Prodigiosin as an antibiofilm agent against multidrug-resistant Staphylococcus aureus

Prodigiosin as an Antibiofilm Agent against the Bacterial Biofilm-Associated Infection of Pseudomonas aeruginosa

Pseudomonas aeruginosa is known to generate bacterial biofilms that increase antibiotic resistance. With the increase of multi-drug resistance in recent years, the formulation of a new therapeutic strategy has seemed urgent. Preliminary findings show that Prodigiosin (PG), derived from chromium-resistant Serratia marcescens, exhibited efficient anti-biofilm activity against Staphylococcus aureus. However, its anti-biofilm activity against P. aeruginosa remains largely unexplored. The anti-biofilm activity of PG against three clinical single drug-resistant P. aeruginosa was evaluated using crystal violet staining, and the viability of biofilms and planktonic cells were also assessed. A model of chronic lung infection was constructed to test the in vivo antibiofilm activity of PG. The results showed that PG inhibited biofilm formation and effectively inhibited the production of pyocyanin and extracellular polysaccharides in vitro, as well as moderated the expression of interleukins (IL-1β, IL-6, IL-10) and tumor necrosis factor (TNF-α) in vivo, which might be attributed to the downregulation of biofilm-related genes such as algA, pelA, and pslM. These findings suggest that PG could be a potential treatment for drug-resistant P aeruginosa and chronic biofilm infections.

Transcriptomic analysis of cell envelope inhibition by prodigiosin in methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading threat to public health as it is resistant to most currently available antibiotics. Prodigiosin is a secondary metabolite of microorganisms with broad-spectrum antibacterial activity. This study identified a significant antibacterial effect of prodigiosin against MRSA with a minimum inhibitory concentration as low as 2.5 mg/L. The results of scanning electron microscopy, crystal violet staining, and confocal laser scanning microscopy indicated that prodigiosin inhibited biofilm formation in S. aureus USA300, while also destroying the structure of the cell wall and cell membrane, which was confirmed by transmission electron microscopy. At a prodigiosin concentration of 1.25 mg/L, biofilm formation was inhibited by 76.24%, while 2.5 mg/L prodigiosin significantly reduced the vitality of MRSA cells in the biofilm. Furthermore, the transcriptomic results obtained at 1/8 MIC of prodigiosin indicated that 235and 387 genes of S. aureus USA300 were significantly up- and downregulated, respectively. The downregulated genes were related to two-component systems, including the transcriptional regulator LytS, quorum sensing histidine kinases SrrB, NreA and NreB, peptidoglycan biosynthesis enzymes (MurQ and GlmU), iron-sulfur cluster repair protein ScdA, microbial surface components recognizing adaptive matrix molecules, as well as the key arginine synthesis enzymes ArcC and ArgF. The upregulated genes were mainly related to cell wall biosynthesis, as well as two-component systems including vancomycin resistance-associated regulator, lipoteichoic acid biosynthesis related proteins DltD and DltB, as well as the 9 capsular polysaccharide biosynthesis proteins. This study elucidated the molecular mechanisms through which prodigiosin affects the cell envelope of MRSA from the perspectives of cell wall synthesis, cell membrane and biofilm formation, providing new potential targets for the development of antimicrobials for the treatment of MRSA.

A comprehensive profiling of quorum quenching by bacterial pigments identifies quorum sensing inhibition and antibiofilm action of prodigiosin against Acinetobacter baumannii

Bacterial pigments represent a diverse group of secondary metabolites, which confer fitness advantages to the producers while residing in communities. The bioactive potential of such metabolites, including antimicrobial, anticancer, and immunomodulation, are being explored. Reckoning that a majority of such pigments are produced in response to quorum sensing (QS) mediated expression of biosynthetic gene clusters and, in turn, influence cell-cell communication, systemic profiling of the pigments for possible impact on QS appears crucial. A systemic screening of bacterial pigments for QS-inhibition combined with exploration of antibiofilm and antimicrobial action against Acinetobacter baumannii might offer viable alternatives to combat the priority pathogen. Major bacterial pigments are classified (clustered) based on their physicochemical properties, and representatives of the clusters are screened for QS inhibition. The screen highlighted prodigiosin as a potent quorum quencher, although its production from Serratia marcescens appeared to be QS-independent. In silico analysis indicated potential interactions between AbaI and AbaR, two major QS regulators in A. baumannii, and prodigiosin, which impaired biofilm formation, a major QS-dependent process in the bacteria. Prodigiosin augmented antibiotic action of ciprofloxacin against A. baumannii biofilms. Cell viability analysis revealed prodigiosin to be modestly cytotoxic against HEK293, a non-cancer human cell line. While developing dual-species biofilm, prodigiosin producer S. marcescens significantly impaired the fitness of A. baumannii. Enhanced susceptibility of A. baumannii toward colistin was also noted while growing in co-culture with S. marcescens. Antibiotic resistant isolates demonstrated varied responsiveness against prodigiosin, with two resistant strains demonstrating possible collateral sensitivity. Collectively, the results underpin the prospect of a prodigiosin-based therapeutic strategy in combating A. baumannii infection.