Coagulase-negatives staphylococci (CNS) are Gram-positives cocci commonly regarded as contaminants in clinical microbiology laboratories. Despite belonging to this group, Staphylococcus lugdunensis may cause complicated infections such as endocarditis, skin infections and soft tissue, osteomyelitis, among others. Apart from the formation of biofilms, it has pathogenic features similar to Staphylococcus aureus. It may be mistakenly identified as S. aureus when using rapid identification tests, such as clumping factor in slide coagulase or in agglutination latex tests. It is easily identified through available biochemical tests, such as the presence of ornithine decarboxylase and pyrrolidonyl arylamidase (PYR). It presents sensitivity to most antimicrobial agents. Furthermore, the presence of beta-lactamase and mecA gene should be routinely investigated by testing with chromogenic cephalosporin and cefoxitin susceptibility, respectively. It is convenient to highlight that the interpretative criteria used to evaluate cefoxitin sensitivity are the same recommended for S. aureus and different from those used for other CNS. Despite the fact it is atypical, S. lugdunensis is a virulent pathogen, which must be accurately identified insofar as it will rarely be deemed as a contaminant when isolated from sterile sites.
Staphylococcus lugdunensis; Coagulase-negative staphylococci; Endocarditis; Clumping factor; Cefoxitin
