Overview on MRSA Superbug and Drug-Resistance: Should We Worry About It?
A microbe which is resistant to treatments such as antibiotics are called superbugs. Methicillin-resistant Staphylococcus aureus (MRSA) is a Gram-positive bacterium, which is classified as a superbug. MRSA strains are resistant to multiple β-lactam antibiotics such as Methicillin (1). MRSA’s can survive in presence of β-lactam antibiotics through the activity mecA gene, which decreases these antibiotic’s activities. Thus, antibiotics cannot inhibit the activity of transpeptidases of MRSA, which have a key role in cell wall synthesis (2). These characteristic factors of MRSA’s make it hard to treat patients who are infected with MRSA strains (1).
There are 2 main types of MRSA: hospital associated MRSA (HA-MRSA), and community associated MRSA (CA-MRSA). The only difference between these 2 types is not the setting they infect humans, there are also key differences between which type of Staphylococcal cassette chromosome mec (SCCmec) they carry (3). SCCmec’s are genetic elements that carry the mecA gene, which spreads between strains only via horizontal gene transfer (4). HA-MRSA’s mostly carry SCCmec I, II, III, whereas CA-MRSA’s carry SCCmec IV or V. Moreover, HA-MRSA’s are resistant against more antibiotics in comparison to CA-MRSA’s (3).
MRSAs remain as a public health threat as there is still no effective treatment against them. Furthermore, unnecessary, and wrong antibiotic prescription and usage, which caused the occurrence of bacterial superbugs, continues (5). MRSA is the main cause of approximately 11.000 deaths and 80.000 infections in United States every year (6). Another concerning factor is the abandonment of antibiotic development in pharmaceutical industry. Big pharmaceutical firms nearly stopped working on novel antibiotics as financial gains are not enough to cover the costs of developing a new antibiotic. Developing a novel antibiotic approximately costs 1.5 billion USD. Whereas sales of an antibiotic generate about 46 million dollars annually. This led to a massive drop approved new antibiotics in US. In comparison, approved new cancer drug numbers increased massively as oncogenic drugs are more profitable than antibiotics (Fig 1.). These problems stacked with the increasing drug-resistant microbes would lead to a catastrophe if no action is taken. Drug-resistant microbe infections are the main cause of death for 700.000 people annually. Experts are predicting a rate of 10 million deaths per year related to drug-resistant microbes if no measures against drug-resistance is taken (7).
Overall, if governments, funding agencies and healthcare professionals don’t take initiative against this growing public health problem, drug-resistance among microbes will grow exponentially in a way that will be nearly impossible to stop.
References
1. Gurusamy, K. S., Koti, R., Toon, C. D., Wilson, P., & Davidson, B. R. (2013). Antibiotic therapy for the treatment of methicillin‐resistant Staphylococcus aureus (MRSA) infections in surgical wounds. Cochrane Database of Systematic Reviews, (8).
2. Chambers, H. F. (2001). Methicillin-resistant Staphylococcus aureus. Mechanisms of resistance and implications for treatment. Postgraduate medicine, 109(2 Suppl), 43–50.
3. Peng, H., Liu, D., Ma, Y., & Gao, W. (2018). Comparison of community-and healthcare-associated methicillin-resistant Staphylococcus aureus isolates at a Chinese tertiary hospital, 2012–2017. Scientific reports, 8(1), 1–8.
4. Hanssen, A. M., & Ericson Sollid, J. U. (2006). SCC mec in staphylococci: genes on the move. FEMS Immunology & Medical Microbiology, 46(1), 8–20.
5. MRSA infection, Mayo Clinic; https://www.mayoclinic.org/diseases-conditions/mrsa/symptoms-causes/syc-20375336
6. MRSA blood infections are less fatal in kids, vs. adults, but cause significant complications, Children’s National; https://childrensnational.org/news-and-events/childrens-newsroom/2017/mrsa-blood-infections-are-less-fatal-in-kids-vs-adults-but-cause-significant-complications
7. Plackett, B. (2020). Why big pharma has abandoned antibiotics. Nature, 586(7830), S50-S50.
