A collaborative team led by researchers from the Great Ormond Street Institute of Child Health (GOSH) in London and involving researchers from the Wyss Institute for Biologically Inspired Engineering at Harvard University and BOA Biomedical in Cambridge has analyzed the process of microbial pathogen identification in the blood revises samples from pediatric sepsis patients using Wyss Institute’s FcMBL broad-spectrum pathogen capture technology. The advance enables accurate pathogen detection with a combination of unprecedented sensitivity and speed and could significantly improve clinical outcomes for pediatric and elderly patients with bloodstream infections (BSIs) and sepsis. The results were published in Plus one.
BSIs involving various microbial pathogens can quickly escalate into life-threatening sepsis as the body becomes overwhelmed by the multiplying invaders and shuts down organ functions. In 2017, there were 48.9 million cases and 11 million deaths related to sepsis worldwide. Importantly, almost half of all sepsis cases worldwide have occurred in children, with an estimated 20 million cases and 2.9 million deaths worldwide in children under the age of five.
To prevent BSIs from progressing to full-blown sepsis, the infection-causing bacterial or fungal species must be identified as soon as possible. Only then can optimal pathogen-specific antibacterial or antifungal treatments be used in good time. The traditional method used in clinical laboratories to identify the causative pathogenic species is lengthy and laborious, requiring two time-consuming culture steps lasting at least 1 to 3 days.
“For all patients with sepsis, their chances of survival decrease dramatically the longer it takes to identify the infection-causing agents and thus receive the most promising antimicrobial treatment,” said Nigel Klein, MD, Ph.D., pls , professor of infectious diseases and immunology at the GOSH and senior author of the study. “At Great Ormond Street Hospital we worked to demonstrate both the importance of rapid diagnosis and the fact that we can use innovative approaches to identify the pathogen in 40 minutes to six hours. Compared to adult patients, sepsis progresses much faster in infants and young children, and there is a real need for diagnostic methods that support early detection. Accurate diagnosis is even more important given the small amounts of blood available from pediatric patients, which can make resampling difficult.”
In 2020, senior authors Klein and Elaine Cloutman-Green, Ph.D., a consulting clinical scientist and infection control physician at GOSH, began working with senior associate Michael Super, Ph.D. and Founding Director Donald Ingber, MD, Ph.D. at the Wyss Institute at Harvard to solve this problem. “Based on our previous success with FcMBL in isolating pathogens from joints, bovine and human blood with exceptional efficiency, we hypothesized that incorporating FcMBL-mediated pathogen detection into a modified clinical blood culture protocol would reduce time and could reduce the size of the patient samples required to achieve the same results that time-consuming blood culture protocols provide,” said Super.
The current method of identifying pathogens in clinical settings involves first placing blood samples in bottles containing liquid media in which infectious microbes, if present, are amplified to a specified density. Then the amplified microbes are grown on solid media as isolated colonies whose constituent cells can finally be identified using a highly sensitive but rapid and relatively inexpensive analytical method known as MALDI-TOF mass spectrometry (MS). “Indeed, isolating the infectious microbes directly from grown liquid blood cultures with FcMBL makes them available for MALDI-TOF-MS analysis much earlier,” Super added.
FcMBL is the key component of a broad spectrum pathogen detection technology. It consists of a genetically engineered human immune protein called mannose-binding lectin (MBL) that is fused to the Fc fragment of an antibody molecule to produce the resulting FcMBL protein. In this configuration, the MBL portion of FcMBL can capture more than 100 [CHECK WITH MIKE] various microbial species with high efficiency, including virtually all bacterial and fungal pathogens that cause sepsis. The Fc portion of FcMBL can be used to couple it to magnetic beads, allowing the captured pathogens to be rapidly extracted from patient samples and liquid blood cultures.
