triplicate in 96 well microtiter plates. Microtiter plates were grown statically at 37°C for 24hrs. Unattached cells are discarded and the remaining attached cells are then stained with crystal violet. Results depicted here represent the mean and standard deviation of 12 replicates of each reference strain type (B) Representative image of the crystal violet staining of microtiter plates for each reference strain. Images are taken from above.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4476556&req=5

pone.0129670.g003: Laboratory strains Newman and UAMS1, together with slow growing HA and CA-MRSA strains exhibit poor biofilm formation.To determine the relative ability of S. aureus to form biofilms we used a standard 96-well plate assay on each of our staphylococcal strains [70,71]. (A) Single colonies of S. aureus were grown overnight in TSB + glucose. Cultures were backdiluted to an OD600 of 0.005 in TSB + glucose and 100ul aliquots of each strain are plated in triplicate in 96 well microtiter plates. Microtiter plates were grown statically at 37°C for 24hrs. Unattached cells are discarded and the remaining attached cells are then stained with crystal violet. Results depicted here represent the mean and standard deviation of 12 replicates of each reference strain type (B) Representative image of the crystal violet staining of microtiter plates for each reference strain. Images are taken from above.
Mentions: To determine the relative ability of the domesticated S. aureus strains to form biofilms we used a standard 96-well plate assay on each of our staphylococcal strains (Materials and Methods). Single colonies of S. aureus were grown overnight in TSB + glucose. Cultures were backdiluted to an OD600 of 0.005 in TSB + glucose and 100ul aliquots of each strain are plated in triplicate in 96 well microtiter plates. Microtiter plates were grown statically at 37°C for 24hrs. The domesticated strains tested in the biofilm assays exhibited a high degree of variation (Fig 3).

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