Human antimicrobial peptide, LL-37, induces non-inheritable reduced susceptibility to vancomycin in Staphylococcus...

Area of Science:

• Immunology
• Microbiology
• Pharmacology

Background:

• Antimicrobial peptides (AMPs) like LL-37 are crucial for innate immunity against pathogens.
• Serum and tissue concentrations of AMPs fluctuate, influencing disease states.
• Vancomycin treatment failures occur in Methicillin-resistant Staphylococcus aureus (MRSA) infections despite standard susceptibility.

Purpose of the Study:

• To investigate the effect of the human AMP LL-37 on vancomycin susceptibility in community-associated MRSA (CA-MRSA).
• To determine if LL-37 influences bacterial growth and survival in the presence of vancomycin.

Main Methods:

• Assessed vancomycin minimum inhibitory concentration (MIC) in S. aureus exposed to LL-37.
• Observed bacterial lag-phase duration and colony formation at sub-inhibitory vancomycin concentrations.
• Utilized computer simulations and a Galleria mellonella infection model to evaluate treatment efficacy.

Main Results:

• LL-37 exposure increased S. aureus vancomycin MIC by 75%.
• LL-37 shortened bacterial lag-phase and enhanced colony formation under sub-inhibitory vancomycin.
• In vivo models showed LL-37 exposure abrogated vancomycin's antimicrobial effect.

Conclusions:

• Physiologically relevant LL-37 concentrations decrease S. aureus susceptibility to vancomycin.
• Host-specific LL-37 levels may significantly impact in vivo vancomycin efficacy for MRSA infections.
• This highlights the need to consider host immune factors in antibiotic treatment strategies.