Antimicrobial Effect of Common Bacterial Pigments on Clinically Significant Microorganisms

The aim of this research is to investigate the antimicrobial characteristics of bacterial pigments. Pigments are vibrant metabolites generated by bacteria, offering defence against radiation, sunlight, stress and competing microorganisms. Bacterial pigments have various applications in cosmetics, pharmaceuticals and food sectors due to their antimicrobial, anticancer and antioxidant properties. In this cross-sectional in vitro study, we used 30 isolates each of Enterococcus faecalis, Klebsiella spp. and Candida spp. isolated from human urine, blood and pus samples to study the antimicrobial effect of pigments produced by Serratia marcescens (prodigiosin), Chromobacterium violaceum (violacein) and Pseudomonas aeruginosa (pyocyanin). At the suitable pH and temperature, pigment-producing bacteria were mass-cultured in nutrient broth. Pigments were extracted from S. marcescens and C. violaceum cultures using acetone and methanol. Pyocyanin from P. aeruginosa was extracted by using hydrochloric acid and chloroform. Extracted pigments were dried and characterised by mass spectrometry. The antimicrobial activity of the crude pigments was determined by the agar dilution method using Muller Hinton agar (MHA) plates for bacterial isolates, and Sabouraud’s Dextrose agar (SDA) for Candida spp. E. faecalis ATCC 29212, K. pneumonia ATCC 700603 and C. albicans ATCC 14053 were used as standards. The minimum concentration of the pigment that supressed the growth of microorganism on the MHA/SDA agar plate was considered as minimum inhibitory concentration (MIC). Data were analysed using the Chi-square statistical method. E. faecalis, which were resistant to teicoplanin, vancomycin, norfloxacin and penicillin, were found susceptible to pyocyanin (p < 0.05). Multidrug-resistant Klebsiella spp. were susceptible to pyocyanin, violacein and prodigiosin (p < 0.05). Candida spp. resistant to caspofungin, micafungin, showed susceptibility to prodigiosin, and those isolates resistant to amphotericin B showed susceptibility to pyocyanin (p < 0.05). Among all clinical isolates, Klebsiella spp. from urine exhibited the highest resistance to the pigments studied. Among the pigments studied, violacein and prodigiosin exhibited superior antimicrobial and antifungal properties. Therefore, violacein and prodigiosin could serve as an alternative antimicrobial substance for addressing multidrug-resistant pathogenic microorganisms.