In the early stages of the project, the Wyss team provided purified bead-coupled FcMBL to the GOSH team, which had access to blood samples from hospitalized pediatric patients. In later phases, sepsis and infectious disease company BOA Biomedical, co-founded by Super and Ingber to commercialize Wyss Institute’s FcMBL technology, provided the FcMBL reagent and critical expertise to the project. BOA Biomedical has now developed the FcMBL manufacturing capabilities required by the US Food and Drug Administration (FDA) and other federal health authorities to manufacture therapeutic and diagnostic products.
“Sepsis is the leading cause of death in hospitals, and initiating the right antibiotic quickly saves lives. Using work originally developed at the Wyss Institute, BOA Biomedical’s revolutionary FcMBL technology helps to quickly and accurately identify the pathogen causing sepsis, ushering in a new era of targeted antimicrobial therapy to benefit individual patients and curbing the deadly problem of antimicrobial resistance in society,” said Mike McCurdy, MD, BOA Biomedical’s chief medical officer.
In addition to using the two-step gold standard blood culture in combination with MALDI-TOF-MS pathogen identification, the team also included Bruker Corporation’s MBT Sepsityper® kit as a comparison. Launched in 2021, MBT Sepsityper® essentially eliminates the time-consuming second microbial culture step by lysing microbial cells from the liquid culture and spinning down the fragments in a centrifuge before analyzing them by MALDI-TOF mass spectrometry analysis. Although it speeds up the overall diagnostic process, the MBT Sepsityper® method produces lower microbial detection rates than the traditional culture method, which means that the infection-causing pathogen still cannot be identified in a significant proportion of blood samples.
“Our FcMBL approach has opened up the possibility of identifying pathogenic organisms to guide treatment 24 to 48 hours earlier than would be possible with standard culture techniques. It has also enabled us to use this identification to better match any running culture for antibiotic susceptibility. This method is not tied to a specific platform or vendor, so we see clear potential to become a new standard processing step for clinical pathogen detection become,” said Cloutman-Green.
“The FcMBL method identified 94.1% of the microbial species found in clinical blood culture analyzes of samples from 68 pediatric patients,” said first author Kerry Kite, who did her thesis with Klein and Cloutman-Green. “We were able to identify more infectious species in positive liquid blood cultures with the FcMBL method than with the MBT Sepsityper® method (25 out of 25 vs. 17 out of 25), and this trend was even more pronounced for the widespread fungal pathogen Candida (24 of 24 vs. 9 of 24).” Candida Types account for approximately 5% of all cases of severe sepsis and are the fourth most common pathogen isolated from the bloodstream of patients in the United States. Not just infections with Candida and other fungi require specific antifungal treatments, and distinguishing between the different types of fungal pathogens helps determine the appropriate antimicrobial therapy. Especially in neonatal intensive care units, CandidaInfections are a major cause of morbidity and mortality, killing up to 40% of infants and often causing neurodevelopmental disorders in survivors.
“By continually adapting the powerful FcMBL pathogen detection technology to address unmet and urgent diagnostic needs, such as: For example, by quickly diagnosing sepsis in pediatric patients, we hope to fundamentally change the often bleak outlook for patients of all ages,” said Ingber. “Our ultimate goal is to be able to identify pathogens directly in small blood samples, precisely and even more quickly, without the need for additional microbial cultures.” Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Children’s Hospital and the Hansjörg Wyss Professor of Bio-Inspired Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences.
The study was also authored by Sahil Loomba and Thomas Elliott at Imperial College London; Francis Yongblah, Lily Gates and Dagmar Alber at GOSH; George Downey and James Hill at BOA Biomedical; and Shanda Lightbown and Thomas Doyle at the Wyss Institute. The authors were supported in their work by the GOSH clinical microbiology staff and by Erika Tranfield with MALDI-TOF-MS expertise. At GOSH, critical financial support for the project was coordinated by the Benecare Foundation, philanthropists Luca Albertini and Professor Pauline Barrieu, and the Office of Vice-President (Advancement) at University College London by Simona Santojanni. At the Wyss Institute, the study was funded by the Defense Advanced Research Projects Agency (DARPA) under Collaborative Agreement Number W911NF-16-C-0050 and the Wyss Institute’s Technology Translation Engine. Additional support was provided by BOA Biomedical.