Occurrence of ica genes for slime synthesis in a collection of Staphylococcus epidermidis strains from orthopedic prosthesis infections.
Staphylococcus epidermidis is a frequent pathogen in infections associated with orthopedic implants. We studied 123 S. epidermidis strains from infections related to orthopedic implants, as regards their ability to express a factor of virulence, namely the slime, an extracellular polysaccharide, which mediates adherence to implants and bacterial colonization. The slime-producing ability was determined by PCR detection of icaA and icaD genes responsible for slime synthesis, and by culture on Congo red agar plates in which slime-producing strains form black colonies, while nonslime-forming ones develop red colonies. 56% of the S. epidermidis isolates were icaA- icaD-positive and grew to become black colonies. In the evaluation of the distribution of slime-forming strains in different sites and types of implants, we found a slight, but not statistically significant, increase in slime-forming strains in total joint prostheses, where tissue compression near the articular faces can form niches in which bacteria crowd, sheltered by the slime. Our findings confirm the role of ica genes as a virulence marker in the pathogenesis of implant-associated orthopedic infections. However, they do not show the existence of a higher frequency of slime-positive strains in a specific type of implant.
Arciola
Carla Renata
CR
Research Laboratory on Biocompatibility of Implant Materials, Rizzoli Orthopedic Institute, Bologna, Italy. carlarenata.arciola@ior.it
Campoccia
Davide
D
Gamberini
Simonetta
S
Donati
M Elena
ME
Baldassarri
Lucilla
L
Montanaro
Lucio
L
D003224:Congo Red; D005798:Genes, Bacterial / Q000502:physiology*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects* / Q000469:parasitology; D009876:Operon; D016133:Polymerase Chain Reaction; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D016459:Prosthesis-Related Infections / Q000382:microbiology*; D013212:Staphylococcus epidermidis / Q000472:pathogenicity*; D014774:Virulence
D011135:Polysaccharides, Bacterial; D003224:Congo Red