Molecular Detection of Streptococcus equi subsp. Zooepidemicus and equi in Guinea Pig with Lymphadenitis by Targeting the comB and seeI Genes

Despite the economic and sanitary relevance of cervical lymphadenitis in guinea pigs, little molecular information is available regarding the role of Streptococcus (S.) equi subspecies in cervical lymphadenitis in Peru. The present study aimed to identify the subspecies S. equi subsp. zooepidemicus (SEZ) and S. equi subsp. equi (SEE) in guinea pigs (Cavia porcellus), with and without cervical lymphadenitis, from the Amazonas and Cajamarca regions of Peru, using PCR amplification of the sodA, comB, and seeI genes. A total of 50 guinea pigs, aged 6-8 months, were evaluated, 30 from Cajamarca (mean weight 1210.1 grams; 22 Peruvian breed, 1 Inti, and 7 Brown) and 20 from Amazonas (mean weight 950 grams; 10 Peruvian breed and 10 Inti), comprising 30 animals with cervical lymphadenitis and 20 clinically healthy animals. The sodA gene was first employed as a preliminary diagnostic marker, which confirmed the presence of S. equi in all animals presenting lymphadenitis. Subsequent amplification of the comB gene confirmed the exclusive presence of SEZ in all clinical cases, with no detection in the 20 clinically healthy guinea pigs analyzed in both study regions. In contrast, the seeI gene, specific to SEE, indicated no amplification in any of the samples, indicating the absence of SEE in the study population. The prevalence of SEZ (positive comB) among guinea pigs with cervical lymphadenitis was 100% in Amazonas (10/10; 95% CI: 69.2-100%) and 100% in Cajamarca (20/20; 95% CI: 83.2-100%), with no significant difference between regions. The present findings established SEZ as the primary etiological agent of cervical lymphadenitis in guinea pigs from both regions, with no molecular evidence of SEE. The present study underscored the utility of comB and seeI as specific and reliable molecular markers for differentiating SEZ and SEE. Keywords: comB gene, Guinea pig, seeI gene, Streptococcus equi subsp. equi, Streptococcus equi subsp. zooepidemicus