Antimicrobial Activity of a Bacteriocin Produced by Enterococcus faecalis KT11 against Some Pathogens and Antibiotic-Resistant Bacteria

Abstract

In this study, the antimicrobial activity of a bacteriocin produced by Enterococcus faecalis KT11, isolated from traditional Kargı Tulum cheese, was determined, and bacteriocin KT11 was partially characterized. The results showed that bacteriocin KT11 was antagonistically effective against various Gram-positive and Gram-negative test bacteria, including vancomycin- and/or methicillin-resistant bacteria. The activity of bacteriocin KT11 was completely abolished after treatment with proteolytic enzymes (proteinase K, α-chymotrypsin, protease and trypsin), which demonstrates the proteinaceous nature of this bacteriocin. Additionally, bacteriocin KT11 remained stable at pH values ranging from 2 to 11 and after autoclaving at 121℃ for 30 min. In addition, the activity of bacteriocin KT11 was stable after treatment with several surfactants (EDTA, SDS, Triton X-100, Tween 80 and urea) and organic solvents (chloroform, propanol, methanol, ethyl alcohol, acetone, hexane and ethyl ether). Cell-free supernatant of E. faecalis KT11 was subjected to ammonium sulfate precipitation and then desalted by using a 3.5-kDa cut-off dialysis membrane. The bacteriocin activity was determined to be 711 AU/mL in the dialysate. After tricine-SDS-PAGE analysis, one peptide band, which had a molecular weight of ~3.5 kDa, exhibited antimicrobial activity. Because the bacteriocin KT11, isolated from E. faecalis KT11, exhibits a broad antimicrobial spectrum, heat stability and stability over a wide pH range, this bacteriocin can be used as a potential bio-preservative in foods. Additionally, bacteriocin KT11 alone or in combination with conventional antibiotics may provide a therapeutic option for the treatment of multidrug-resistant clinical pathogens after further in vivo studies.

Optimization and characterization of enterocin Enterococcus faecalis K2B1 isolated from Toraja’s Belang Buffalo Milk, South Sulawesi, Indonesia

“…When exposed to range of pH, it seems that BLIS E. faecalis K2B1 stable when exposed to acidic and alkaline. Similar to our finding, Enterocin from E. hirae LD3 (Gupta et al 2016), E. durans 152 (Du et al 2017), E. faecalis CV7 (Perumal and Vankatesen 2017), E. faecalis KT11 (Abanoz and Kunduhoglu 2018) were stable in the pH range 2-8, 2-6, 4-6, 2-11, respectively. This characteristic determines its usefulness in food system especially food manufacturing process.…”

“…The gel was transferred into a petri dish, and then overlaid with 15 mL of soft nutrient agar (seeded with indicator test strain at 10 6 CFU/mL). After incubation at 37℃ for 24 h, the gel was examined for the presence of an inhibitory zone (Goh and Philip 2015;Braiek et al 2017;Abanoz and Kunduhoglu 2018;Bello et al 2018;Sidek et al 2018).…”

“…The unstained gel SDS-PAGE was used for a direct examination of antimicrobial activity using agar overlaid method, for the presence of an inhibitory zone. The inhibition zones were observed from the gel containing crude enterocin for determination of enterocin MW (Pingitore et al 2007;Abanoz and Kunduhoglu 2018). SDS-PAGE gel without staining was washed with sterile aquadest so the remaining SDS can be cleaned.…”

Bacteriocins, Potent Antimicrobial Peptides and the Fight against Multi Drug Resistant Species: Resistance Is Futile?

“…All major lineages of bacteria and archaea are believed to produce at least one bacteriocin. Typically, bacteriocins are very potent but have a limited spectrum of activity, only being effective on species that are phylogenetically related to the bacteriocin-producing bacteria itself [9]. At present, there are four classes (Class I to IV) of bacteriocins (Table 1), categorised based on the host producer, intrinsic function, molecular weight, physicochemical properties, and amino acid sequence.…”

“…Disruption of the outer membrane of Gram-negative bacteria by the metal chelating agent ethylenediaminetetraacetic acid (EDTA) aids in the antimicrobial activity of the class II bacteriocins carnocyclin A [27], an effect also observed with nisin. The globular lantibiotics (e.g., mersacidin) of class I bacteriocins act via enzyme inhibition on essential enzymes of the target cell [9], whereas class III bacteriocins have antibacterial activity via the lysis of sensitive cells by catalysing cell-wall hydrolysis [33]. Gram-negative colicins (large peptides) and microcins (small peptides) possess several cytotoxic mechanisms, such as pore formation, degradation of peptidoglycan precursors, phosphatase activity, activity targeting 16S rRNA and specific tRNAs and DNAse activity [33].…”