OBJECTIVES To investigate quinolone resistance mechanisms in an Escherichia coli clinical isolate (Ar2) resistant to ofloxacin but susceptible to nalidixic acid selected after 10 days of ofloxacin therapy in a patient with prostatitis. METHODS Molecular typing (ERIC-PCR and RAPD), antibiotic susceptibility and gyrA, gyrB, parC and parE QRDR sequences were compared for E. coli Ar2 and a wild-t...

The low prevalence of ciprofloxacin-resistant (Cp r) Streptococcus pneumoniae isolates carrying recombinant topoisomerase IV genes could be attributed to a fitness cost imposed by the horizontal transfer, which often implies the acquisition of larger-than-normal parE-parC intergenic regions. A study of the transcription of these genes and of the fitness cost for 24 isogenic Cp r strains was per...

Two different type II topoisomerases are known in bacteria. DNA gyrase (Gyr) introduces negative supercoils into DNA. Topoisomerase IV (Par) relaxes DNA supercoils. GyrA and ParC subunits of bacterial type II topoisomerases are involved in breakage and reunion of DNA. The spatial structure of the C-terminal fragment in GyrA/ ParC is not available. We infer homology between the C-terminal domain...

To determine if susceptibility testing of Streptococcus pneumoniae could detect those isolates that had one of the recognized mechanisms of fluoroquinolone resistance, 101 isolates were selected; the levofloxacin MIC for 28 of these isolates was > or =4 microg/ml. Only isolates with both parC and gyrA mutations or with no recognized resistance mechanisms were reliably identified by using these ...

Sir, In Gram-positive cocci, fluoroquinolone resistance is associated with mutational alterations in DNA gyrase and/or topoisomerase IV or with active efflux of the drugs. In Streptococcus pneumoniae, fluoroquinolone resistance is mainly due to substitutions in ParC (Ser-79→Phe or Tyr, Asp-83→Asn), ParE (Asp-435→Asn) or GyrA (Ser-81→Phe or Tyr, Glu-85→Lys or Gly).1,2 Therefore, detection of the...

To evaluate the molecular mechanism of fluoroquinolones resistance in Mycoplasma hominis (MH) clinical strains isolated from urogenital specimens. 15 MH clinical isolates with different phenotypes of resistance to fluoroquinolones antibiotics were screened for mutations in the quinolone resistance-determining regions (QRDRs) of DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE) in ...

In the treatment of serious bacterial infections, the rapid institution of appropriate antimicrobial chemotherapy may be lifesaving. Choosing the correct antibiotic or combination of antibiotics is becoming very important, as multidrug resistance is found in many pathogens. Using a collection of 75 well-characterized multidrug-resistant (MDR) Acinetobacter sp. isolates, we show that PCR followe...

BACKGROUND/PURPOSE The purpose of this study is to describe clinical characteristics of Salmonella bacteremia in adult patients and analyze ciprofloxacin-nonsusceptible isolates. METHODS A total of 101 Salmonella blood isolates from adult patients were collected from January 2011 to December 2013 in MacKay Memorial Hospital. Eight ciprofloxacin-nonsusceptible Salmonella blood isolates were sc...

To the Editor: In pneumococci, resistance to fluoroquinolones is associated with chromosomal mutations in the quinolone-resistance–determining regions (QRDR) of type II topoiso-merase enzymes, predominantly gyrA and parC. Several mutations have been described in these enzymes, but only a few have been shown by in vitro studies to confer resistance: S81F or Y, C, or I and E85K in gyrA; E474K in ...

Quinolones and fluoroquinolones are widely used to treat uropathogenic Escherichia coli infections. Bacterial resistance to these antimicrobials primarily involves mutations in gyrA and parC genes. To date, no studies have examined the potential relationship between biochemical characteristics and quinolone resistance in uropathogenic E. coli strains. The present work analyzed the quinolone sen...