Novel biomarkers for the detection of wound infection by wound fluid RT-PCR in rats

Wound infection is a form of host damage resulting from an imbalance in pathogen virulence and the host immune response. However, at present, diagnosis is based solely on bacterial numbers or inflammatory signs and is therefore not precise. Thus, infection diagnosis requires indicators of both of these factors. We focused on wound fluid because it includes both bacteria and host cells. The purpose of this study was to establish biomarkers that reflect both bacterial and host factors using the reverse transcription-polymerase chain reaction method on the centrifugal precipitation of wound fluids (wound fluid RT-PCR). We created full thickness wounds in animal models of the three groups: control, colonization and infection, which were conditioned by administration of different concentrations of Pseudomonas aeruginosa dispersion. Messenger RNA expression in bacteria and host cells was analysed. Expression of bacterial housekeeping genes was detected in the samples in the colonization and infection groups. Expression of host housekeeping genes was detected in all samples from the three groups. Expression of toxA, encoding the virulence factor exotoxin A, was detected in 90% of samples in the infection group only. Expression of Foxp3, encoding the transcription factor forkhead box P3, was detected in 100% of samples only in the colonization group. These results revealed that wound fluid RT-PCR analysis reflected both bacterial virulence and the host immune status, and we determined the combination of novel biomarkers that can discriminate these three groups. We anticipate that wound fluid RT-PCR could be applied in the future to diagnose wound infection.