Differentiating Viral from Bacterial Infections
Estimates claim that over 1.2 million people died in 2019 as a direct result of an antibiotic-resistant bacterial infection. Statistics show that up to 4.95 million deaths in the same year were associated with antimicrobial resistance (AMR)1. The overuse and misuse of antibiotics is considered to be the largest contributing factor to the rise of AMR. Antibiotics are effective at treating a wide range of bacterial infections, however, when used to treat viral infections, they have little to no effect. Even still, many physicians continue to prescribe so-called empirical antibiotics as an all-encompassing treatment strategy. In their defence, differentiating viral from bacterial infections can be troublesome. Traditional testing takes the form of paired serology, which requires patients to visit a healthcare facility twice during a 2–4-week period. Many of these infections have distressing symptoms, making this an unreasonable time-to-diagnosis period. Novel molecular techniques can reduce the time to result in the determination of many infections. However, some of these methods are associated with high false positive rates and low specificity resulting in further misuse of antibiotics.
Mxyovirus resistance protein A (MxA) is a biomarker associated with viral infections. It displays antiviral activity against positive, double-stranded RNA viruses and some DNA viruses2. In a study from earlier this year, MxA was used to differentiate viral from bacterial infections in a cohort of 61 adults with an AUROC of 0.9 and a sensitivity and specificity of 92.3% and 84.6% respectively3. An additional study, known as the TREND study, found that a cut-off of 430μg/L could effectively differentiate bacterial and viral infections with an AUROC of 0.9, a sensitivity of 92% and a specificity of 100%4.
C-reactive protein (CRP) is a non-specific acute phase protein which is associated with bacterial infection. However, CRP levels have also been shown to be elevated in response to various viral infections such as Influenza virus, malaria5 and SARS-COV-26, limiting its utility in differentiating the aetiology of an infection.
Using both biomarkers in combination can help physicians determine the true aetiology of infection with high specificity, supporting antimicrobial stewardship and reducing the harmful use of these drugs. Available on the VeraSTAT, Randox provides tests for MxA and CRP, which together provide a fast and accurate method of detection and differentiation of bacterial and viral infections from a small sample.
We have provided an educational guide which describes these biomarkers and their usefulness in the arena of viral and bacterial detection. If you’re interested in learning more, you can find our educational guide here.
Differentiating Viral from Bacterial Infections
- Murray CJL, Ikuta KS, Sharara F, et al. Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis. The Lancet. 2022;399(10325):629-655. doi:10.1016/S0140-6736(21)02724-0
- Liao S, Gao S. MxA: a broadly acting effector of interferon-induced human innate immunity. Visualized Cancer Medicine. 2022;3:2. doi:10.1051/vcm/2022002
- Metz M, Gualdoni GA, Winkler HM, et al. MxA for differentiating viral and bacterial infections in adults: a prospective, exploratory study. Infection. Published online February 3, 2023. doi:10.1007/s15010-023-01986-0
- Rhedin S, Eklundh A, Ryd-Rinder M, et al. Myxovirus resistance protein A for discriminating between viral and bacterial lower respiratory tract infections in children – The TREND study. Clinical Microbiology and Infection. 2022;28(9):1251-1257. doi:10.1016/j.cmi.2022.05.008
- Joseph P, Godofsky E. Outpatient Antibiotic Stewardship: A Growing Frontier—Combining Myxovirus Resistance Protein A With Other Biomarkers to Improve Antibiotic Use. Open Forum Infect Dis. 2018;5(2). doi:10.1093/ofid/ofy024
- Paranga TG, Pavel-Tanasa M, Constantinescu D, et al. Comparison of C-reactive protein with distinct hyperinflammatory biomarkers in association with COVID-19 severity, mortality and SARS-CoV-2 variants. Front Immunol. 2023;14. doi:10.3389/fimmu.2023.1213246
Over the course of human history, few events have had such a dramatic impact as the COVID-19 pandemic. According to the World Health Organization (WHO), as of 12th July 2023, the SARS-CoV-2 virus has claimed almost 7 million lives and figures continue to rise1. While many who become infected are only subject to mild symptoms, those who develop a more severe form of the infection are encumbered with a debilitating flu-like condition, often requiring days, if not weeks of bed rest. In a paper from June 20232, the Rx Imola was used to study C reactive protein concentrations, along with other biomarkers, in mild and severe COVID-19 patients in order to develop novel risk stratification methods for this potentially life-threatening viral infection.
