Detection of biofilm formation ability of Streptococcus agalactiae isolated from bovine mastitis cases

Bacterial biofilms are thought to be the predominant growth mode in their natural environments and increasing evidence implicates biofilm as the cause of various animal infections. In this study biofilm forming ability was demonstrated in Streptococcus agalactiae isolated from bovine mastitis using 96-well microtiter plates. Twelve isolates were screened for biofilm formation using Luria-Bertani (LB) medium with one per cent glucose. Twenty five per cent of the isolates were strong biofilm producers with OD values of ≥1.0, 16.67 per cent were moderate biofilm producers with OD values between 0.5 and 1 and 58.33 per cent were considered as non-biofilm producers with OD value of <0.5. The influence of addition of glucose on S agalactiae biofilm formation was studied by subjecting all the isolates for biofilm formation using LB medium with and without glucose. In LB glucose medium the similar results were obtained as above but in LB without glucose medium only 16.67 per cent isolates were moderate biofilm producers and 85.33 per cent did not produce biofilms. Biofilm forming ability of S agalactiae was also studied in Todd-Hewitt broth (THB) and tryptone soya broth (TSB) media supplemented with 1 per cent glucose. In case of THB glucose only 8 and 17 per cent of the isolates produced strong and moderate biofilms respectively whereas 75 per cent of the isolates were non-biofilm producers. In TSB glucose only 8 per cent of the isolates produced strong biofilms and 92 per cent were non-biofilm producers. This study suggests that S agalactiae of bovine origin is a biofilm producer and the type of medium and glucose concentration influence its biofilm production.