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Updated: Jul 6, 2026
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Increased resistance to cationic antimicrobial peptide LL-37 in methicillin-resistant strains of Staphylococcus
Kazuhisa Ouhara1, Hitoshi Komatsuzawa, Toshihisa Kawai
1Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan.
Objectives:
The susceptibility of clinical isolates of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), to host-derived cationic antimicrobial peptides was investigated.
Methods:
We examined the susceptibility of 190 clinical strains of methicillin-susceptible S. aureus (MSSA) and 304 strains of MRSA to two different classes of cationic antimicrobial peptides: LL-37 and human beta-defensin-3 (hBD3). Out of the total 494 clinical strains, a random selection of 54 S. aureus strains was examined to establish the relationship between the net charge, or zeta potential, of each strain and its susceptibility to hBD3 or LL-37. To further confirm bacterial susceptibility to either hBD3 or LL-37, we concurrently measured: (i) percentage survival after in vitro bacterial exposure and (ii) MBCs for both MRSA and MSSA strains.
Results:
Of the 54 randomly selected S. aureus strains, those MRSA strains resistant to LL-37 showed significantly higher zeta potentials than those susceptible to LL-37 (P < 0.05). In contrast, there was no difference in bacterial zeta potentials for MRSA strains that showed either resistance or susceptibility to hBD3. In addition, resistance to LL-37, but not to hBD3, as determined by either percentage survival or MBC, was significantly elevated in highly methicillin-resistant strains of S. aureus when compared with MSSA strains (P < 0.01).
Conclusions:
Clinical strains of MRSA, but not MSSA, that demonstrated an increased net charge also showed elevated resistance to LL-37, but not to hBD3.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) with higher net charge shows increased resistance to the antimicrobial peptide LL-37, but not human beta-defensin-3 (hBD3). This finding is crucial for understanding MRSA infections and developing new treatments.
Area of Science:
- Microbiology
- Infectious Diseases
- Biochemistry
Background:
- Staphylococcus aureus, including methicillin-resistant strains (MRSA), poses a significant threat due to antimicrobial resistance.
- Host-derived cationic antimicrobial peptides (CAPs) are crucial components of the innate immune system against bacterial pathogens.
Purpose of the Study:
- To investigate the susceptibility of clinical Staphylococcus aureus isolates, including MRSA, to host-derived CAPs LL-37 and human beta-defensin-3 (hBD3).
- To determine the relationship between bacterial net charge (zeta potential) and resistance to LL-37 and hBD3 in MRSA and methicillin-susceptible S. aureus (MSSA).
Main Methods:
- Examined susceptibility of 190 MSSA and 304 MRSA clinical strains to LL-37 and hBD3.
- Assessed zeta potential in 54 S. aureus strains to correlate with CAP susceptibility.
- Measured percentage survival and Minimum Bactericidal Concentrations (MBCs) to confirm resistance.
Main Results:
- MRSA strains resistant to LL-37 exhibited significantly higher zeta potentials compared to susceptible strains.
- No significant difference in zeta potential was observed for MRSA strains resistant or susceptible to hBD3.
- Resistance to LL-37, but not hBD3, was significantly elevated in highly methicillin-resistant S. aureus compared to MSSA.
Conclusions:
- Increased net charge in clinical MRSA strains correlates with elevated resistance to LL-37, but not hBD3.
- These findings highlight a potential mechanism of resistance to specific CAPs in MRSA.
- Understanding these interactions may inform the development of novel therapeutic strategies against MRSA infections.
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