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Pathophysiological Mechanisms of Staphylococcus Non-aureus Bone and Joint Infection: Interspecies Homogeneity and Specific Behavior of S. pseudintermedius.

Maali Y, Martins-Simões P, Valour F, Bouvard D, Rasigade JP, Bes M, Haenni M, Ferry T, Laurent F, Trouillet-Assant S - Front Microbiol (2016)

Bottom Line: Compared to S. aureus, S. pseudintermedius was the only species that significantly adhered to human fibronectin.These results suggest the involvement of β1 integrin in the invasion process, although this mechanism was previously restricted to S. aureus.In summary, our results suggest that internalization into NPPCs is not a classical pathophysiologic mechanism of SNA BJIs.

View Article: PubMed Central - PubMed

Affiliation: Centre International de Recherche en Infectiologie, INSERM U1111, CNRS UMR5308, Université de Lyon 1, ENS de Lyon, Team "Pathogenesis of staphylococcal infections"Lyon, France; Department of Clinical Microbiology, Northern Hospital Group, Hospices Civils de LyonLyon, France.

ABSTRACT
Implicated in more than 60% of bone and joint infections (BJIs), Staphylococci have a particular tropism for osteoarticular tissue and lead to difficult-to-treat clinical infections. To date, Staphylococcus aureus internalization in non-professional phagocytic cells (NPPCs) is a well-explored virulence mechanism involved in BJI chronicity. Conversely, the pathophysiological pathways associated with Staphylococcus non-aureus (SNA) BJIs have scarcely been studied despite their high prevalence. In this study, 15 reference strains from 15 different SNA species were compared in terms of (i) adhesion to human fibronectin based on adhesion microplate assays and (ii) internalization ability, intracellular persistence and cytotoxicity based on an in vitro infection model using human osteoblasts. Compared to S. aureus, S. pseudintermedius was the only species that significantly adhered to human fibronectin. This species was also associated with high (even superior to S. aureus) internalization ability, intracellular persistence and cytotoxicity. These findings were confirmed using a panel of 17 different S. pseudintermedius isolates. Additionally, S. pseudintermedius internalization by osteoblasts was completely abolished in β1 integrin-deficient murine osteoblasts. These results suggest the involvement of β1 integrin in the invasion process, although this mechanism was previously restricted to S. aureus. In summary, our results suggest that internalization into NPPCs is not a classical pathophysiologic mechanism of SNA BJIs. S. pseudintermedius appears to be an exception, and its ability to invade and subsequently induce cytotoxicity in NPPCs could explain its severe and necrotic forms of infection, notably in dogs, which exhibit a high prevalence of S. pseudintermedius infection.

No MeSH data available.


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Determination of the involvement of β1 integrin in the S. pseudintermedius internalization process using murine osteoblast cell lines (OB-β1fl/fl and OB-β1-/-) with functional and non-functional β1 subunits, respectively. Internalization capacity of S. aureus 8325-4 (positive control), DU5883 S. aureus Δfnb (negative control) and the reference strain S. pseudintermedius LMG 22219 in OB-β1fl/fl and OB-β1-/- osteoblasts measured 3 h post-infection derived from three experiments performed in triplicate. The bilateral Mann–Whitney test was used to compare the data obtained for the OB-β1fl/fl and OB-β1-/- osteoblasts at an α risk of 0.05 (∗∗∗p < 0.001).
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Figure 3: Determination of the involvement of β1 integrin in the S. pseudintermedius internalization process using murine osteoblast cell lines (OB-β1fl/fl and OB-β1-/-) with functional and non-functional β1 subunits, respectively. Internalization capacity of S. aureus 8325-4 (positive control), DU5883 S. aureus Δfnb (negative control) and the reference strain S. pseudintermedius LMG 22219 in OB-β1fl/fl and OB-β1-/- osteoblasts measured 3 h post-infection derived from three experiments performed in triplicate. The bilateral Mann–Whitney test was used to compare the data obtained for the OB-β1fl/fl and OB-β1-/- osteoblasts at an α risk of 0.05 (∗∗∗p < 0.001).

Mentions: To determine if the internalization mechanism of S. pseudintermedius in osteoblasts involves the cellular integrin α5β1, as described for S. aureus, an in vitro model comparing two murine osteoblast cell lines, OB-β1fl/fl and OB-β1-/- (i.e., with and without β1 integrins, respectively), was used (Figure 3). We evaluated the internalization ability of S. aureus 8325-4 (positive control), S. aureus DU5883 (negative control), and S. pseudintermedius LMG 22219 (reference strain). As expected, although the rate of internalization of the OB-β1fl/fl cells reached 1.14 ± 0.41% of the inoculum for S. aureus 8325-4, a complete loss of internalization was observed for the OB-β1-/- cells (0.01 ± 0.01%, p < 0.001). Similarly, the S. pseudintermedius strain demonstrated a high capacity of internalization among OB-β1fl/fl cells (3.12 ± 1.2% of the inoculum), but this capacity was abolished in OB-β1-/- cells (0.03 ± 0.02%, p < 0.001). Of note, internalization of S. pseudintermedius into OB-β1fl/fl osteoblasts was 2.7-fold higher than the internalization of the S. aureus strain (p < 0.001). These data demonstrated that the mechanism underlying S. pseudintermedius internalization is β1 integrin dependent.


