Differential expression of antioxidant genes during clinical mastitis of cow caused by Staphylococcus aureus and Escherichia coli

Abstract

There is considerable interest in the hypothesis that oxidative stress is enhanced in the pathophysiology of clinical mastitis. The main goal of this research was to establish profiles of antioxidant gene expression in the milk of cows with clinical mastitis. Standard bacteriology was conducted on pretreatment milk specimens from 77 cows with clinical mastitis between 15 and 70 days in milk (DIM). Examinations were performed on mRNA expression of antioxidant genes, such as catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD). Additionally, levels of lipid peroxidation were measured in milk samples from healthy cows and those with clinical mastitis. The isolated bacteria consisted of Staphylococcus aureus (S. aureus, 10.48%), Streptococcus agalactiae (7.69%), Streptococcus dysagalactiae (6.29%), and Escherichia coli (E. coli, 29.37%). E. coli was the most prevalent pathogen found in the milk of cows with clinical mastitis in early lactation. The mean level of malondialdehyde (MDA) in clinical mastitis samples was significantly higher (P<0.05) than that of healthy cows. The results revealed that the expression profiles of SOD in mastitis milk induced by S. aureus were significantly (P<0.0001) up-regulated compared with E.coli. In addition, the mRNA levels of GPx in mastitis milk due to E.coli were significantly (P<0.0001) over expressed compared to S. aureus. CAT gene expression had a tendency to be enhanced in mastitis milk induced by S. aureus compared with mastitis in cows due to E.coli. These results showed that the mRNA levels of antioxidant genes may differ depending on the type of bacteria, and diminished expression of antioxidant genes might increase susceptibility to mastitis.