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

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 × 103 to 6.6 × 105 CFU/cm2. 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 MIC50 and MIC90 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%).

► All the 256 pig colons examined contained Tet-R lactobacilli (TRL) in each sample.
► A total of 159 TRL isolates were obtained and identified as belonging to 11 species.
► The TRL isolates displayed a high resistance potency of MIC50 and MIC90.
► REP-PCR demonstrated a notable genotypic strain-diversity (%) of the TRL isolates.
► PCR-detection identified tet (W), (M), (L), (K), and (Q) genes in the TRL isolates.