Emergence of moxifloxacin resistance in Swedish epidemic Clostridium difficile isolates in the era of the global NAP1/027 epidemic
Abstract number: P1209
Norén T., Akerlund T., Andersson J., Alriksson I., Unemo M.
Objectives: In recent years global outbreaks of Clostridium difficile associated diarrhoea (CDAD) in the western world involve the epidemic strain of C. difficile characterised as PCR ribotype 027 and PFGE type NAP1. Increased infection rates and more severe cases of diarrhoea have featured these epidemics. Use of modern fluoroquinolones (moxifloxacin/gatifloxacin) has been thought to be the epidemic trigger selecting moxifloxacin resistance NAP1/027 isolates. In Sweden the epidemic strain SE17 (Serogroup C, PCR ribotype 012) has been dominant in nosocomial clustering. Retrospectively only three historical isolates of NAP1/027 have yet been found in Sweden without increased morbidity or epidemic clustering. Prior to 2004 both these Swedish NAP1/027 strains and the SE17 have been fully susceptible to moxifloxacin as opposed to the epidemic NAP1/027 being resistant. Hence we used moxifloxacin resistance as a surveillance marker when testing clinical isolates 2004 (n = 300) and 2007 (n = 300) for any emergence of moxifloxacin resistance.
Aim: To determine whether moxifloxacin resistance is a useful general marker of epidemic isolates or exclusively a screening tool of NAP1/027.
Material and Methods: MIC determination. Anaerobically cultured isolates were suspended in nutrient broth (Oxoid) to a turbidity of 1.0 and seeded on IsoSensitest agar (Oxoid). Etest strips (Biodisk AB) were placed on top followed by anaerobic incubation at 37°C for 48 h. PCR ribotyping of C. difficile isolates. Preparation of template, PCR reaction, separation of PCR products and analysis of banding patterns were according to Stubbs et al (1999, J. Clin. Microbiol. 37:461463) with minor modifications (Norén et al, 2004, J. Clin. Microbiol. 42:36353643) and, accordingly, use of our own nomenclature (prefix SE, Sweden).
Results: In 2004 4% of the clinical isolates showed moxifloxacin resistance (MIC > 32 mg/l) and in 2007 we noted a significant increase of resistant isolates, i.e. the prevalence of resistance was almost six times as high (22.5%). The antibiograms indicated epidemic SE17 uniformly and current nosocomial clusters of disease were located mainly in two geographically distant Dialysis departments and in the Department of Infectious diseases.
Conclusion: Moxafloxacin resistance may not only be a selecting factor and screening marker for NAP1/027 but also useful to detect other virulent C. difficile like for example SE17 (Ribotype 012) in Sweden.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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