Purpose: This study focused on the molecular and phenotypical characterization of Enterococcus isolates obtained from raw milk and cheese, aiming the determination of their bacteriocinogenic activity and virulence potential.
Methods: Forty-three bacteriocinogenic enterococci isolates, obtained from raw milk and cheese and identified by 16s rDNA, were fingerprinted by RAPD-PCR analysis, and tested for the presence of genes for lantibiotics (lanM, lanB and lanC) and enterocins (entA, entB, entP, entL50AB and entAS48) by PCR. Isolates were also tested for bacteriocins production and inhibitory spectrum using phenotypical tests. Also, the virulence potential of the isolates was evaluated by investigation of genes gelE, hyl, asa1, esp, cylA, efaA, ace, vanA, vanB, hdc1, hdc2, tdc, and odc and by testing the capability to produce gelatinase, lipase, DNAse and α and β-hemolysis.
Results: RAPD analysis divided the 43 isolates in 20 groups (I to XX), being groups III and IV those that contained more isolates (9 and 6, respectively). The antimicrobial substances produced by most isolates were sensitive to α-chymotrypsin, proteinase K, and trypsin, indicating their proteinaceous nature. The isolates presented antimicrobial activity against most Listeria spp. Among the 21 isolates that contained genes for lantibiotics, 14 contained only lanB, 3 contained only lanC, 3 contained lanB and lanC, and 1 contained lanB and lanM. Genes for enterocins P, A and AS48 were detected in isolates from 11, 6 and 5 different RAPD groups. Most RAPD groups contained isolates positive for the tested virulence genes, mainly asa1 (100%), gelE (93.0%), and efaA (83.7%). 53.5% of the isolates presented β-hemolysis.
Significance: The study demonstrated the contradictory characteristics of the tested Enterococcus isolates: they presented a good potential for application in food biopreservation but contained several virulence factors.