Staphylococcus epidermidis - virulence factors and innate ... - Munin

excluded from the analyses, and the remaining 18 values were averaged. S. epidermidis ATCC
35984 (RP62A) was the positive and S. epidermidis ATCC 122228 was negative control. Isolates
with OD 570 > 0.12 were defined as biofilm producers.
3.2.3 Antimicrobial susceptibility testing
Paper I:
We determined the minimal inhibitory concentration (MIC) of oxacillin, gentamicin, fusidic acid,
clindamycin and vancomycin with Etest (AB Biodisk, Solna, Sweden) and ciprofloxacin by disk
diffusion test. Antibiotic susceptibility was interpreted according to the Clinical and Laboratory
Standards Institute guidelines (411).
3.2.4 Detection of resistance and virulence genes
Paper I:
Detection of central resistance- and virulence genes was done by polymerase chain reaction
(PCR). Bacterial DNA was extracted by the boiling method (409). We performed PCRs using
previously reported primers for i) the methicillin resistance gene (mecA) (412), ii) SCCmec type
(413) iii) one central aminoglycoside resistance gene (aac(6')-Ie-aph(2")-Ia) (288), iv) a marker
of the ica-operon encoding biofilm accumulation (icaD) (312) and v) ACME-arcA and ACMEopp3
(391, 397).
3.2.5 Phylogenetic analysis
Paper I:
Pulsed Field Gel Electrophoresis (PFGE) was used to determine the relatedness between the
bacterial isolates as described previously (409). PFGE patterns were analyzed by GelCompar II
version 2.5 (Applied Maths, Belgium). Isolates with ≥ 95 % similarity were considered to be
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