Antibacterial Activity of the Non-Cytotoxic Peptide (p-BthTX-I)2 and Its Serum Degradation Product against Multidrug-Resistant Bacteria

Abstract

Antimicrobial peptides can be used systemically, however, their susceptibility to proteases is a major obstacle in peptide-based therapeutic development. In the present study, the serum stability of p-BthTX-I (KKYRYHLKPFCKK) and (p-BthTX-I)2, a p-BthTX-I disulfide-linked dimer, were analyzed by mass spectrometry and analytical high-performance liquid chromatography (HPLC). Antimicrobial activities were assessed by determining their minimum inhibitory concentrations (MIC) using cation-adjusted Mueller–Hinton broth. Furthermore, biofilm eradication and time-kill kinetics were performed. Our results showed that p-BthTX-I and (p-BthTX-I)2 were completely degraded after 25 min. Mass spectrometry showed that the primary degradation product was a peptide that had lost four lysine residues on its C-terminus region (des-Lys12/Lys13-(p-BthTX-I)2), which was stable after 24 h of incubation. The antibacterial activities of the peptides p-BthTX-I, (p-BthTX-I)2, and des-Lys12/Lys13-(p-BthTX-I)2 were evaluated against a variety of bacteria, including multidrug-resistant strains. Des-Lys12/Lys13-(p-BthTX-I)2 and (p-BthTX-I)2 degraded Staphylococcus epidermidis biofilms. Additionally, both the peptides exhibited bactericidal activities against planktonic S. epidermidis in time-kill assays. The emergence of bacterial resistance to a variety of antibiotics used in clinics is the ultimate challenge for microbial infection control. Therefore, our results demonstrated that both peptides analyzed and the product of proteolysis obtained from (p-BthTX-I)2 are promising prototypes as novel drugs to treat multidrug-resistant bacterial infections.

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“…This led to a more potent antibacterial action, but also increased the hemolytic effect (Yu et al, 2010). ably, the peptide showed no effect against C. albicans, epithelial cells, erythrocytes and macrophages, demonstrating in this way that it is selective against prokaryotic cells (Santos-Filho et al, 2015).…”

“…According to the authors, p-BthTX-I exerts a mechanism of action different from the peptide-membrane interaction models most frequently associated to α-helical AMPs (Santos-Filho et al, 2015). This was supported by CF assays also performed, as measurement of fluorescence emission upon calcein release demonstrated that p-BthTX-I had a low interaction with membrane models (POPC and POPC:POPG).…”

“…This was supported by CF assays also performed, as measurement of fluorescence emission upon calcein release demonstrated that p-BthTX-I had a low interaction with membrane models (POPC and POPC:POPG). Hence, it appears that p-BthTX-I mode of antimicrobial action does not involve bacterial membrane permeabilization (Santos-Filho et al, 2015).…”

“…Actually, the degradation peptide product exhibited an increased antibacterial effect against strains of S. aureus , Enterococcus faecium , multidrug‐resistant K. pneunomniae and E. coli . The ability of (pBthTX‐I) 2 and KKYRYHLKPFC to eliminate Staphylococcus epidermidis biofilms was also tested, with both peptides revealing identical anti‐biofilm activity, as well as activity against the planktonic forms of that bacterial species (Santos‐Filho et al, ).…”

“…The ability of (pBthTX-I) 2 and KKYRYHLKPFC to eliminate Staphylococcus epidermidis biofilms was also tested, with both peptides revealing identical anti-biofilm activity, as well as activity against the planktonic forms of that bacterial species (Santos-Filho et al, 2017). .…”