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Persistence of bacterial DNA in orthopedic infections
Heidi B Kaplan1, Justin A Miranda2, Gloria R Gogola3
1Department of Microbiology and Molecular Genetics, University of Texas Health Science Center at Houston, Houston, TX.
Abstract:
Polymerase chain reaction (PCR) has been proposed as a method to identify bacteria in clinical samples because it is more sensitive than culture techniques and can produce results rapidly. However, PCR can detect DNA from dead cells and thus cannot distinguish between live and dead cells in a tissue sample. Killed Staphylococcus aureus cells were implanted into the femurs and knee joints of rats to determine the length of time that DNA from dead cells is detectable in a living animal under conditions similar to common orthopedic infections. In the joint infection model studied here, the DNA from the dead planktonic bacteria was detected using PCR immediately after injection or 24 h later, but was undetectable 48 and 72 h after injection. In the biofilm implanted-device model studied, the DNA from these dead biofilm cells was detected by PCR immediately after implantation and at 24 h, but not at 48 or 72 h. Thus, our results indicate that DNA from dead cells does not persist in these animal model systems for more than 2 days, which should reduce concerns about possible false positive results using molecular DNA-based techniques for the detection of pathogens.
Insights
Polymerase chain reaction (PCR) can detect bacterial DNA from dead cells. This study found that dead bacterial DNA is undetectable in animal models after 48 hours, reducing concerns about false positives in pathogen detection.
Area of Science:
- Microbiology
- Molecular Biology
- Infectious Diseases
Background:
- Polymerase chain reaction (PCR) offers sensitive and rapid bacterial identification in clinical samples compared to traditional culture methods.
- A key limitation of PCR is its inability to differentiate between DNA from live and dead cells, potentially leading to false positive results.
- The persistence of DNA from dead bacterial cells in vivo remains a concern for molecular diagnostic accuracy in orthopedic infections.
Purpose of the Study:
- To determine the duration of detectable DNA from dead bacterial cells in a living animal model.
- To assess the persistence of DNA from both planktonic and biofilm-forming bacteria in orthopedic infection models.
- To evaluate the implications of dead cell DNA persistence on the reliability of PCR for pathogen detection.
Main Methods:
- Killed Staphylococcus aureus cells (both planktonic and biofilm forms) were implanted into rat femurs and knee joints.
- PCR was employed to detect the presence of bacterial DNA at various time points post-implantation (immediately, 24, 48, and 72 hours).
- Two distinct animal models were utilized: a joint infection model and an implanted-device biofilm model.
Main Results:
- DNA from dead planktonic bacteria was detectable by PCR immediately and 24 hours after injection, but not at 48 or 72 hours.
- DNA from dead biofilm bacteria was detectable by PCR immediately and 24 hours after implantation, but became undetectable by 48 hours.
- In both models, DNA from dead bacterial cells did not persist for longer than 2 days.
Conclusions:
- Bacterial DNA from dead cells is transient in these animal models, with detectability limited to approximately 48 hours.
- These findings suggest that concerns regarding false positive results due to dead cell DNA in PCR-based pathogen detection may be reduced.
- Molecular DNA-based techniques, such as PCR, are likely reliable for detecting viable pathogens in orthopedic infection settings within this timeframe.
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