Evaluation of postmortem bacterial migration using culturing and real-time quantitative PCR

Area of Science:

• Forensic microbiology
• Postmortem investigations
• Bacteriology

Background:

• Postmortem bacteriology aids in determining cause of death and disease research.
• Understanding bacterial migration postmortem is crucial for accurate interpretation of microbiological findings.

Purpose of the Study:

• To analyze time-dependent bacterial migration into various tissues and fluids postmortem.
• To compare bacterial culturing and real-time quantitative polymerase chain reaction (RT-qPCR) for postmortem sample analysis.
• To identify optimal postmortem sampling sites for microbiological analysis.

Main Methods:

• Analysis of 33 autopsy cases.
• Bacterial culturing and RT-qPCR were used to assess bacterial presence.
• Samples analyzed included liver, mesenteric lymph node, pericardial fluid, portal vein, and peripheral vein.
• Time-dependent bacterial migration was evaluated from 1 to 7 days postmortem.

Main Results:

• Pericardial fluid and liver were the most sterile samples up to 5 days postmortem, with rare detection of multigrowth and staphylococci via culturing.
• RT-qPCR demonstrated higher sensitivity and bacterial positivity across all sample types compared to culturing.
• Relative amounts of intestinal bacterial DNA (e.g., bifidobacteria, bacteroides) increased over time.
• Blood samples exhibited low sterility throughout the 1-7 day postmortem period.

Conclusions:

• Pericardial fluid and liver are the most reliable postmortem sampling sites for microbiological analysis up to 5 days after death.
• RT-qPCR is a more sensitive method for detecting postmortem bacterial presence than traditional culturing.
• Intestinal bacteria show a time-dependent increase in detectable DNA in postmortem samples.