Snake Cathelicidin NA-CATH and Smaller Helical Antimicrobial Peptides Are Effective against Burkholderia thailandensis

Abstract

Burkholderia thailandensis is a Gram-negative soil bacterium used as a model organism for B. pseudomallei, the causative agent of melioidosis and an organism classified category B priority pathogen and a Tier 1 select agent for its potential use as a biological weapon. Burkholderia species are reportedly “highly resistant” to antimicrobial agents, including cyclic peptide antibiotics, due to multiple resistance systems, a hypothesis we decided to test using antimicrobial (host defense) peptides. In this study, a number of cationic antimicrobial peptides (CAMPs) were tested in vitro against B. thailandensis for both antimicrobial activity and inhibition of biofilm formation. Here, we report that the Chinese cobra (Naja atra) cathelicidin NA-CATH was significantly antimicrobial against B. thailandensis. Additional cathelicidins, including the human cathelicidin LL-37, a sheep cathelicidin SMAP-29, and some smaller ATRA peptide derivatives of NA-CATH were also effective. The D-enantiomer of one small peptide (ATRA-1A) was found to be antimicrobial as well, with EC50 in the range of the L-enantiomer. Our results also demonstrate that human alpha-defensins (HNP-1 & -2) and a short beta-defensin-derived peptide (Peptide 4 of hBD-3) were not bactericidal against B. thailandensis. We also found that the cathelicidin peptides, including LL-37, NA-CATH, and SMAP-29, possessed significant ability to prevent biofilm formation of B. thailandensis. Additionally, we show that LL-37 and its D-enantiomer D-LL-37 can disperse pre-formed biofilms. These results demonstrate that although B. thailandensis is highly resistant to many antibiotics, cyclic peptide antibiotics such as polymyxin B, and defensing peptides, some antimicrobial peptides including the elapid snake cathelicidin NA-CATH exert significant antimicrobial and antibiofilm activity towards B. thailandensis.

Antimicrobial and Antibiofilm Peptides

“…For both of them, minimal biofilm inhibitory concentration (MBIC) values ranging from 8 to 35 µg/mL against five clinical strains of P. aeruginosa have been obtained [95]. Moreover, Blower et al [86] demonstrated that the SMAP-29 peptide is able to inhibit biofilm production in Burkholderia thailandensis by about 50% at peptide concentrations at or above 3 µg/mL. Anunthawan et al studied KT2 and RT2, two synthetic tryptophan-rich cationic peptides, which showed activity against multidrug-resistant E. coli biofilms at sub-MIC levels [96].…”

Antimicrobial activity of Tachyplesin 1 againstBurkholderia pseudomallei: an in vitro and in silico approach

“…AMPs have made a big impact in antimicrobial research, to diminish the inefficacy of antimicrobial therapy in immunocompromised hosts and also ongoing emergence of resistance to conventional antibiotics worldwide (Giuliani, Pirri & Nicoletto, 2007). Among the AMPs which were reported to demonstrate potential to inhibit B. pseudomallei include LL-37 (Kanthawong et al, 2012), PG1 (Sim et al, 2011), bovine lactoferrin (Puknun et al, 2013), phospholipase A2 (Samy et al, 2015), and SMAP-29 (Blower, Barksdale & van Hoek, 2015). However, there are more potential AMPs that are yet to be tested against B. pseudomallei .…”

“…Groups of AMP’s i.e., defensins, cathelicidins, and dermicins have previously been reported to show potential against various pathogens (Wiesner & Vilcinskas, 2010). However, to date, only a few cathelicidin AMPs have been reported to be effective against B. pseudomallei, including LL-37 (Kanthawong et al, 2012), protegrin 1 (PG1) (Sim et al, 2011), bovine lactoferrin (Puknun et al, 2013), phospholipase A2 inhibitors (Samy et al, 2015), and sheep cathelicidin (SMAP-29) (Blower, Barksdale & van Hoek, 2015). …”

Hitchhiking with Nature: Snake Venom Peptides to Fight Cancer and Superbugs

“…This hypothesis was further confirmed in vitro by Gupta el al. and Juba et al, who described membrane depolarization and transient-pore formation in Mycobacterium smegmatis [103], as well as in E.coli and B. cereus [119] after Na-CATH treatment. However, Samuel et al suggested a more detailed mechanism changing from membrane disruption to pore-based lysis, depending on liposome lipid composition and phase [120].…”

“…• Na-CATH: this CATH from the venom gland of the Chinese cobra N. atra [76] also demonstrated powerful, salt-resistant, antimicrobial activity against Gram-positive and Gram-negative bacteria, including Francisella novicida (the non-virulent strain in humans related to Francisella tularensis, the causative agent of tularemia) [98], E.coli, Aggregatibacter actinomycetemcomitans, Bacillus cereus [99], P. aeruginosa [100], and S. aureus [101] at low concentrations (EC 50 < 3 µg/mL). Na-CATH is also active against Mycobacterium smegmatis [102], Burkholderia thailandensis (closely related to B. pseudomallei, the causative agent of melioidosis) [103] and Bacillus anthracis (anthrax) [104]. The last two strains are of particular relevance due to their potential use as biological weapons.…”