Inhibition of biofilm formation and quorum sensing mediated virulence in Pseudomonas aeruginosa by marine sponge symbiont Brevibacterium casei strain Alu 1.

The alternative antimicrobial strategies that mitigate the threat of antibiotic resistance is the quorum-sensing inhibition (QSI) mechanism, which targets autoinducer dependent virulence gene expression in bacterial pathogens. N-acyl homoserine lactone (AHL) acts as a key regulator in the production of virulence factors and biofilm formation in Pseudomonas aeruginosa PAO1 and violacein pigment production in Chromobacterium violaceum ATCC 12472. In the present study, the marine sponge Haliclona fibulata symbiont Brevibacterium casei strain Alu 1 showed potential QSI activity in a concentration-dependent manner (0.5-2% v/v) against the N-acyl homoserine lactone (AHL)-mediated violacein production in C. violaceum (75-95%), and biofilm formation (53-96%), protease (27-82%), pyocyanin (82-95%) and pyoverdin (29-38%) productions in P. aeruginosa. Further, the microscopic analyses validated the antibiofilm activity of the cell-free culture supernatant (CFCS) of B. casei against P. aeruginosa. Subsequently, the biofilm and pyoverdin inhibitory efficacy of the ethyl acetate extract of B. casei CFCS was assessed against P. aeruginosa. Further, the gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of variety of components in which diethyl phthalate was found to be a major active component. This phthalate ester, known as diethyl ester of phthalic acid, could act as a potential therapeutic agent for preventing bacterial biofilm and virulence associated infectious diseases.

Extended spectrum ß-lactamase producing Escherichia coli and Klebsiella pneumoniae: critical tools for antibiotic resistance pattern.

Drug resistance is a phenomenon where by an organism becomes fully or partially resistant to drugs or antibiotics being used against it. Antibiotic resistance poses an exacting intimidation for people with underlying medical immune conditions or weakened immune systems. Infections caused by the enzyme extended spectrum ß-lactamase (ESBL) producing multi drug resistance (MDR) Enterobacteriaceae especially Escherichia coli and Klebsiella pneumoniae are resistant to a broad range of beta lactams, including third generation cephalosporins. Among all the pathogens, these two MDR E. coli and K. pneumoniae have emerged as one of the world's greatest health threats in past two decades. The nosocomial infections caused by these ESBL producing MDR E. coli and K. pneumoniae complicated the therapy and limit treatment options.

Production of naphthoquinones and phenolics by a novel isolate Fusarium solani PSC-R of Palk Bay and their industrial applications.

The present study was attempted to enhance the production of naphthoquinones and phenolics by Fusarium solani PSC-R of Palk Bay origin, which exhibited potent antibacterial, antioxidant and dyeing activity. Maximum productivity of naphthoquinones and phenolics was achieved in potato infusion medium supplemented with 2% sucrose. Addition of nitrogen sources to the medium adversely affected the production of both naphthoquinones and phenolics. An initial pH of 5 and incubation at 31°C for six days at 140rpm was found to increase the yield (123.65mg/g of DW), concentration (867.33mg/l) and total naphthoquinones (602.8µM/g DW) by 7.58, 10.44 and 3.68-fold respectively. Similarly, the antioxidant and antibacterial activity associated with the phenolics of PSC-R increased by 1.5-fold in the optimized medium. The obtained results document the effective means of enhanced production of naphthoquinones and phenolics in the suspension culture of F. solani PSC-R at bioreactor level.