The impact on healthcare services around the world cannot be understated. In developed countries, access to services for both COVID-related and other conditions took a catastrophic hit. In low-to-middle-income countries, the impact has been even more distressing, all but eliminating basic medical care in favour of combating COVID-19, partly due to inferior resources and facilities3.
In times of medical emergency, it is crucial to have an efficient and effective means of stratifying the risk to patients and a process for suitably categorising those into the least and most at risk of severe complications or death. Due to the rate at which COVID-19 spread, unfortunately, the world lacked these mechanisms for SARS-CoV-2, resulting in mass hospital overpopulation, cancelled appointments for other life-threatening conditions and ultimately the staggering mortality statistics we’ve been bombarded with since January 2022. This prompted an unprecedented surge in medical research and major advances in testing capabilities, giving us new methods of detecting SARS-CoV-2 and determining the risk posed to individuals.
One such investigation, by Paranga et al., (2023) studied a total of 13 biomarkers to determine which could accurately differentiate mild, moderate, and severe cases and identify biomarkers which were good predictors of fatality2. C reactive protein (CRP) was the best-described biomarker relating to COVID-19 throughout the pandemic. This paper compares it to 12 other biomarkers including suPAR, sTREM-1, ferritin, MCP-1 and Lactate dehydrogenase. Of these, it was discovered that CRP was clearly the most effective biomarker for differentiating mild from severe cases, with concentrations in those with severe infection being, on average, 45% higher than in those with mild symptoms2. Additionally, the authors discovered that CRP levels were not significantly affected by age, a factor known to affect the inflammation and immune responses, providing a powerful and inclusive risk stratification tool. Some of the additional conclusions drawn from this paper can be seen below2:
- Lactate dehydrogenase, sTREM-1 and HGF were good predictors of mortality in COVID-19.
- suPAR was identified as a crucial molecule in characterising Delta variant infection and mortality.
- The initial values of inflammatory biomarkers were good to excellent predictors of disease severity in COVID-19 patients.
- Disease severity and mortality are associated with a higher rate of comorbidities including thrombocytopenia and other blood diseases, circulatory and respiratory system diseases and liver diseases such as cirrhosis.
So, what is CRP and how does it become elevated in response to a SARS-CoV-2 infection? CRP is a non-specific, acute-phase protein, meaning its concentration is altered in response to inflammation4. The acute respiratory distress syndrome induced by SARS-CoV-2 is, in part, a result of the hyperinflammation caused by the virus2. CRP is a well-characterised inflammatory biomarker and is therefore well-suited for identification and risk stratification in an emerging disease.
This investigation2 utilised the RX Imola, a rapid, comprehensive clinical chemistry platform, to quantify CRP. With the RX Imola, laboratories can gain access to the world’s largest clinical chemistry test menu covering routine chemistries as well as specific proteins, lipids, and more providing a cost-effective and user-friendly platform. With 60 cooled reagent positions and a sample carousel with 20 cooled positions for controls and calibrators, the RX Imola is an ideal solution for small to medium-throughput laboratories seeking an innovative and reliable clinical chemistry system. Randox also supplies suitable, high-quality reagents, and through Acusera, state-of-the-art controls and calibrators, completing the clinical chemistry portfolio.
1. World Health Organisation. WHO Coronavirus (COVID-19) Dashboard. https://covid19.who.int/.
2. Paranga TG, Pavel-Tanasa M, Constantinescu D, et al. Comparison of C-reactive protein with distinct hyperinflammatory biomarkers in association with COVID-19 severity, mortality and SARS-CoV-2 variants. Front Immunol. 2023;14. doi:10.3389/fimmu.2023.1213246
3. Jain P. Impact of COVID-19 Pandemic on Global Healthcare Systems and the role of a new era of global collaborations. Sushruta Journal of Health Policy & Opinion. 2021;14(3):1-5. doi:10.38192/14.3.2
4. Nehring S. C Reactive Protein . https://www.statpearls.com/articlelibrary/viewarticle/18744/.