In vitro antibacterial effect of Lemna minuta , Chlorella vulgaris and Spirulina sp . extracts against fish pathogen Aeromonas hydrophila

The aim of the present study was to test extracts from Spirulina sp., Chlorella vulgaris and Lemna minuta against fish pathogen Aeromonas hydrophila. The water extract of these three aquatic plants were prepared. The plants were extracted in water solution at proportion 1:10. The received homogeny solutions were filtered and centrifuged at 7000 rpm for 30 minutes. Afterwards the extracts were filtered with sterile syringe filters with the size 0.2 μm. The bacterial strain of Aeromonas hydrophila (АТСС 7965) was used in current research. The bacterial activities of plant extract against A. hydrophila were tested with disk diffusion method. The aqueous extracts of all three test plants showed a good inhibitory effect against the fish pathogen. From the in vitro test conducted it was observed that the aqueous extract of C. vulgaris showed the highest zone of inhibition against A. hydrophila (12 mm).