In vitro activity of fluoroquinolones against clinical isolates of Nocardia identified by partial 16S rRNA sequencing

Abstract

Fluoroquinolones have several properties that make them potentially attractive candidates for the treatment of Nocardia infections, but information regarding their in vitro activity is limited. Minimum inhibitory concentrations (MIC) of five fluoroquinolones and other antimicrobials were determined by the reference broth dilution and E-test methods for 33 consecutive clinical isolates of Nocardia speciated by 16S rRNA gene sequences. The isolates included: Nocardia cyriacigeorgica (n = 6), N. nova (n = 8), N. farcinica (n = 8), N. brasiliensis (n = 3), N. asteroides (n = 4), and N. veterana (n = 4). MIC50/MIC90 results for ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin by broth dilution were 32/32, 2/4, 1/4, 32/32, and 2/2 microg/ml, respectively. The MICs by broth dilution and E-test were within a two-fold doubling dilution for 94%, 97%, 97%, 100%, and 100% of isolates for ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin, respectively. For ciprofloxacin, the E-test results showed either complete categorical agreement or minor error compared to the reference broth dilution method for 97% (32/33) of the isolates. For other fluoroquinolones, using Streptococcus pneumoniae breakpoints, 94% (124/132) of MIC results by E-test showed either complete agreement or minor error compared to the reference broth dilution method. Fluoroquinolones show variable in vitro activity against clinical isolates of Nocardia spp., and MICs determined by the E-test show reasonable agreement with those determined by the reference broth dilution method.

Nocardia in Solid Organ Transplant Recipients

“…Moxifloxacin therapy was successful in two cases of N. farcinica CNS infection (89,90), but there is a report of recurrent N. farcinica CNS infection in a patient receiving moxifloxacin despite in vitro susceptibility and high levels of the drug in the abscess material (91). Moxifloxacin appears to be more active in vitro against N. farcinica than against other Nocardia species (4,57).…”

Evaluation of tcdB Real-Time PCR in a Three-Step Diagnostic Algorithm for Detection of Toxigenic Clostridium difficile

“…Because several GDH-Q-positive specimens had no detectable C. difficile 16S rRNA gene and were culture negative for C. difficile, an additional amplification control of heatextracted DNA from a nontoxigenic C. difficile isolate was added to each extracted specimen and a reagent control in a 1/15 dilution. Subsequently, amplification with universal bacterial 16S rRNA gene primers (25) was employed as an internal extraction and amplification control, with an expected melt peak of 86.5 Ϯ 2°C and fewer than 20 cycles.…”

Species Spectrum of <I>Nocardia</I> spp. Isolated from Suspected Tuberculosis Patients

“…Infection due to this species was previously reported from Iran based on phenotypic methods and 16S rRNA sequencing [23]. Disease due to this species has recently been reported [25] and it represents 10.2% and 18% of the Nocardia isolates in Japan and Thailand [26] and USA [27] respectively and 22% and 32.5% from two different studies from Spain [16] [24]. Together our finding from present study and several cases of nocardiosis by N. cyriacigeorgica from other parts of the world confirm major role of the latter species in the clinical settings.…”