Norén T, Alriksson I, Akerlund T, Burman LG, Unemo M
In vitro susceptibility to 17 antimicrobials among clinical Clostridium difficile isolates collected 1993 - 2007 in Sweden. [JOURNAL ARTICLE]
Clin Microbiol Infect 2009 Sep 3.
Abstract This study investigated the minimum inhibitory concentrations (MICs) of 17 antimicrobials, among 606 clinical toxigenic Clostridium difficile isolated between 1993 and 2007 in Sweden. Low MIC(90) values were found for metronidazole (0.5 mg/L), vancomycin (1.0 mg/L), teicoplanin (0.125 mg/L), fusidic acid (1.0 mg/L), linezolid (2.0 mg/L), daptomycin (2.0 mg/L) and tigecycline (0.064 mg/L). Three isolates (0.5%) had elevated MICs to vancomycin (4-8 mg/L), however, these isolates originated from the same patient with long-term intravenous vancomycin treatment. Clindamycin high-level resistance (MIC>256 mg/L) peaked in 1997 (41% of isolates), of which 36% were highly resistant also to erythromycin. beta-lactams like penicillin V and piperacillin displayed MIC(90) of 8 and 32 mg/L, respectively, whereas for cefuroxime, all isolates displayed MICs of >256 mg/L. Universal resistance to ciprofloxacin and levofloxacin was found, while resistance to moxifloxacin emerged from 4% in 2004 to 23% of isolates in 2007. Notable, these moxifloxacin resistant isolates were not belonging to the recent epidemic PCR ribotype 027, but to the pre-existing epidemic type 012 (82%) accounting for the majority of resistance to clindamycin (70%), tetracycline (84%) and rifampicin (92%) as well. In conclusion this overview of susceptibility data in clinical C. difficile explained variations of multiresistance to be due to a specific PCR ribotype 012, emphasizing the importance of susceptibility testing and genotyping when evaluating emerging resistance over time.
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