Fighting Multidrug Resistance with Herbal Extracts, Essential Oils and their Components offers scientists a single source aimed at fighting specific multidrug-resistant (MDR) microorganisms such as bacteria, protozoans, viruses and fungi using natural products. This essential reference discusses herbal extracts and essential oils used or under investigation to treat MDR infections, as well as those containing antimicrobial activity that could be of potential interest in future studies against MDR microorganisms. The need to combat multidrug-resistant microorganisms is an urgent one and this book provides important coverage of mechanism of action, the advantages and disadvantages of using herbal extracts, essential oils and their components and more to aid researchers in effective antimicrobial drug discovery - Addresses the need to develop safe and effective approaches to coping with resistance to all classes of antimicrobial drugs - Provides readers with current evidence-based content aimed at using herbal extracts and essential oils in antimicrobial drug development - Includes chapters devoted to the activity of herbal products against herpes, AIDS, tuberculosis, drug-resistant cancer cells and more

Many bacterial diseases affect animals, causing important economic losses in livestock. Subtherapeutic antibiotic use in production animals as antibiotic growth promoters has been implicated as a causative factor in the development of resistance of bacterial pathogens toward several classes of antimicrobials, some of which are used therapeutically in humans. This has led to the banning of antibiotic growth promoters by the European Union, and such a precedent may be followed in other countries. Alternatives to antibiotic growth promoters are necessary to enable the production of animal protein to keep pace with the expanding world population. One approach is to use plant extracts or essential oils as supplements to provide beneficial effects, including direct antibacterial activity and stimulation of the immune system, or enhancement of ruminal digestion. The risk of resistance developing to a combination of phytochemicals is lower than the risk of resistance against a single antibiotic, and synergistic effects of plant constituents may contribute to the overall activity of the preparation.

The genus Candida comprises more than 200 species, but few of them have been associated with human infections. C. albicans is the most important cause of disease. Other species such as C. dubliniensis, C. glabrata, C. guilliermondii, C. krusei, C. parapsilosis, and C. tropicalis are also being increasingly recognized as significant human pathogens. In recent years, the number of clinical infections caused by Candida species worldwide has risen considerably, and the incidence of resistance to traditional antifungal therapies is also increasing. There is an exigent need for novel antifungal remedies, and plants remain a vital source of these new substances, especially in low-resource countries. Natural compounds are potential antimycotic agents either in their nascent form or as template structures for more effective derivatives. The data and studies described in this chapter document the antimicrobial activity of plant extracts and essential oils against Candida species and show that medicinal plants can be a rich source of potential antifungal compounds.

High prevalence of multidrug-resistant microorganisms in the etiologic structure of different infectious processes significantly decreases the effectiveness of the treatment and enhances the probability of an unfavorable outcome from the infection. Combinations between antibiotics and other antimicrobial agents represent one of the most promising approaches for combating multidrug-resistant bacteria. A high therapeutic potential exists for combinations of antibiotics and natural antimicrobial substances with complex mechanisms of action and multiple healing properties, such as plant essential oils. The purpose of the present chapter is to review published studies on antibiotic-essential oil combinations and discuss the prospects for future studies. In general, many studies have shown the potential for essential oils to act synergistically with antibiotics in vitro. The main proposed mechanism of this beneficial effect is through inhibition of efflux pumps by some essential oils, which restores the activity of the antibiotic. Future efforts should be directed into further studies of antibiotic-essential oil combinations against multidrug-resistant bacteria, with an emphasis on understanding the mechanisms of the produced effect. Combinations of essential oils with different types of antimicrobial agents, such as bacteriophages, nanoparticles, and quorum-sensing inhibitors, require greater attention and are worthy of future investigations.

