Xiaoquan  Wang, Xiaowen  Liu, Yanhong  Wang, 
    Characteristics of Fluoroquinolone-Resistant of Avian Pathogenic <i>Escherichia coli</i> Isolates in China,
    Journal of Animal and Veterinary Advances,
    Volume 11,Issue 23,
    2012,
    Pages 4406-4412,
    ISSN 1680-5593,
    javaa.2012.4406.4412,
    (https://makhillpublications.co/view-article.php?doi=javaa.2012.4406.4412)
    Abstract: A total of 121 Avian Pathogenic <I>Escherichia coli</I> (APEC) 
  isolates recovered from diagnosed cases of avian colibacillosis from China during 
  2009 and 2011 were serotyped and examined for susceptibility to nalidixic acid 
  and 6 fluoroquinolones. About 23 different serotypes were determined by agglutination 
  using antisera and 078 (28/121), O143 (21/121) and O2 (15/121) were predominant 
  serotypes. APEC isolates displayed resistance to nalidixic acid (95.9%), norfloxacin 
  (95.0%), ciprofloxacin (94.2%), enrofloxacin (86.8%), levofloxacin (75.2%), 
  lomefloxacin (63.6%) and ofoxacin (61.2%), respectively. Single gyrA changes 
  (mainly Ser 83 to Leu) correlated with nalidixic acid MICs &ge;32 &#956;g mL<SUP>-1</SUP>. 
  The Asp87 changes (mainly Asp87 to Asn) in gyrA were associated with higher 
  ciprofloxacin MICs. ParC alterations comprised amino acid changes Ser 80 to 
  Ile, Ser 80 to Arg, Glu84 to Gly, Glu84 to Lys. The fluoroquinolone-resistant 
  strains for which nalidixic acid MICs were &gt;256 &#956;g mL<SUP>-1</SUP> had 
  both gyrA sand parC QRDR point mutations. The fluoroquinolone-resistant isolates 
  had common point mutations in gyrA (Ser 83 to Leu, Asp87 to Asn) and parC (Ser80 
  to Ile). These strains for which ciprofloxacin MICs were &gt;8 &#956;g mL<SUP>-1</SUP> 
  had double gyrA mutations, accompanying with ParC alterations. Seven recent 
  isolates carried <I>qnrS</I> gene and three carried <I>aac(6')-Ib-cr</I> gene. 
  This suggests that the widespread mutations at position 83, 87 of gyrA and position 
  80 of parC were crucial for resistance to fluoroquinolone and showed significant 
  relation to the high-level fluoroquinolone resistance in APEC.
    Keywords: Fluoroquinolone;resistant;avian pathogenic Escherichia coli;nalicliuic acid;China