2.4. Antibacterial activity of extracts
2.4.1. Well-diffusion method
P. aeruginosa was used in the study. The plates were inoculatedwith
the bacterial pathogen by swabbing the bacterial culture on the Muller
Hinton agar and maintained under sterile condition until the inoculum
dried. Two 8mmdiameterwells weremade on the agar surface of each
plate (Thanigaivel et al., 2014). 30 μl of the ethanol and aqueous extracts
of both seaweeds were then added separately into each well. Milli-Q
water was kept as a control for the aqueous extract and ethanol was
added as control for ethanol extract. The samples were allowed to diffuse.
The plates were monitored for 48 h for antibacterial activity. The
zone inhibition zone was measured at the end of 48 h (Thanigaivel
et al., 2014, 2015a).
2.4.2. Antibiotic disc test
The antibiotic sensitivity test was carried out by the method of
Thanigaivel et al. (2015b). The antibiotic disc used in the studywas gentamicin.
After making a lawn culture of the bacterial inoculum, the extract
loaded disc was placed on the lawn culture of the test organism.
The plates were incubated for 48 h at 37 °C for circular clear area
(zone of inhibition) around the discs. Zone of inhibition was measured.
2.5. Experimental pathogenicity
Pathogenicity of P. aeruginosa was reported in our earlier paper,
Pathogenicity of P. aeruginosa was confirmed by satisfying Koch's postulates
(Thomas et al., 2014).