Abstract
Lactococcus lactis subsp. lactis MK02R, isolated from rocket salad and previously characterized as a bacteriocin producer strain, was evaluated for its beneficial and safety properties. Genetic and physiological tests indicatedthat this strain has some probiotic properties such as tolerance to low pH and high levels of ox- bile, production of ß-galactosidase, deconjugation of bile salts, high level of hydrophobicity, functional auto- and co- aggregation properties, few virulence factors and absence of genes related to production of biogenic amines and antibiotic resistance. Tests performed with thirty-one antibiotic disks indicated that Lc. lactis subsp. lactis MK02R is resistant to metronidazol, trimetoprime and nalidixic acid, but all other tested antibiotics inhibited its growth to some extent.
The strain grew well in the presence of various commercial medicaments (34 tested) spotted on the surface on of MRS agar inoculated with Lc. lactis subsp. lactis MK02R (106 CFU/mL), being inhibited only by thosecontaining amoxicillin (ß-lactam antibiotic, MIC = 0.39 mg/mL), amiodarone, (antiarrhythmic, MIC = 5.0 mg/mL), diclofenac (non-steroidal anti-inflammatory, MIC = 0.62 mg/mL and 1.25 mg/mL, depending on the manufacturer), dimenhydrinate (antiemetic, MIC = 20.0 mg/mL), ibuprofen arginine (non-steroidal anti- inflammatory, MIC = 15.0 mg/mL) and norfloxacin (antibiotic, MIC = 5.0 mg/mL). PCR analysis evidenced that DNA of Lc. lactis subsp. lactis MK02R lacks the majority of the tested virulence genes, except esp (enterococal surface protein), tdc (tyrosine decarboxilase) and vanA (vancomycin resistance) genes. These results suggest that bacteriocinogenic Lc. lactis subsp. lactis MK02R is a promising probiotic candidate, with low virulence features, complementing its antimicrobial activity.
