| Abstract | ABSTRACT This study presents the characterization of some strains of lactic acid bacteria (LAB) from traditional Egyptian dairy products. Isolated LAB (623 isolates) were studied for their antimicrobial activity against taxonomically related microorganisms. Selected LAB were identified by PCR method as Enterococcus faecium IM1 and Enterococcus hirae IM1. Partially purified enterocins showed antimicrobial activity against Lactobacillus bulgaricus 340, Lb. brevis F104 and F145, Lb. sakei, Brochothrix thermosphacta DSMZ20171T and DSMZ20599, Carnobacterium maltaromaticum CIP103135T, C. piscicola S4312, E. faecalis JH2-2 and JH2-2rr04, E. faecium CTC492/t1362 and P13, Listeria grayi CLIP12518, L. innocua 1, CIP80.11T, F and P, L. ivanovii ATCC and CIP78.42T, L. monocytogenes CIP78.35, DSM12464, EGDe, RF124, RF125, RF131, RF132, RF133, RF142, RF151 and RF152, and Vagococcus penaei CIP 109914T but have no effect against Bacillus subtilis 168T, Moellerella wisconsensis MIP2451, Morganella psychrotolerans MIP2488, Pseudomonas fluorescens 10, Salmonella enterica, Sal. montevideo, Sal. typhimurium and Serratia liquefaciens CIP103238T. The inhibitory activity was not due to hydrogen peroxide for E. hirae IM1, but strain E. faecium IM1 may excrete diverse antimicrobial compounds such as hydrogen peroxide and bacteriocins. Antimicrobial activity of E. faecium IM1 was initially detected during exponential phase of growth, and the maximal level (1,300 AU/mL) was observed at 12 h and remained stable till the end of incubation time (48 h). Maximum of activity of E. hirae IM1 was observed during the logarithmic phase (6 h) and then decreased after 12 h. Bacteriocins produced by E. faecium IM1 and E. hirae IM1 were stable between pH 5 and pH 8 and stable also until 100 °C/20 min. Tested strains were free from virulence determinant genes as well as hemolytic and gelatinase activities. E. faecium IM1 was sensitive to penicillin, kanamycin, vancomycin, gentamicin and tetracycline but resistant to ampicillin. Otherwise, E. hirae IM1 was sensitive to penicillin, kanamycin, vancomycin and tetracycline but resistant to ampicillin and gentamicin. The isolated cultures with antimicrobial activities may be used as safe and useful starter cultures or co-cultures.
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