Hop Extract: An Efficacious Antimicrobial and Anti-biofilm Agent Against Multidrug-Resistant Staphylococci Strains and Cutibacterium acnes

Abstract

Bacteria belonging to Staphylococcus genus, in particular methicillin-resistant Staphylococcus aureus and multidrug-resistant Staphylococcus epidermidis , together with Cutibacterium acnes are the main strains involved in skin disease. The increase in multidrug-resistant bacteria has revived attention on natural compounds as alternative agents for the treatment management. Among these, hop extract, a hydroalcoholic solution obtained from experimental crops of Humulus lupulus L. variety cascade (hop), displays diverse biological properties including an antimicrobial one. The aim of this study was to evaluate the antimicrobial activity and the capacity to inhibit the biofilm formation of a characterized hop extract against S. aureus and S. epidermidis multidrug-resistant strains and against a C. acnes strain. The hop extract was characterized by (i) phytochemical analysis through a reversed-phase high-performance liquid chromatography (HPLC)–fluorimetric method, (ii) biocompatibility test with Artemia salina L., (iii) cytotoxicity against two cell lines, (iv) docking analysis, and (v) antimicrobial and antibiofilm activities by detection of zones inhibition, minimal inhibitory concentrations (MICs), biomass quantification, and cell viability. The hop extract was biocompatible and non-cytotoxic at all tested concentrations. HPLC analysis revealed significant levels of gallic acid, resveratrol, and rutin. This last compound was the most representative displaying a high affinity against PBP2a and KAS III (Ki values in the submicromolar range). The characterized hop extract showed a good antimicrobial action with MICs ranging from 1 to 16 μg/mL and was able to inhibit the biofilm formation of all tested strains, except for two S. aureus strains. The biofilm formed in presence of the hop extract was significantly reduced in most cases, even when present at a concentration of 1/4 MIC. The live/dead images showed a remarkable inhibition in the biofilm formation by hop extract with a weak killing action. Overall, the tested hop extract is a good candidate to further explore for its use in the prevention of infection particularly, by multidrug-resistant Gram-positive pathogens.

Prebiotic Combinations Effects on the Colonization of Staphylococcal Skin Strains

“…Anonymized Staphylococcus aureus 815, S. aureus PECHA 10, S. epidermidis 317 and S. epidermidis MDG1 clinical strains, coming from the private collection of the Bacteriology Laboratory of Pharmacy Department, were used in this study. Staphylococcus aureus 815 [ 17 , 18 , 19 ], S. aureus PECHA 10 [ 20 ] and S. epidermidis 317 [ 21 ] were previously characterized for their biofilm-related properties.…”

Searching for New Tools to Counteract the Helicobacter pylori Resistance: The Positive Action of Resveratrol Derivatives

“…pylori strains were inoculated in a Petri dish (3.5 cm) and incubated at 37 °C in a microaerobic condition for 48 h. After incubation, the planktonic phase was removed and the sessile bacterial populations were washed with PBS and stained with Backlight Live/Dead Viability staining (Molecular Probes, Invitrogen detection technologies, USA) as indicated by the manufacturer [ 61 ]. The images were observed at Leica 4000 DM fluorescent microscopy (Leica Microsystems, Milan, Italy), and more fields of view were examined randomly [ 14 ]. Moreover, the samples were also observed under a phase contrast light microscope (Leica 4000 DM) to observe the H. pylori morphology.…”

“…Recent literature displays the synergistic effect of non-antibiotic compounds when combined with standard therapies with the aim to restore the antimicrobial drug efficacy [ 13 , 14 , 15 , 16 ]. This hopeful scenario could be related to the manifold effect on different target sites on the bacterial cell, pharmacokinetic or physicochemical effects (e.g., improvement of solubility or bioavailability), and/or action on a bacterial resistance mechanism [ 17 , 18 ].…”

Xanthohumol from Hop: Hope for cancer prevention and treatment

“…87 The extracts from H. lupulus were also reported to induce anti-microbial activity against Staphylococcus epidermidis and Cutibacterium acnes that are prevalent in skin disease. 88 The bitter extracts from Hop are also effective against inflammation and metabolic disorders. They are also a potential candidate for the treatment of diabetes mellitus and cardiovascular diseases.…”

“…The components of Hop plant such as bitter resins, essential oil (EO), tannins, and terpenes were reported for various biological activities such as anti‐microbial, anti‐oxidant, and anti‐cancer 87 . The extracts from H. lupulus were also reported to induce anti‐microbial activity against Staphylococcus epidermidis and Cutibacterium acnes that are prevalent in skin disease 88 . The bitter extracts from Hop are also effective against inflammation and metabolic disorders.…”