Herpes simplex virus (HSV) infections comprise one of the most important health problems worldwide. HSV-1 and HSV-2 that are the types most frequently seen in disease, manifested by sores and blisters on the mouth, tongue, skin, and genitals of infected individuals. Moreover, herpetic infections can reach life-threatening levels; for instance, HSV-2 prevalence has increased greatly in human immunodeficiency virus-positive patients. This indicates that the herpetic infection could be a major cause of morbidity in immunosuppressed patients. Unfortunately, resistance against antiherpetic drugs has recently been reported. Therefore there is an immediate need to search for new antiviral agents in order to cope with HSV infections. Recently, it has been demonstrated that traditional medicinal plants have strong antiviral activity and some are already being used in the treatment of viral infections, including herpes simplex infections. Accordingly, this chapter aims to present published information on various herbal compounds, investigate the antiherpetic effectiveness of these compounds, and determine the potential of plants as herpetic treatments in the future.

Aromatic and medicinal plants, through their secondary metabolism, provide a complex mixture of volatile molecules known as essential oils. These volatile molecules exert antibacterial activity that has been used in folk medicine for centuries. During the last few decades, the emergence of antibacterial resistance has forced us to search for new and efficient antimicrobial agents. The significant number of studies on the use of essential oils and their components against multidrug-resistant bacteria, such as Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus, Mycobacterium tuberculosis, and Pseudomonas aeruginosa show the exceptional potential of these natural products to curb the development of antibacterial resistance. Moreover, the use of essential oils and their components in combination with antibiotics may increase bacterial susceptibility, thus limiting resistance.

The development of vancomycin resistance by some microbial strains has made the treatment of some infections more difficult and, in many cases, impossible. Although the search for new drugs against vancomycin-resistant organisms has been very successful, resistance can arise against many of these compounds. Natural products are an invaluable source of a diversity of biologically active compounds for addressing the challenges facing drug development initiatives to combat vancomycin-resistant enterococcal infections. Despite the fact that scientific data on plant metabolites active against vancomycin-resistant enterococci remain scarce, some compounds (including terpenoids and phenolics) have been reported to have inhibitory effects at various levels. This chapter describes the state of the art of research into plant bioactive metabolites against vancomycin-resistant enterococci, highlighting the hit compounds.

Methicillin-resistant Staphylococcus aureus (MRSA) is currently one of the most common causes of serious infections, in both hospital and community environments. This type of resistance was discovered in the 1960s, and now (50 years later) it has not been possible to develop an effective therapy to fight against it. This chapter compiles the results of several studies demonstrating the activity (mainly in vitro) of various extracts, essential oils, and plant-derived molecules that can act alone or in combination against MRSA. In addition, natural alternatives (other than from plants) being studied for the same purpose are described. Finally, the important role of phytotherapy in the development of new therapies against multidrug-resistant bacteria such as MRSA is emphasized.

The global increase in antimicrobial resistance has led to renewed interest in alternative antimicrobial treatment strategies. Research is being done into a wide range of possible treatment regimens, including phage therapy, novel vaccines, and novel peptides, to name a few. Many microbiologists continue to lobby their governments to ensure that the available antibiotics are retained for the treatment of serious infections and their inappropriate use is stopped. In addition, large pharmaceutical companies are being encouraged to develop new treatments for the future. Much research now focuses on medicinal plants and essential oils. These and other alternative approaches are outlined in this chapter.

Leishmaniasis is an infectious disease caused by parasites belonging to the Leishmania genus. This disease has a prevalence that exceeds 12 million, and approximately 350 million individuals are currently residing in areas at risk for contracting the infection. The standard drugs employed in the treatment pose serious side effects for patients. Moreover, some reports suggested that the Leishmania species present different degrees of resistance to conventional drugs, which justifies the ongoing search for novel leishmanicidal molecules. In only a few decades, the available research pertaining to plant-derived leishmanicidal compounds has increased considerably; however, the majority of bioguided studies have only shown antileishmanial activity in vitro, thus ignoring the potential in vivo effects of different classes of plant-derived compounds on Leishmania species. This chapter will discuss the main findings of works published from 2002 to 2012 on purified plant compounds and their leishmanicidal effects in vivo.