Inhibitory activity of Lactobacillus curvatus CWBI-B28 against Listeria monocytogenes and ST2-verotoxin producing Escherichia coli O157

A bacteriocin-producing strain of Lactobacillus curvatus CWBI-B28 isolated from raw meat was shown to inhibit Listeria monocytogenes and pathogenic strains of Escherichia coli by the well diffusionassay. To confirm whether the bacteriocin was involved in E. coli O157 inhibition, growth of the pathogen was monitored in the neutralized cell-free supernatant (NCFS) pre-treated with pronase E orcatalase. Alternatively, E. coli O157 (VH21) was co-cultured with Lb. curvatus CWBI-B28 in MRS broth. The results of the well-diffusion assay suggested that the inhibition of E. coli O157 (VH21) was partially due to the bacteriocin; however, growth monitoring indicated that such inhibition is exclusively due to hydrogen peroxide. In pronase-added NCFS (i.e., absence of bacteriocin) the colony forming units (cfus) of E. coli O157 (VHA21) declined to below the detectable limit after 24 h of incubation at 37°C. However, in presence of catalase no inhibition of the pathogen was observed and the cfus increasedsteadily to reach 8 log units in 24 h. Moreover, in co-culture, a significantly accelerated inhibition of E. coli O157 (VH21) was observed in MRS broth as compared to the NCFS without added catalase and the cfus decreased to below the detectable limit in 8 h instead of 24 h, respectively

Description of two Enterococcus strains isolated from traditional Peruvian artisanal-produced cheeses with a bacteriocin-like inhibitory activity

The aim of this work was to isolate and to characterize strains of lactic acid bacteria (LAB) with bacteriocin-like inhibitory activity from 27 traditional cheeses artisanal-produced obtained from different Peruvian regions. Twenty Gram+ and catalasenegative strains among 2,277 isolates exhibited bacteriocin-like inhibitory activity against Listeria monocytogenes CWBIB2232 as target strain. No change in inhibitory activity was observed after organic acid neutralization and treatment with catalase of the cell-free supernatant (CFS). The proteinic nature of the antimicrobial activity was confirmed for the twenty LAB strains by proteolytic digestion of the CFS. Two strains, CWBI-B1431 and CWBI-B1430, with the best antimicrobial activity were selected for further researches. These strains were taxonomically identified by phenotypic and genotypic analyses as Enterococcus mundtii (CWBI-B1431) and Enterococcus faecium (CWBI-B1430). The two strains were sensitive to vancomycin (MIC 2 μg.ml-1) and showed absence of haemolysis

Inhibitory activity of lactobacillus curvatus CWBI-B28 against Listeria monocytogenes and ST2-verotoxin producing Escherichia coli O157

peer reviewedA bacteriocin- producing strain of Lactobacillus curvatus CWBI- B28 isolated from raw meat was shown to inhibit Listeria monocytogenes and pathogenic strains of Escherichia coli by the well diffusion assay. To confirm whether the bacteriocin was involved in E. coli O157 inhibition, growth of the pathogen was monitored in the neutralized cell- free supernatant ( NCFS) pre- treated with pronase E or catalase. Alternatively, E. coli O157 ( VH21) was co- cultured with Lb. curvatus CWBI- B28 in MRS broth. The results of the well- diffusion assay suggested that the inhibition of E. coli O157 ( VH21) was partially due to the bacteriocin; however, growth monitoring indicated that such inhibition is exclusively due to hydrogen peroxide. In pronase- added NCFS ( i. e., absence of bacteriocin) the colony forming units ( cfus) of E. coli O157 ( VHA21) declined to below the detectable limit after 24 h of incubation at 37 C. However, in presence of catalase no inhibition of the pathogen was observed and the cfus increased steadily to reach 8 log units in 24 h. Moreover, in co- culture, a significantly accelerated inhibition of E. coli O157 ( VH21) was observed in MRS broth as compared to the NCFS without added catalase and the cfus decreased to below the detectable limit in 8 h instead of 24 h, respectively

Bacteriocin Activity By Lactobacillus Curvatus Cwbi-B28 To Inactivate Listeria Monocytogenes In Cold-Smoked Salmon During 4 Degrees C Storage

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