3. Results and discussion
Table 1 shows the results of the MIC of silver–zinc crystals. The
minimal concentration at which the active agent inhibits
microbial growth corresponded to 2.5% for P. aeruginosa ATCC
27853 and P. chrysogenum ATCC 8507; 5% for L. acidophilus ATCC
4356 and L. monocytogenes ATCC 19112, and 10% for S.
typhimurium ATCC 14028, strain that presented the greatest
resistance to the bacteriostatic action of Ag+ ions, according to
reported by McHugh, Moellering, Hopkins, and Swartz (1975)
and it is due to that in Gram-negative bacteria, biocides are
blocked when they reach specific targets in the bacterial outer
membrane related protein pump activation energy dependent
ion (Li, Nikaido, & Williams, 1997); it has also been reported
that mutants of Escherichia coli showed a greatest resistance by
a decrease in permeability of the outer membrane (Li et al.,
1997), caused by the formation of irregularly shaped wells and
a gradual release of lipopolysaccharides and proteins in the
membrane, in the first instance due to reduced metal (Amro
et al., 2000).