Sniffing Out Pseudomonas Aeruginosa Wound Infections with Vitamin B12: A Simple and Selective Colorimetric Biosensor for Early Diagnosis

Abstract

Abstract Background The vacuum-assisted closure (VAC) system is a useful tool to promote wound healing. However, due to its occlusive system, the wound is often prone to Pseudomonas aeruginosa (PA) infections. Early detection and initiation of treatment is essential to limit the damage (e.g., saving a skin graft), but the black sponge occludes the wound and prevents its visual assessment leading to delayed diagnosis. Fortunately, each bacterium emits a spectrum of specific volatile organic compounds that can be used for detection. For PA, the signature compound is hydrogen cyanide. Aims We aimed to develop a colorimetric biosensor for “naked-eye” detection of PA that takes advantage of the negative pressure created by the VAC to collect hydrogen cyanide. Methods We used aquocyanocobinamide, a derivative of vitamin B12, as a colorimetric chemosensor of biological cyanide. By binding cyanide, the color of the sensor changes from orange to violet, which can be quantified with UV-VIS spectroscopy. The sensor was delivered onto the carrier material polyvinyl acetate. Its sensitivity was assessed using laboratory strains and clinical isolates of PA in-vitro and on an ex vivo skin model. Results UV-VIS spectroscopy readings of the sensor were calibrated for the cyanide concentration 0-250ppm. Cyanide produced by 30 laboratory and 20 clinical PA isolates were quantified based on the colorimetric changes of the sensor. While the sensor detected all PA strains, it did not falsely react to other wound pathogens such as Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Enterococci, suggesting a high specificity. In a proof-of-principle experiment, the colorimetric change of the sensor was detected by eye after 3 hours incubation with a PA culture. Conclusions The presence of Pseudomonas aeruginosa can be quickly and reliably detected by our vitamin B12-based colorimetric biosensor. Its incorporation inside the VAC-system can allow physicians to detect PA wound infections early on.