Comparative Diagnostic Evaluation of Real-Time PCR and Culture for Detecting Pathogens in Podiatric Wound Infections
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Background
Culture-based wound infection diagnostics have well-recognized limitations in detecting fastidious, anaerobic, or polymicrobial pathogens. This study compared the performance of a PCR wound panel with traditional culture.
Methods
Dual-swab specimens from 93 clinical wound cases underwent both culture and PCR testing. Analyses included organism-level concordance, Gram stain correlation, and resistance gene detection. Logistic regression, Receiver Operating Characteristic (ROC), and latent class analysis (LCA) were used to evaluate diagnostic performance.
Results
Under the conventional (culture-referenced) framework, PCR sensitivity was 98.3% and specificity was 73.5%. LCA (model M3) estimated PCR sensitivity at 95.6% and specificity at 91%. PCR detected 110 clinically significant pathogens missed or ambiguously reported (∼ 30%) by culture. A logistic model incorporating 16S rRNA Ct values and Gram morphology found that 73.8% of PCR-only detections had infection probabilities >75%. Applying these probabilities and resistance gene codetection data in a symmetric framework improved PCR specificity from 45% to 86% with 95% sensitivity, while culture specificity remained high but suffered notable underdetection of known clinically significant pathogens. Many PCR-only detections, especially in polymicrobial wounds, were supported by high bacterial burden, Gram concordance, and resistance markers. For three key pathogens ( S. aureus, P. aeruginosa, S. agalactiae ), analysis showed PCR specificity ≥95% when compared to culture, suggesting that culture underdetection may partly reflect colony selection and prioritization during workup.
Conclusion
These results underscore the known limitations of culture in resolving polymicrobial podiatric wound infections and highlight PCR’s role in providing significantly faster and more comprehensive organism-level detection to guide clinical decisions.
