Influence of Peganum harmala peptides on the transcriptional activity of biofilm related genes in sensitive and resistant strains of Pseudomonas aeruginosa and Staphylococcus aureus.

Microbial biofilms have gathered interest in recent years as they have become the major cause of nosocomial infections. The abuse and misuse of antibiotics have created a selective pressure that results in widespread formation of resistant bacterial strains and a need to devise novel plant based antimicrobials. In this study, antimicrobial peptides were isolated from Peganum harmala and their effect was examined on biofilm related colonization genes of Pseudomonas aeruginosa and Staphylococcus aureus isolated from burn and surgical wounds. Results showed that in P. aeruginosa isolated from burn wound, the expression of flagellar gene (flgK), pilin gene (pilA) and fimbriae gene (cupA1) was significantly down-regulated indicating that Peganum harmala antimicrobial peptides (PhAMP) damage locomotors of planktonic cells by affecting the gene expression while in resistant biofilm cells, the expression of flgK, cupA1 and polysaccharide synthesis gene (pslA) was enhanced in the presence of PhAMP. In P. aeruginosa isolated from surgical wounds which was more sensitive; the expression of flgK, pilA, cupA1 and pslA was significantly down-regulated in biofilms and planktonic cells in the presence of PhAMP thus disrupting locomotors of planktonic as well as biofilm cells. In S. aureus isolated from burn wounds; the expression of capsular polysaccharide synthesis gene (CPS5) and inter cellular adhesion gene (icaA) was significantly up-regulated in biofilms as well as in planktonic cells in response to PhAMP stress showing resistance mechanism. Thus these genes can be used as efficient resistance markers for bacterial pathogens against antimicrobial agents.