AUTHOR=Weng Rui , Gu Yihai , Zhang Wei , Hou Xuan , Wang Hui , Tao Junqi , Deng Minghui , Zhou Mengrong , Zhao Yifei 

TITLE=Whole-Genome Sequencing Provides Insight Into Antimicrobial Resistance and Molecular Characteristics of Salmonella From Livestock Meat and Diarrhea Patient in Hanzhong, China

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.899024

DOI=10.3389/fmicb.2022.899024

ISSN=1664-302X

ABSTRACT=<p><italic>Salmonella</italic> is a major zoonotic pathogen, which usually contaminates food resulting in salmonellosis in humans. Exploring the characteristics and origins of <italic>Salmonella</italic> is essential in formulating prevention and control measures for <italic>Salmonella</italic> infection. We used slide agglutination, antimicrobial susceptibility testing, and whole-genome sequencing to analyze and compare <italic>Salmonella</italic>’s phenotype, genotyping diversity, and genetic relatedness from livestock meat and diarrhea patients in Hanzhong, China, from 2018 to 2020. Totally 216 <italic>Salmonella</italic> enterica isolates were screened from frozen whole chicken carcasses (44.3%, 70/158), frozen raw ground pork (36.2%, 59/163), and diarrhea patients (4.4%, 87/1964). <italic>Salmonella</italic> Typhimurium was the dominant serotype. Notably, compared with other sources, isolates obtained from frozen whole chicken carcasses showed significant resistance to third-generation cephalosporin and fluoroquinolones (<italic>p</italic> &lt; 0.05). All strains were assigned into 36 sequence types (STs) and two novel STs, and an excellent consistency was observed between ST and serotype. Genomic data revealed that extended-spectrum β-lactamase genes were responsible for third-generation cephalosporin resistance in 52 <italic>Salmonella</italic> strains, and the most predominant resistance determinant was <italic>bla</italic><sub>CTX–M</sub>. Furthermore, of the 60 ciprofloxacin-resistant isolates, five single-base mutations in quinolone resistance-determining regions were identified in <italic>gyrA</italic> or <italic>parC</italic>, and the plasmid-mediated quinolone resistance gene <italic>aac(6’)Ib-cr</italic> was most often detected. The cgMLST clusters show that five clusters among four serotypes (including <italic>S</italic>. Typhimurium, <italic>S</italic>. London, <italic>S</italic>. Derby, and <italic>S</italic>. Agona) cover samples from diarrhea patients and livestock meat pathway isolate, indicating a possibility of cross-host transmission. In conclusion, the livestock meat isolates have a higher level of resistance than diarrhea patients’ isolates and could be an essential source of human <italic>Salmonella</italic> infection.</p>