## 4 Discussion
1, the three different treatments of CFS did not significantly change the distribution of LAB and _Bifidobacterium_ to the different classes of inhibition zones (Table 3), which means that the potency of their antimicrobial action was not significantly modified when the organic acids and hydrogen peroxide were eliminated from the CFS. It follows that it was the action of BLS that exerted the inhibition zones observed and the contribution of organic acids and hydrogen peroxide to this effect was minimal, if not negligible. If the contribution of organic acids or activity of hydrogen peroxide was important, the distribution of the LAB and _Bifidobacterium_ would have been significantly different. The exact same conclusions are also valid in the cases of theother two strains of _E. coli_, the two strains _of L. monocytogenes_, the two strains of _Salmonella_ spp., the two strains of _B. cereus_ and the reference strain _E. coli_ O157:H7. In the case of _L. innocua_ (ATOC 33090 TM), the picture is completely different (Table 3). Under Category A, 10 strains showed inhibition zones between 12.1 and 14.0 mm (Class III) and four strains showed inhibition zones between 14.1 and 18 mm (Class IV). When the organic acids were eliminated by the addition of NaOH (Treatment B), five strains showed inhibition zones between 12.1 and 14.0 mm (Class III) and one strain showed inhibition zones between 14.1 and 18 mm (Class IV). Finally, when hydrogen peroxide was eliminated by the addition of catalase (Treatment C), four strains showed inhibition zones between 12.1 and 14.0 mm (Class III) and no strains showed inhibition zones between 14.1 and 18 mm (Class IV). The entire Class IV antibacterial action was due to organic acids (in three out of four strains) and to a lesser extent to hydrogen peroxide (one strain out of four). In Class III, the antibacterial activity of 5 out of 10 strains was due to organic acid production, while the antibacterial activity of one strain was due to hydrogen peroxide. Similar findings are also valid in the case of the two _E. carovova_ strains and the _Xanthomonas_ strain. A possible explanation is that these bacteria were, to some extent, resistant to the activity of the BLS produced by LAB and _Bifidocaterium_, thus leaving space for the organic acids and hydrogen peroxide to act. Another indirect way to check the susceptibility of each pathogen and spoilage bacteria is to compare the bacterial target cells of each species under the same treatment. The three _E.coli_ strains, isolated from fruits and vegetables, showed exactly the same sensitivity to the bacteriocins produced by the LAB and _Bifidobacterium_ trains under Category A (Table 3). A similar observation was valid for Treatments B and C. However, when compared with the reference _E. coli_ O157:H7 strain, significant differences arose for all treatments, showing that the latter strain is more resistant to the BLS than the others. The same resistance to the BLS showed the reference _L. innocua_ strain (a surrogate microorganism for _L. monocytogenes_) while the two strains of _L. monocytogenes_, when compared with each other under each treatment, showed no differences. It seems that the wild types are more sensitive to the action of BLS than the standard registered strains. The two _Salmonella_ spp. strains also showed no differences when compared under the same treatment. However, the two _B. cereus_ strains showed significant differences under all treatments, implying that strain No. 1 was more susceptible than strain No. 2. Finally, the _E. carovova_ strains showed no significant differences under Category A and Treatment B, but showed significant differences under Treatment C. Since in Treatment C the organic acids and the hydrogen peroxide are eliminated, this finding suggests that _E. carovova_ strain No. 1 was more susceptible to the action of BLS than strain No. 2. These findings strongly point out that susceptibility to the BLS is not only species-specific but also, even within the same species, for some species, it is cell-specific.