Abstract:To evaluate the antibiotic susceptibility of 635 strains of L.monocytogenes isolated from 10 types of food origins in 23 provinces in China in 2012, and analyze the multilocus sequence typing (MLST) of resistant strains.MethodsEight kinds of antibiotics, including ampicillin (AMP), trimethoprim-sulfamethoxazole (TMP-SMZ), chloroamphenicol (CHL), erythromycin (ERY), gentamicin (GEN), vancomycin (VAN), ciprofloxacin (CIP) and tetracycline (TET) were chosen to conduct broth microdilution susceptibility tests according to CLSI protocols. MLST was conducted on the resistant strains. Results66 L.monocytogenes isolates were determined as resistant by CLSI interpretive criteria. The average resistant rate was 10.39%. Among them, TET contributed 49 resistant strains, which was the most. The number of the resistant strains of the rest antibiotics were separately 20 (CIP), 10 (ERY), 7 (CHL), 3 (TMP-SMZ), 1 (AMP), 1 (GEN), and 1 (VAN). 8 strains were resistant to two kinds of antibiotics and 7 strains were resistant to at least 3 antibiotics. 77 strains were determined as intermediate, among which 75 belonged to CIP intermediate. The MLST of resistant strains demonstrated that ST155, ST9, ST705 and ST87 were the major ST categories. The antibiotic resistance spectrum of TET and TET-ERY-CHL were seemingly clustered with certain STs from cooked meat products and Chinese cold dishes with meat.ConclusionCurrently in China, despite the average resistance rate was relatively low compared with other foodborne pathogens, it was gradually growing annually. The major STs of resistant strains of foodborne L.monocytogenes were correlated with two antibiotic resistance spectrums.