Antimicrobial susceptibilities and molecular characterization of toxin-positive Clostridium difficile isolates: the first report on the presence of hypervirulent strains from Turkey

Clostridium difficile infection is one of the most important hospital-acquired infections. Infections caused by hypervirulent C.difficile strains which produce toxins at high levels, have higher morbidity and mortality rates, more complications and relapses. They are characterized by higher sporulation ratios and resistance rates for fluoroquinolones. In order to prevent serious morbidities, mortalities and remarkable increase in health costs, highly pathogenic C.difficile strains must be identified before causing severe outbreaks. The aim of this study was to determine the antimicrobial susceptibilities and molecular characteristics of 61 C.difficile strains isolated by culture from toxin-positive fecal samples of patients who were admitted to three different laboratories in Ankara, between September 2012 and November 2014. Antimicrobial susceptibilities were determined by using gradient test strips and results were interpreted according to the current CLSI and EUCAST criteria. The presence of toxin genes was investigated by polymerase chain reaction (PCR), and mutations in the tcdC gene were determined by sequence analysis following PCR amplification. Genetic characterization of one hypervirulent strain was performed by Public Health Institution of Turkey using the GenoType CDiff (Hain Lifescience, Germany) test. All strains were susceptible to vancomycin and metronidazole. Three (4.9%) isolates were resistant to moxifloxacin with a minimum inhibitory concentration (MIC) of > 8 µg/ml. The MIC50 and MIC90 values for erythromycin and clindamycin were 1.5-3 µg/ml, and 2-4 µg/ml, respectively. All strains carried the tcdA and tcdB genes, and 1 (1.6%) was positive for the binary-toxin (cdtA and cdtB) genes. The binary-toxin positive strain carried a 54 bp deletion as well as a single nucleotide change in the tcdC gene. Various single nucleotide changes were found in the tcdC gene of 12 strains (19.6%). Our results have shown that, hypervirulent strains exist in our country, but we have no evidence for the presence of ribotype 027 yet. On the other hand, when the increasing incidence of these strains through out the world is taken into consideration, it would be of great importance to perform surveillance studies and characterize the isolated strains.