title: Fluoroquinolone-resistant and extended-spectrum β-lactamase-producing Escherichia coli from the milk of cows with clinical mastitis in Southern Taiwan.
abstract: OBJECTIVE
  Escherichia coli is a common pathogen to cause clinical and subclinical mastitis in cows. A total of 57 E. coli isolates from raw milk from cows were characterized genetically and biochemically.
  
  
  METHODS
  Extended-spectrum β-lactamase (ESBL) genes, the mechanism for fluoroquinolone resistance, and variations in virulence genes and genomes of these E. coli isolates were investigated by the antimicrobial susceptibility test, simplex and multiplex polymerase chain reaction (PCR), and pulsed-field gel electrophoresis (PFGE).
  
  
  RESULTS
  All E. coli isolates were resistant to cloxacillin (100%) and to a lesser extent (50%) to tetracycline, neomycin, gentamycin, ampicillin, ceftriaxone, cefotaxime (CTX), and ceftazidime (CAZ). Nearly 70% of the isolates were resistant to at least two antimicrobials and 28.1% carried AmpA and AmpC genes simultaneously. The predominant bla gene was blaTEM, followed by blaCMY, blaCTX, blaSHV, and blaDHA.Among the six (10.5%) ESBL-producing E. coli carrying blaCTX-M15, blaCTX-M55, or blaCTX-M14, two isolates 31 of ST410 in the ST23 complex and 58 of ST167 in the ST10 complex were also resistant to ciprofloxacin, enrofloxacin, and levofloxacin, with mutations at codon 83 from serine to leucine and codon 87 from aspartic acid to asparagine in GyrA and at codon 80 from serine to isoleucine in ParC. These isolates were genetically diverse in pulsotype analysis, lacked toxin genes of human pathogenic E. coli and carried mostly the prevalent virulence genes fimH, papGII, and α-hemolysin.
  
  
  CONCLUSIONS
  Lacking virulence genes examined, genetic diverse E. coli isolates are unrelated to human pathogenic E. coli. Enhancing sanitation in milk processing and transportation is needed to eliminate multidrug-resistant (MDR), fluoroquinolone-resistant, and ESBL-producing E. coli isolates.
authors.affiliation: Department of Veterinary Sciences, National Chiayi University, Chiayi, Taiwan, ROC.
authors.forename: Yaochi
authors.initials: Y
authors.lastname: Su
authors.affiliation: Department of Veterinary Sciences, National Chiayi University, Chiayi, Taiwan, ROC.
authors.forename: Chang-You
authors.initials: CY
authors.lastname: Yu
authors.affiliation: Department of Microbiology, Immunology, and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan, ROC.
authors.forename: Yilin
authors.initials: Y
authors.lastname: Tsai
authors.affiliation: Department of Microbiology, Immunology, and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan, ROC.
authors.forename: Shao-Hung
authors.initials: SH
authors.lastname: Wang
authors.affiliation: Department of Microbiology, Immunology, and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan, ROC.
authors.forename: Chihan
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Microbiology, Immunology, and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan, ROC. Electronic address: cschu@mail.ncyu.edu.tw.
authors.forename: Chishih
authors.initials: C
authors.lastname: Chu
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002417:Cattle; D003023:Cloxacillin / Q000494:pharmacology; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics*; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D008414:Mastitis, Bovine / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D060885:Multiplex Polymerase Chain Reaction; D013624:Taiwan; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D024841:Fluoroquinolones; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; C000602253:beta-lactamase CTX-M, E coli; D003023:Cloxacillin
keywords: Escherichia coli; cow; extended-spectrum β-lactamase; fluoroquinolone; mastitis