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In vitro susceptibility of Actinobaculum schaalii to 12 antimicrobial agents and molecular analysis of fluoroquinolone resistance

Cattoir V, Varca A, Greub G, Prod'hom G, Legrand P, Lienhard R

The Journal of antimicrobial chemotherapy, 2010

47 participants

Abstract

OBJECTIVES: To assess the in vitro susceptibility of Actinobaculum schaalii to 12 antimicrobial agents as well as to dissect the genetic basis of fluoroquinolone resistance.

METHODS: Forty-eight human clinical isolates of A. schaalii collected in Switzerland and France were studied. Each isolate was identified by 16S rRNA sequencing. MICs of amoxicillin, ceftriaxone, gentamicin, vancomycin, clindamycin, linezolid, ciprofloxacin, levofloxacin, moxifloxacin, co-trimoxazole, nitrofurantoin and metronidazole were determined using the Etest method. Interpretation of results was made according to EUCAST clinical breakpoints. The quinolone-resistance-determining regions (QRDRs) of gyrA and parC genes were also identified and sequence analysis was performed for all 48 strains.

RESULTS: All isolates were susceptible to amoxicillin, ceftriaxone, gentamicin, clindamycin (except three), vancomycin, linezolid and nitrofurantoin, whereas 100% and 85% were resistant to ciprofloxacin/metronidazole and co-trimoxazole, respectively. Greater than or equal to 90% of isolates were susceptible to the other tested fluoroquinolones, and only one strain was highly resistant to levofloxacin (MIC ≥32 mg/L) and moxifloxacin (MIC 8 mg/L). All isolates that were susceptible or low-level resistant to levofloxacin/moxifloxacin (n = 47) showed identical GyrA and ParC amino acid QRDR sequences. In contrast, the isolate exhibiting high-level resistance to levofloxacin and moxifloxacin possessed a unique…

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