Antibiotic Resistance/Susceptibility Profiles of Strains from Cheese, and Genome Analysis for Antibiotic Resistance Genes.

In food, bacteria carrying antibiotic resistance genes could play a prominent role in the spread of resistance. populations can become large in a number of fermented foods, yet the antibiotic resistance properties of this species have been little studied. In this work, the resistance/susceptibility (R/S) profile of strains ( = 30) from cheese to 16 antibiotics was determined by broth microdilution. The minimum inhibitory concentration (MIC) for all antibiotics was low in most strains, although higher MICs compatible with acquired genes were also noted. Genome analysis of 13 strains showed the resistome to be composed of intrinsic mechanisms, acquired mutations, and acquired genes. As such, a plasmidic gene providing resistance to chloramphenicol was found in one strain; this was able to provide resistance to after electroporation. An (A) polymorphic gene was identified in five strains. The Mrs(A) variants were associated with variable resistance to erythromycin. However, the genetic data did not always correlate with the phenotype. As such, all strains harbored a polymorphic / gene, although only one acquired copy was associated with strong resistance to fosfomycin. Similarly, a plasmid-associated operon encoding a penicillinase system was identified in five ampicillin- and penicillin G-susceptible strains. Identified genes not associated with phenotypic resistance further included (C) in two strains and in all strains. The antibiotic R/S status and gene content of strains intended to be employed in food systems should be carefully determined.