Corynebacterium diphtheriae is the etiological agent of diphtheria, a potential 
fatal disease caused by a corynephage toxin. The expression of this diphtheria 
toxin is controlled via an iron-dependent repressor with various functions 
(DtxR). Some mutations in the dtxR gene are associated with diminished activity 
or even with total loss of DtxR function. We conducted a molecular study to 
characterize the dtxR alleles harbored by 34 isolates of C. diphtheriae 
recovered from Romanian patients between 1961 and 2007. Three of the seven 
alleles identified in this study have not previously been described. Two new 
DtxR types were identified, one of which has an unusual polypeptide length. All 
the new DtxR types were found in toxigenic isolates, suggesting that they 
effectively regulate the expression of diphtheria toxin. Furthermore, one of the 
new DtxR identified was also found in a non-toxigenic isolate, making it a 
potential source of toxigenic isolates after lysogenic conversion.