Isolation And Identification Of Pathogenic Bacterium From Subclinical Mastitis And Detection Of Bacterial Biofilm

Bovine mastitis is a kind of serious diseases which led large loss to the dairyindustry. It is classified into clinical and subclical mastitis. The subclinical mastitisshowed little symptom and was difficult to be found. Therefore subclinical mastitisis very popular in dairy farms and causes a great threat to dairy industry.This study was aimed to isolate bacteria from milk of cows with mastitis,analyze the biological properties, test the virulent factors and antimicrobialresistance. It would provide the evidence to guide clinical treatment and preventionof cow mastitis. Nine herds from two main districts for raising cows were chosen tocollect samples.A total of 200 milk samples were collected from two main dairy cow districtsDongxihu and Yichang of Hubei Province and detected for mastitis. As a result, 50samples were diagnosed as mastitis. Among them, 3 were clinical mastitis, and 47subclinical mastitis. The incidences of subclinical mastitis in these two districts were38.5%(20/52) and 20 % (29/145) respectively. From these 50 samples, 55 strains ofbacteria were isolated including 11 strains of Staphylococcus aureus, 10 ofStaphylococcus epidermidis; 10 of Streptococcus agalactiae, 14 of Streptococcusdysgalactiae, 2 of Streptococcus uberis; 4 of E. coli; 4 of Klebsietla. Hemolysis testand coagulase test were used to detect the virulence factors of Staphylococcus aureu,and three strains were positive.In addition, the bacterial distribution was different in these two districts.We isolated 24 strains of bacteria from Dongxihu district of Wuhan including 8strains of Streptococcu dysgalactiae. The isolating rate of Streptococcu dysgalactiaewas 33.3 % (8/24) and was highest. The isolating rate of other bacteria was20.8% ofStaphylococcus epidermidis(5/24); 16.7% of E. coli(4/24); 8.3% of Staphylococcusaureus(2/24); 8.3%of Streptococcus agalactiae(2/24); 8.3%of Klebsietla(2/24);4.2%of Streptococcus uberis(1/24).We isolated 31 strains of bacteria from Yiling district of Yichang including 9strains of Staphylococcus aureus. The isolating rate of Staphylococcus aureus was 29% (9/31) and was highest. The isolating rate of other bacteria was 25.8% ofStreptococcus agalactiae(8/31); 19.4% of Streptococcus dysgalactiae(6/31); 16.1%of Staphylococcus epidermidis (5/31); 3.2%of Streptococcus uberis(1/31); 6.5%ofKiebsietla(2/31). E. coli was not isolated.The sensitivity of all the strains to 12 antimicrobials was tested. Although thestrains showed different resistance profiles, they were sensitive to Cephalosporinâ…¤, Gentamicin, and Ciprofloxacin, and highly resistant to penicillin and streptomycin.Furthermore, this study analyzed the generation of bacterial biofilm inqualitation and quantitation. In qualitative analysis, the results showed 36 strainscould generate bacterial biofilm, but 26 strains could generate bacterial biofilm inquantitation. Although there was difference between two methods, the high ratio ofbiofilm generating bacteria would be related to the pathogenesis of mastitis.