Identification and molecular characterization of Corynebacterium xerosis isolated from a sheep cutaneous abscess: first case report in Mexico.

Background: Corynebacterium xerosis is a commensal organism found in skin and mucous membranes of humans. It is considered an unusual pathogen, and it is rarely found in human and animal clinical samples. Here we describe the isolation of C. xerosis from a 4-months-old Pelifolk lamb located in Tesistán, central western Mexico. This microorganism should be considered for differential diagnosis in cutaneous abscessed lesions in sheep, as it represents a zoonotic risk factor for human infection in sheep farms.

Case Presentation: The animal exhibited a hard-consistency, 5 cm diameter abscess, without drainage, in the neck. The presumptive clinical diagnosis was caseous lymphadenitis, caused by Corynebacterium pseudotuberculosis. Samples were obtained by puncture and cultured in 8 % sheep blood agar under microaerophilic conditions. Colonies were non-haemolytic, brown-yellowish and showed microscopic and biochemical features similar to C. pseudotuberculosis, except for the urea test. A multiplex-PCR for the amplification of partial sequences of the pld, rpoB and intergenic fragment from 16S to 23S genes suggested that isolate could be C. xerosis, which was later confirmed by sequencing analysis of the rpoB gene.

Conclusions: This study shows for the first time isolation and molecular characterization of C. xerosis from a clinical sample of an ovine cutaneous abscess in Mexico. This finding highlights the need for differential diagnosis of this pathogen in ovine skin abscesses, as well as epidemiological and control studies of this pathogen in sheep farms.