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Key role for clumping factor B in Staphylococcus aureus nasal colonization of humans.

Wertheim HF, Walsh E, Choudhurry R, Melles DC, Boelens HA, Miajlovic H, Verbrugh HA, Foster T, van Belkum A - PLoS Med. (2008)

Bottom Line: Staphylococcus aureus permanently colonizes the vestibulum nasi of one-fifth of the human population, which is a risk factor for autoinfection.The precise mechanisms whereby S. aureus colonizes the nose are still unknown.The human colonization model, in combination with in vitro data, shows that the ClfB protein is a major determinant of nasal-persistent S. aureus carriage and is a candidate target molecule for decolonization strategies.

View Article: PubMed Central - PubMed

Affiliation: Erasmus MC, University Medical Center Rotterdam, Department of Medical Microbiology and Infectious Diseases, Rotterdam, The Netherlands. h.wertheim@erasmusmc.nl

ABSTRACT

Background: Staphylococcus aureus permanently colonizes the vestibulum nasi of one-fifth of the human population, which is a risk factor for autoinfection. The precise mechanisms whereby S. aureus colonizes the nose are still unknown. The staphylococcal cell-wall protein clumping factor B (ClfB) promotes adhesion to squamous epithelial cells in vitro and might be a physiologically relevant colonization factor.

Methods and findings: We define the role of the staphylococcal cytokeratin-binding protein ClfB in the colonization process by artificial inoculation of human volunteers with a wild-type strain and its single locus ClfB knock-out mutant. The wild-type strain adhered to immobilized recombinant human cytokeratin 10 (CK10) in a dose-dependent manner, whereas the ClfB(-) mutant did not. The wild-type strain, when grown to the stationary phase in a poor growth medium, adhered better to CK10, than when the same strain was grown in a nutrient-rich environment. Nasal cultures show that the mutant strain is eliminated from the nares significantly faster than the wild-type strain, with a median of 3 +/- 1 d versus 7 +/- 4 d (p = 0.006). Furthermore, the wild-type strain was still present in the nares of 3/16 volunteers at the end of follow-up, and the mutant strain was not.

Conclusions: The human colonization model, in combination with in vitro data, shows that the ClfB protein is a major determinant of nasal-persistent S. aureus carriage and is a candidate target molecule for decolonization strategies.

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Survival in the Nose of the Wild-Type Strain versus the Mutant Strain(A) Kaplan-Meier survival curve of the 8325–4 S. aureus (solid line) and its ClfB− mutant (DU5997) strain (dashed line) in human nose (last cultured strain in either nostril). All cells of the mutant strain were eliminated after a period of 14 d, which is significantly faster than the elimination rate for the 8325–4 S. aureus strain.(B) Kaplan-Meier survival curve of the 8325–4 S. aureus (WT) and ClfB− mutant (DU5997; dashed line) that were inoculated together as a mix in one nostril.(C) Number of cfu of 8325–4 and DU5997 in follow-up samples.
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pmed-0050017-g004: Survival in the Nose of the Wild-Type Strain versus the Mutant Strain(A) Kaplan-Meier survival curve of the 8325–4 S. aureus (solid line) and its ClfB− mutant (DU5997) strain (dashed line) in human nose (last cultured strain in either nostril). All cells of the mutant strain were eliminated after a period of 14 d, which is significantly faster than the elimination rate for the 8325–4 S. aureus strain.(B) Kaplan-Meier survival curve of the 8325–4 S. aureus (WT) and ClfB− mutant (DU5997; dashed line) that were inoculated together as a mix in one nostril.(C) Number of cfu of 8325–4 and DU5997 in follow-up samples.

Mentions: The overall median survival time of the 8325–4 strain was significantly higher than the DU5997 strain: a median of 7.0 (95% confidence interval [CI], ±4 d; interquartile range: 2–21 d) compared to 3 (95% CI, ±1 d; interquartile range: 2–4 d; log-rank: p = 0.006; Figure 4A). The viable counts of S. aureus after inoculation were always higher for the 8325–4 strain (Figure 4C), but not significantly. Inoculated S. aureus cells could be cultured for a longer mean follow-up period from intermittent carriers (18.3 ± 12.1 d) than from persistent (7.0 ± 8.6 d) or non-carriers (5.4 ± 6.3 d; one-way ANOVA: p = 0.025). None of the volunteers used antibiotics during the follow-up period. Identification of the inoculation strains was confirmed by tetracycline susceptibility testing, PFGE, and PCR analysis of the clfB locus.


