Antimicrobial Susceptibility, Multilocus Sequence Typing, and Virulence of Listeria Isolated From A Slaughterhouse [post]

Liting Wu, Hongduo Bao, Zhengquan Yang, Tao He, Yuan Tian, Yan Zhou, Maoda Pang, Ran Wang, Hui Zhang
2021 unpublished
Background: Listeria monocytogenes is one of the deadliest foodborne pathogens, and the bacterium can tolerate severe environments through biofilm formation and antimicrobial resistance. The objective of this study was to investigate the antimicrobial susceptibility, resistance genes,virulence and molecular epidemiology about Listeria from meat processing environments. Methods: This study evaluated the antibiotic resistance and virulence of Listeria isolates from slaughtering and processing
more » ... and processing plants. All isolates were subjected to antimicrobial susceptibility testing by using a standard microbroth dilution method. The carrying of resistant genes were identified by Polymerase Chain Reaction (PCR). The multilocus sequence typing (MLST) was determined subtyping of the isolates and to characterize possible routes of contamination from meat processing environments. The virulence of different STs of L. monocytogenes isolates were evaluated by Caco-2 cells invasion assay. Results: A total of 59 Listeria isolates were identified from 320 samples, including 37 L. monocytogenes (62.71%). This study evaluated the virulence of L. monocytogenes and antibiotic resistance of Listeria isolates from slaughtering and processing plants. The susceptibility of these 59 isolates against eight antibiotics was analyzed, and the resistance levels to ceftazidime, ciprofloxacin, and lincomycin were as high as 98.31% (L. m 37; L. innocua 7; L. welshimeri 14), 96.61% (L. m 36; L. innocua 7; L. welshimeri 14), and 93.22% (L. m 35; L. innocua 7; L. welshimeri 13) respectively. Over 90% of the isolates were resistant to 3-6 antibiotics, indicating that Listeria isolated from meat processing environments has high antimicrobial resistance. Up to 60% of the isolates carried the tetracycline-resistance genes tetA and tetM. The frequencies of ermA, ermB, ermC, and aac(6')-Ib were 16.95%, 13.56%, 15.25%, and 6.78%, respectively. Notably, the resistant phenotype and genotype did not match exactly, suggesting that the mechanisms of antibiotic resistance of these isolates were likely related to the processing environment. Multilocus sequence typing (MLST) revealed that 59 Listeria isolates were grouped into 10 sequence types (STs). The dominant L. monocytogenes STs were ST5, ST9, and ST121 in the slaughtering and processing plant of Jiangsu province. Moreover, ST5 subtypes exhibited high invasion in Caco-2 cells compared with ST9 and ST121. Conclusions: The results of this study predict a prevalence of Listeria contamination in the slaughtering and processing plant , and resistance of the ST5 subtypes isolates to the antimicrobials may cause potential public health risks.
doi:10.21203/rs.3.rs-590420/v1 fatcat:ba52v62rj5c7dor5ujnodpeifu