Dr Julianne Brown, who leads the hospital’s metagenomics service and served as co-senior author of the paper, said the technology proved critical for 10-year-old Willow Crowther, who fell gravely ill in March after contracting severe pneumonia. Her condition deteriorated rapidly, with a seizure and several cardiac arrests following.Clinicians at Great Ormond Street Hospital used the metagenomic test and discovered she was harbouring a bacterial infection resistant to the antibiotics she had been receiving. A different drug was needed.Her mother, Stacey Moore, said: “The consultant said… we should bring our family up to say goodbye to her. This is how critical and in how much danger she was of passing away.”