A Time-Kill Assay Study on the Synergistic Bactericidal Activity of Pomegranate Rind Extract and Zn (II) against Methicillin-Resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa

Abstract

There is a need for new antimicrobial systems due to increased global resistance to current antimicrobials. Pomegranate rind extract (PRE) and Zn (II) ions both possess a level of antimicrobial activity and work has previously shown that PRE/Zn (II) in combination possesses synergistic activity against Herpes simplex virus and Micrococcus luteus. Here, we determined whether such synergistic activity extended to other, more pathogenic, bacteria. Reference strains of methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa were cultured and subjected to challenge by PRE, Zn (II), or PRE + Zn (II), in time-kill assays. Data were obtained independently by two researchers using different PRE preparations. Statistically significant synergistic activity for PRE + Zn (II) was shown for all four bacterial strains tested compared to untreated controls, although the extent of efficacy and timescales varied. Zn (II) exerted activity and at 1 h, it was not possible to distinguish with PRE + Zn (II) combination treatment in all cases. PRE alone showed low activity against all four bacteria. Reproducible synergistic bactericidal activity involving PRE and Zn (II) has been confirmed. Potential mechanisms are discussed. The development of a therapeutic system that possesses demonstrable antimicrobial activity is supported which lends itself particularly to topical delivery applications, for example MRSA infections.

Synergistic activity of pomegranate rind extract and Zn (II) against Candida albicans under planktonic and biofilm conditions, and a mechanistic insight based upon intracellular ROS induction

“…To conclude, this work successfully demonstrates that the polyphenol-rich composition of PRE and the addition of Zn (II), which is already known for its synergistic antibacterial, antiviral and anti-in ammatory properties, could also make this combination a promising treatment for C. albicans infections [14,19,20,21,28]. Taken together with previous results, the results reported herein against Candida albicans supports the development of a novel broadspectrum antiinfective system.…”

“…Previously, PRE and Zn (II) in combination showed a synergistic antimicrobial activity in vitro against a range of bacteria and HSV [19][20][21]. PRE and copper combination exhibited an enhanced antimicrobial activity against E. coli, Ps.…”

“…The mechanism for the synergistic antimicrobial activity of pomegranate extracts and metal salts is not fully understood, but suggested mechanisms involve the phenolic chemicals forming a complex with metal ions, which has increased antimicrobial action [41]. Also, interaction on the microbe surface could disrupt pump activity, facilitated where a low pH is employed such that the polyphenols would have little surface charge and electrostatic repulsion (21). However, the time kill data alludes to a diffusional aspect as the synergy is not observed in this work until 240 min contact time.…”

“…Recently, the enhancement of the antimicrobial activity of PRE has been explored by the co-application of Zn (II), with signi cant synergistic (potentiated) virucidal activity having been found against herpes simplex virus (HSV) [19] and bactericidal activity against Micrococcus luteus [20], methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, Pseudomonas aeruginosa and S. epidermidis [21]. The signi cance of combination therapy in combating resistance is known, including that for C. albicans [22].…”

Synergistic activity of pomegranate rind extract and Zn (II) against Candida albicans under planktonic and biofilm conditions, and a mechanistic insight based upon intracellular ROS induction

“…The antimicrobial activity of pomegranate extracts has been largely attributed to its polyphenolic content, in particular the hydrolysable ellagitannin, punicalagin, which is particularly abundant in the fruit rind or exocarp 18 , 19 . Recently, the enhancement of the antimicrobial activity of PRE has been explored by the co-application of Zn (II), with significant synergistic (potentiated) virucidal activity having been found against Herpes simplex virus (HSV) 20 and bactericidal activity against Micrococcus luteus 21 , methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, Pseudomonas aeruginosa and S. epidermidis 22 . The significance of combination therapy in combating resistance is known, including that for C. albicans 23 .…”