Pythium Insidiosum Biological Characteristics and Treatment: A Strain Cured by Repurposing of Existing Drugs in China

Background Pythiosis is an infectious disease caused by P. insidiosum that threatens humans and animals. The number of people being diagnosed with this disease has been increasing worldwide. Pythiosis has a high rate of morbidity and mortality. Early diagnosis and prompt treatment are crucial in determining the prognosis of patients. The character of P. insidiosum has geographical variants, and a comprehensive investigation of it is essential in China. Methods In this study, a strain of P. insidiosum was visually and genetically identified, and isolated from a patient at a hospital in Guangzhou. A novel sporulation technique was used to produce zoospores. Microscopic observation was employed to understand the biological properties of P. insidiosum . Drug susceptibility studies on the isolates were conducted in vitro and in vivo. Results Our results provide comprehensive evidence that this strain was P. insidiosum , supported by molecular biology, morphology, and biological processes. Drug susceptibility studies showed P. insidiosum was more sensitive to antibiotics than antifungals, with tetracyclines and macrolides being the most sensitive in vitro. In vivo, doxycycline and azithromycin were administered to immunodeficient mice infected with P. insidiosum subcutaneously. The treatment significantly increased the survival rate of infected mice (p < 0.05) and alleviated the histopathology while decreasing the fungal burden in infected mice. Conclusion Our study provides theoretical and technical support for effectively treating pythiosis in humans and animals in China.