Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) has become an important cause of hospital-acquired infections worldwide. It is one of the most threatening pathogens due to its multi-drug resistance and strong biofilm-forming capacity. Thus, there is an urgent need for novel alternative strategies to combat bacterial infections. Recently, we demonstrated that a novel antimicrobial surface coating, AGXX®, consisting of micro-galvanic elements of the two noble metals, silver and ruthenium, surface-conditioned with ascorbic acid, efficiently inhibits MRSA growth. In this study, we demonstrated that the antimicrobial coating caused a significant reduction in biofilm formation (46%) of the clinical MRSA isolate, S. aureus 04-02981. To understand the molecular mechanism of the antimicrobial coating, we exposed S. aureus 04-02981 for different time-periods to the coating and investigated its molecular response via next-generation RNA-sequencing. A conventional antimicrobial silver coating served as a control. RNA-sequencing demonstrated down-regulation of many biofilm-associated genes and of genes related to virulence of S. aureus. The antimicrobial substance also down-regulated the two-component quorum-sensing system agr suggesting that it might interfere with quorum-sensing while diminishing biofilm formation in S. aureus 04-02981.
Highlights
Staphylococcus aureus is an opportunistic pathogen commonly found in the human respiratory tract, nasal areas and skin
5 days to check if Ag or AGXX R exhibited an inhibitory effect on the pathogen, in the form of a zone of inhibition on the agar plate
The Colony forming units (CFU)/mL of S. aureus 04-02981 grown in the batch culture with AGXX R increased from 2.77 × in the 1st hour to 3.99 × 1010 in the 4th hour, but decreased to 1.08 × in the 8th hour
Summary
Staphylococcus aureus is an opportunistic pathogen commonly found in the human respiratory tract, nasal areas and skin. Methicillin-resistant Staphylococcus aureus (MRSA) is a crucial human pathogen causing infections ranging from skin and soft tissue infections to fatal sepsis (Marathe et al, 2015). It is one of the leading pathogens that cause nosocomial infections (Paniagua-Contreras et al, 2012; Lister and Horswill, 2014); it is resistant to methicillin and many other antibiotics (Marathe et al, 2015), and it is known to produce thick biofilm (Paniagua-Contreras et al, 2012; Qin et al, 2014). Its firm attachment to medical devices and host tissues, and its ability to form robust biofilms makes it a cause of chronic infections (Yarwood et al, 2004). Around 90% of the infections caused by the bacterium are skin and soft tissue infections, and the agrQS system is associated with these infections (Sully et al, 2014)
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