AUTHOR=Cheng Ke , Fang Liang-Xing , Ge Qian-Wen , Wang Dong , He Bing , Lu Jia-Qi , Zhong Zi-Xing , Wang Xi-Ran , Yu Yang , Lian Xin-Lei , Liao Xiao-Ping , Sun Jian , Liu Ya-Hong 

TITLE=Emergence of fosA3 and blaCTX–M–14 in Multidrug-Resistant Citrobacter freundii Isolates From Flowers and the Retail Environment in China

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.586504

DOI=10.3389/fmicb.2021.586504

ISSN=1664-302X

ABSTRACT=<p>We examined the prevalence and transmission of the <italic>fosA3</italic> gene among <italic>Citrobacter freundii</italic> isolates from flowers and the retail environments. We identified 11 fosfomycin-resistant <italic>C. freundii</italic> strains (&gt;256 μg/mL) from 270 samples that included petals (<italic>n</italic> = 7), leaves (<italic>n</italic> = 2), dust (<italic>n</italic> = 1) and water (<italic>n</italic> = 1). These 11 isolates were multidrug-resistant and most were simultaneously resistant to fosfomycin, cefotaxime, ciprofloxacin and amikacin. Consistently, all 11 isolates also possessed <italic>bla</italic><sub><italic>CTX–M–</italic></sub><sub>14</sub>, <italic>bla</italic><sub><italic>CMY–</italic></sub><sub>65</sub><sub>/</sub><sub>122</sub>, <italic>aac(6’)-Ib-cr</italic>, <italic>qnrS1</italic>, <italic>qnrB13/6/38</italic> and <italic>rmtB</italic>. These <italic>fosA3</italic>-positive isolates were assigned to two distinct PFGE patterns and one (<italic>n</italic> = 9) predominated indicating clonal expansion of <italic>fosA3</italic>-positive isolates across flower markets and shops. Correspondingly, <italic>fosA3</italic> was co-transferred with <italic>bla</italic><sub><italic>CTX–M–</italic></sub><sub>14</sub><italic>via</italic> two plasmid types by conjugation possessing sizes of 110 kb (<italic>n</italic> = 9) and 260 kb (<italic>n</italic> = 2). Two representatives were fully sequenced and p12-1 and pS39-1 possessed one and two unclassified replicons, respectively. These plasmids shared a distinctive and conserved backbone in common with <italic>fosA3</italic>-carrying <italic>C. freundii</italic> and other <italic>Enterobacteriaceae</italic> from human and food animals. However, the <italic>fosA3</italic>-<italic>bla</italic><sub><italic>CTX–M–</italic></sub><sub>14</sub>-containing multidrug resistance regions on these untypable plasmids were highly heterogeneous. To the best of our knowledge, this is the first report of <italic>fosA3</italic> and <italic>bla</italic><sub><italic>CTX–M–</italic></sub><sub>14</sub> that were present in bacterial contaminants from flower shops and markets. These findings underscore a public health threat posed by untypable and transferable p12-1-like and pS39-1-like plasmids bearing <italic>fosA3</italic>-<italic>bla</italic><sub><italic>CTX–M–</italic></sub><sub>14</sub> that could circulate among <italic>Enterobacteriaceae</italic> species and in particular <italic>C. freundi</italic> in environmental isolates.</p>