to extended-spectrum cephalosporins and fluoroquinolones
among Thai isolates might have been underestimated, since some
of the isolates included in the study were selected based on the
results of a disk diffusion screening, which was not reliable for the
detection of extended-spectrum cephalosporin and fluoroquinolone
resistance. A subset of isolates that were defined as intermediately
resistant to extended-spectrum cephalosporins and were
included in the study as representative of the regional zones and
not as potential extended-spectrum cephalosporinase producers
were shown to harbor extended-spectrum cephalosporinaseencoding
genes, and the detection of PMQR genes by disk diffusion
is notoriously difficult (8).