Characterization of tetracycline resistance lactobacilli isolated from swine intestines at western area of Taiwan.

Abstract To investigate the frequency of tetracycline resistance (Tet-R) lactobacilli in pig intestines, a total of 256 pig colons were analyzed and found to contain typical colonies of Tet-R lactic acid bacteria in every sample, ranging from 3.2 × 10 3 to 6.6 × 10 5  CFU/cm 2 . From these samples, a total of 159 isolates of Tet-R lactobacilli were obtained and identified as belonging to 11 species, including Lactobacillus reuteri , Lactobacillus amylovorus , Lactobacillus salivarius , Lactobacillus plantarum , Lactobacillus ruminis , Lactobacillus kefiri , Lactobacillus fermentum , Lactobacillus sakei , Lactobacillus coryniformis , Lactobacillus parabuchneri and Lactobacillus letivazi . Based on the EFSA (2008) breakpoints, all isolates, after MIC analysis, were qualified as Tet-R, from which the significant high Tet-R MIC 50 and MIC 90 values indicated an ecological distribution of Tet-R lactobacilli mostly with high resistance potency in pig colons. PCR-detection identified 5 tet genes in these isolates, the most predominant one being tet (W), followed by tet (M), (L), (K), and (Q). Their detection rates were 82.0%, 22.5%, 14.4%, 8.1% and 0.9%, respectively. Noteworthily, isolates of the same species carrying identical tet gene(s) usually had a wide different MIC values. Furthermore, strain-subtyping of these isolates by REP-PCR demonstrated a notable genotypic biodiversity % (average = 62%).