SORDELLI Daniel Oscar
Capsule expression and genotypic differences among Staphylococcus aureus isolates from patients with chronic or acute osteomyelitis.
LATTAR SM; TUCHSCHERR LPN; CENTRON D; CACCURI RP; ALONSO CA; BARBERIS C; MIRANDA G; BUZZOLA FR; VON EIFF C; SORDELLI DO
INFECTION AND IMMUNITY
Lugar: WASHINGTON DC; Año: 2009 vol. 77 p. 1968 - 1975
There is ample evidence that S. aureus capsule polysaccharide (CP) promotes virulence. Loss of capsule expression, however, may lead to S. aureus persistence in the chronically infected host. This study was conducted to determine the relative prevalence of non-encapsulated 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 expressed CP (P=0.0001). A significantly higher prevalence of non-encapsulated S. aureus was found in patients with chronic (53%) compared with 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, á-hemolysin, â-hemolysin, slime and small-colony variant (SCV) phenotype] and/or genotypic (PFGE and spa typing) differences. Non-encapsulated S. aureus was recovered from at least one specimen from each chronic 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 non-encapsulated S. aureus are more frequently isolated from patients with chronic osteomyelitis, compared with those with acute osteomyelitis, suggesting that loss of CP expression may be advantageous to S. aureus during chronic infection. Our findings in multiple S. aureus isolates from individual patients allowed us to suggest that selection of non-encapsulated S. aureus may have likely occurred in the patient during long term bone infection.