Enhanced efficacy of tylvalosin tartrate enteric-coated granules against Mycoplasma hyopneumoniae in pigs: in vitro activity and clinical dosage optimization

Background Mycoplasma hyopneumoniae (Mhp), the etiological agent of enzootic pneumonia in pigs, poses significant challenges to swine production. This study evaluated the anti-Mhp efficacy of a novel enteric-coated granules of tylvalosin tartrate (ETT) through comprehensive in vitro and in vivo assessments. Methods The in vitro evaluation was determined by the minimum inhibitory concentration (MIC) and biofilm inhibition assays. The 60 pigs grouped into six groups were treated with (ETT) at doses of 25, 50, 62.5, 75, or 100 g/1000 kg feed, or with a premix (62.5 g/1000 kg feed) for 7 consecutive days with positive and negative control groups. Efficacy was determined based on clinical symptom scores, pulmonary lesion scores, Mhp antigen, weight gain, and hematological parameters. Results In vitro , the ETT exhibited significantly enhanced antibacterial activity with a MIC of 0.015625 μg/mL compared to premix (0.125 μg/mL). Additionally, both formulations significantly inhibited the biofilm formation, with enteric-coated granules showed stronger inhibition at 2 MIC. Pre-clinical trial found that nasal swabs collected at 21 dpi showed 100% sIgA detection, while throat swabs at 28 dpi had an 89.47% antigen detection rate. In clinical trial, ETT at 50–75 g/1000 kg feed significant improvements such as lower lung lesion score ( p < 0.01), 70% cure rate, effective Mhp antigen clearance, and restored weight gain. Conclusion The novel ETT showed significantly stronger in vitro antibacterial and anti-biofilm activity against Mhp. The clinical trials indicate an optimal dose of 50–75 g per 1,000 kg of feed for 7 days, can improve Mhp infection in pigs.