Coughing, sneezing, runny nose, wheezing; respiratory tract infections are extremely common, with the average American adult enduring two to four each year. Typically, the symptoms last for seven to ten days while you struggle through, and then you get better. If you go to a doctor with these symptoms, they will likely prescribe you a broad-range antibiotic. This may sound fine, but there is a big issue with that: not all respiratory tract infections are caused by a bacterial infection. Over-use of antibiotics has been leading to increased antibiotic resistance for decades. The only way to prevent the over-prescribing of antibiotics for these respiratory tract infections is to determine the cause of each infection. Unfortunately, current technologies for diagnosing these infections are not fast and specific enough to allow timely and proper diagnosis. New technology has emerged that may help with the diagnosis and cut down on the over-use of antibiotics.
When exposed to different pathogens, the body's immune system responds in different ways. A virus, for example, causes cells to react in a different way than a bacterium. The cells of the immune system that can be found in the blood can be profiled to understand what type of infection they are fighting. This has been done by studying the messenger RNAs (mRNAs), also known as transcripts, found within monocytes, a specific subset of immune cells. mRNAs lead to the proteins being made by a cell and often play key roles in regulating the activation of pathways involved in an immune response. A recent study identified ten different mRNAs that could be used to determine if the body was responding to a bacterial or a viral respiratory tract infection. A more recent study further validated these ten mRNAs by confirming their use in 94 hospitalized adults with respiratory tract infections and identified even more mRNAs that could differentiate a bacterial infection from a viral infection. This allows for more appropriate use of antibiotics in these patients and avoids the potential over-use of antibiotics that threatens their effectiveness.
As more and more antibiotic-resistant infections emerge, it is becoming more important than ever to safeguard our potent antibiotics by only using them when necessary. When antibiotics are used, they kill off whatever bacteria are susceptible to their effects, leaving behind only those that are resistant. This helps select for antibiotic-resistant bacteria within a population. The over-use of antibiotics has sped this natural selection process, allowing for the rapid development of resistance even to the newest antibiotics. Using technologies such as this transcript profiling of immune cells will help slow the selection process by ensuring antibiotics are only introduced when they can be of help, allowing our antibiotics to maintain their usefulness longer before resistance develops.
The technology to profile transcripts of immune cells in the blood has the opportunity for application far beyond the identification of bacterial versus viral respiratory infection. Individual pathogens themselves can produce unique immune profiles that could one day be categorized using similar methods. With the standard diagnostics of the past, it is nearly impossible to diagnose a bacterial or viral infection unless the bacteria can be cultured or the virus can be isolated. Knowing the unique transcript profile induced by a pathogen could someday allow for molecular diagnosis of a number of pathogens without the need to culture the bacteria or isolate the virus, allowing for an even more significant reduction in antibiotic over-use. This would also provide more rapid diagnosis; transcript analysis could be performed in a matter of hours, while the diagnostics of the past frequently require days. With emerging technologies, these goals become even more achievable every day, and we may soon see a time when antibiotics are only used for infections confirmed to be caused by a susceptible bacteria.