Early wound infection monitoring via headspace O₂ micro-respirometry

A luminescence based, inexpensive, 3D printed O₂ indicator is incorporated into a commercial, clear, occlusive wound dressing, which allows the %O₂ in the headspace above a simulated wound to be monitored. Two wound models are used to evaluate this micro-respirometry-based system for monitoring wound infection namely, a simple 'agar plug' model and a wounded porcine skin model. Inoculation of either wound model with E. coli, E. cloacae, or A. baumannii, produces the typical 'S'-shaped, τ vs incubation time, t, profiles, associated with micro-respirometry, due to the decrease in %O₂ in the headspace above the wound. A threshold value for the lifetime, τ_TT, of 21.1 μs, is identified at which the bacterial load is equal to the critical colonization threshold, CCT, ca. 10⁶ colony forming units, CFU/mL, above which infection is highly likely. The agar plug wound model/O₂ indicator combination is used to identify when the CCT is reached for a wide range of inoculant concentrations, spanning the range 10⁸-10¹ CFU/mL, for all three microbial species. The O₂ indicator is also successfully evaluated using a porcine skin wound model inoculated with E. coli. The results of this work are compared to other reported, usually invasive, smart wound monitoring systems. The possible use of this new, non-invasive smart-wound dressing technology, both at the point of care and at home, are discussed briefly.