A brand new genomic test could help distinguish between viral and bacterial infections in patients, through measurement of the patient’s immunological response coordinated against the viral infection.
The study, which was published in the journal Science Translational Medicine, and funded by a grant from the Defense Advance Research Project Agency (DARPA), is thought to provide hope in combating new viral outbreaks. For example, cases of the latest viral scare spreading through the Arabian Peninsula, manifesting as the Middle East Respiratory Syndrome (MERS), could be diagnosed more effectively and quicker than compared to traditional testing.
The research team, operating from the Duke University Medical Center, developed a specialized assay, involving a technique called reverse transcription polymerase chain reaction (RT-PCR) TaqMan low-density array (TLDA).
The assay was essentially used to measure the level of gene activation in patient blood cells, as opposed to attempting to detect genetic material derived from the viral pathogen itself. The immune system essentially provides “genetic breadcrumbs,” hinting at its response to invasion.
As the virus enters the human body, different genes become activated. The principle advantage of this technique is that a viral infections can be detected prior to the emergence of characteristic symptoms. Most of the symptoms witnessed during an infection are actually provoked by the immune system, fighting back against an invading nemesis. It is the genetic changes of the immune system, gearing up to combat the virus, that is being measured.
The team established 30 different genes become activated, following a viral assault. Dr. Aimee Zaas, an expert in infectious disease, claims the team were creating a snap-shot of what the genes were doing at the time of laboratory testing.
The researchers deliberately infected volunteers with different strains of the influenza virus and performed a real-world simulation. Two different cohorts were infected with influenza A H3N2/Wisconsin and influenza A H1N1/Brisbane and were used to experimentally validate the genomic assay comparing patients presenting to an emergency medical department with fever-like symptoms, caused by either a viral or bacterial infection, relative to healthy subjects.
Ribonucleic acid (RNA) samples were obtained from patient blood and the assay was used to try and classify patients infected by H3N2 or H1N1. The success rate was relatively high, with 100% accuracy in diagnosing H3N2 and 87% accuracy in diagnosing H1N1.
Testing took around 12 hours to complete for over 100 patients. The team hope to accelerate the process to put it in line with other laboratory testing methods, however.
In drawing their conclusions, the team suggest the RT-PCR-based assay was suitable for use in a clinical setting:
“RT-PCR-based detection of a host gene expression signature can classify individuals with respiratory viral infection and sets the stage for prospective evaluation of this diagnostic approach in a clinical setting.”
Antibiotic Drug Resistance
Antibiotics have been used to treat a huge range of bacterial illnesses over the past 70 years, reducing the death toll considerably. When taken correctly, antibiotics still serve as powerful tools in eliminating harmful bacterial infections.
Alas, the drugs have been wielded with high frequency, over a long period of time, causing bacteria to adapt and develop antibiotic resistance. This situation is worsened by patients failing to adhere to prescription courses, and doctors carelessly overprescribing. What’s more, doctors who misdiagnose an infection, confusing symptoms of viral infections with bacterial, may inappropriately prescribe antibiotics.
Indeed, Christopher W. Woods, one of the paper’s co-authors, discusses the significance of bacterial resistance, describing it as a global problem and a major public health concern. He suggests that his team’s novel new diagnostic tool could “… curb the indiscriminate use of antibiotics…” thereby halting the creation of resistant pathogens.
According to the Centers for Disease Control and Prevention (CDC), approximately two million people a year become infected with bacteria resistant to antibiotics drugs, resulting in 23,000 deaths. Meanwhile, the World Health Organization (WHO) cite tuberculosis, malaria and hospital-acquired MRSA infections as being some of the biggest concerns, mutating to produce strains that are resistant to some of the latest antibiotics; with TB alone, there were 630,000 people infected with the multi-drug resistant form in 2011.
The team hope to patent their genomic test, with the hope that it could gain widespread acceptance in clinical settings. The ability to distinguish between bacterial and viral infection could play a small part in curbing antibiotic resistance, and offers the potential to save many lives.
By: James Fenner