In vitro Antimicrobial Activity of Nanoencapsulated Bromelain against Bacteria Isolated from Milk of

goats is managed by a variety of antibiotics. Due to the emergence of antibiotic resistance, there is need for development of new antimicrobial agents. In the current study, the in vitro activity of nanoencapsulated bromelain, using bromelain extracted from the pineapple fruit, Annanus comosus was investigated against bacteria isolated from milk of dairy goats with sub-clinical mastitis. Nanoencapsulation of bromelain was done using the ionic gelation method of chitosan nanoparticles with sodium trypolyphosphate as the cross linking agent. In this study, the agar well diffusion method was used to test for antimicrobial activity while the broth microdilution method was used to test for the Minimum Inhibitory Concentration (MIC). The isolates used were Staphylococcus aureus, Coagulase Negative Staphylococci, Serratia spp., Klebsiella spp., Enterobacter spp., Citrobacter spp. and Escherichia coli isolated from milk of dairy goats with sub-clinical mastitis in Thika East Sub-county, Kenya. The agar well diffusion method showed that bromelain and nanoencapsulated bromelain had antimicrobial activity. All of the tested bacteria were sensitive to extracted bromelain at 5 mg/ml and less. The tested bacteria were less sensitive to commercial bromelain (57.1%) at 5 mg/ml and less. The MIC of nanoencapsulated bromelain against Enterobacter spp., Citrobacter spp., Serratia spp. and Coagulase Negative Staphylococci was 25 µg/ml, while that of Escherichia coli was 50 µg/ml. The MIC of nanoencapsulated bromelain against Klebsiella spp. and Staphylococcus aureus was 200 µg/ml. The low MICs recorded in this study shows that nanoencapsulated bromelain has high antimicrobial potential which warrants further in vivo studies in dairy goats to determine its efficacy against sub-clinical mastitis.

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