Broad impact of extracellular DNA on biofilm formation by clinically isolated Methicillin-resistant and -sensitive strains of Staphylococcus aureus

Abstract

Staphylococcus aureus is a major causative agent for biofilm-associated infections. Inside biofilms, S. aureus cells are embedded in an extracellular matrix (ECM) composed of polysaccharide-intercellular adhesins (PIA), proteins, and/or extracellular DNA (eDNA). However, the importance of each component and the relationship among them in biofilms of diverse strains are largely unclear. Here, we characterised biofilms formed by 47 S. aureus clinical isolates. In most (42/47) of the strains, biofilm formation was augmented by glucose supplementation. Sodium chloride (NaCl)-triggered biofilm formation was more prevalent in methicillin-sensitive S. aureus (15/24) than in methicillin-resistant strain (1/23). DNase I most effectively inhibited and disrupted massive biofilms, and Proteinase K was also effective. Anti-biofilm effects of Dispersin B, which cleaves PIA, were restricted to PIA-dependent biofilms formed by specific strains and showed significant negative correlations with those of Proteinase K, suggesting independent roles of PIA and proteins in each biofilm. ECM profiling demonstrated that eDNA was present in all strains, although its level differed among strains and culture conditions. These results indicate that eDNA is the most common component in S. aureus biofilms, whereas PIA is important for a small number of isolates. Therefore, eDNA can be a primary target for developing eradication strategies against S. aureus biofilms.

RETRACTED: Sanguinarine Inhibits Mono- and Dual-Species Biofilm Formation by Candida albicans and Staphylococcus aureus and Induces Mature Hypha Transition of C. albicans

“…The results obtained here suggested that sanguinarine reduced the biofilm formation of S. aureus single species mainly by mediating polysaccharides and eDNA levels, while for C. albicans single species and dual species, sanguinarine inhibited biofilm formation mainly by reducing protein and polysaccharide levels. The results were in line with previous reports that showed that the main components of S. aureus biofilms are composed of extracellular polysaccharides and eDNA, while the C. albicans biofilm matrix predominantly consists of extracellular proteins (55%), polysaccharides (25%), lipids (15%), and eDNA (5%) [31,32]. In agreement, for dual culture of C. albicans and S. aureus, sanguinarine reduced biofilm formation by synchronously reducing extracellular proteins, polysaccharides, and eDNA levels in a dose-dependent manner.…”

Redundant and Distinct Roles of Secreted Protein Eap and Cell Wall-Anchored Protein SasG in Biofilm Formation and Pathogenicity of Staphylococcus aureus

“…MR23 is a hyper-Eap-producing strain compared with other clinical isolates, as recently reported (34). In addition, the protein level of SasG in MR23 was similar to or higher than those in most other strains ( Fig.…”

“…It would be interesting to determine whether the latter mutation is also involved in the overproduction of Eap. Glucose was shown to repress SaeS, leading to downregulation of Eap (59); however, MR23 still produced a large amount of Eap even in the presence of glucose (34). Therefore, other factors, apart from SaeS, should also be involved in the extremely large amount of Eap in MR23.…”

Underrated Staphylococcus species and their role in antimicrobial resistance spreading

“…As observed for many bacteria, during biofilm maturation S. aureus can suffer lysis and release its genomic DNA, producing the so-called external DNA (eDNA), which is a major component of the matrix of biofilms established by this bacterium (Sugimoto et al, 2018). The eDNA adsorbs to the surface of a single cell in long loop structures, which act as an adhesive substance that facilitates cell attachment, in addition to influence the hydrophobicity of the bacterial cell surface (Okshevsky and Meyer, 2015).…”