Research Background
Mycoplasma pneumoniae (MP) infection is a common illness in children. Although community-acquired pneumonia caused by MP is often mild, it can progress to severe cases due to factors such as inflammation and antibiotic resistance, leading to complications like atelectasis and bronchiolitis obliterans, which can seriously affect children's long-term quality of life.
Currently, common detection methods include antibody testing, DNA testing, and RNA testing.
Antibody testing is fast and suitable for outpatient and emergency screening, but it has low sensitivity and a high risk of false negatives.DNA testing generally meets clinical requirements for sensitivity and specificity; however, DNA can persist for 7 weeks to 7 months after bacterial death. As a result, a positive DNA result may represent residual DNA from a recent MP infection, leading to false positives and making it unreliable for accurately assessing treatment efficacy. RNA testing, on the other hand, is currently a reliable method for the early diagnosis of Mycoplasma pneumoniae infection and for accurately evaluating therapeutic outcomes.
RNA detection technology, also known as real-time fluorescence-based isothermal amplification technology (SAT), is a first-line diagnostic method recommended by expert consensus.
A study published in Pediatric Pulmonology by Professor Deyu Zhao and Professor Qian Chen from the Children's Hospital of Nanjing Medical University detailed the use of SAT technology to investigate the degradation differences of Mycoplasma pneumoniae DNA and RNA under inactivated conditions across different microenvironments.
Research Objective
To compare the degradation differences of DNA and RNA from inactivated Mycoplasma pneumoniae under different microenvironments, evaluate their detection characteristics, and provide a theoretical basis for the early clinical diagnosis of MP infection, particularly for distinguishing current from past infections.
Research Methods
Experimental Design:
Inactivated standard MP strain M129 and clinical isolates were placed in three different microenvironments:
(1) Sterile conditions
(2) BEAS-2B cell matrix
(3) Lung tissue microenvironment
Research Results
Degradation Trends in Different Microenvironments
Sterile environment (0–16 days): No significant decrease in DNA copy number was observed, while RNA showed marked degradation within 4–6 days.
BEAS-2B cell environment (0–48 hours): Both DNA and RNA levels decreased, with RNA degradation being more pronounced.
Lung tissue environment (0–56 hours): RNA levels fell below the detectable limit after 56 hours, whereas DNA degradation occurred more slowly.
Clinical samples: RNA degraded significantly faster than DNA, showing a trend consistent with that observed in the experimental groups.
Figure 1: Degradation Differences of DNA and RNA in Different Microenvironments.
(a) Sterile conditions (b) BEAS-2B cell matrix (c) Lung tissue microenvironment (d) Clinical samples
Initial Copy Number Differences
Whether using the standard strain M129 or the clinical isolate, the initial RNA copy number was higher than the DNA copy number at the time of first detection (Figure 2).
Figure 2: Initial Copy Number Differences of DNA and RNA in Different Microenvironments.
(a) Sterile conditions (b) BEAS-2B cell matrix (c) Lung tissue microenvironment (d) Clinical samples
Research Conclusion
RNA degrades faster than DNA, especially during the early stages of infection (e.g., in lung tissue, RNA becomes undetectable after 56 hours), suggesting that RNA testing is more suitable for distinguishing current infection from past infection. The higher initial RNA copy number, combined with its rapid degradation, indicates that RNA testing offers higher sensitivity and specificity in early diagnosis.
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