Abstract
BackgroundThe zoonotic bacterium Corynebacterium ulcerans may be pathogenic both in humans and animals: toxigenic strains can cause diphtheria or diphtheria-like disease in humans via diphtheria toxin, while strains producing the dermonecrotic exotoxin phospholipase D may lead to caseous lymphadenitis primarily in wild animals. Diphtheria toxin-positive Corynebacterium ulcerans strains have been isolated mainly from cattle, dogs and cats.ResultsHere, we report a series of ten isolations of Corynebacterium ulcerans from a group of water rats (Hydromys chrysogaster) with ulcerative skin lesions, which were kept in a zoo. The isolates were clearly assigned to species level by biochemical identification systems, Fourier-transform infrared-spectroscopy, Matrix-assisted laser desorption/ionization-time of flight mass spectrometry and partial rpoB sequencing, respectively. All ten isolates turned out to represent the same sequence type, strongly indicating a cluster of infections by clonally-related isolates as could be demonstrated for the first time for this species using multilocus sequence typing. Unequivocal demonstration of high relatedness of the isolates could also be demonstrated by Fourier-transform infrared-spectroscopy. All isolates were lacking the diphtheria toxin encoding tox-gene, but were phospholipase D-positive.ConclusionsOur results indicate that water rats represent a suitable new host species that is prone to infection and must be regarded as a reservoir for potentially zoonotic Corynebacterium ulcerans. Furthermore, the applied methods demonstrated persistent infection as well as a very close relationship between all ten isolates.
Highlights
The zoonotic bacterium Corynebacterium ulcerans may be pathogenic both in humans and animals: toxigenic strains can cause diphtheria or diphtheria-like disease in humans via diphtheria toxin, while strains producing the dermonecrotic exotoxin phospholipase D may lead to caseous lymphadenitis primarily in wild animals
The three Corynebacterium (C.) species C. diphtheriae, C. ulcerans and C. pseudotuberculosis form the C. diphtheriae group as recently shown by 16S rRNA gene sequence analysis and DNA-DNA hybridization studies [1,2,3]. Strains of this group might carry lysogenic β-corynephages which can harbor the tox-gene encoding diphtheria toxin (DT), a virulence factor inhibiting protein synthesis [4,5,6]. Both C. ulcerans and C. pseudotuberculosis may produce the dermonecrotic exotoxin phospholipase D, a major virulence factor involved in caseous lymphadenitis affecting mainly sheep, goats, and horses [4]
While C. diphtheriae carriage is nearly exclusively restricted to humans, toxigenic C. ulcerans are zoonotic pathogens and have been found in various animal species with contact to humans such as livestock as well as companion and laboratory animals including cows with mastitis [8,9,10], a goat with meningoencephalitis [11], an asymptomatic farm pig linked to a human case of diphtheria [12], macaques with mastitis or respiratory disease [13,14] or without symptoms [15], ferrets with infection derived from cephalic implants [16], pet dogs and cats displaying nasal discharge [17,18,19,20,21,22] and asymptomatic shelter dogs [17,23]
Summary
The zoonotic bacterium Corynebacterium ulcerans may be pathogenic both in humans and animals: toxigenic strains can cause diphtheria or diphtheria-like disease in humans via diphtheria toxin, while strains producing the dermonecrotic exotoxin phospholipase D may lead to caseous lymphadenitis primarily in wild animals. The three Corynebacterium (C.) species C. diphtheriae, C. ulcerans and C. pseudotuberculosis form the C. diphtheriae group as recently shown by 16S rRNA gene sequence analysis and DNA-DNA hybridization studies [1,2,3] Strains of this group might carry lysogenic β-corynephages which can harbor the tox-gene encoding diphtheria toxin (DT), a virulence factor inhibiting protein synthesis [4,5,6]. Both C. ulcerans and C. pseudotuberculosis may produce the dermonecrotic exotoxin phospholipase D, a major virulence factor involved in caseous lymphadenitis affecting mainly sheep, goats, and horses [4]. While C. diphtheriae carriage is nearly exclusively restricted to humans, toxigenic C. ulcerans are zoonotic pathogens and have been found in various animal species with contact to humans such as livestock as well as companion and laboratory animals including cows with mastitis [8,9,10], a goat with meningoencephalitis [11], an asymptomatic farm pig linked to a human case of diphtheria [12], macaques with mastitis or respiratory disease [13,14] or without symptoms [15], ferrets with infection derived from cephalic implants [16], pet dogs and cats displaying nasal discharge [17,18,19,20,21,22] and asymptomatic shelter dogs [17,23].
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