Abstract
BackgroundOver 65% of human infections are ascribed to bacterial biofilms that are often highly resistant to antibiotics and host immunity. Staphylococcus epidermidis is the predominant cause of recurrent nosocomial and biofilm-related infections. However, the susceptibility patterns of S. epidermidis biofilms to physico-chemical stress induced by commonly recommended disinfectants [(heat, sodium chloride (NaCl), sodium hypochlorite (NaOCl) and hydrogen peroxide (H2O2)] in domestic and human healthcare settings remains largely unknown. Further, the molecular mechanisms of bacterial biofilms resistance to the physico-chemical stresses remain unclear. Growing evidence demonstrates that extracellular DNA (eDNA) protects bacterial biofilms against antibiotics. However, the role of eDNA as a potential mechanism underlying S. epidermidis biofilms resistance to physico-chemical stress exposure is yet to be understood. Therefore, this study aimed to evaluate the susceptibility patterns of and eDNA release by S. epidermidis biofilm and planktonic cells to physico-chemical stress exposure.ResultsS. epidermidis biofilms exposed to physico-chemical stress conditions commonly recommended for disinfection [heat (60 °C), 1.72 M NaCl, solution containing 150 μL of waterguard (0.178 M NaOCl) in 1 L of water or 1.77 M H2O2] for 30 and 60 min exhibited lower log reductions of CFU/mL than the corresponding planktonic cells (p < 0.0001). The eDNA released by sub-lethal heat (50 °C)-treated S. epidermidis biofilm and planktonic cells was not statistically different (p = 0.8501). However, 50 °C-treated S. epidermidis biofilm cells released significantly increased eDNA than the untreated controls (p = 0.0098). The eDNA released by 0.8 M NaCl-treated S. epidermidis biofilm and planktonic cells was not significantly different (p = 0.9697). Conversely, 5 mM NaOCl-treated S. epidermidis biofilms exhibited significantly increased eDNA release than the corresponding planktonic cells (p = 0.0015). Further, the 50 μM H2O2-treated S. epidermidis biofilms released significantly more eDNA than the corresponding planktonic cells (p = 0.021).ConclusionsS. epidermidis biofilms were less susceptible to physico-chemical stress induced by the four commonly recommended disinfectants than the analogous planktonic cells. Further, S. epidermidis biofilms enhanced eDNA release in response to the sub-lethal heat and oxidative stress exposure than the corresponding planktonic cells suggesting a role of eDNA in biofilms resistance to the physico-chemical stresses.
Highlights
IntroductionOver 65% of human infections are ascribed to bacterial biofilms that are often highly resistant to antibiotics and host immunity
S. epidermidis biofilms enhanced extracellular DNA (eDNA) release in response to the sub-lethal heat and oxidative stress exposure than the corresponding planktonic cells suggesting a role of eDNA in biofilms resistance to the physico-chemical stresses
These results indicated that 60 °C was less effective against S. epidermidis biofilms compared to the corresponding planktonic cells
Summary
Over 65% of human infections are ascribed to bacterial biofilms that are often highly resistant to antibiotics and host immunity. The molecular mechanisms of bacterial biofilms resistance to the physico-chemical stresses remain unclear. The role of eDNA as a potential mechanism underlying S. epidermidis biofilms resistance to physico-chemical stress exposure is yet to be understood. This study aimed to evaluate the susceptibility patterns of and eDNA release by S. epidermidis biofilm and planktonic cells to physico-chemical stress exposure. Bacterial biofilms are less susceptible to antibiotics and host immunity [4, 5]. S. epidermidis adopts a biofilm lifestyle that enables resistance to antibiotics and host immunity, which potentially could lead to severe conditions such as bacteremia and sepsis, and if left untreated could result in death [7]. Up to 80% of infections of medical implant devices such as central venous catheters, cardiac pacemakers, tissue fillers, intrauterine devices and joint prostheses are caused by S. epidermidis biofilms [8]
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