Screening of antimicrobial metabolite yeast isolates derived biome Ceará against pathogenic bacteria, including MRSA : antibacterial a ctivity and mode of action evaluated by flow cytometry

Abstract

Antimicrobials benefited the history of medicine by revolutionizing the treatment of infectious diseases. However, its consequent and continuous use has led to the emergence of microorganisms which once were considered safe, but have become feared as potentially lethal pathogens (Bowler et al., 2012). Staphylococcus aureus infections are highlighted for being a major cause of systemic infections, and for being the microorganism that has the highest morbidity and mortality rates in hospital infections (Smith et al., 2009). In addition, these strains have a remarkable ability to acquire antimicrobial resistance, with methicillin (MRSA) resistance being an increasing public health issue(Rodriguez-Noriega and Seas, 2010). In Brazil, in a study by Santos et al. (2010) in a tertiary hospital, a high incidence of MRSA colonization was reported, in which the acquisition rate was of 5.5/1.000 patient-days for adults. In another study performed in northeastern Brazil with hospitalized patients, Almeida et al., (2014) reported that among the colonized wounds by S. aureus, 32% were MRSA. Within this context, the emergence of strains with reduced sensitivity accompanied by a limited antimicrobial therapy causes the need of a search for new therapeutic options (Boucher et al., 2009). Antibacterial agents are the most important natural products, in which prokaryotes organisms and some fungi deserve special mention for playing an important role in the production of secondary metabolites with potential therapeutic applications (Singh and Macdonald, 2010). Throughout the world, approximately 99.000 fungi species were described (Kirk et al. 2008), of which approximately 3.7% of the world's diversity exist in Brazil, and the Brazilian Northeastern region has the largest number of records related to fungal diversity (Maia and Carvalho Junior 2010). In this study, isolate yeasts from the northeastern region of Brazil, more specifically from the state of Ceará, were analyzed. This area ecosystem is diverse and little investigated regarding the isolation of yeasts that produce metabolites with antimicrobial activity. Thus, this research aims to contribute to increase knowledge about the activity of extracts derived from isolated yeasts from Ceará with antimicrobial potential, as well as to contribute with a possible description of their mechanisms of action.