Key role for clumping factor B in Staphylococcus aureus nasal colonization of humans.

Wertheim HF, Walsh E, Choudhurry R, Melles DC, Boelens HA, Miajlovic H, Verbrugh HA, Foster T, van Belkum A - PLoS Med. (2008)

Survival in the Nose of the Wild-Type Strain versus the Mutant Strain(A) Kaplan-Meier survival curve of the 8325–4 S. aureus (solid line) and its ClfB− mutant (DU5997) strain (dashed line) in human nose (last cultured strain in either nostril). All cells of the mutant strain were eliminated after a period of 14 d, which is significantly faster than the elimination rate for the 8325–4 S. aureus strain.(B) Kaplan-Meier survival curve of the 8325–4 S. aureus (WT) and ClfB− mutant (DU5997; dashed line) that were inoculated together as a mix in one nostril.(C) Number of cfu of 8325–4 and DU5997 in follow-up samples.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2194749&req=5

pmed-0050017-g004: Survival in the Nose of the Wild-Type Strain versus the Mutant Strain(A) Kaplan-Meier survival curve of the 8325–4 S. aureus (solid line) and its ClfB− mutant (DU5997) strain (dashed line) in human nose (last cultured strain in either nostril). All cells of the mutant strain were eliminated after a period of 14 d, which is significantly faster than the elimination rate for the 8325–4 S. aureus strain.(B) Kaplan-Meier survival curve of the 8325–4 S. aureus (WT) and ClfB− mutant (DU5997; dashed line) that were inoculated together as a mix in one nostril.(C) Number of cfu of 8325–4 and DU5997 in follow-up samples.
Mentions: The overall median survival time of the 8325–4 strain was significantly higher than the DU5997 strain: a median of 7.0 (95% confidence interval [CI], ±4 d; interquartile range: 2–21 d) compared to 3 (95% CI, ±1 d; interquartile range: 2–4 d; log-rank: p = 0.006; Figure 4A). The viable counts of S. aureus after inoculation were always higher for the 8325–4 strain (Figure 4C), but not significantly. Inoculated S. aureus cells could be cultured for a longer mean follow-up period from intermittent carriers (18.3 ± 12.1 d) than from persistent (7.0 ± 8.6 d) or non-carriers (5.4 ± 6.3 d; one-way ANOVA: p = 0.025). None of the volunteers used antibiotics during the follow-up period. Identification of the inoculation strains was confirmed by tetracycline susceptibility testing, PFGE, and PCR analysis of the clfB locus.

Bottom Line: Staphylococcus aureus permanently colonizes the vestibulum nasi of one-fifth of the human population, which is a risk factor for autoinfection.The precise mechanisms whereby S. aureus colonizes the nose are still unknown.The human colonization model, in combination with in vitro data, shows that the ClfB protein is a major determinant of nasal-persistent S. aureus carriage and is a candidate target molecule for decolonization strategies.

View Article: PubMed Central - PubMed

Affiliation: Erasmus MC, University Medical Center Rotterdam, Department of Medical Microbiology and Infectious Diseases, Rotterdam, The Netherlands. h.wertheim@erasmusmc.nl

ABSTRACT

Background: Staphylococcus aureus permanently colonizes the vestibulum nasi of one-fifth of the human population, which is a risk factor for autoinfection. The precise mechanisms whereby S. aureus colonizes the nose are still unknown. The staphylococcal cell-wall protein clumping factor B (ClfB) promotes adhesion to squamous epithelial cells in vitro and might be a physiologically relevant colonization factor.

Methods and findings: We define the role of the staphylococcal cytokeratin-binding protein ClfB in the colonization process by artificial inoculation of human volunteers with a wild-type strain and its single locus ClfB knock-out mutant. The wild-type strain adhered to immobilized recombinant human cytokeratin 10 (CK10) in a dose-dependent manner, whereas the ClfB(-) mutant did not. The wild-type strain, when grown to the stationary phase in a poor growth medium, adhered better to CK10, than when the same strain was grown in a nutrient-rich environment. Nasal cultures show that the mutant strain is eliminated from the nares significantly faster than the wild-type strain, with a median of 3 +/- 1 d versus 7 +/- 4 d (p = 0.006). Furthermore, the wild-type strain was still present in the nares of 3/16 volunteers at the end of follow-up, and the mutant strain was not.

Conclusions: The human colonization model, in combination with in vitro data, shows that the ClfB protein is a major determinant of nasal-persistent S. aureus carriage and is a candidate target molecule for decolonization strategies.

Show MeSH
Related in: MedlinePlus