Susceptibility patterns and the role of extracellular DNA in Staphylococcus epidermidis biofilm resistance to physico-chemical stress exposure

Table 2 Impacts of sub-lethal physico-chemical stresses on eDNA release by S. epidermidis biofilm and planktonic cells

Type of culture	Mean ± SEM of eDNA yield in ng/μL by cells exposed to sub-lethal stresses
Type of culture	Heat	NaCl	NaOCl	H₂O₂
Biofilm
Untreated controls	0.110 ± 0.019	0.482 ± 0.159	0.089 ± 0.021	0.231 ± 0.056
Treated cells	0.221 ± 0.058	0.285 ± 0.095	0.292 ± 0.072	0.451 ± 0.095
	p = 0.0098	p = 0.3271	p = 0.0005	p = 0.0005
Planktonic
Untreated controls	0.405 ± 0.101	0.242 ± 0.067	0.526 ± 0.128	0.137 ± 0.031
Treated cells	0.394 ± 0.071	0.219 ± 0.089	0.536 ± 0.123	0.112 ± 0.015
	p = 0.7910	p = 0.6772	p = 0.9097	p = 0.7910

S. epidermidis biofilm and planktonic cultures were subjected to heat (25 and 50 °C), NaCl (0 and 0.8 M), NaOCl (0 and 5 mM) and H₂O₂ (0 and 50 μM) for 60 min. Italics indicate statistical significance (p < 0.05) between stress treated cultures and the untreated controls as determined by Wilcoxon matched-pairs signed rank test

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