AUTHOR=Ni Juan , Long Xiaoqian , Wang Mengmeng , Ma Jiangang , Sun Yangying , Wang Wen , Yue Min , Yang Hua , Pan Daodong , Tang Biao 

TITLE=Transmission of linezolid-resistant Enterococcus isolates carrying optrA and poxtA genes in slaughterhouses

JOURNAL=Frontiers in Sustainable Food Systems

VOLUME=Volume 7 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2023.1179078

DOI=10.3389/fsufs.2023.1179078

ISSN=2571-581X

ABSTRACT=<sec><title>Introduction</title><p>The presence of linezolid-resistant enterococci found in animal-derived food has attracted attention for possible transmission to human-derived enterococci through the food chain. Linezolid-resistant enterococci in farms have been widely reported, but enterococci carrying antimicrobial resistance (AMR) genes  <italic>poxtA</italic>, <italic>optrA</italic>, or <italic>cfr</italic>(D) in slaughterhouse environments have not been well addressed.</p></sec><sec><title>Methods</title><p>Enterococcus was isolated from the samples collected from two slaughterhouses in Hangzhou, and the Enterococcus carrying linezolidin-resistant genes was identified by PCR. The minimum inhibitory concentration (MIC) of the Enterococcus carrying linezolidin-resistant genes was determined by microbroth dilution method. Finally, the whole genome of strains carrying two or more linezoline resistance genes was sequenced using the Oxford Nanopore Technology</p></sec><sec><title>Results</title><p>Here, 291 enterococci strains were isolated from 309 samples (94.17%). A total of 4 <italic>poxtA</italic>-positive enterococci and 42 <italic>optrA</italic>-positive enterococci were identified based on PCR. The antimicrobial susceptibility test showed that the highest rate of florfenicol resistance was 97.82% and the rate of multidrug resistance (MDR) was 95.65%. Two strains carried multiple linezolid resistance genes, among which <italic>Enterococcus casseliflavus</italic> CQFYY22-063 cocarrying  <italic>optrA</italic>, <italic>poxtA</italic>, and <italic>cfr</italic>(D) was isolated from the duck cecum, and <italic>Enterococcus faecium</italic> CQFYH22-006 cocarrying  <italic>optrA</italic> and <italic>poxtA</italic> was isolated from slaughterhouse sewage for the first time. Furthermore, Oxford Nanopore Technology revealed that the <italic>optrA</italic> gene of strain CQFYY22-063 was located on the Inc18-type plasmid pFYY063-optrA-70K, and the  <italic>poxtA</italic> and <italic>cfr</italic>(D) genes were located on the Inc18-type plasmid pFYY063- poxtA-12K. Meanwhile, the <italic>poxtA</italic> gene of strain CQFYH22-006 was located on the Rep3-type plasmid pFYH006-poxtA-25K, and the <italic>optrA</italic> gene was located on the chromosome.</p></sec><sec><title>Discussion</title><p>Together, linezolid resistance in slaughterhouses deserves extensive attention, indicating the need to strengthen the monitoring of different links in the food production chain within the One Health concept.</p></sec>