Research Information System
in: Essential Oils and Nanotechnology for Treatment of Microbial Diseases, M. Rai,S. Zucchino and M.G. DeritM. Rai,S. Zucchino and M.G. Derita, Editor, CRC Press, Florida, pp.143-158, 2017
Infectious diseases caused by bacteria, viruses, parasites and fungi, and their interaction with hosts and the environment are a global public health threat. Initially, at the time when antibiotics were discovered, the infections that affected humankind could be readily eradicated. But their indiscriminate use has led to the emergence of multidrug-resistant microorganisms (MDR) which are hard to control (Hemaiswarya et al. 2008). The infections produced by MDR cause appreciable patient mortality and morbidity. In 2005, in the United States about 95,000 people acquired methicillin-resistant Staphylococcus aureus (MRSA) infections and 19,000 people died of this cause (Worthington and Melander 2013). The microorganisms that pose a threat to human beings comprise ESKAPE pathogens (Enterococcus faecium, S. aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) as well as emerging and re-emerging pathogens such as carbapenem-resistant K. pneumoniae (CRKP), the New Delhi metallo-β-lactamase-containing Enterobacteriaceae, MDR and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis (MDR-TB and XDRTB) and non-tubercular mycobacteria, Candida albicans and pathogenic fungi (Tegos and Hamblin 2013). Of these, the most dangerous MDR, XDR and pandrug-resistant (PDR) strains have currently been redefined as follows: MDR are the organisms that are drug-resistant at least to one medication belonging to three or more antimicrobial groups and XDR are the drug-resistant organisms to at least one medication belonging all but located in two or fewer classes of antibiotics. Also PDR are defined as drug resistant organism to all antimicrobial medications across classes. Therefore, it is assumed that a clinical isolate that is defined as XDR is a MDR and a XDR strain can be defined as PDR (Magiorakos et al. 2012). Equally, antiviral drug resistance is a rising concern particularly in immune-compromised patient populations, where prolonged exposure to drugs causes the selection of resistant mutants due to viral factors as viral mutation frequency, virus replication as well as viral replication fitness. This is compounded by the contribution of other host factors that increase the risks such as older age and no adherence to medication (Strasfeld and Chou 2010). On the other hand, the emergence of drug-resistant parasites (mainly malaria) to the commonly used drugs, has been a great cost to human health and quality of life (Lin et al. 2010). These resistance patterns are further modified by factors similar to those found in other microorganisms such as mutation rate, fitness associated with the resistance mutations, microbial load, the strength of drug selection and the treatment adherence .