title: Mechanism of azithromycin inhibition of HSL synthesis in Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa is an opportunistic pathogen and a leading cause of nosocomial infections. Unfortunately, P. aeruginosa has low antibiotic susceptibility due to several chromosomally encoded antibiotic resistance genes. Hence, we carried out mechanistic studies to determine how azithromycin affects quorum sensing and virulence in P. aeruginosa. lasI and rhlI single and double mutants were constructed. We then undertook a quantitative approach to determine the optimal concentration of azithromycin and culture time that can affect the expression of HSLs. Furthermore, based on the above results, the effect on quorum sensing was analyzed at a transcriptional level. It was found that 2 μg/mL azithromycin caused a 79% decrease in 3-oxo-C12-HSL secretion during cultivation, while C4-HSL secretion was strongly repressed in the early stages. Azithromycin acts on ribosomes; to determine whether this can elicit alternative modes of gene expression, transcriptional regulation of representative virulence genes was analyzed. We propose a new relationship for lasI and rhlI: lasI acts as a cell density sensor, and rhlI functions as a fine-tuning mechanism for coordination between different quorum sensing systems.
authors.affiliation: Dept. of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou Higher Education Mega Center, 55 Neihuan Xi Road, Panyu District, Guangzhou 510006, China.
authors.forename: Jianming
authors.initials: J
authors.lastname: Zeng
authors.affiliation: Clinical Microbiology Laboratory, Guangdong Academy of Medical Sciences &Guangdong General Hospital, Guangzhou 510080, China.
authors.forename: Ni
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Dept. of Laboratory Medicine, the First Affiliated Hospital of Sun Yat-sen University, 58 Zhongshan Er Road, Guangzhou 510080, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Huang
authors.affiliation: Dept. of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou Higher Education Mega Center, 55 Neihuan Xi Road, Panyu District, Guangzhou 510006, China.
authors.forename: Renxin
authors.initials: R
authors.lastname: Cai
authors.affiliation: Dept. of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou Higher Education Mega Center, 55 Neihuan Xi Road, Panyu District, Guangzhou 510006, China.
authors.forename: Binning
authors.initials: B
authors.lastname: Wu
authors.affiliation: Dept. of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou Higher Education Mega Center, 55 Neihuan Xi Road, Panyu District, Guangzhou 510006, China.
authors.forename: Shunmei
authors.initials: S
authors.lastname: E
authors.affiliation: Dept. of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou Higher Education Mega Center, 55 Neihuan Xi Road, Panyu District, Guangzhou 510006, China.
authors.forename: Chengcai
authors.initials: C
authors.lastname: Fang
authors.affiliation: Dept. of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou Higher Education Mega Center, 55 Neihuan Xi Road, Panyu District, Guangzhou 510006, China.
authors.forename: Cha
authors.initials: C
authors.lastname: Chen
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008025:Ligases / Q000096:biosynthesis / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D053038:Quorum Sensing / Q000187:drug effects; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D014774:Virulence / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C081237:LasI protein, Pseudomonas aeruginosa; D014157:Transcription Factors; C088386:homoserine lactone; D017963:Azithromycin; D008025:Ligases; C096955:RHLI protein, Pseudomonas aeruginosa; D015107:4-Butyrolactone