AUTHOR=Zhang Anyun , Li Yunxia , Guan Zhongbin , Tuo Hongmei , Liu Dan , Yang Yanxian , Xu Changwen , Lei Changwei , Wang Hongning 

TITLE=Characterization of Resistance Patterns and Detection of Apramycin Resistance Genes in Escherichia coli Isolated from Chicken Feces and Houseflies after Apramycin Administration

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.00328

DOI=10.3389/fmicb.2018.00328

ISSN=1664-302X

ABSTRACT=<p>The aim of this study was to evaluate the influence of apramycin administration on the development of antibiotic resistance in <italic>Escherichia coli</italic> (<italic>E. coli</italic>) strains isolated from chicken feces and houseflies under field conditions. Chickens in the medicated group (<italic>n</italic> = 25,000) were given successive prophylactic doses (0.5 mg/l) of apramycin in their drinking water from Days 1 to 5, while no antibiotics were added to the un-medicated groups drinking water (<italic>n</italic> = 25,000). Over 40 days, a total of 1170 <italic>E. coli</italic> strains were isolated from fecal samples obtained from medicated and un-medicated chickens and houseflies from the same chicken farm. Apramycin MIC90 values for <italic>E. coli</italic> strains obtained from the medicated group increased 32–128 times from Days 2 to 6 (256–1024 μg/ml) when compared to those on Day 0 (8 μg/ml). Strains isolated from un-medicated chickens and houseflies had consistently low MIC90 values (8–16 μg/ml) during the first week, but showed a dramatic increase from Days 8 to 10 (128–1024 μg/ml). The apramycin resistance gene <italic>aac(3)-IV</italic> was detected in <italic>E. coli</italic> strains from medicated (<italic>n</italic> = 71), un-medicated (<italic>n</italic> = 32), and housefly groups (<italic>n</italic> = 42). All strains positive for <italic>aac(3)-IV</italic> were classified into 12 pulsed-field gel electrophoresis (PFGE) types. PFGE types A, E, and G were the predominant types in both the medicated and housefly groups, suggesting houseflies play an important role in spreading <italic>E. coli</italic>-resistant strains. Taken together, our study revealed that apramycin administration could facilitate the occurrence of apramycin-resistant <italic>E. coli</italic> and the apramycin resistance gene <italic>acc(3)-IV</italic>. In turn, these strains could be transmitted by houseflies, thus increasing the potential risk of spreading multi-drug-resistant <italic>E. coli</italic> to the public.</p>