Use of a clinical Escherichia coli isolate expressing lux genes to study the antimicrobial pharmacodynamics of moxifloxacin

Salisbury, Vyv; Pfoestl, Andreas; Wiesinger-Mayr, Herbert; Lewis, Roger J.; Bowker, Karen E.; MacGowan, Alasdair

doi:10.1093/jac/43.6.829

Cited by 30 publications

(28 citation statements)

References 8 publications

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“…As the production of bioluminescence from recombinant bacteria containing the lux genes depends on biochemically active bacterial cells, it can be assumed that any compound that impairs the biochemistry and thus compromises cellular viability leads to a rapid reduction in luminescence. The effects of antimicrobial compounds on lux-containing recombinant bacteria can therefore be readily assessed (36,37,39,41,46). Figure 1C shows that the growth-dependent bioluminescence of S. aureus RN6390(pSB2030) was completely inhibited by 10 M 3-oxo-C 12 -HSL.…”

Section: Resultsmentioning

confidence: 99%

N -Acylhomoserine Lactones Antagonize Virulence Gene Expression and Quorum Sensing in Staphylococcus aureus

et al. 2006

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Many gram-negative bacteria employ N-acylhomoserine lactone (AHL)-mediated quorum sensing to control virulence. To determine whether gram-positive bacteria such as Staphylococcus aureus respond to AHLs, we used a growth-dependent lux reporter fusion. Exposure of S. aureus to different AHLs revealed that 3-oxosubstituted AHLs with C 10 to C 14 acyl chains inhibited light output and growth in a concentration-dependent manner, while short-chain AHLs had no effect. N-(3-Oxododecanoyl)-L-homoserine lactone (3-oxo-C 12 -HSL) inhibited the production of exotoxins and cell wall fibronectin-binding proteins but enhanced protein A expression. Since these processes are reciprocally regulated via the S. aureus agr quorum-sensing system, which in turn, is regulated via sar, we examined the effect of AHLs on sarA and agr. At sub-growth-inhibitory concentrations of 3-oxo-C 12 -HSL, both sarA expression and agr expression were inhibited, indicating that the action of 3-oxo-C 12 -HSL is mediated at least in part through antagonism of quorum sensing in S. aureus. Spent culture supernatants from Pseudomonas aeruginosa, which produces both 3-oxo-C 12 -HSL and N-butanoylhomoserine lactone (C 4 -HSL), also inhibited agr expression, although C 4 -HSL itself was inactive in this assay. Since quorum sensing in S. aureus depends on the activities of membrane-associated proteins, such as AgrB, AgrC, and AgrD, we investigated whether AHLs perturbed S. aureus membrane functionality by determining their influence on the membrane dipole potential. From the binding curves obtained, a dissociation constant of 7 M was obtained for 3-oxo-C 12 -HSL, indicating the presence of a specific saturable receptor, whereas no binding was observed for C 4 -HSL. These data demonstrate that long-chain 3-oxo-substituted AHLs, such as 3-oxo-C 12 -HSL, are capable of interacting with the S. aureus cytoplasmic membrane in a saturable, specific manner and at sub-growth-inhibitory concentrations, down-regulating exotoxin production and both sarA and agr expression.

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Section: Resultsmentioning

confidence: 99%

N -Acylhomoserine Lactones Antagonize Virulence Gene Expression and Quorum Sensing in Staphylococcus aureus

et al. 2006

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“…By this methodology we have demonstrated that not only antibacterial properties but also the course and the relapse of the infection can be monitored optically in vivo in real time in living animals. In addition, the approach resulted in a considerable savings in Bioluminescent bacteria have previously been used successfully for the measurement of antibacterial activity in vitro (14,22,33,36,38,40,41) and for the measurement of activity against acute in vivo infections (5,6,10,11,16,34). The model presented here permits for the first time longitudinal monitoring of chronic biofilm infections and the response to therapy.…”

