Staphylococcus aureus infections were once benign infections that were easily treated with common antibiotics. However, S. aureus along with other strains of bacteria are becoming resistant. There is a need to find new solutions to these antibiotic resistant organisms. One such organism that is plaguing our healthcare system is Methicillin Resistant Staphylococcus aureus or MRSA.
MRSA infections are associated with high rates of morbidity and mortality sometimes leading to endocarditis, septic arthritis, osteomyelitis (Hassoun et al. 2017). This gram positive bacteria is resistant to beta-lactam antibiotics which eliminates many of the conical options typically used and has placed it on the World Health Organization’s high priority pathogen list. Alternatively vancomycin and daptomycin are now the recommended antibiotic treatment method for MRSA. However, they are not optimal due to limitations including low tissue penetration, slow bactericidal activity in vancomycin and treatment-emergent non-susceptibility in daptomycin when previous vancomycin treatments have been used. Reports indicate that increasing resistance to vancomycin is now occurring. Subsequently many experts agree that swift diagnosis along with identifying alternative agents for the treatment of MRSA is vital.
In this race against resistance researchers are working, to limited success, at developing novel antibiotics to outsmart MRSA. However, what our team is working on is not to outpace resistance by finding new antibiotics, but to attack the problem in a new way all together using gene silencing.
MRSA is most easily spread through contaminated surfaces or infected people making hospitals an optimal setting for colonization. Patients who are more vulnerable to this disease include those with open wounds, weak immune systems, and those who recently have undergone surgery. Additionally, contamination through health care workers cannot be understated with reports stating that 4.6% or more of healthcare workers may be carriers of the bacterium at one time (Dulon, et al. 2014). Thus, intervention strategies that target unsanitary behaviors in health care workers are essential in reducing the spread of MRSA.
We plan to address policy-based shortcomings in hospitals in the hopes of amending some of the non-conducive behaviors that contribute to the spread of MRSA. In the form of a policy brief based off both interviews with health care professionals and the analysis of current protocols we hope to make progressive policy suggestions in the areas of both hygiene and the screening process for MRSA.
This is the second year, of our two year plan; last year we identified vital pathways in MRSA for survival, as well as the pathways vital to the virulence and resistance. This years plan is to target essential genes using sRNA’s, and to develop a non-replicating phage as a delivery system with potential therapeutic value.
sRNA are used as a post transcriptional gene control mechanism, however, synthetic sRNA’s can be used to generate knockout phenotypes. Current treatment plans for bacterial infections utilizes antibiotics, as small molecule inhibitors resistance is inevitable. sRNA’s show promise as they can be modified in relatively short periods of time in the case of a mutation and they have been shown to have knockdown results approximating 99% (Park et al.).
We have chosen SecA as our model target gene as it is an ATPase transporter that is responsible for polypeptide translocation of virulence factors and glycoproteins. SecA is also known to be responsible for the secretion of proteins essential in bacterial growth (Driessen, Nouwen 2008). By preventing the translation of this gene it has been shown to reduce virulence factors such as enterotoxin B (Jin et al. 2015) and will hopefully cause a stress response leading to cell death.
We have turned to bacteriophages as our delivery system as they are highly specific and can be genetically modified. Delivery of our custom designed sRNA’s will be mediated through a non-replicating phage (Bikard et al. 2014) with subsequent chromosomal integration. Due to the small size of synthetic sRNA’s, multiple essential genes can be targeted through one phage infection. The fact that the phages are non-replicating ensures that no specialized transduction events are possible.
- Bikard, D., and Barrangou, R. (2017) Using CRISPR-Cas systems as antimicrobials. Curr. Opin. Microbiol.
- Driessen, A. J. M., and Nouwen, N. (2008) Protein Translocation Across the Bacterial Cytoplasmic Membrane. Annu. Rev. Biochem.
- Dulon, M., Peters, C., Schablon, A., and Nienhaus, A. (2014) MRSA carriage among healthcare workers in non-outbreak settings in Europe and the United States: A systematic review. BMC Infect. Dis.
- Hassoun, A., Linden, P. K., and Friedman, B. (2017) Incidence, prevalence, and management of MRSA bacteremia across patient populations—a review of recent developments in MRSA management and treatment. Crit. Care.
- Jin, J., Cui, J., Chaudhary, A. S., Hsieh, Y.-H., Damera, K., Zhang, H., Yang, H., Wang, B., and Tai, P. C. (2015) Evaluation of small molecule SecA inhibitors against methicillin-resistant Staphylococcus aureus. Bioorg. Med. Chem.
- Park, H., Bak, G., Kim, S. C., and Lee, Y. (2013) Exploring sRNA-mediated gene silencing mechanisms using artificial small RNAs derived from a natural RNA scaffold in Escherichia coli. Nucleic Acids Res.