Multidimensional analysis of pathogen epidemic patterns, their correlation with milk quality, and drug resistance and virulence traits of dominant pathogenic Escherichia coli in high-somatic-cell buffalo milk: Guangxi, China.

A high somatic cell count (SCC) is one of the indicative markers for mastitis in buffalo milk production. However, current research on high SCC in buffalo milk and the characteristics of related pathogens remains scarce, leading to limited attention from the farming sector and thus posing a serious threat to food quality and safety. This study systematically tested 1,971 dairy water buffaloes in Guangxi. The results showed that the prevalence of clinical mastitis (CM) was 3.4% (67/1,971), and the proportion of high SCC (≥200,000/mL) was 20.48% (390/1,904). A total of 460 bacterial strains were isolated from 390 high-SCC samples, with Escherichia coli (E. coli) as the dominant species (isolation rate 15.22%). Among these, 70 clinical strains were highly homologous to multi-pathogenic E. coli O26, exhibiting strong motility, an 87.14% biofilm formation rate, an 85.72% multi-drug resistance rate, and high pathogenicity to Galleria mellonella larvae. Genetic testing revealed that 100% of the strains carried multiple virulence genes (e.g., bor, papA, ompA), and 98.57% carried multiple drug resistance genes (e.g., gyrA, parC, marA). Milk quality correlation analysis showed that SCC was significantly negatively correlated with milk yield, lactose content, and weighted heritability index. This study is the first to reveal the epidemic patterns of mastitis in dairy water buffaloes, the characteristics of pathogenic bacteria in high-SCC milk, and the application value of SCC in milk quality assessment in Guangxi, China. It provides scientific support for the precise prevention and control of dairy water buffalo mastitis and the improvement of buffalo milk quality.