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Comparative Analysis of Single-Species and Polybacterial Wound Biofilms Using a Quantitative, In Vivo, Rabbit Ear Model
ARMY INST OF SURGICAL RESEARCH FORT SAM HOUSTON TX
Pagination or Media Count:
Introduction The recent literature suggests that chronic wound biofilms often consist of multiple bacterial species. However, without appropriate in vivo, polybacterial biofilm models, our understanding of these complex infections remains limited. We evaluate and compare the effect of single- and mixed-species biofilm infections on host wound healing dynamics using a quantitative, in vivo, rabbit ear model. Methods Six-mm dermal punch wounds in New Zealand rabbit ears were inoculated with Staphylococcus aureus strain UAMS-1, Pseudomonas aeruginosa strain PAO1, or both, totaling 10 exp 6 colony-forming unitswound. Bacterial proliferation and maintenance in vivo were done using procedures from our previously published model. Wounds were harvested for histological measurement of wound healing, viable bacterial counts using selective media, or inflammatory cytokine IL-1beta TNF-alpha expression via quantitative reverse-transcription PCR. Biofilm structure was studied using scanning electron microscopy SEM. For comparison, biofilm deficient mutant UAMS-929 replaced strain UAMS-1 in some mixed-species infections. Results Bacterial counts verified the presence of both strains UAMS-1 and PAO1 in polybacterial wounds. Over time, strain PAO1 became predominant p0.001. SEM showed colocalization of both species within an extracellular matrix at multiple time-points. Compared to each monospecies infection, polybacterial biofilms impaired all wound healing parameters p0.01, and increased expression of IL-1beta and TNF-alpha p0.05. In contrast, mixed-species infections using biofilm-deficient mutant UAMS-929 instead of wild-type strain UAMS-1 showed less wound impairment p0.01 with decreased host cytokine expression p0.01, despite a bacterial burden and distribution comparable to that of mixed-wild-type wounds. Conclusions This study reveals that mixed-species biofilms have a greater impact on wound healing dynamics than their monospecies counterparts.
APPROVED FOR PUBLIC RELEASE