Researchers at Great Ormond Street Hospital in London have demonstrated the clinical benefits of metagenomic testing, a diagnostic approach that sequences all genetic material in a sample to identify infections. The hospital deployed this technology on respiratory samples from more than 100 critically ill children in its pediatric intensive care unit during a study conducted in 2024-5, with findings published in the Lancet Microbe.
Metagenomic testing differs substantially from conventional diagnostic methods. Traditional bacterial identification relies on culturing samples in Petri dishes, a technique in use since the Victorian era. PCR testing can identify viruses and certain bacteria but requires clinicians to specify which pathogens they suspect beforehand. In contrast, metagenomic testing analyzes all genetic material present without requiring advance assumptions about potential infections. At GOSH, the technology identified approximately nine in 10 bacteria and viruses, as well as all fungi present in samples.
The clinical impact proved significant, with test results influencing treatment decisions in approximately a quarter of cases. These changes included initiating antibiotics, discontinuing medications, or switching to alternative treatments. The metagenomic approach also detected 50 organisms that routine diagnostic methods failed to identify, potentially serving as an early warning system for emerging infections. One case involved a 10-year-old patient from Kent who developed severe pneumonia complicated by seizures and cardiac arrests. Metagenomic testing revealed a drug-resistant bacterial infection requiring different antibiotic therapy than initially prescribed, and the patient ultimately recovered after several months of hospitalization.
Dr. Sam Ray, a consultant in pediatric intensive care medicine at GOSH, emphasized that conventional testing required educated guessing about which infections to investigate. The metagenomic approach enables clinicians to identify infections that would otherwise remain undetected, initiate appropriate treatment, and discontinue ineffective antibiotics—a factor significant for combating antimicrobial resistance. Dr. Julianne Brown noted that metagenomic testing is being gradually rolled out to approximately 30 intensive care units across the UK treating both adult and pediatric patients, with potential applications for identifying novel pathogens that could pose pandemic threats.
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