Anyone that occasionally glances at the news looking for a newfound faith in humanity or has even a remote interest in the microbial world has heard of MRSA. MRSA is short for methicillin-resistant Staphylococcus aureus, which means these particular, pathogenic bacteria are doing their part to increase the growing worldwide problem of antibiotic-resistance! In fact, the problem of antibiotic resistance is so menacing and concerning, that in November of 2015, the World Health Organization (WHO) started a World Antibiotic Awareness Week to educate the public. With incorrect antibiotic use and increasing numbers of resistant strains, the time will come when antibiotics become completely ineffective against any sort of bacterial infection. We are progressing toward an era where if any infection is not self-limiting, no matter how minor, it can lead to sepsis and ultimately death. In the United States alone, 5-10% of people are colonized by MRSA, and 20,000 people a year die from the infection (Pettengill). The prevalence of this life-threatening organism makes it everyone’s problem. Wouldn’t it be nice if there was a way to know if you had MRSA colonizing your nares (nose holes) before it costs you hundreds of dollars in hospital bills or potentially even your life? Well, clinicians are working to do just that, and a kind blog writer from ASM (American Society for Microbiology), Matthew Pettengill has kindly broken it down for us.
The way to screen for MRSA (or any kind of Staphylococcus aureus colonization) is to swab the inside of an individual’s nose, but you can also swab multiple anatomical sites in order to improve the sensitivity. If an individual is hospitalized and/or immunocompromised, it seems important to recognize the presence of MRSA to prevent complications or more serious infections. The controversy comes from how exactly these swabs are tested, once they are collected. You could opt for a traditional culture method which requires using selective medias in which either MRSA or MSSA (methicillin-susceptible S. aureus) can be detected. There is also the molecular approach to detection which would require some sort of nucleic acid amplification-based testing, such as PCR. Many labs will perform a culture test to verify their molecular test results, allowing you to verify the presence of the potential pathogen, using two techniques. The ability to reliably test for these bacteria is essential, however both methods have their advantages and disadvantages.
Testing for MRSA seems to be a win-win situation, but as with most things in life, there are some pros and cons associated with the different methods of screening for this extremely dangerous pathogen. The culture method of detection is not terribly sensitive, and while some studies have shown there are ways to improve this method, the improvements would make the process more labor intensive, expensive, and slow (Wolk). The molecular method of testing can improve sensitivity, but the tests can cost anywhere from $45 per test for single specimen random access assays or $20-30 per test for batch tests which are run twice a day. While there are ways to slightly cut the costs of moleculer testing, traditional culture-based testing is only $1-3 per test. Clinical labs can also run significantly more tests in a smaller period of time (Pettengill).
Everyone can agree that MRSA is a huge burden on the healthcare system. While many strides have been made to detect the presence of these bacteria, healthcare providers still have to choose between cost-efficiency, sensitivity, and speed. More research needs to be done to perfect a detection method that would allow MRSA-testing to become a common practice.
References:
Antibiotic resistance. (n.d.). Retrieved January 6, 2020, from https://www.who.int/news-room/fact-sheets/detail/antibiotic-resistance.
Pettengill, M. (2019, July 23). Retrieved from https://www.asm.org/Articles/2019/July/MRSA-Screening-You-or-Someone-You-Love-has-MRSA-in
Wolk, D. M., Marx, J. L., Dominguez, L., Driscoll, D., & Schifman, R. B. (2009). Comparison of MRSASelect Agar, CHROMagar Methicillin-Resistant Staphylococcus aureus (MRSA) Medium, and Xpert MRSA PCR for Detection of MRSA in Nares: Diagnostic Accuracy for Surveillance Samples with Various Bacterial Densities. Journal of Clinical Microbiology, 47(12), 3933–3936. doi: 10.1128/jcm.00601-09
