Attachment and Biofilm Forming Capabilities of Staphylococcus epidermidis Strains Isolated from Preterm Infants
Staphylococcus epidermidis, a human commensal, is an important opportunistic, biofilm-forming pathogen and the main cause of late onset sepsis in preterm infants, worldwide. In this study we describe the characteristics of S. epidermidis strains causing late onset (>72 h) bloodstream infection in preterm infants and skin isolates from healthy newborns. Attachment and biofilm formation capability were analyzed in microtiter plates and with transmission electron microscopy (TEM). Clonal relationship among strains was studied with pulsed-field gel electrophoresis. Antimicrobial susceptibility testing was performed, as well as the detection of biofilm-associated genes and of the invasiveness marker IS256 with polymerase chain reaction. Blood and skin isolates had similar attachment and biofilm-forming capabilities and biofilm formation was not related to the presence of specific genes. Filament-like membrane structures were seen by TEM early in the attachment close to the device surface, both in blood and skin strains. Nine of the ten blood isolates contained the IS256 and were also resistant to methicillin and gentamicin in contrast to skin strains. S. epidermidis strains causing bloodstream infection in preterm infants exhibit higher antibiotic resistance and are provided with an invasive genetic equipment compared to skin commensal strains. Adhesion capability to a device surface seems to involve bacterial membrane filaments.
We are grateful to Eva Andersson, Birgitta Byström, and Ingrid Lindell for invaluable technical assistance. Parts of this study were presented as a poster presentation at the 3rd Congress of the European Academy of Paediatric Societies, Copenhagen 23–26 October 2010. The study was supported by Grants from the Swedish Research Council (Grant No. 0855), ALF (Karolinska Institutet–Stockholm County Council, Agreement on Medical Research and Training) funding, and the Karolinska Institute Research Funds, as well as from Stiftelsen Samariten, Stiftelsen Barncentrum, Sällskapet Barnavård, Lilla Barnets Fond, and Frimurarbarnhuset Stockholm.
Conflict of interests
The authors have no conflict of interests
This study was approved by the regional ethical committee for medical research (EPN) in Stockholm, Sweden (2007/674-31/1).
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