[Clinically significant coagulase-negative staphylococci: most frequent species and virulence factors]

Coagulase-negative staphylococci have emerged as responsible for a large number of infections. However, it is often difficult to assess its pathogenic role or to discard it as a contaminant.

The goal of this study was to identify clinically significant coagulase-negative staphylococci to the species level and their virulence factors. Isolates came from patients consulting at the San Roque Laboratory from 2009 to 2011.

Species identification was performed by De Paulis et al simplified method. Production of biofilm, hemolysins, lipases, lecithinases and DNase were determined by conventional methods; methicillin-resistance by diffusion method and mecA and Panton-Valentine genes, by multiplex PCR.

Out of 64 isolates, 40.6% were S. epidermidis; 20.3%, S. haemolyticus, and 15.6%, S. lugdunensis. Biofilm production was detected in 73.1% of S. epidermidis, 53.8% of S. haemolyticus and 40% of S. lugdunensis. mecA gene was identified in 69.2% of S. epidermidis, 92.3% of S. haemolyticus and none of S. lugdunensis. 83% of mecA (+) S. epidermidis isolates were biofilm producers as compared to 50% of the mecA (-).

The frequency of S. lugdunensis, the most virulent coagulase-negative staphylococci species, was relatively high. The main virulence factor in S. epidermidis was biofilm production, being higher in those resistant to methicillin.