Expression of type II toxin-antitoxin systems and ClpP protease of methicillin-resistant Staphylococcus aureus under thermal and oxidative stress conditions

Samira Karimaei; Behrooz Sadeghi Kalani; Nader Shahrokhi; Rahil Mashhadi; Mohammad Reza Pourmand

doi:10.18502/ijm.v13i2.5982

Samira Karimaei Department of Pathobiology, School of Public Health and Biotechnology Research Center, Tehran University of Medical Sciences, Tehran, Iran
Behrooz Sadeghi Kalani Department of Medical Microbiology, School of Medicine, Ilam University of Medical Sciences, Ilam, Iran
Nader Shahrokhi Department of Molecular Biology, Pasteur Institute of Iran, Tehran, Iran
Rahil Mashhadi Urology Research Center, Tehran University of Medical Sciences, Tehran, Iran
Mohammad Reza Pourmand Department of Pathobiology, School of Public Health and Biotechnology Research Center, Tehran University of Medical Sciences, Tehran, Iran

DOI: https://doi.org/10.18502/ijm.v13i2.5982

Keywords: Staphylococcus aureus; Oxidative stress; Toxin-antitoxin systems; Cold-shock response; Heat-shock response

Abstract

Background and Objectives: Staphylococcus aureus is a main human pathogen that causes a variety of chronic to persistent infections. Across the diverse factors of pathogenesis in bacteria, Toxin-Antitoxin (TA) systems can be considered as an antibacterial target due to their involvement in cellular physiology counting stress responses. Here, the expression of TA system genes and ClpP protease was investigated under the thermal and oxidative conditions in S. aureus strains.

Materials and Methods: The colony-forming unit (CFU) was used to determine the effects of thermal and oxidative stresses on bacterial survival. Moreover, the expressions of TA system genes in S. aureus strains were evaluated 30 min and 1 h after thermal and oxidative stresses, respectively, by quantitative reverse transcriptase real-time PCR (qRT-PCR).

Results: The cell viability was constant across thermal stress while oxidative stress induction showed a significantly decrease in the growth of Methicillin-Resistant S. aureus (MRSA) strain. Based on the qRT-PCR results, the expression of mazF gene increased under both thermal and oxidative stresses in the MRSA strain.

Conclusion: A putative TA system (namely immA/irrA) most likely has a role under the stress condition of S. aureus. The MRSA strain responds to stress by shifting the expression level of TA genes that has diverse effects on the survival of the pathogen due to the stress conditions. The TA systems may be introduced as potential targets for antibacterial treatment.