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Chapter – 6 Biological evaluation of newly.....
MICs can be determined by agar or broth dilution methods usually
following the guidelines of a reference body such as the CLSI, BSAC or
EUCAST. There are several commercial methods available, including the well
established Etest strips and the recently launched Oxoid MIC Evaluator
method.
The Etest system comprises a predefined and continuous
concentration gradient of different antimicrobial agents, which when applied to
inoculated agar plates and incubated, create ellipses of microbial inhibition.
The MIC is determined where the ellipse of inhibition intersects the strip, and
is easily read off the MIC reading scale on the strip.
Clinically, the minimum inhibitory concentrations are used not only to
determine the amount of antibiotic that the patient will receive but also the
type of antibiotic used, which in turn lowers the opportunity for microbial
resistance to specific antimicrobial agents.
The antimicrobial activity of newly synthesized 2-methyl indoline
derivatives and isatin derivatives synthesized in Chapter – 1 and Chapter – 2
(i.e. DNJ-101 to DNJ-111, DNJ-210 to DNJ-210, DNJ-301 to DNJ-305, DNJ-
401 to DNJ-405, DNJ-501 to DNJ-505 and DNJ-601 to DNJ-605) is reported
here in, while the compounds are under investigation for another biological
activities.
6.1.2 PROTOCOL FOR ANTIBACTERIAL ACTIVITY
The minimum inhibitory concentrations (MIC) of the compounds for the
microorganisms were determined by preparing working solution for each
compound of concentration of 128 µg/ml after dissolving it in DMSO. Two fold
serial dilution of above solution was prepared in duplicate using Muller Hinton
Borth, in well tissue culture plate with cover flat bottom wells to give a final
volume of 150 and concentration of compound ranging from 64 µg/ml – 0.12
µg/ml. 30 µg/ml of standard suspension of each organism which was prepared
with turbidity equivalent to the 1:10 diluted 0.5 McFarland standard with
density 10 7 CFU/ml. These 96-well tissue culture plate containing the test
Department of Chemistry, Saurashtra University, Rajkot – 360 005 328