Pathophysiological Mechanisms of Staphylococcus Non-aureus Bone and Joint Infection: Interspecies Homogeneity and Specific Behavior of S. pseudintermedius.

Maali Y, Martins-Simões P, Valour F, Bouvard D, Rasigade JP, Bes M, Haenni M, Ferry T, Laurent F, Trouillet-Assant S - Front Microbiol (2016)

Determination of the involvement of β1 integrin in the S. pseudintermedius internalization process using murine osteoblast cell lines (OB-β1fl/fl and OB-β1-/-) with functional and non-functional β1 subunits, respectively. Internalization capacity of S. aureus 8325-4 (positive control), DU5883 S. aureus Δfnb (negative control) and the reference strain S. pseudintermedius LMG 22219 in OB-β1fl/fl and OB-β1-/- osteoblasts measured 3 h post-infection derived from three experiments performed in triplicate. The bilateral Mann–Whitney test was used to compare the data obtained for the OB-β1fl/fl and OB-β1-/- osteoblasts at an α risk of 0.05 (∗∗∗p < 0.001).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940379&req=5

Figure 3: Determination of the involvement of β1 integrin in the S. pseudintermedius internalization process using murine osteoblast cell lines (OB-β1fl/fl and OB-β1-/-) with functional and non-functional β1 subunits, respectively. Internalization capacity of S. aureus 8325-4 (positive control), DU5883 S. aureus Δfnb (negative control) and the reference strain S. pseudintermedius LMG 22219 in OB-β1fl/fl and OB-β1-/- osteoblasts measured 3 h post-infection derived from three experiments performed in triplicate. The bilateral Mann–Whitney test was used to compare the data obtained for the OB-β1fl/fl and OB-β1-/- osteoblasts at an α risk of 0.05 (∗∗∗p < 0.001).
Mentions: To determine if the internalization mechanism of S. pseudintermedius in osteoblasts involves the cellular integrin α5β1, as described for S. aureus, an in vitro model comparing two murine osteoblast cell lines, OB-β1fl/fl and OB-β1-/- (i.e., with and without β1 integrins, respectively), was used (Figure 3). We evaluated the internalization ability of S. aureus 8325-4 (positive control), S. aureus DU5883 (negative control), and S. pseudintermedius LMG 22219 (reference strain). As expected, although the rate of internalization of the OB-β1fl/fl cells reached 1.14 ± 0.41% of the inoculum for S. aureus 8325-4, a complete loss of internalization was observed for the OB-β1-/- cells (0.01 ± 0.01%, p < 0.001). Similarly, the S. pseudintermedius strain demonstrated a high capacity of internalization among OB-β1fl/fl cells (3.12 ± 1.2% of the inoculum), but this capacity was abolished in OB-β1-/- cells (0.03 ± 0.02%, p < 0.001). Of note, internalization of S. pseudintermedius into OB-β1fl/fl osteoblasts was 2.7-fold higher than the internalization of the S. aureus strain (p < 0.001). These data demonstrated that the mechanism underlying S. pseudintermedius internalization is β1 integrin dependent.

Bottom Line: Compared to S. aureus, S. pseudintermedius was the only species that significantly adhered to human fibronectin.These results suggest the involvement of β1 integrin in the invasion process, although this mechanism was previously restricted to S. aureus.In summary, our results suggest that internalization into NPPCs is not a classical pathophysiologic mechanism of SNA BJIs.

View Article: PubMed Central - PubMed

Affiliation: Centre International de Recherche en Infectiologie, INSERM U1111, CNRS UMR5308, Université de Lyon 1, ENS de Lyon, Team "Pathogenesis of staphylococcal infections"Lyon, France; Department of Clinical Microbiology, Northern Hospital Group, Hospices Civils de LyonLyon, France.

ABSTRACT
Implicated in more than 60% of bone and joint infections (BJIs), Staphylococci have a particular tropism for osteoarticular tissue and lead to difficult-to-treat clinical infections. To date, Staphylococcus aureus internalization in non-professional phagocytic cells (NPPCs) is a well-explored virulence mechanism involved in BJI chronicity. Conversely, the pathophysiological pathways associated with Staphylococcus non-aureus (SNA) BJIs have scarcely been studied despite their high prevalence. In this study, 15 reference strains from 15 different SNA species were compared in terms of (i) adhesion to human fibronectin based on adhesion microplate assays and (ii) internalization ability, intracellular persistence and cytotoxicity based on an in vitro infection model using human osteoblasts. Compared to S. aureus, S. pseudintermedius was the only species that significantly adhered to human fibronectin. This species was also associated with high (even superior to S. aureus) internalization ability, intracellular persistence and cytotoxicity. These findings were confirmed using a panel of 17 different S. pseudintermedius isolates. Additionally, S. pseudintermedius internalization by osteoblasts was completely abolished in β1 integrin-deficient murine osteoblasts. These results suggest the involvement of β1 integrin in the invasion process, although this mechanism was previously restricted to S. aureus. In summary, our results suggest that internalization into NPPCs is not a classical pathophysiologic mechanism of SNA BJIs. S. pseudintermedius appears to be an exception, and its ability to invade and subsequently induce cytotoxicity in NPPCs could explain its severe and necrotic forms of infection, notably in dogs, which exhibit a high prevalence of S. pseudintermedius infection.

No MeSH data available.


Related in: MedlinePlus