Anti-Biofilm and Associated Anti-Virulence Activities of Selected Phytochemical Compounds against Klebsiella pneumoniae

Abstract

The ability of Klebsiella pneumoniae to form biofilm renders the pathogen recalcitrant to various antibiotics. The difficulty in managing K. pneumoniae related chronic infections is due to its biofilm-forming ability and associated virulence factors, necessitating the development of efficient strategies to control virulence factors. This study aimed at evaluating the inhibitory potential of selected phytochemical compounds on biofilm-associated virulence factors in K. pneumoniae, as well as authenticating their antibiofilm activity. Five phytochemical compounds (alpha-terpinene, camphene, fisetin, glycitein and phytol) were evaluated for their antibacterial and anti-biofilm-associated virulence factors such as exopolysaccharides, curli fibers, and hypermucoviscosity against carbapenem-resistant and extended-spectrum beta-lactamase-positive K. pneumoniae strains. The antibiofilm potential of these compounds was evaluated at initial cell attachment, microcolony formation and mature biofilm formation, then validated by in situ visualization using scanning electron microscopy (SEM). Exopolysaccharide surface topography was characterized using atomic force microscopy (AFM). The antibacterial activity of the compounds confirmed fisetin as the best carbapenem-resistant K. pneumoniae, demonstrating a minimum inhibitory concentration (MIC) value of 0.0625 mg/mL. Phytol, glycitein and α-terpinene showed MIC values of 0.125 mg/mL for both strains. The assessment of the compounds for anti-virulence activity (exopolysaccharide reduction) revealed an up to 65.91% reduction in phytol and camphene. Atomic force microscopy detected marked differences between the topographies of untreated and treated (camphene and phytol) exopolysaccharides. Curli expression was inhibited at both 0.5 and 1.0 mg/mL by phytol, glycitein, fisetin and quercetin. The hypermucoviscosity was reduced by phytol, glycitein, and fisetin to the shortest mucoid string (1 mm) at 1 mg/mL. Phytol showed the highest antiadhesion activity against carbapenem-resistant and extended-spectrum beta-lactamase-positive K. pneumoniae (54.71% and 50.05%), respectively. Scanning electron microscopy correlated the in vitro findings, with phytol significantly altering the biofilm architecture. Phytol has antibiofilm and antivirulence potential against the highly virulent K. pneumoniae strains, revealing it as a potential lead compound for the management of K. pneumoniae-associated infections.

Downregulation of the Gene Expression of Efflux Pump Gene (acrA) and its Regulator (ramA) in Klebsiella pneumoniae by Quaternary Ammonium Compounds

“…A study of Dettol's effect on the formation of biofilm by pathogenic microorganisms conducted by Najim 27 revealed that the biofilm inhibition appeared at the dilution of 1:10 (MIC) of the detergent for most bacterial isolates when compared with the positive control, and the highest dilution of detergent (more than 1:10) lost the ability to eradicate biofilm growth. Adeosun et al 29 employed SEM micrographs to examine the biofilms formed by K. pneumoniae strains after exposure to phytol and glycitein as compared to untreated biofilms.…”

Extracts of Selected South African Medicinal Plants Mitigate Virulence Factors in Multidrug‐Resistant Strains of Klebsiella pneumoniae

“…CBR- K. pneumoniae was investigated in this study due to its intriguing ability to produce carbapenemases (KPC), a common resistance mechanism seen in K. pneumoniae . This resistance mechanism poses a significant challenge for effective treatment, leading to a global health concern associated with high mortality rates [ 12 ]. Carbapenem-resistant K. pneumoniae exhibits rapid transmission, extensive resistance to antibiotics, and limited treatment options [ 12 ].…”

“…It has also been reported to be implicated with septicaemia, soft tissue infections, intraabdominal infections, and wound and blood infections [ 11 ]. K. pneumoniae possesses virulence factors such as capsular antigens, adherence factors for biofilm formation, O -lipopolysaccharide, exopolysaccharides, and siderophores linked to its infectivity and virulence [ 12 , 13 ]. Combating its virulence has been challenging due to antibiotic resistance, which has increased dramatically over the last few decades [ 14 ], with resistance to β -lactams having the most significant impact on treatment efficacy [ 15 ].…”

Editorial: Pathoblockers and antivirulence agents of plant-origin for the management of multidrug resistant pathogens

“…Among their bioactivities, plant metabolites, which are the most powerful and promising elements of plants, have been shown to possess antimicrobial potential. It is well known that plant extracts act as antibacterial and antifungal agents (Anand et al, 2019 ; Mandrone et al, 2019 ; Adeosun et al, 2022 ), but they are also a valuable source of anti-virulence compounds with unique mechanism of action targeting pathogenicity or virulence. In addition, some phytochemicals, despite not being directly microbial inhibitors by themselves, show antibiotic adjuvant activity or bio-enhancing activity to attain bactericidal synergism (Patil et al, 2011 ; Dudhatra et al, 2012 ); moreover, they serve as reducing and stabilizing agents for the effective synthesis of plant-based metal nanoparticles, improving the antibacterial properties of these nanomaterials (Guleria et al, 2022 ).…”