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Infection and Immunity, May 2009, p. 1968-1975, Vol. 77, No. 5
0019-9567/09/$08.00+0     doi:10.1128/IAI.01214-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Capsule Expression and Genotypic Differences among Staphylococcus aureus Isolates from Patients with Chronic or Acute Osteomyelitis{triangledown}

Santiago M. Lattar,1 Lorena P. N. Tuchscherr,2 Roberto L. Caccuri,1,3 Daniela Centrón,1,3 Karsten Becker,2 Claudio A. Alonso,4 Claudia Barberis,4 Graciela Miranda,5 Fernanda R. Buzzola,1,3 Christof von Eiff,2 and Daniel O. Sordelli1,3*

Departamento de Microbiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina,1 Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany,2 CONICET, Buenos Aires, Argentina,3 Hospital de Clínicas José de San Martín, Universidad de Buenos Aires, Buenos Aires, Argentina,4 Policlínico Bancario, Buenos Aires, Argentina5

Received 2 October 2008/ Returned for modification 20 December 2008/ Accepted 27 February 2009

There is ample evidence that Staphylococcus aureus capsular polysaccharide (CP) promotes virulence. Loss of capsule expression, however, may lead to S. aureus persistence in a chronically infected host. This study was conducted to determine the relative prevalence of nonencapsulated S. aureus in patients with chronic and acute osteomyelitis. Only 76/118 (64%) S. aureus isolates from patients with osteomyelitis expressed CP, whereas all 50 isolates from blood cultures of patients with infections other than osteoarticular infections expressed CP (P = 0.0001). A significantly higher prevalence of nonencapsulated S. aureus was found in patients with chronic osteomyelitis (53%) than in those with acute osteomyelitis (21%) (P = 0.0046). S. aureus isolates obtained from multiple specimens from five of six patients with chronic osteomyelitis exhibited phenotypic (expression of CP, {alpha}-hemolysin, β-hemolysin, slime, and the small-colony variant phenotype) and/or genotypic (pulsed-field gel electrophoresis and spa typing) differences. Nonencapsulated S. aureus was recovered from at least one specimen from each chronic osteomyelitis patient. Fourteen isolates obtained from two patients with acute osteomyelitis were indistinguishable from each other within each group, and all produced CP5. In conclusion, we demonstrated that nonencapsulated S. aureus is more frequently isolated from patients with chronic osteomyelitis than from those with acute osteomyelitis, suggesting that loss of CP expression may be advantageous to S. aureus during chronic infection. Our findings on multiple S. aureus isolates from individual patients allow us to suggest that selection of nonencapsulated S. aureus is likely to have occurred in the patient during long-term bone infection.

* Corresponding author. Mailing address: Departamento de Microbiología, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 P-12, C1121ABG Buenos Aires, Argentina. Phone: 54-11 5950 9618. Fax: 54-11 4964 2554. E-mail: sordelli{at}fmed.uba.ar

{triangledown} Published ahead of print on 9 March 2009.

Editor: V. J. DiRita

Infection and Immunity, May 2009, p. 1968-1975, Vol. 77, No. 5
0019-9567/09/$08.00+0     doi:10.1128/IAI.01214-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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