Background: Corynebacterium ulceranscan cause a diphtheria-like illness, especially when the bacterium is lysogenized with atoxgene-carrying bacteriophage that produces diphtheria toxin. Acquisition of toxigenicity upon phage lysogenization is a common feature ofC. ulceransandC. diphtheriae. However, because of a lack ofC. ulceransgenome information, a detailed comparison of prophages has not been possible between these two clinically important and closely related bacterial species.Results: We determined the whole genome sequence of the toxigenicC. ulcerans0102 isolated in Japan. The genomic sequence showed a striking similarity with that ofCorynebacterium pseudotuberculosisand, to a lesser extent, with that ofC. diphtheriae. The 0102 genome contained three distinct prophages. One of these, ΦCULC0102-I, was atox-positive prophage containing genes in the same structural order as fortox-positiveC. diphtheriaeprophages. However, the primary structures of the individual genes involved in the phage machinery showed little homology between the two counterparts.Conclusion: Taken together, these results suggest that thetox-positive prophage in this strain ofC. ulceranshas a distinct origin from that ofC. diphtheriaeNCTC 13129.

Diphtheria-like human illness caused by Corynebacterium ulcerans is an emerging threat in developed countries, with incidence sometimes higher than that of diphtheria caused by Corynebacterium diphtheriae. Companion animals are considered a potential source of human infections. In order to determine the prevalence of C. ulcerans among dogs, we performed a screening for the bacterium in 583 dogs in the custody of the Osaka Prefectural government. Forty-four dogs (7.5 %) were positive for the bacterium, although they did not show any clinical symptoms. All bacterial isolates showed resistance or decreased sensitivity to clindamycin, and some showed decreased sensitivity to levofloxacin. Comparative analysis of isolates using PFGE, toxin gene typing and antibiotic sensitivities suggests that transmission between asymptomatic dogs might have occurred.

Two toxigenic Corynebacterium ulcerans isolates recovered from pharyngeal swabs of two patients from the same hospital in Japan during 2001–2002 were characterized by PFGE and ribotyping. Toxin production in different culture media was examined and serological analysis of patient sera was performed. The two isolates could not be distinguished by PFGE; however, their ribotypes were distinguishable. One of the isolates could represent a novel ribotype. Analysis of toxin production in different culture media demonstrated that the two isolates produced varying amounts of the diphtheria toxin. Serological analysis showed a greater than sevenfold increase in the serum antitoxin titre during the course of infection in one patient.

Corynebacterium diphtheriaeis the causative agent of diphtheria. In 2003, the complete genomic nucleotide sequence of an isolate (NCTC13129) from a large outbreak in the former Soviet Union was published, in which the presence of 13 putative pathogenicity islands (PAIs) was demonstrated. In contrast, earlier work on diphtheria mainly employed the C7(−) strain for genetic analysis; therefore, current knowledge of the molecular genetics of the bacterium is limited to that strain. However, genomic information on the NCTC13129 strain has scarcely been compared to strain C7(−). Another importantC. diphtheriaestrain is Park-Williams no. 8 (PW8), which has been the only major strain used in toxoid vaccine production and for which genomic information also is not available. Here, we show by comparative genomic hybridization that at least 37 regions from the reference genome, including 11 of the 13 PAIs, are considered to be absent in the C7(−) genome. Despite this, the C7(−) strain still retained signs of pathogenicity, showing a degree of adhesion to Detroit 562 cells, as well as the formation of and persistence in abscesses in animal skin comparable to that of the NCTC13129 strain. In contrast, the PW8 strain, suggested to lack 14 genomic regions, including 3 PAIs, exhibited more reduced signs of pathogenicity. These results, together with great diversity in the presence of the 37 genomic regions among variousC. diphtheriaestrains shown by PCR analyses, suggest great heterogeneity of this pathogen, not only in genome organization, but also in pathogenicity.

Corynebacterium ulcerans is a pathogen causing diphtheria-like illness to humans. In contrast to diphtheria by Corynebacterium diphtheriae circulating mostly among humans, C. ulcerans infection is zoonotic. The present study aimed to clarify how a zoonotic pathogen C. ulcerans circulates among wild birds and animals. By screening 380 birds, a single strain of toxigenic C. ulcerans was isolated from a carnivorous bird, ural owl (Strix uralensis). The bacterium was also isolated from two individuals of Japanese shrew-mole (Urotrichus talpoides), a food preference of the owl. Analysis by ribotyping showed that the owl and mole isolates were classified in a group, suggesting that C. ulcerans can be transmissible among wild birds and their prey animals. Moreover, our isolates were found to belong to a group of previously reported C. ulcerans isolates from dogs and a cat, which are known to serve as sources for human infection. The findings suggest that the shrew-mole may be a potential reservoir of a zoonotic pathogen C. ulcerans.