Diagnostic comparison of Corynebacterium pseudotuberculosis through microbiological culture and PCR in sheep samples

Caseous lymphadenitis is a chronic infectious disease caused by Corynebacterium pseudotuberculosis , which is a bacterium responsible for a great number of economic losses on goat and sheep production. It is characterized by the formation of abscesses in superficial lymph nodes and in internal organs and lymph nodes. This study aimed at determining the agreement between microbiological culture and PCR in the identification of C. pseudotuberculosis , in samples collected from animals in slaughterhouses and in animals that presented lymph node enlargement in field conditions. From the 202 samples analyzed through microbiological culture, 113 (56%) were positive for Corynebacterium sp.; from these positive samples, 38 (34%) were identified as C. pseudotuberculosis by microbiological culture. From the amount of samples, 110 (54%) were positive and 92 (46%) were negative in the PCR. Kappa index (0.193) presented a weak agreement between PCR and microbiological culture. We concluded that molecular diagnosis (PCR) in clinical samples proved to be more efficient, reproducible, and faster than the microbiological culture, both on clinical samples analyses and in the confirmation of C. pseudotuberculosis in colonies that were classified by Corynebacterium genus. Thus, the present study demonstrated the importance of PCR to confirm C. pseudotuberculosis diagnosis, and the best contribution for the epidemiological surveillance of the disease in sheep.