Micrococcal Nuclease stimulates Staphylococcus aureus Biofilm Formation in a Murine Implant Infection Model

Abstract

Advancements in contemporary medicine have led to an increasing life expectancy which has broadened the application of biomaterial implants. As each implant procedure has an innate risk of infection, the number of biomaterial-associated infections keeps rising. Staphylococcus aureus causes 34% of such infections and is known as a potent biofilm producer. By secreting micrococcal nuclease S. aureus is able to escape neutrophil extracellular traps by cleaving their DNA-backbone. Also, micrococcal nuclease potentially limits biofilm growth and adhesion by cleaving extracellular DNA, an important constituent of biofilms. This study aimed to evaluate the impact of micrococcal nuclease on infection persistence and biofilm formation in a murine biomaterial-associated infection-model with polyvinylidene-fluoride mesh implants inoculated with bioluminescent S. aureus or its isogenic micrococcal nuclease deficient mutant. Supported by results based on in-vivo bioluminescence imaging, ex-vivo colony forming unit counts, and histological analysis it was found that production of micrococcal nuclease enables S. aureus bacteria to evade the immune response around an implant resulting in a persistent infection. As a novel finding, histological analysis provided clear indications that the production of micrococcal nuclease stimulates S. aureus to form biofilms, the presence of which extended neutrophil extracellular trap formation up to 13 days after mesh implantation. Since micrococcal nuclease production appeared vital for the persistence of S. aureus biomaterial-associated infection, targeting its production could be a novel strategy in preventing biomaterial-associated infection.

Anthraquinone‐Based Ligands as MNase Inhibitors: Insights from Inhibition Studies and Generation of a Payload Nanocarrier for Potential Anti‐MRSA Therapy

“…It is well established that S. aureus secretes a thermostable nuclease enzyme, which is implicated in biofilm dispersal and resistance against the antibacterial activity of NETs [18–22] . Based on the inhibition of MNase rendered by C1 (Figure 4), it was pertinent to ascertain whether the ligand C1 could also inhibit nuclease secreted by a clinical isolate of MRSA.…”

“…It is well established that S. aureus secretes a thermostable nuclease enzyme, which is implicated in biofilm dispersal and resistance against the antibacterial activity of NETs. [18][19][20][21][22] Based on the inhibition of MNase rendered by C1 (Figure 4), it was pertinent to ascertain whether the ligand C1 could also inhibit nuclease secreted by a clinical isolate of MRSA. To this end, a toluidine blue DNA agar assay was performed to detect the presence of an extracellular nuclease in the cell-free supernatant (CFS) of the clinical MRSA strain S. aureus MRSA 100.…”

“…Literature reports indicate that staphylococcal nuclease is implicated in the modulation of biofilm structure and cell aggregation [18] . It has also been demonstrated that MNase production is instrumental in persistence of biomaterial‐associated S. aureus biofilm infection in a murine model [19] . Staphylococcal nuclease is also implicated in evading the host‐mediated defense response by disrupting the neutrophil extracellular traps (NETs) and thereby promoting dissemination of the pathogen and persistence of systemic infection [20–22] …”

“…[18] It has also been demonstrated that MNase production is instrumental in persistence of biomaterial-associated S. aureus biofilm infection in a murine model. [19] Staphylococcal nuclease is also implicated in evading the host-mediated defense response by disrupting the neutrophil extracellular traps (NETs) and thereby promoting dissemination of the pathogen and persistence of systemic infection. [20][21][22] Based on the profound role of nuclease in staphylococcal pathogenesis and virulence, it can be envisaged that exploring staphylococcal nuclease as a drug target is likely to yield therapeutic dividends.…”

Pathogen-Derived Nucleases: An Effective Weapon for Escaping Extracellular Traps

“…S. aureus eDNA maintains the structural stability of the biofilm during bacterial colonization. During the early stage of S. aureus biofilm formation, Nuc1 is expressed, which was responsible for infection persistence in a mouse subcutaneous implant model ( 76 ). Nuc1 can degrade the DNA scaffold in neutrophil NETs, thereby evading the host immune response ( 34 ).…”