Antimicrobial Susceptibility of Food-Borne Pathogens Isolated from Frequently Consumed Cheeses in Bulgaria

Cheese is essential to the daily human diet. Rich in nutrients such as proteins and carbohydrates, it is the perfect environment for developing microorganisms. The study aimed to screen the antimicrobi¬al resistance of pathogenic microorganisms isolated from imported Bulgarian cheeses. Randomly picked isolates of bacteria and fungi were cultured in selective and differential media. Isolates were identified using the Crystal Gram-positives system, catalase, PYR-test, and API 20 C AUX Candida. Antimicrobial susceptibility screening was performed against 19 antibiotics and three antifungal substances, according to EUCAST-2023 (The European Committee on Antimicrobial Susceptibility Testing). Isolated bacteria were identified as pathogenic Enterococcus durans, two strains of Enterococcus faecalis 1 and 2, and Staphy¬lococcus simulans. Isolated yeasts belong also to pathogenic Candida krusei – four strains, and Candida glabrata – one strain. Only one strain - E. faecalis-2 showed resistance to three antibiotics from the class of Fluoroquinolones (Ciprofloxacin, Levofloxacin, and Norfloxacin) while the other bacterial strains: E. fae¬calis-1, E. durans, and S. simulans, were susceptible to all tested antibiotics. The fungal isolates C. krusei and C. glabrata demonstrated susceptibility to all three tested antifungal drugs.