Authors: Gabriela Gonzalez Matheus 1,2, Michelle Chamoun,1* Yenkai Lim1, Yogeesan Sivakumaran2, Kiarash Khosrotehrani1,2, Timothy Wells 1
Institutions:
1Frazer Institute, The University of Queensland, Translational Research Institute, Australia
2Princess Alexandra Hospital, Brisbane, Australia
*Presenting author
Abstract:
Chronic leg wounds are a significant healthcare problem causing substantial morbidity. Numerous bacterial species may colonise wounds, however notably infection by Pseudomonas aeruginosa contributes to delayed healing and high recurrence rates. Resistance to complement-mediated lysis (commonly known as serum killing) is a vital virulence factor for P. aeruginosa to survive in the complement-rich wound environment. Despite this, almost 50% of wound isolates still remain sensitive to killing by healthy control serum. We have previously described antibody-mediated serum resistance in P. aeruginosa infections, whereby ‘cloaking antibodies’ (cAbs) specific for lipopolysaccharide (LPS) form a physical barrier and prevent complement-mediated killing. The prevalence and impact of cAbs in P. aeruginosa wounds however is unknown.
In this prospective cohort study, 45 patients with chronic wounds were recruited. At baseline, clinical data, wound swabs and serum were collected. Cloaking antibody prevalence and titres were determined using serum bactericidal assay and ELISA. Bacterial species identification was done via MALDI-TOF. Clinical follow-up is being carried out at 12, 24 and 48 weeks.
Eleven patients’ wounds (26.8%) of the 45 were culture-positive for P. aeruginosa. Over half (57.7%) of patients showed high titres of serum cAb IgG, with 9/11 patients with P. aeruginosa isolates positive for cAbs. Eight of these 11 isolates were sensitive to healthy control serum killing, and the presence of cAbs could inhibit this killing for 4 strains. Clinical follow up is ongoing.
Thus, there is a high prevalence of cAbs in patients with chronic wounds. These antibodies can protect their cognate isolates from complement-killing. Clinical follow up and cAb association with wound healing or recurrence is ongoing.