Biofilm inhibitory efficiency of phytol in combination with cefotaxime against nosocomial pathogen Acinetobacter baumannii.

AIMS: This study aimed to evaluate the antibiofilm potential of phytol and cefotaxime combinations (PCCs) against Acinetobacter baumannii and to elucidate the molecular mechanism of their antibiofilm potential through the transcriptomic approach. METHODS AND RESULTS: Phytol and cefotaxime combination(s) (PCC(s) [160 µg ml-1  + 8 µg ml-1 for microbial type culture collection (MTCC) strain and 160 µg ml-1  + 0.5 µg ml-1 for clinical isolate] effectively inhibited the A. baumannii biofilm formation. Additionally, light, confocal laser scanning and scanning electron microscopic analyses validated the antibiofilm potential of PCCs. Furthermore, PCCs treated A. baumannii cells showed a decreased level of hydrophobicity index compared to their respective controls. Fourier-transform infrared (FT-IR) spectra of exopolysaccharide matrix extracted from PCCs-treated A. baumannii cells showed a visible decrease in absorbance of polysaccharides, nucleic acids and protein regions compared to the spectra of untreated controls. In the blood sensitivity assay, the PCCs-treated A. baumannii plates showed reduced a number of bacterial colonies compared to their control plates. Reduced level of catalase production was also observed in the PCCs treatment compared to their controls. Transcriptomic analysis revealed the downregulation of bfmR, bap, csuA/B, ompA, pgaA, pgaC and katE biofilm virulence genes in both the A. baumannii strains on treatment with PCCs. CONCLUSION: The obtained results of this study indicate that PCCs have potent antibiofilm activity and downregulate the biofilm-related virulence genes expression in A. baumannii. SIGNIFICANCE AND IMPACT OF THE STUDY: To the best of our knowledge, this is the pioneering study, which shows the antibiofilm effect of PCCs against A. baumannii along with their molecular mechanism. The antibiofilm effect of PCCs could be a successful strategy for eradicating infections related to A. baumannii biofilms in nosocomial settings.

Phytosynthesized silver nanoparticles as antiquorum sensing and antibiofilm agent against the nosocomial pathogen Serratia marcescens: an in vitro study.

AIM: Serratia marcescens is an important multidrug-resistant human pathogen. The pathogenicity of S. marcescens mainly depends on the quorum sensing (QS) mechanism, which regulates the virulence factors production and biofilm formation. Hence, targeting QS mechanism in S. marcescens will ultimately pave the way to combat its pathogenicity. Thus, the present study is intended to evaluate the efficacy of Vetiveria zizanioides root extract-mediated silver nanoparticles (AgNPs) as a potent anti-QS and antibiofilm agent against S. marcescens. METHODS AND RESULTS: The AgNPs were synthesized using V. zizanioides aqueous root extract and the physiochemical properties of V. zizanioides-based AgNPs (VzAgNPs) were evaluated using analytical techniques such as ultraviolet-visible absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, dynamic light scattering and scanning and transmission electron microscopic techniques. VzAgNPs were found to attenuate the QS-dependent virulence factors, namely prodigiosin, protease, lipase, exopolysaccharide productions and biofilm formation of S. marcescens, without inhibiting its growth. Further, the transcriptomic analysis confirmed the down-regulation of QS-dependent genes, which encode for the production of virulence factors and biofilm formation. CONCLUSION: The current study confirms VzAgNPs as an ideal anti-QS and antibiofilm agent against S. marcescens. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first approach that validates the anti-QS and antibiofilm potential of phytosynthesized VzAgNPs against the nosocomial pathogen, S. marcescens. As VzAgNPs exhibits potent antivirulent activities, it could be used to treat hospital-acquired S. marcescens infections.