The intrinsic nature of erythromycin resistance in enterobacteria
(Liu et al., 2010) was the cause for identical counts and the same PCRDGGE
patterns of this group in the absence of antibiotics and in
the presence of erythromycin. E. coli was the only enterobacterial
species resistant to tetracycline. Its resistance to this antibiotic has been extensively documented, particularly in pathogenic strains of animal
and human origin (Karczmarczyk et al., 2011; Guerra et al., 2003).
The abrupt changes in the band of E. coli from consecutive samples
may be a reflection of a heterogeneous spatial distribution for E. coli
within the cheese matrix. As mentioned earlier, the presence of
enterobacteria-related bands in the profiles for total cultivable bacteria
grown with erythromycin was due to intrinsic resistance.