(From the April 2015 issue of Research Now)
Lower respiratory tract infections (LRTIs) are one of the most frequent reasons for hospitalization in adults and children worldwide. However, in most cases establishing the cause of the infection is challenging and many patients undergo unnecessary treatment with antibiotics which facilitates the development of antimicrobial resistance and contributes to increased health care costs.
Octavio Ramilo, MD, chief of Infectious Diseases at Nationwide Children’s Hospital and colleagues from Nationwide Children’s and the University of Rochester, have completed a study showing that transcriptional profiling can accurately determine whether LRTIs are bacterial or viral in origin. Published in the Journal of Infectious Diseases, Dr. Ramilo and his colleagues provide evidence that transcriptional profiling through a single blood sample obtained within 24 hours of hospitalization can help diagnose bacterial LRTIs.
“Transcriptional profiling is a promising tool that allows a comprehensive and efficient analysis of a large number of genes. This analysis helps us more fully understand the host response to the disease,” says Asuncion Mejias, MD, PhD, principal investigator in the Center for Vaccines and Immunity at Nationwide Children’s, assistant professor of Pediatrics at The Ohio State University, and co-author of the study. “This approach has been applied to patients with other infectious diseases – particularly in pediatric populations – and has successfully demonstrated the potential to differentiate bacterial and viral infections.”
In addition to being a frequent cause of hospitalization, LRTIs are a major reason for treatment with antibiotics worldwide. Until recently bacterial pathogens were considered the leading cause of LRTI in adults. However, increasing evidence suggests that viral infections may also be a significant cause.
“The role of respiratory viruses, rather than bacteria, in LRTIs in older adults is becoming more commonly recognized. Thus, an accurate diagnostic test to identify the cause of LRTIs has the potential to reduce overall antibiotic use and be a pivotal factor for the most effective patient treatment,” states Dr. Ramilo, who is also a professor of Pediatrics at The Ohio State University.
During the study 118 patients and 40 healthy adults were enrolled at Rochester General Hospital in Rochester, NY. Of the 118 patients hospitalized with LRTI, a respiratory viral infection was diagnosed in 71 patients, a bacterial pathogen was found in 22 patients and a combined viral-bacterial co-infection was diagnosed in 25 patients.
LRTI patients’ systemic response to the infection displayed highly specific characteristics depending on whether the LRTI was bacterial or viral. “We observed that the major difference between the groups was found in the interferon response, with the viral infection group showing the highest expression levels,” Dr. Ramilo explains.
By using transcriptional profiling to identify specific biomarkers, the team could demonstrate that viral and bacterial infections can be differentiated with a high degree of accuracy. Dr. Ramilo noted that for each group of patients, a distinct systemic host response is elicited and that this response can be detected in the blood at an early stage of the disease, providing more accurate information for effectively treating the infection.
“Our next goal is to apply this assay to improve the diagnosis and management of children with pneumonia,” notes Dr. Ramilo.
Suarez NM, Bunsow E, Falsey AR, Walsh EE, Mejias A, Ramilo O. Superiority of transcriptional profiling over procalcitonin for distinguishing bacterial from viral lower respiratory tract infections in hospitalized adults. Journal of Infectious Diseases. 2015 January 29 [epub ahead of print]