Summary
Resistance
to fluoroquinolones was evaluated in 17 nalidixic acid-resistant
Escherichia coli strains isolated from animal faeces. Polymerase
chain reaction (PCR), restriction fragment length polymorphism (RFLP),
hybridisation and sequencing were used to reveal point mutations
in DNA gyrase subunits A and B and the presence of the qnr
gene as evidence of plasmid resistance. Chromosomal resistance and
class 1 integrons were found in 10 of the 17 E. coli strains
examined, while the qnr gene was not found in any of these.
Mutation Ser83-Leu was found in six strains and in one strain mutation
Ser83-Ala was found in gyrA. Mutations in gyrA Asp87 codons
and in gyrB Asp426 or Lys 447 codons were not identified.
Sequencing of the E. coli strain ATCC 25922 subjected to
resistance induction revealed a gyrB mutation of the Lys
447 residue which had been replaced by arginine.
Keywords
Antimicrobial
resistance, Escherichia coli, Hybridisation, Nalidixic acid,
Polymerase chain reaction, Restriction fragment length polymorphism,
Sequencing, Resistance. |