Changes in antibiotic susceptibility and ribotypes in Clostridium difficile isolates from southern Scotland, 1979-2004

1 Medical Microbiology, Centre for Infectious Diseases, University of Edinburgh College of Medicine and Veterinary Medicine, Edinburgh, UK 2 Anaerobe Reference Laboratory, NPHS, Microbiology Cardiff, University Hospital of Wales, Cardiff, UK Correspondence Ian R. Poxton i.r.poxton{at}ed.ac.uk Received July 28, 2009 Accepted November 22, 2009 An increase in the incidence of clinical cases of Clostridium difficile infection has been reported in recent years, but few studies have examined changes in molecular epidemiology and antibiotic resistance over a long period of time. A collection of 179 isolates of C. difficile obtained from symptomatic adult patients in southern Scotland between 1979 and 2004 was used to determine changes in the prevalence of epidemiological types and antibiotic susceptibilities to common antibiotics. PCR ribotyping and MIC determination were performed on all isolates. A total of 56 different ribotypes were identified, among which ribotype 002 was the commonest type overall (14 .0%), followed by ribotypes 014 (7.3 %), 012 (5 .0%), 015 (5.0 %), 020 (5 .0%) and 001 (4.5 %). Ribotype 078 was also identified. The 10 commonest ribotypes comprised 55 % of the total isolates. Ribotype 001 increased in prevalence from 1.5 to 12.2 % over the study years, whereas the prevalence of ribotype 012 decreased from 8.7 to 2 .0%. Resistance to clindamycin, erythromycin and ceftriaxone was found in 95.5, 14.0 and 13.4 % of isolates, respectively. Resistance to vancomycin or metronidazole was not detected. Thirty-two (17.9 %) and 14 (7.8 %) isolates were resistant to two and three or more antibiotics, respectively. Ribotype 001 displayed maximum resistance, with 50 % of isolates resistant to erythromycin, moxifloxacin and ceftriaxone, and 100 % resistant to clindamycin. Over the 26 years of the study, antibiotic resistance and ribotype prevalence have changed, and antibiotic pressures may have been the major driver of this change.