Evaluation of chicken serum and chicken egg yolk as novel supplements for the in vitro cultivation of Mycoplasma hyorhinis

Abstract

Mycoplasma hyorhinis is a significant pathogen in swine, yet its fastidious nutritional requirements present challenges for in vitro cultivation. Conventional supplements like horse serum (HS) often suffer from batch variability and potential inhibitors. This study aimed to evaluate chicken serum (CS) and chicken egg yolk (CY) as novel alternatives to develop a reliable cultivation method for M. hyorhinis. Five clinical isolates were cultured for 10 days in a basal medium supplemented with CS or CY at 10%, 20%, or 30%, with 30% HS as the control. Growth was quantified daily using a Color Changing Unit (CCU) assay. CS supported robust growth across strains, with 10% CS outperforming the 30% HS control in most isolates. The 10% CS formulation consistently yielded the highest titers (7.0 Log₁₀ CCU/mL) and area under the curve (AUC) values. Notably, increasing CS concentration led to slightly reduced growth. In contrast, CY was less effective, and 30% CY completely inhibited growth. To our knowledge, this is the first comparative study evaluating both chicken serum and egg yolk as alternative supplements for M. hyorhinis cultivation, showing that 10% chicken serum is a superior and cost-effective alternative to horse serum, while egg yolk was not supportive under the tested conditions.