Takashi Amoh1, Keiji Murakami1, Reiko Kariyama2,3, Kenji Hori4, Darija Viducic1, Katsuhiko Hirota1, Jun Igarashi5, Hiroaki Suga6, Matthew R Parsek7, Hiromi Kumon2, Yoichiro Miyake1. 1. Department of Oral Microbiology, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8504, Japan. 2. Department of Urology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Okayama 700-8558, Japan. 3. Department of Food and Nutrition, Okayama Gakuin University, 787 Aruki, Kurashiki, Okayama 710-0031, Japan. 4. Innovation Center Okayama for Nanobio-targeted Therapy, Okayama University, 2-5-1 Shikata-cho, Okayama 700-8558, Japan. 5. Discovery Research Lab., Otsuka Chemical Co. Ltd., 463, Kagasuno, Kawauchi, Tokushima 771-0193, Japan. 6. Department of Chemistry, Graduate School of Science, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. 7. Department of Microbiology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
Abstract
Objectives: Antibiotic tolerance causes chronic, refractory and persistent infections. In order to advance the development of a new type of drug for the treatment of infectious diseases, we herein investigated the effects of a newly synthesized analogue of the Pseudomonas aeruginosa quorum-sensing autoinducer named AIA-1 ( a uto i nducer a nalogue) on antibiotic tolerance in P. aeruginosa . Methods: A P. aeruginosa luminescent strain derived from PAO1 was injected into neutropenic ICR mice and bioluminescence images were acquired for a period of time after treatments with antibiotics and AIA-1. In vitro susceptibility testing and killing assays for the planktonic and biofilm cells of PAO1 were performed using antibiotics and AIA-1. The expression of quorum-sensing-related genes was examined using real-time PCR. Results: In vivo and in vitro assays showed that AIA-1 alone did not exert any bactericidal effects and also did not affect the MICs of antibiotics. However, the combined use of AIA-1 and antibiotics exerted markedly stronger therapeutic effects against experimental infection than antibiotics alone. The presence of AIA-1 also enhanced the killing effects of antibiotics in planktonic and biofilm cells. Although AIA-1 did not inhibit the expression of lasB and rhlA genes, which are directly regulated by quorum sensing, it clearly suppressed expression of the rpoS gene. Conclusions: The new compound, AIA-1, did not alter the antibiotic susceptibility of P. aeruginosa by itself; however, its addition enhanced the antibacterial activity of antibiotics. AIA-1 did not inhibit quorum sensing, but reduced the antibiotic tolerance of P. aeruginosa by suppressing rpoS gene expression.
Objectives: Antibiotic tolerance causes chronic, refractory and persistent infections. In order to advance the development of a new type of drug for the treatment of infectious diseases, we herein investigated the effects of a newly synthesized analogue of the Pseudomonas aeruginosa quorum-sensing autoinducer named AIA-1 ( a uto i nducer a nalogue) on antibiotic tolerance in P. aeruginosa . Methods: A P. aeruginosa luminescent strain derived from PAO1 was injected into neutropenic ICR mice and bioluminescence images were acquired for a period of time after treatments with antibiotics and AIA-1. In vitro susceptibility testing and killing assays for the planktonic and biofilm cells of PAO1 were performed using antibiotics and AIA-1. The expression of quorum-sensing-related genes was examined using real-time PCR. Results: In vivo and in vitro assays showed that AIA-1 alone did not exert any bactericidal effects and also did not affect the MICs of antibiotics. However, the combined use of AIA-1 and antibiotics exerted markedly stronger therapeutic effects against experimental infection than antibiotics alone. The presence of AIA-1 also enhanced the killing effects of antibiotics in planktonic and biofilm cells. Although AIA-1 did not inhibit the expression of lasB and rhlA genes, which are directly regulated by quorum sensing, it clearly suppressed expression of the rpoS gene. Conclusions: The new compound, AIA-1, did not alter the antibiotic susceptibility of P. aeruginosa by itself; however, its addition enhanced the antibacterial activity of antibiotics. AIA-1 did not inhibit quorum sensing, but reduced the antibiotic tolerance of P. aeruginosa by suppressing rpoS gene expression.
Authors: Joe J Harrison; Carol A Stremick; Raymond J Turner; Nick D Allan; Merle E Olson; Howard Ceri Journal: Nat Protoc Date: 2010-06-10 Impact factor: 13.491