Assessment of antibiotic susceptibility within lactic acid bacteria strains isolated from wine

Susceptibility to 12 antibiotics was tested in 75 unrelated lactic acid bacteria strains of wine origin of the following species: 38 Lactobacillus plantarum, 3 Lactobacillus hilgardii, 2 Lactobacillus paracasei, 1 Lactobacillus sp, 21 Oenococcus oeni, 4 Pediococcus pentosaceus, 2 Pediococcus parvulus, 1 Pediococcus acidilactici, and 3 Leuconostoc mesenteroides. The Minimal Inhibitory Concentrations of the different antibiotics that inhibited 50% of the strains of the Lactobacillus, Leuconostoc and Pediococcus genera were, respectively, the following ones: penicillin (2, ≤ 0.5, and ≤ 0.5 μg/ml), erythromycin (≤ 0.5 μg/ml), chloramphenicol (4 μg/ml), ciprofloxacin (64, 8, and 128 μg/ml), vancomycin (≥ 128 μg/ml), tetracycline (8, 2, and 8 μg/ml), streptomycin (256, 32, and 512 μg/ml), gentamicin (64, 4, and 128 μg/ml), kanamycin (256, 64, and 512 μg/ml), sulfamethoxazole (≥ 1024 μg/ml), and trimethoprim (16 μg/ml). All 21 O. oeni showed susceptibility to erythromycin, tetracycline, rifampicin and chloramphenicol, and exhibited resistance to aminoglycosides, vancomycin, sulfamethoxazole and trimethoprim, that could represent intrinsic resistance. Differences were observed among the O. oeni strains with respect to penicillin or ciprofloxacin susceptibility. Antibiotic resistance genes were studied by PCR and sequencing, and the following genes were detected: erm(B) (one P. acidilactici), tet(M) (one L. plantarum), tet(L) (one P. parvulus), aac(6′)-aph(2ʺ) (four L. plantarum, one P. parvulus, one P. pentosaceus and two O. oeni), ant(6) (one L. plantarum, and two P. parvulus), and aph(3′)-IIIa (one L. plantarum and one O. oeni). This is the first time, to our knowledge, that ant(6), aph(3′)-IIIa and tet(L) genes are found in Lactobacillus and Pediococcus strains and antimicrobial resistance genes are reported in O. oeni strains.