The ideal diagnostic method for veterinary purposes, particularly for the field practitioner, must be reliable, cost-effective and demonstrate good sensitivity and specificity. Although an ideal test with such characteristics does not yet exist, in a short horizon the most probable tests that could reach those goals are those based on molecular biology, particularly real-time PCR and its analogues. PCRbased methods, as a powerful tool for pathogen detection, have been frequently used in the identification of veterinary bacterial pathogens. This chapter focuses on the PCR method, some related important variations and their applications for the diagnosis of veterinary bacterial infections. The concepts such as restriction fragment length polymorphism analysis, multiplex PCR, nested PCR, allele-specific PCR, reverse transcription-PCR, real-time PCR and DNA sequencing are also discussed. This chapter particularly emphasizes the PCR-based diagnostic assays for Brucella sp., Leptospira sp., Mycobacterium bovis, Staphylococcus aureus and Mycoplasma sp. Real-time PCRs that could quantify the presence of the bacterial agents in a reliable way and identify the antimicrobial resistance and virulence factors genes have revolutionized veterinary medicine, making the diagnosis of infectious diseases rapid, reliable and cost-effective.
Keywords: PCR-based diagnosis; genotyping; multiplex PCR; nested PCR; allele-specific PCR; reverse transcription-PCR; Real-time PCR; Brucella; Leptospira; Mycobacterium bovis; Staphylococcus aureus; Mycoplasma.