Epidemiological survey of diarrheal pathogens and pathogenicity of fimbrial-type Escherichia coli, with development of a multiplex qPCR assay in Southern China

Diarrheal diseases in piglets are a major cause of morbidity and mortality in swine production, resulting in significant economic losses worldwide. This study aimed to investigate the prevalence of diarrheal pathogens and develop a multiplex Quantitative Real-time Polymerase Chain Reaction (qPCR) assay for detecting four major fimbrial adhesins (F4, F17, F18, F41) of pathogenic Escherichia coli (E. coli). A total of 951 diarrheic samples from four large-scale farms in Guangdong and Guangxi provinces were analyzed. The results revealed that E. coli was the most prevalent pathogen (80.76%), followed by rotaviruses and Porcine Epidemic Diarrhea Virus (PEDV). A multiplex qPCR assay was established, showing high sensitivity and specificity, with detection limits as low as 10² copies/µL and over 90% concordance to conventional PCR.The assay successfully detected fimbrial genes in 69.61% of diarrheic samples, indicating its potential applicability for preliminary screening of fimbrial gene–positive samples in veterinary diagnostic settings. These findings emphasize the ongoing significance of fimbriated pathogenic Escherichia coli in southern China and the utility of multiplex qPCR for rapid, efficient pathogen detection in large-scale pig farms. This method provides an effective tool for improving disease surveillance, management, and control strategies in swine production. Pathogenic E. coli was identified as the main cause of piglet diarrhea in southern China. Distinct pathogenicity was observed among F4⁺, F17⁺, and F41⁺ E. coli isolates. A multiplex qPCR assay was developed to simultaneously detect four fimbrial genes.