Section: Discussionmentioning

confidence: 99%

Rapid Direct Method for Monitoring Antibiotics in a Mouse Model of Bacterial Biofilm Infection

Kadurugamuwa¹,

Sin²,

Yu³

et al. 2003

Antimicrob Agents Chemother

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We have developed a rapid, continuous method for monitoring the effectiveness of several antibacterial agents in real time, noninvasively, by using a recently described mouse model of chronic biofilm infection (J. L. Kadurugamuwa et al., Infect. Immun. 71:882-890, 2003), which relies on biophotonic imaging of bioluminescent bacteria. To facilitate real-time monitoring of infection, we used a Staphylococcus aureus isolate that was made bioluminescent by inserting a modified lux operon into the bacterial chromosome. This bioluminescent reporter bacterium was used to study the antimicrobial effects of several antibiotics belonging to different molecular families. Treatment with rifampin, tobramycin, and ciprofloxacin was started 7 days after subcutaneous implantation of catheters precolonized with 10 4 CFU of S. aureus. Three different doses of antibiotics were administered twice a day for 4 consecutive days. The number of metabolically active bacteria in untreated mice and the tobramycin-and ciprofloxacin-treated groups remained relatively unchanged over the 4-week observation period, indicating poor efficacies for tobramycin and ciprofloxacin. A rapid dose-dependent decline in metabolic activity in rifampin-treated groups was observed, with almost a 90% reduction after two doses and nearly undetectable levels after three doses. The disappearance of light emission correlated with colony counts. After the final treatment, cell numbers rebounded as a function of concentration in a time-dependent manner. The staphylococci isolated from the catheters of mice treated with rifampin were uniformly resistant to rifampin but retained their in vitro susceptibilities to tobramycin and ciprofloxacin. Since the metabolic activities of viable cells and a postantibiotic effect could be detected directly on the support matrix nondestructively and noninvasively, the methodology is specifically appealing for investigating the effects of antibiotics on biofilms in vivo. Moreover, our study points to the possible use of biophotonic imaging for the detection of the development of resistance to therapeutic agents during treatment of chronic infections in vivo.

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“…Measurements of optical density are often used to assess antibiotic efficacy and pharmacokinetics prior to testing in mouse models. Bacteria expressing bioluminescent [9,10], or fluorescent [11,12] genetic reporters have been incorporated in these basic in vitro systems as a way of enhancing the sensitivity of the toxicity assays. More sophisticated in vitro models of infection employ a mixed culture of mammalian and bacteria cells.…”

Section: Imaging In Vitro Models Of Bacterial Infectionmentioning

confidence: 99%

Optical imaging of bacterial infection models

Leevy¹,

Serazin²,

Smith³

2007

Drug Discovery Today: Disease Models

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Over the last thirteen years, the field of optical imaging has expanded from in vitro fluorescence microscopy of cells to in vivo imaging of living animals. Recent advances in optical imaging of bacterial infection have been propelled by the invention of genetic methods that produce fluorescent and bioluminescent bacteria, and also the discovery of synthetic fluorescent probes that selectively target bacterial cell surfaces. Optical imaging is an effective method of conducting longitudinal studies of bacterial infection in small animals such as nude mice. It can be used to address questions in medical microbiology concerning migration and colonization and it is an attractive method for determining the efficacy of antibiotic therapies.

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Use of a clinical Escherichia coli isolate expressing lux genes to study the antimicrobial pharmacodynamics of moxifloxacin

Cited by 30 publications

References 8 publications

N -Acylhomoserine Lactones Antagonize Virulence Gene Expression and Quorum Sensing in Staphylococcus aureus

N -Acylhomoserine Lactones Antagonize Virulence Gene Expression and Quorum Sensing in Staphylococcus aureus

Rapid Direct Method for Monitoring Antibiotics in a Mouse Model of Bacterial Biofilm Infection

Optical imaging of bacterial infection models

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