title: [Identification of lactic acid bacteria in commercial yogurt and their antibiotic resistance].
abstract: OBJECTIVE
  To identify lactic acid bacteria (LAB) in commercial yogurts and investigate their antibiotic resistance.
  
  
  METHODS
  LABs were cultured from 5 yogurt brands and the isolates were identified at the species level by 16S rRNA sequence. Genotyping was performed by repetitive extragenic palindromic PCR (rep-PCR). The sensitivity to 7 antibiotics was tested for all LAB isolates by Kirby-Bauer paper diffusion (K-B method). Meanwhile, 9 antibiotic resistance genes (ARGs), including erythromycin resistance genes (ermA and ermB) and tetracycline resistance genes (tetM, tetK, tetS, tetQ, tetO, tetL and tetW), were detected by PCR amplification in the identified LAB isolates. The PCR products were confirmed by sequencing.
  
  
  RESULTS
  Total 100 LABs were isolated, including 23 Lactobacillus delbrueckii ssp. bulgaricus, 26 Lactobacillus casei, 30 Streptococcus thermophilus, 5 Lactobacillus acidophilus, 6 Lactobacillus plantarum, and 10 Lactobacillus paracasei. The drug susceptibility test shows that all 100 isolates were resistant to gentamicin and streptomycin, 42 isolates were resistant to vancomycin, and on the contrary all were sensitive to cefalexin, erythromycin, tetracycline and oxytetracycline. Moreover, 5 ARGs were found in the 28 sequencing confirmed isolates, ermB gene was detected in 8 isolates, tet K in 4 isolates, tetL in 2 isolates, tetM in 4 isolates, tetO in 2 isolates. erm A, tet S, tet Q and tet W genes were not detected in the isolates. Antibiotic resistance genes were found in 53.57% (15/28) sequenced isolates, 2 -3 antibiotic resistance genes were detected in 4 isolates of L. delbrueckii ssp. bulgaricus.
  
  
  CONCLUSIONS
  Some LABs were not labeled in commercial yogurt products. Antibiotic resistance genes tend to be found in the starter culture of L. delbrueckii ssp. Bulgaricus and S. thermophilus. All the LAB isolates were sensitive to erythromycin and tetracycline, even though some carried erythromycin and/or tetracycline resistance genes. We proved again that LAB could carry antibiotic resistance gene(s) though it is sensitive to antibiotics.
authors.affiliation: College of Life Sciences, Guizhou University, Guiyang 550025, China. qinyuxuan8899@163.com
authors.forename: Yuxuan
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: The High School Attached to Tsinghua University, Beijng 100084, China.
authors.forename: Qiuya
authors.initials: Q
authors.lastname: Wang
authors.affiliation: The High School Affiliated to Renmin University of China, Beijing 100080, China.
authors.forename: Kexin
authors.initials: K
authors.lastname: Gao
authors.affiliation: Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Baoli
authors.initials: B
authors.lastname: Zhu
authors.affiliation: Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Na
authors.initials: N
authors.lastname: Lv
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D019344:Lactic Acid / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D015014:Yogurt / Q000191:economics / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D019344:Lactic Acid