Antimicrobical resistance of Listeria monocytogenes and Listeria innocua isolated from fish processing plant environment and raw salmon

Abstract

Antimicrobical resistance in foodborne pathogens and therapeutical intervention has always been an important issue in public health context. Listeria monocytogenes unlike other food-borne infectious pathogens can multiply in foods stored in the refrigerator. Because of mortality up to 30%, L.monocytogenes can be dangerous, especially for neonates and older people. It can be a reason for antibiotic resistance transfer to humans via the food chain because of using the antimicrobical agents in veterinary for food animals treatment (Teuber, 2001). The aim of the present study was to identify antimicrobial resistance of Listeria spp. and Listeria monocytogenes isolated from salmon processing plant environment and raw salmon. The study was performed at Lithuanian University of Health Sciences in December 2013–February 2014. In total, 30 Listeria species, 6 Listeria innocua isolated from the food-processing environment, 15 Listeria monocytogenes strains, isolated from the food-processing environment and 9 Listeria monocytogenes strains isolated from raw fish, were analysed.Antimicrobical susceptibility was tested by the agar dilution method in accordance with CLSI (2006). Four antimicrobial agents were tested: tetracycline (TE), erythromycin (ERY), streptomycin (S), and ciprofloxacin (CIP) (all Sigma-Aldrich, MO, USA). The MIC (Minimum inhibitory concentration) was defined as the lowest concentration that produces complete inhibition of growth of Listeria species. MIC study showed that all L. monocytogenes and L. innocua strains isolated from raw salmon samples and processing environments are equally resistant to all tested antimicrobial and were resistant to less than 8 μg ml-1 streptomycin concentration. The lowest concentration of antimicrobial agents inhibits growth L. monocytogenes and L. innocua was ciprofloxacin (1 μg ml-1). Less sensitive Listeria spp., were to erythromycin (2 μg ml-1) and tetracycline (2 μg m [...].