The In Vitro/in Vivo Antibacterial Effect Of Ph-PA Against Pseudomonas Aeruginosa

Pseudomonas aeruginosa is a Gram-negative bacterium. It is a major opportunistic pathogen in compromised patients, such as burn patients and cancer patients undergoing chemotherapy. P. aeruginosa is susceptible to only a limited number of antibiotic agents. Infections caused by P. aeruginosa are often to require the combination therapy. Bacteremia, pneumonia, osteomyelitis, and endocarditis came by P. aeruginosa have notablely higher therapeutic failure and mortality rates than that of other bacterial pathogen. For P. aeruginosa, antibiotic resistance is an increasing problem. Multi-drug resistance have posed a serious threat to human beings, there is an urgent demanding to develop new type of antibiotics against P. aeruginosa infection.Colicin Ia is a bacteriocin produced by E. coli, which is bactericidal only to E. coli and related species by forming a voltage-activated channel in the cell membrane. AgrD1 is a pheromone of Staphylococcus aureuas, which has auto-inducing ability to interact with the receptor of the targeted cell membrane. Qiu constructed a peptide consisting of a AgrD1 pheromone fused to the channel-forming domain of colicin Ia and named it pheromonicin-SA(Ph-SA). The in intro and in vivo antibacterial tests suggested Ph-SA had bactericidal effects against Staphylococcus aureuas, on molar basis, was approximately 500 times as effective as that of methicillin against methicillin-resistant Staphylococcus aureuas(MRSA).As a control of Ph-SA, Qiu constructed a new peptide consisting of AgrD1 pheromone fused to the N-terminus of colicin Ia. Intersting, We found the fusion peptide had bacterial effects against Pseudomonas aeruginosa, but not against Staphylococcus aureus, we named it Pheromonicin- Pseudomonas aeruginosa (Ph-PA).Mutated plasmid containing the gene of Pheromonicin-PA was transformed into E.coli TG1 cells to produce Ph-PA, which purified by CM sepharose ion-exchange column. To test the minimal inhibitory concentration (MIC) of prepared Ph-PA against 30 strains pathogens by using micro dilution assay and comparing the antimicrobial activity with that of ceftazidime, piperacillin, levofloxacin, gentamicin. And in vivo bactericidal activity of Ph-PA was tested via intraperitoneal infected mice with intravenous drug treatment.In in vitro test, the antibacterial effect of Ph-PA represented a dose dependent effect, as a bactericidal agent, it showed strongest bactericidal effect against P. aeruginosa among test antibiotic agents, on molar basis, which was approximately 220 times greater than that of ceftazidime, over 2200 times greater than that of piperacillin, over 85 times greater than that of levofloxacin, and over 150 times greater than that of gentamicin. In vivo results showed that Ph-PA presented strongest bactericidal effect against multidrug-resistance P. aeruginosa that of in in vitro experiments, on molar basis, which was approximately 1100 times greater than that of ceftazidime, over 2300 times greater than that of piperacillin, over 280 times greater than that of levofloxacin, and over 440 times greater than that of amikacin.The results suggest that Ph-PA may be of value as a novel model to develop antibiotics against P. aeruginosa infection.