Novel enterocin E20c purified from Enterococcus hirae 20c synergised with ß-lactams and ciprofloxacin against Salmonella enterica

Abstract

Background An increasing rate of antibiotic resistance among Gram-negative bacterial pathogens has created an urgent need to discover novel therapeutic agents to combat infectious diseases. Use of bacteriocins as therapeutic agents has immense potential due to their high potency and mode of action different from that of conventional antibiotics. Results In this study, a novel bacteriocin E20c of molecular weight 6.5 kDa was purified and characterized from the probiotic strain of Enterococcus hirae. E20c had bactericidal activities against several multidrug resistant (MDR) Gram-negative bacterial pathogens. Flow cytometry and scanning electron microscopy studies showed that it killed the Salmonella enterica cells by forming ion-permeable channels in the cell membrane leading to enhanced cell membrane permeability. Further, checkerboard titrations showed that E20c had synergistic interaction with antibiotics such as ampicillin, penicillin, ceftriaxone, and ciprofloxacin against a ciprofloxacin- and penicillin-resistant strain of S. enterica. Conclusion Thus, this study shows the broad spectrum antimicrobial activity of novel enterocin E20c against various MDR pathogens. Further, it highlights the importance of bacteriocins in lowering the minimum inhibitory concentrations of conventional antibiotics when used in combination.

Mining, heterologous expression, purification, antibactericidal mechanism, and application of bacteriocins: A review

“…When salivaricin mmaye1 was added to M. luteus , fluorescence intensity of M. luteus stained with SYTOX Green was more than that of untreated cells (Wayah & Philip, 2018), which is similar to plantaricin K25 against B. cereus (Wen et al., 2016). Similarly, the PI intake was improved in indicator bacteria after adding E20c (Sharma et al., 2020), BM1029 (Yan et al., 2020), and plantaricin GZ1‐27 (Du et al., 2018a). Interestingly, the phenomenon of pore formation caused by bacteriocins can be investigated by scanning electron microscopy and transmission electron microscopy in several studies (Qiao et al., 2020; Wen et al., 2016; Yan et al., 2020).…”

“…As shown in Table 6, the range of bacteriocin‐producing microbiota was widened. Those bacteria come from different sources, including meat and vegetables (Gao, Li, Liu, & Zhang, 2015; Hu et al., 2017; Rumjuankiat et al., 2015), soil (Odah et al., 2020; Qin et al., 2019), human skin (Liu et al., 2020; Lynch et al., 2019; O'Sullivan et al., 2020), animal gut (O'Connor, O'Shea, Cotter, Hill, & Ross, 2018; Sahoo, Jena, Patel, & Seshadri, 2015; Sugrue, O'Connor, Hill, Stanton, & Ross, 2020; Wayah & Philip, 2018), and human vagina (Maldonado‐Barragan, Caballero‐Guerrero, Martin, Ruiz‐Barba, & Rodriguez, 2016; Sharma, Rashid, & Kaur, 2020). Interestingly, many novel bacteriocins showed broad‐spectrum antibacterial activity (Lee & Chang, 2018; Sahoo et al., 2015; Sugrue et al., 2020).…”

“…Similarly, the level of ATP and LDH in tested bacteria was also improved when exposed to different kinds of bacteriocins (Lu et al., 2020; Lv et al., 2018; Qiao et al., 2020; Yan et al., 2020). Besides, the K + concentration in the cell supernatants treated with bacteriocins could be determined by flame photometry (Sharma et al., 2020), Inductively coupled plasma mass spectrometry (ICP–MS) (Zhu et al., 2014), and Optima 8000 plasma atomic emission spectrometry (Du et al., 2018a). At the same time, electrical conductance of the L. monocytogenes supernatant was improved after the treatment of PE‐ZYB1 tested by a conductivity meter (Zhang et al., 2020).…”

Application of bacteriocins in food preservation and infectious disease treatment for humans and livestock: a review

“…There have been so many previous research studies done on investigating the inhibitory effects of enterocin on the pathogens found in milk and milk products. 31,55,56 Enterocin A from E. faecium CTC492 and Enterocin 416K1 from E. casseli-avus IM 416K1 were found to be used in cottage cheese to inhibit the growth of L. monocytogenes with 4.57 mg mL À1 of MIC. 57 The combination of enterocins A and B was also applied in the bio-preservation of munster cheese against the pathogen L. monocytogenes.…”

“…The MIC of enterocin E20C needed for the inhibition of the growth of S. enterica was 0.5 mg mL À1 . 55…”