Antifungal potential of multi-drug-resistant Pseudomonas aeruginosa: harnessing pyocyanin for candida growth inhibition

Abstract

Introduction: Pseudomonas aeruginosa is notorious for its multidrug resistance and its involvement in hospital-acquired infections. In this study, 20 bacterial strains isolated from soil samples near the Hindan River in Ghaziabad, India, were investigated for their biochemical and morphological characteristics, with a focus on identifying strains with exceptional drug resistance and pyocyanin production.

Methods: The isolated bacterial strains were subjected to biochemical and morphological analyses to characterize their properties, with a particular emphasis on exopolysaccharide production. Strain GZB16/CEES1, exhibiting remarkable drug resistance and pyocyanin production. Biochemical and molecular analyses, including sequencing of its 16S rRNA gene (accession number LN735036.1), plasmid-curing assays, and estimation of plasmid size, were conducted to elucidate its drug resistance mechanisms and further pyocynin based target the Candida albicans Strain GZB16/CEES1 demonstrated 100% resistance to various antibiotics used in the investigation, with plasmid-curing assays, suggesting plasmid-based resistance gene transmission. The plasmid in GZB16/CEES1 was estimated to be approximately 24 kb in size. The study focused on P. aeruginosa's pyocyanin production, revealing its association with anticandidal activity. The minimum inhibitory concentration (MIC) of the bacterial extract against Candida albicans was 50 μg/ml, with a slightly lower pyocyanin-based MIC of 38.5 μg/ml. Scanning electron microscopy illustrated direct interactions between P. aeruginosa strains and Candida albicans cells, leading to the destruction of the latter.

Discussion: These findings underscore the potential of P. aeruginosa in understanding microbial interactions and developing strategies to combat fungal infections. The study highlights the importance of investigating bacterial-fungal interactions and the role of pyocyanin in antimicrobial activity. Further research in this area could lead to the development of novel therapeutic approaches for combating multidrug-resistant infections.

Keywords: Pseudomonas aeruginosa; anti-candida; antifungal; drug resistance; exopolysaccharide; plasmid; pyocyanin.

Figure 1

In a culture incubator at 35°C, the Pseudomonas aeruginosa bacterial strain displayed a greenish pyocyanin pigmentation when exposed to ultraviolet light after a 3-days. (A) A plate showing the bacterial colony on Kings B agar plates, with the characteristic greenish pigmentation visible under ultraviolet light. (B) A purified bacterial culture demonstrating fluorescent pigmentation on a medium plate, with the pigmentation appearing greenish under ultraviolet light. (C) A liquid medium containing the bacterial strain GZB16/CEES1 exhibits the distinctive greenish pigmentation of pyocyanin.

Figure 2

The Neighbor-Joining method constructed the evolutionary relationships of GZB16/CEES1 strains of Pseudomonas aeruginosa. The phylogenetic tree was created according to the scale and branch lengths in the same units. The analysis involved nucleotide sequences, and gaps and missing data were eliminated in all positions. Evolutionary analyses were conducted in MEGA7.

Figure 3

Susceptibility patterns of bacterial strains against the applied total antibiotics.

Figure 4

Plasmid DNA isolation and purification by gel electrophoresis analysis, Lane 1 shows the ladder, and Lane 2 reveals the plasmid band. Further, these plasmid bands appeared in the transformed E. coli cells when incubated with P. aeruginosa.

Figure 5

Bacterial strain of P. aeruginosa (A) plasmid containing bacterial strain showed resistance against multiple antibiotic discs (B) without plasmid bacteria stain highly sensitive against similar antibiotics.

Figure 6

Exopolysaccharide synthesis by Pseudomonas isolates at 5% sucrose as an external C- source.

Figure 7

Bacterial pyocyanin synthesis with bacterial biomass at optimum condition.

Figure 8

Pyocyanin effect on the candida albicans growth in (A) zone inhibition assay (B) pyocyanin production and effect on candida survivability.

Figure 9

The scanning electron microscope image reveals the Pseudomonas aeruginosa bacterial cells directly attached to the Candida albicans cells and damaged them.