Chitosan synergistic effect with antibiotic
The antimicrobial activity of ceftazidime antibiotics against P.
aeruginosa was assessed using the macro dilution method. The
minimum inhibitory concentrations
(MICs) were determined by dissolving the antibiotic in distilled water
to create a stock concentration of 10000 μg/ml. The stock concentration
was then filtered through a 0.22 μm millipore filter. Serial dilutions
of the antibiotic were prepared in nutrient broth, ranging from 1 to
5000 μg/ml. Sterile-capped test tubes were inoculated with 100 μl of a
bacterial suspension containing 104 cfu/ml.
Additionally, 50 μl from each dilution was placed in 7 mm diameter wells
on Mueller-Hinton agar medium. Subsequently, all tubes and plates were
incubated at 37°C for 18-24 hours. The lowest concentration of
antibiotic that showed no visible growth in tubes or inhibition zones in
plates was recorded as the MIC. To test the combination of chitosan
extract with ceftazidime, the same methods as mentioned above were
followed. In this case, 100 μl of bacterial suspension and chitosan were
added separately to the serial dilutions of the antibiotic. Once again,
50 μl from each dilution was placed in wells on Mueller-Hinton agar
medium, followed by incubation at 37°C for 18-24 hours. The lowest
concentration of antibiotic that exhibited no visible growth in tubes or
inhibition zones in plates was considered as the MIC.