Occurence, phenotypic and genotypic characterization of strains of Corynebacterium pseudotuberculosis isolated from lynph nodes of sheep with and without lymphadenitis

Author(s)

Thiago de Oliveira Zamprogna

• Document type: Master's Dissertation
• Press: Botucatu. 2022-05-23.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Medicina Veterinária e Zootecnia. Botucatu
• Defense date: 2013-07-29
• Advisor: Márcio Garcia Ribeiro

Abstract

Caseous lymphadenitis is an infectious disease which etiology is considered very complex, even with frequently isolation of Corynebacterium pseudotuberculosis from lesions in both sheep and goats. The main sources of infection are infected animals in the herd and lymphadenitis is the most important clinical sign, from which the disease is known. Microbiological culture is still the most suitable test for routine diagnostic, however fine needle aspiration cytology (FNAC) is being widely applied in recent years as triage to assess possibly infected animals. Further, molecular diagnostic has been promising in identification of the microorganism and its respective biotypes In the present study, 14 sheep herds were evaluated. From the total of animals,197 sheeps presented enlarged lymph nodes (submandibular, superficial parotid, prefemoral, popliteal, prescapular) suggesting presence of existing disease. Fine needle aspiration citology was performed in animals with lymphadenitis in order to collect samples for microbiological and cytological exams. Therefore, 202 visceral lymph nodes (mesenteric and mediastinic) were collected from slaughtered sheep without signs of lymphadenitis. All lymph nodes were submitted to cytological evaluation, microbiological culture and, in samples where the pathogen was obtained, traditional polymerase chain reaction (PCR) and antimicrobial resistance test were also performed. In culture, 86 samples presented the isolation of C. pseudotuberculosis, from which, 64 (74%) were confirmed as C. pseudotuberculosis by PCR and 22 (26%) as negative. The cytology presented caracteristics of pleomorphism in 97 (49.2%) of the samples whilst 100 (50.8%) lymph nodes did not present any cytological modification. Among the lymph nodes obtained from carcasses, no C. pseudotuberculosis isolation was observed. Moreover, the isolates submitted to antimicrobial resistance test presented high susceptibility to all antimicrobials tested (ampicillin, azithromycin, ceftiofur, enrofloxacin, erythromycin, florfenicol, penicillin G, rifampicin and sulfadiazine-trimethoprim. Additionally, we conducted an epidemiological survey of the main risk factors associated with caseous lymphadenitis in farms. We isolated 86 strains of C. pseudotuberculosis, of which 64 (74.0%) were confirmed as C. pseudotuberculosis by PCR-multiplex in cytological diagnosis were considered positive 97 (49.2%) samples that had micro-organisms or aspect pleomorphic. Of the 202 samples taken from mediastinal and mesenteric lymph nodes of sheep slaughterhouse was observed prevalence of isolation of staphylococci, streptococci and enterobacteria. In none of these samples was isolated C. pseudotuberculosis. We observed a high "odds ratio" and statistical association (P <0.05) in the presence of the disease in sheep reproductive age in herds with marketing of animals. Despite the high sensitivity "in vitro" of C. pseudotuberculosis to different antimicrobials, treatment of disease is usually ineffective, indicating the need to adopt strict measures to prevent and control the disease in farms, particularly as to the movement of animals. It was also observed good agreement between FNAC and microbiological culture and between microbiological culture and PCR, reinforcing the association of methods increases the diagnostic efficacy of C. pseudotuberculosis in ovine caseous lymphadenitis. (AU)

• FAPESP's process: 11/03120-1 - Occurrence, phenotypic and genotypic characterization of strains of Corynebacterium pseudotuberculosis and Mycobacterium spp. isolated from lymph nodes of sheep with and without lymphadenitis
• Grantee: Thiago de Oliveira Zamprogna
• Support Opportunities: Scholarships in Brazil - Master