Microbiota of Fresh and Canned Green Table Olives and Antibiotic Resistance of Foodborne Pathogens

Olives are the main part of the healthy, largely vegetarian, Mediterranean diet known to have aquin¬tessential role in prolonging lifespan. All parts of the olive plant - leaves, roots, flowers and fruits are rich in beneficial bacteria. Often, during olive processing and storage foodborne bacteria grow and spoil the prod¬uct. The aim of this study was dual - to investigate the microbiota in fresh and canned green table olives, and to test foodborne bacteria isolated from olives for their antibiotic resistance. The presence of pathogens as clostridia, Staphylococci, fecal enterococci, yeasts, Candida spp. and Escherichia coli and coliforms was assessed using selective, differential and chromogenic media. Randomly picked colonies were further sub-cultured and tested for antibiotic resistance towards 17 antibiotics and six antifungals. Our results showed that fresh olives contained total number of microorganisms (CFU) - 3x102, fecal enterococci - 2.4x104, Candida – 1.5x102 CFU/g and total number of yeasts and molds - 2.3x103. Staphylococci, clostridia and E. coli and coliforms were not detected in fresh olives. In contrast, no bacteria, yeasts and molds, Candida, Staphylococci, clostridia and E. coli and coliforms were observed in canned green olives. Two isolates from fresh olives were further analyzed. They were identified as Enterococcus faecium and Candida krusei. The antibiotic resistance analysis demonstrated resistance of E. faecium 3391 to nine out of 17 antibiotics, in¬cluding Linezolid, an antibiotic used for treatment of severe infections. C. krusei 3389 showed resistance to two out of six antifungals – to Itraconazole and Fluconazole, belonging to the class of triazole compounds.