AUTHOR=Wang Jing , Wang Yan , Wang Zhen-Yu , Wu Han , Mei Cai-Yue , Shen Peng-Cheng , Pan Zhi-Ming , Jiao Xinan 

TITLE=Chromosomally Located fosA7 in Salmonella Isolates From China

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.781306

DOI=10.3389/fmicb.2021.781306

ISSN=1664-302X

ABSTRACT=<p>This study aimed to investigate the prevalence of fosfomycin <italic>fosA7</italic> in <italic>Salmonella enterica</italic> isolates from food animals and retail meat products in China and the impact of <italic>fosA7</italic> on bacterial fitness. A total of 360 <italic>Salmonella</italic> isolates collected from 11 provinces and cities in China were detected for <italic>fosA7</italic>. All <italic>fosA7</italic>-positive <italic>Salmonella</italic> isolates were determined minimum inhibitory concentrations (MICs) and sequenced by Illumina Hiseq. The <italic>fosA7</italic> gene of <italic>S</italic>. Derby isolate HA2-WA5 was knocked out. The full length of <italic>fosA7</italic> was cloned into vector pBR322 and then transformed into various hosts. MICs of fosfomycin, growth curves, stability, and fitness of <italic>fosA7</italic> were evaluated. The <italic>fosA7</italic> gene was identified in <italic>S</italic>. Derby (ST40, <italic>n</italic> = 30) and <italic>S</italic>. Reading (ST1628, <italic>n</italic> = 5). MICs to fosfomycin of 35 <italic>fosA7</italic>-positive isolates were 1 to 32 mg/L. All <italic>fosA7</italic> were located on chromosomes of <italic>Salmonella</italic>. The deletion of <italic>fosA7</italic> in HA2-WA5 decreased fosfomycin MIC by 16-fold and slightly affected its fitness. The acquisition of plasmid-borne <italic>fosA7</italic> enhanced MICs of fosfomycin in <italic>Salmonella</italic> (1,024-fold) and <italic>Escherichia coli</italic> (16-fold). The recombinant plasmid pBR322-<italic>fosA7</italic> was stable in <italic>Salmonella</italic> Typhimurium, <italic>S</italic>. Pullorum, <italic>S</italic>. Derby, and <italic>E. coli</italic>, except for <italic>Salmonella</italic> Enteritidis, and barely affected on the growth of them but significantly increased biological fitness in <italic>Salmonella</italic>. The spread of specific <italic>Salmonella</italic> serovars such as <italic>S</italic>. Derby ST40 will facilitate the dissemination of <italic>fosA7</italic>. <italic>fosA7</italic> can confer high-level fosfomycin resistance and enhance bacterial fitness in <italic>Salmonella</italic> if transferred on plasmids; thus, it has the potential to be a reservoir of the mobilized fosfomycin resistance gene.</p>