Résumé:
The intense use of antibiotics has resulted in the emergence of extremely resistant pathogenic
strains, which is difficult to treat their infections that can only be effectively treated with a small
group of antimicrobial agents. For this reason, it has become very important to look for new
unconventional antibiotics.
Pseudomonas aeruginosa produces numerous secondary metabolites with a significant
biological effect against different pathogens responsible for these different infections.
In this work we have tried to evaluate the antimicrobial activity of the pyocyanin of 9 isolates
of Pseudomonas aeruginosa. All isolates are of clinical origin except one that is obtained from
the roots of a wild grass plant (Rat barley = Hordeum murinum). The results of antagonism of
these isolates against Gram-positive, Gram-negative bacteria and yeast showed significant areas
of inhibition among which an isolate S2 had an effect on all target strains.
Determination of pyocyanin produced in 4 isolates by spectrophotometry showed that the
best production is found in strain S2. This isolat is subsequently selected to test the antimicrobial
activity of its pyocyanin against pathogenic germs. Pyocyanin is extracted by Chloroform and its
effect is evaluated by disk diffusion method on Mueller-Hinton medium. The results obtained
revealed a greater susceptibility of Gram-positive bacteria and yeasts than Gram-negative ones
with 15 mm inhibition zones for Staphylococcus aureus ATCC 33862 and Candida albicans of
genital origin.
The effect of temperature and incubation time on pyocyanin production was performed for
the 4 best performing isolates. The best production (15.9 μg / ml) is reached during incubation at
37 ° C for 48 hours by the isolate S2.
A characterization of the pyocyanin by UV-visible spectrophotometry showed a spectrum
containing 3 peaks, two in the UV (at 300 and 380nm) and one in the visible (at 520nm). A
maximum of absorption was recorded at 380nm.
