Antimicrobial Activity of Pyocyanin Produced by Pseudomonas aeruginosa Isolated from Surgical Wound-Infections

Abstract

2 Abstract: Five different isolates of Pseudomonas aeruginosa were obtained from surgical specimens and minced meat. The isolates were tested for the production of the blue pigment; pyocyanin. Considerable amounts of blue pigment were produced by P. aeruginosa isolates when on the four tested media. Muller-Hinton agar was further used for growth, pigment production and sensitivity tests. Pigment production began during the first 24 hrs of growth and maximal pigment production was achieved after 48 hrs by isolates No. 1, 2 and 3. At this time, isolate No. 5 produced only moderate level of pyocyanin. While isolate No. 4 reached the highest yield after 72 hrs. Pyocyanin pigments obtained from culture supernatants of the tested P.aeruginosa isolates grown in peptone water liquid medium by serial chloroform extractions reached about 62.8µg/ml. The growth of all Gram-positive bacteria and Candida species was completely inhibited when cultivated on the agar plates containing the blue pigment. Whereas, Gram negative bacteria; Klebsiella pneumoniae and P. aeruginosa were resistant to pyocyanin. Salmonella typhi and Proteus mirabilis were intermediately affected. Thus, the five tested P. aeruginosa isolates were resistant to their own produced pyocyanin pigments. In a Conclusion, the Gram-positive bacteria were more susceptible as a group to the antibiotic action of pyocyanin than were the Gram negative bacteria. The antibacterial and antifungal nature of the pigment is attractive for the topical treatment of wound infections.