Immune Modulating Topical S100A8/A9 Inhibits Growth of Pseudomonas aeruginosa and Mitigates Biofilm Infection in Chronic Wounds

Abstract

Pseudomonas aeruginosa biofilm maintains and perturbs local host defense, hindering timely wound healing. Previously, we showed that P. aeruginosa suppressed S100A8/A9 of the murine innate host defense. We assessed the potential antimicrobial effect of S100A8/A9 on biofilm-infected wounds in a murine model and P. aeruginosa growth in vitro. Seventy-six mice, inflicted with a full-thickness burn wound were challenged subcutaneously (s.c.) by 106 colony-forming units (CFUs) of P. aeruginosa biofilm. Mice were subsequently randomized into two treatment groups, one group receiving recombinant murine S100A8/A9 and a group of vehicle controls (phosphate-buffered saline, PBS) all treated with s.c. injections daily for up to five days. Wounds were analyzed for quantitative bacteriology and contents of key inflammatory markers. Count of blood polymorphonuclear leukocytes was included. S100A8/A9-treatment ameliorated wound infection, as evaluated by quantitative bacteriology (p ≤ 0.05). In vitro, growth of P. aeruginosa was inhibited dose-dependently by S100A8/A9 in concentrations from 5 to 40 μg/mL, as determined by optical density-measurement (OD-measurement) and quantitative bacteriology. Treatment slightly augmented key inflammatory cytokine Tumor Necrosis Factor-α (TNF-α), but dampened interferon-γ (IFN-γ) levels and blood polymorphonuclear count. In conclusion, topical S100A8/A9 displays remarkable novel immune stimulatory and anti-infective properties in vivo and in vitro. Importantly, treatment by S100A8/A9 provides local infection control. Implications for a role as adjunctive treatment in healing of chronic biofilm-infected wounds are discussed.

Insights into Host–Pathogen Interactions in Biofilm-Infected Wounds Reveal Possibilities for New Treatment Strategies

“…Interestingly, Sroussi and colleagues reported an inhibitory effect of S100A8 and A9 on neutrophil migration in vitro [ 63 ]. This observation is in accordance with our finding that topical treatment with S100A8/A9 for 5 days dampened the PMN count in blood from infected BALB/c mice [ 64 ].…”

“…Topical recombinant S100A8/A9 injected underneath the wounds of P. aeruginosa -biofilm infected wounds in BALB/c mice ameliorated local wound infection after 5 days of treatment [ 64 ]. In a later study, S100A8/A9 augmented the effect of 1 mg of systemic ciprofloxacin in the same model of chronic biofilm-infected wounds in BALB/c mice [ 82 ].…”

Implementing TIMERS: the race against hard-to-heal wounds

“…Biofilm expresses inflammatory signals 153 that attract neutrophils 154,155 and may interfere with neutrophil function, causing inappropriate degranulation releasing proinflammatory cytokines. 156 Biofilm inhibits activation of the complement cascade, 157 induces microRNAs that inhibit tight junction proteins that maintain skin barrier function, 158 reduces the effect of host defences 159 and affects pH and local oxygen concentrations. 160,161 Preclinical 162 Overall, current opinion supports the importance of biofilm as a mediator of chronicity in hard-to-heal wounds.…”

Adjunctive S100A8/A9 Immunomodulation Hinders Ciprofloxacin Resistance in Pseudomonas aeruginosa in a Murine Biofilm Wound Model

“…Biofilm infections with Pseudomonas aeruginosa, one of the ESCAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, P. aeruginosa, and Enterobacter species) are associated with chronic wounds (Rice, 2008), affect the immune homeostasis and suppress neutrophil markers (Trøstrup et al, 2017b).…”