Health & Medicine

Discovery of Antimicrobial Peptides from Soil Bacteria Shows Promise Against Methicillin-resistant Staphylococcus aureus Infections

It has been almost a hundred years since the world has known antibiotics – drugs used to fight infections caused by bacteria. This major medical breakthrough began when a Scottish physician and Nobel prize winner Sir Alexander Fleming discovered Penicillin, an antibiotic agent widely used to treat various infections. Since then, human life expectancy at birth has increased from 47 years in 1950 to 73 years in 2020. However, due to the misuse of antibiotics in both humans and animals, the world is facing a problem of antibiotic resistance, leading to more complicated treatments and deaths. This has drawn the attention of a group of researchers at Walailak University who are trying to tackle this problem. 

“Soil is one of the largest sources of bacteria, where they live. Our team collected soil samples and suspended them in isotonic solution. Then, we cultivated the soil bacteria in petri-dishes to see if there are any bacteria producing substances that exhibit antimicrobial activity,” said Lecturer Nuttapon Songnaka from School of Pharmacy, Walailak University. Lecturer Nuttapon and his team collected the soil samples from Walailak Botanic Park, a diverse area with many trees and herb species. The researchers discovered that Brevibacillus sp. SPR19 and SPR 20 produce antimicrobial peptides - groups of amino acids that demonstrate antimicrobial activity – that fight against Methicillin-resistant Staphylococcus aureus (MRSA). 

These peptides make the cell walls of MRSA damaged, which contribute for the bacterial killing effect. As a result, the treatment is effective against antibiotic-resistant strains. Additionally, previous research found that antimicrobial peptides are easily degraded when excreted out of the body into the environment. This helps delay the development of antibiotic resistance in bacteria that come in contact with these residual peptides compared to residual antibiotic agents left in the environment [1].

According to World Health Organization (WHO) priority pathogens list for research and development of new antibiotics, MRSA is listed in Category 2: High Priority out of three categories: critical, high, and medium. Although Staphylococcus aureus can be found on our skin and can cause infections in both community and hospital settings, people who have infections caused by Staphylococcus aureus that is resistant to Methicillin have a 64 percent higher mortality rate compared to those with infections that can be treated with antibiotics or other medicines. And symptoms from MRSA infections can vary, ranging from red, swollen, and painful skin to pneumonia and bloodstream infection. 

“Currently, we can identify the order of amino acids consisting of these peptides. After examining their toxicity to cells, we will determine whether it can be further developed into topical medication. And I would like to give sincere thanks to Assistant Professor Dr. Apichart Atipairin, Associate Professor Dr. Monthon Lertcanawanichakul, Ms. Thamonwan Wanganuttara, Ms. Thapanee Chinnawong, Sucheewin Krobthong, and Yodying Yingchutrakul, who have been wonderful colleagues and team members, for putting in the hard effort until our work is successful." The issue of antibiotic resistance needs a global response and cooperation from every sector for helping to solve the problem before it gets worse and could cause greater losses.

Soil bacteria cultured in liquid media (left) and soil sample dissolved in isotonic solution (right)

Bacterial colonies from soil samples are growing on a solid medium 

Bacteria demonstrating antimicrobial activity against MRSA

The cell morphology of S. aureus cells (Methicillin-resistant strain) before and after being treated by the antimicrobial peptides produced from Brevibacillus sp. SPR-20 

Colony morphology of Brevibacillus sp. SPR-20 on solid medium

Cite reference
[1]. Arsène, M. M. J., Davares, A. K. L., Viktorovna, P. I., Andreevna, S. L., Sarra, S., Khelifi, I., & Sergueïevna, D. M. (2022). The public health issue of antibiotic residues in food and feed: Causes, consequences, and potential solutions. Veterinary world, 15(3), 662–671.

For further reading please visit

Photos by Nuttapon Songnaka
Article by Settaboot onphakdee