AUTHOR=Liao Xiao-Ping , Xia Jing , Yang Lei , Li Liang , Sun Jian , Liu Ya-Hong , Jiang Hong-Xia 

TITLE=Characterization of CTX-M-14-producing Escherichia coli from food-producing animals

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.01136

DOI=10.3389/fmicb.2015.01136

ISSN=1664-302X

ABSTRACT=<p>Bacterial resistance to the third-generation cephalosporin antibiotics has become a major concern for public health. This study was aimed to determine the characteristics and distribution of <italic>bla</italic><sub>CTX-M-14</sub>, which encodes an extended-spectrum β-lactamase, in <italic>Escherichia coli</italic> isolated from Guangdong Province, China. A total of 979 <italic>E. coli</italic> isolates isolated from healthy or diseased food-producing animals including swine and avian were examined for <italic>bla</italic><sub>CTX-M-14</sub> and then the <italic>bla</italic><sub>CTX-M-14</sub><sub>-</sub>positive isolates were detected by other resistance determinants [extended-spectrum β-lactamase genes, plasmid-mediated quinolone resistance, <italic>rmtB</italic>, and <italic>floR</italic>] and analyzed by phylogenetic grouping analysis, PCR-based plasmid replicon typing, multilocus sequence typing, and plasmid analysis. The genetic environments of <italic>bla</italic><sub>CTX-M-14</sub> were also determined by PCR. The results showed that fourteen CTX-M-14-producing <italic>E. coli</italic> were identified, belonging to groups A (7/14), B1 (4/14), and D (3/14). The most predominant resistance gene was <italic>bla</italic><sub>TEM</sub> (<italic>n</italic> = 8), followed by <italic>floR</italic> (<italic>n</italic> = 7), <italic>oqxA</italic> (<italic>n</italic> = 3), <italic>aac(6′)-1b-cr</italic> (<italic>n</italic> = 2), and <italic>rmtB</italic> (<italic>n</italic> = 1). Plasmids carrying <italic>bla</italic><sub>CTX-M-14</sub> were classified to IncK, IncHI2, IncHI1, IncN, IncFIB, IncF or IncI1, ranged from about 30 to 200 kb, and with insertion sequence of IS<italic>Ecp1</italic>, IS<italic>26</italic>, or ORF513 located upstream and IS<italic>903</italic> downstream of <italic>bla</italic><sub>CTX-M-14</sub>. The result of multilocus sequence typing showed that 14 isolates had 11 STs, and the 11 STs belonged to five groups. Many of the identified sequence types are reported to be common in <italic>E. coli</italic> isolates associated with extraintestinal infections in humans, suggesting possible transmission of <italic>bla</italic><sub>CTX-M-14</sub> between animals and humans. The difference in the flanking sequences of <italic>bla</italic><sub>CTX-M-14</sub> between the 2009 isolates and the early ones suggests that the resistance gene context continues to evolve in <italic>E. coli</italic> of food producing animals.</p>