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. 2005 Jan;43(1):223-8.
doi: 10.1128/JCM.43.1.223-228.2005.

Molecular characterization of diphtheria toxin repressor (dtxR) genes present in nontoxigenic Corynebacterium diphtheriae strains isolated in the United Kingdom

Aruni De Zoysa  1 , Androulla Efstratiou, Peter M Hawkey
Affiliations

Molecular characterization of diphtheria toxin repressor (dtxR) genes present in nontoxigenic Corynebacterium diphtheriae strains isolated in the United Kingdom

Aruni De Zoysa et al. J Clin Microbiol. 2005 Jan.

Abstract

Nontoxigenic strains of Corynebacterium diphtheriae represent a potential reservoir for the emergence of toxigenic C. diphtheriae strains if they possessed functional diphtheria toxin repressor (dtxR) genes. We studied the predominant strain of nontoxigenic C. diphtheriae circulating in the United Kingdom to see if they possessed dtxR genes and ascertain whether they were functional. A total of 26 nontoxigenic C. diphtheriae strains isolated in the United Kingdom during 1995 and 4 nontoxigenic strains isolated in other countries were analyzed by PCR and direct sequencing to determine the presence and intactness of the dtxR genes. The functionality of the DtxR proteins was assayed by testing for the production of siderophore in medium containing high and low concentrations of iron. PCR amplification and sequence analysis of the dtxR genes revealed four variants of the predicted DtxR protein among the nontoxigenic strains isolated in the United Kingdom. Production of siderophore in medium containing a low concentration of iron and repression of siderophore production in medium containing a high concentration of iron demonstrated that in all the strains the dtxR genes were functional. These findings demonstrate that, if lysogenised by a bacteriophage, nontoxigenic strains circulating in the United Kingdom could produce toxin and therefore represent a potential reservoir for toxigenic C. diphtheriae.

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Figures

FIG. 1.
FIG. 1.
Deduced amino acid sequences of the dtxR alleles. Amino acids are shown only where changes were identified; amino acids identical to the consensus sequence are indicated by dots. The numbers on the left at the beginning of the sequences represent the different variants of the DtxR protein. (a) 95/392, 95/421, 95/12, 95/357, 95/313, 95/329; (b) 95/211, 95/212; (c) 95/343, 95/282, 95/311, 95/454, 95/476, 95/312, 95/411, 95/475, 95/395, 95/390, 95/451, 95/409, 95/22, 95/403, 92/100 (strain from Australia).
FIG. 2.
FIG. 2.
Production of siderophore. An agar plate containing deferrated TY agar medium was inoculated with a strain of nontoxigenic C. diphtheriae isolated in the United Kingdom with positive and negative control strains and was overlaid with CAS top agarose. Halos indicate siderophore production.
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References

    1. Bagg, A., and J. B. Neilands. 1987. Molecular mechanism of regulation of siderophore-mediated iron assimilation. Microbiol. Rev. 51:509-518. - PMC - PubMed
    1. Boyd, J. M., K. C. Hall, and J. R. Murphy. 1992. DNA sequences and characterization of dtxR alleles from Corynebacterium diphtheriae PW8(−), 1030(−), and C7hm723(−). J. Bacteriol. 174:1268-1272. - PMC - PubMed
    1. Boyd, J. M., M. N. Oza, and J. R. Murphy. 1990. Molecular cloning and DNA sequence analysis of a diphtheria tox iron-dependent regulatory element (dtxR) from Corynebacterium diphtheriae. Proc. Natl. Acad. Sci. USA 87:5968-5972. - PMC - PubMed
    1. Bullen, J. J., H. J. Rogers, and E. Griffiths. 1978. Role of iron in bacterial infection. Curr. Top. Microbiol. Immunol. 80:1-35. - PubMed
    1. De Zoysa, A., A. Efstratiou, R. C. George, M. Jahkola, J. Vuopio-Varkila, S. Deshevoi, G. Tseneva, and Y. Rikushin. 1995. Molecular epidemiology of Corynebacterium diphtheriae from northwestern Russia and surrounding countries studied by using ribotyping and pulsed-field gel electrophoresis. J. Clin. Microbiol. 33:1080-1083. - PMC - PubMed

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