Effects of the antimicrobial peptide L12 against multidrug‑resistant Staphylococcus aureus

Abstract

Methicillin-resistant Staphylococcus aureus (S. aureus; MRSA) is one of the most common bacterial pathogens and MRSA infections are characterized by high mortality rates. Antimicrobial peptides are considered one of the most promising drugs for the treatment of resistant strains of S. aureus. The present study aimed to examine the antimicrobial activity of L12 against numerous bacterial species using the broth microdilution method. Furthermore, the synergistic effect of L12 combined with various antibacterial drugs was tested, and its antibacterial mechanism was investigated by a checkerboard assay. The alterations in bacterial morphology were detected by electron microscopy, and biofilm formation and removal were tested by crystal violet staining. The present results suggested that L12 affected the growth of gram-positive strains, particularly S. aureus. Electron microscopy analysis suggested that L12 may target the cell membrane, and L12 increased the antibacterial activity of vancomycin and levofloxacin, exerting a synergistic effect. However, the minimal inhibitory concentrations (MICs) of L12 were not correlated with antibiotic resistance, the strains resistant to more antibiotics were not more resistant to L12. A sub-MIC of L12 was able to inhibit biofilm formation in a dose-dependent manner; however, concentrations of L12 ≤10 times the MIC were not sufficient to degrade previously formed biofilm. Collectively, the present study suggested that L12 may represent a novel potential therapeutic molecule for the treatment of S. aureus infections.

Evaluation of the Antimicrobial Activity in Host-Mimicking Media and In Vivo Toxicity of Antimicrobial Polymers as Functional Mimics of AMPs

“…With regard to S. aureus, our findings are reminiscent of what was seen after treatment with AMPs (L12) at the MIC . Similarly, our observations using SEM are consistent with what has been reported for synthetic AMPs (PA-13) against P.…”

“…With regard to S. aureus, our findings are reminiscent of what was seen after treatment with AMPs (L12) at the MIC. 62 Similarly, our observations using SEM are consistent with what has been reported for synthetic AMPs (PA-13) against P. aeruginosa cells, where significant changes in the bacterial membrane were observed, manifesting as roughening and corrugation. 63 ■ CONCLUSIONS It has been made clear in recent years that the activity of polymeric materials designed to mimic AMPs depends on factors, such as charge and hydrophobicity, and that some of these parameters can confer certain specificity toward Grampositive or Gram-negative organisms.…”

Artesunate inhibits Staphylococcus aureus biofilm formation by reducing alpha-toxin synthesis

“…The antibacterial activity of AS was tested using the broth microdilution method (Xiong et al 2019). AS was diluted into a series of concentrations using Mueller-Hinton (MH) broth (beef powder 6.0 g/L, starch 1.5 g/L, casein hydrolysate 17.5 g/L).…”

Complementary Activities of Host Defence Peptides and Antibiotics in Combating Antimicrobial Resistant Bacteria

“…Durancin 61A also synergised with other HDPs, reuterin and pediocin, against Clostridium dificile. L12, derived from a clinical E. faecium strain, synergises with FQ and GP classes, acts additively with AG and TC classes, and is indifferent with CS class antibiotics, all against S. aureus [37].…”