Biofilm formation by Staphylococcus aureus clinical isolates correlates with the infection type

Abstract

Background: Biofilms are involved in many Staphylococcus aureus infections, but relation of biofilm formation and the infection types or the clinical outcomes remain unclear.

Methods: We measured biofilm formation, with a microtiter plate assay, of a collection of methicillin-sensitive clinical isolates from 159 invasive S. aureus infections, encompassing all cases occurring within a hospital catchment area during two years, and from additional 49 non-invasive skin infections from the same region. Results were related to available clinical and microbiological documentation.

Results: Isolates from medical device infections (intravenous line-associated and prosthetic joint infections), as well as isolates from superficial skin infections, were particularly proficient in forming biofilms. No increased biofilm-forming capacity was seen in isolates from endocarditis, osteomyelitis, or other infections. There was also a correlation of biofilm formation with the agr type of the isolates. Thicker biofilms were more resistant to antibiotic treatment in vitro. No correlation between biofilm formation and clinical outcomes was noted.

Conclusions: S. aureus isolates from ‘classical’ biofilm-related infections, but also from superficial skin infections, are especially proficient in forming biofilms. There is, however, no obvious relation of biofilm-forming capacity of isolates and the clinical outcome of the infection, and more studies on this issue are needed.

Keywords:

• Biofilm
• Staphylococcus aureus
• clinical outcome
• skin
• antibiotic sensitivity
• agr

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Swedish Society for Medical Research under Fellowship for Postdoctoral Scholars; Swedish Medical Research Council under Grant 523-2013-2750; Gothenburg Medical Society under Grant 778031; Scandinavian Society for Antimicrobial Chemotherapy Foundation under Grant 781191; Rune och Ulla Amlövs Stiftelse för Neurologisk och Reumatologisk Forskning; Adlerbertska Forskningsstiftelsen; Institute for Medicine, Gothenburg University; NIH Public Health Service Grant AI083211 (Project 3); and Department of Veteran Affairs Merit Award [I01 BX002711].