Effects of extracts from Italian medicinal plants on planktonic growth, biofilm formation and adherence of methicillin-resistant Staphylococcus aureus

Abstract

Aim of study: One-third of botanical remedies from southern Italy are used to treat skin and soft tissue infection (SSTI). Staphylococcus aureus, a common cause of SSTI, has generated increasing concern due to drug resistance. Many plants possess antimicrobial agents and provide effective remedies for SSTI. Our aim was to investigate plants from different ethnobotanical usage groups for inhibition of growth and biofilms in methicillin-resistant Staphylococcus aureus (MRSA).

Materials and methods: Three groups were assessed: plant remedies for SSTI, plant remedies not involving the skin, and plants with no ethnomedical application. We screened 168 extracts, representing 104 botanical species, for activity against MRSA (ATCC 33593). We employed broth dilution methods to determine the MIC after 18 h growth using an optical density (OD 600 nm) reading. Anti-biofilm effects were assessed by growing biofilms for 40 h, then fixing and staining with crystal violet. After washing, 10% Tween 80 was added and OD 570 nm readings were taken.

Results: Extracts from 10 plants exhibited an IC50<or=32 microg/ml for biofilm inhibition: Lonicera alpigena, Castanea sativa, Juglans regia, Ballota nigra, Rosmarinus officinalis, Leopoldia comosa, Malva sylvestris, Cyclamen hederifolium, Rosa canina, and Rubus ulmifolius. Limited bacteriostatic activity was evident.

Conclusion: This study has demonstrated that the anti-biofilm activity of medicinal plants used for SSTI is significantly greater than plants without any ethnomedical applications.

Figure 1

Map of the study area: Vulture-Alto Bradano, Basilicata Province, Italy.

Figure 2

The percent inhibition of extracts for planktonic growth, biofilm formation and adherence in MRSA. (a) Arundo donax, aqueous extract of nodes; (b) Ballota nigra, aqueous extract of aerial parts; (c) Juglans regia, ethanolic extract of immature fruits; (d) Leopoldia comosa, ethanolic extract of bulbs; (e) Marrubium vulgare, ethanolic extract of roots.

Figure 2

The percent inhibition of extracts for planktonic growth, biofilm formation and adherence in MRSA. (a) Arundo donax, aqueous extract of nodes; (b) Ballota nigra, aqueous extract of aerial parts; (c) Juglans regia, ethanolic extract of immature fruits; (d) Leopoldia comosa, ethanolic extract of bulbs; (e) Marrubium vulgare, ethanolic extract of roots.

Figure 3

The white hemicellulose membrane found at the node of the giant reed (Arundo donax L. [Poaceae]) is used as a haemostatic agent for minor lacerations.