Abstract
The objective of this study was to analyze the antimicrobial effect of nisin against MRSA (Methicillin-Resistant Staphylococcus aureus) and MSSA (Methicillin-Sensitive Staphylococcus aureus), and at the same time examine the possibility of the bacteria to develope nisin resistance. The antimicrobial susceptibility of the strains was tested using the agar diffusion and/or microdilution methods. To select nisin-resistant strains, bacteria were grown consecutively at sublethal concentrations of the bacteriocin. Nisin showed bactericidal activity against most of the tested strains. MRSA required higher doses of bacteriocin compared to MSSA both for inhibition and cell death. However, transfers in the presence of nisin could completely eliminate nisin activity with an increase in minimal inhibitory concentration value of up to 250 times. Nisin-resistance could be maintained in MRSA and MSSA even in the absence of the bacteriocin. Nisin resistance affected antibiotic susceptibility of both MRSA and MSSA to mainly Cefoxitin, Oxacillin, and Erythromycin. These results indicate that nisin-resistance is a complex trait among MSSA and MRSA and must be elucidated before the therapeutic recommendation of nisin to treat infections caused by these bacterial species.
Highlights
Antibiotic resistance among bacteria is one of the greatest challenges experienced by the health sector all over the world (Bauer & Sampathkumar, 2017; Saha et al, 2017; Vivas et al, 2019)
3.2 Antimicrobial Activity of Nisin Against methicillin-resistant Staphylococcus aureus (MRSA) and MSSA Strains Among the MSSA strains (n=30) analyzed in this study, approximately 83% were sensitive to nisin forming inhibition zones
For 48% of the MSSA strains, Minimal Bactericidal Concentration (MBC) reached a superior value of 50000 IU/mL, probably because in these strains nisin exerts only a bacteriostatic effect
Summary
Antibiotic resistance among bacteria is one of the greatest challenges experienced by the health sector all over the world (Bauer & Sampathkumar, 2017; Saha et al, 2017; Vivas et al, 2019). This phenomenon implies a diminishing existence of effective antimicrobial agents to treat infections caused by these bacteria (Magiorakos et al, 2012; Lin et al, 2017). Infections caused by MRSA constitute one of three major infectious diseases, threatening human health (Center for Disease Control and Prevention, 2015; Lozano et al, 2020; Togneri et al., 2017). One of the major concerns today is the emergence of vancomycin and daptomycin-resistant S. aureus (Cafiso et al, 2020; Kang et al, 2015; Pader & Edwards, 2017)
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