title: Rapid, serial, non-invasive assessment of drug efficacy in mice with autoluminescent Mycobacterium ulcerans infection.
abstract: BACKGROUND
  Buruli ulcer (BU) caused by Mycobacterium ulcerans is the world's third most common mycobacterial infection. There is no vaccine against BU and surgery is needed for patients with large ulcers. Although recent experience indicates combination chemotherapy with streptomycin and rifampin improves cure rates, the utility of this regimen is limited by the 2-month duration of therapy, potential toxicity and required parenteral administration of streptomycin, and drug-drug interactions caused by rifampin. Discovery and development of drugs for BU is greatly hampered by the slow growth rate of M. ulcerans, requiring up to 3 months of incubation on solid media to produce colonies. Surrogate markers for evaluating antimicrobial activity in real-time which can be measured serially and non-invasively in infected footpads of live mice would accelerate pre-clinical evaluation of new drugs to treat BU. Previously, we developed bioluminescent M. ulcerans strains, demonstrating proof of concept for measuring luminescence as a surrogate marker for viable M. ulcerans in vitro and in vivo. However, the requirement of exogenous substrate limited the utility of such strains, especially for in vivo experiments.
  
  
  RESULTS
  For this study, we engineered M. ulcerans strains that express the entire luxCDABE operon and therefore are autoluminescent due to endogenous substrate production. The selected reporter strain displayed a growth rate and virulence similar to the wild-type parent strain and enabled rapid, real-time monitoring of in vitro and in vivo drug activity, including serial, non-invasive assessments in live mice, producing results which correlated closely with colony-forming unit (CFU) counts for a panel of drugs with various mechanisms of action.
  
  
  CONCLUSIONS
  Our results indicate that autoluminescent reporter strains of M. ulcerans are exceptional tools for pre-clinical evaluation of new drugs to treat BU due to their potential to drastically reduce the time, effort, animals, compound, and costs required to evaluate drug activity.
authors.affiliation: Center for Tuberculosis Research, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America ; State Key Laboratory of Respiratory Diseases, Center for Infection and Immunity, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangdong, the People's Republic of China.
authors.forename: Tianyu
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Center for Tuberculosis Research, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Si-Yang
authors.initials: SY
authors.lastname: Li
authors.affiliation: Center for Tuberculosis Research, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Converse
authors.affiliation: Center for Tuberculosis Research, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Jacques H
authors.initials: JH
authors.lastname: Grosset
authors.affiliation: Center for Tuberculosis Research, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America ; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Nuermberger
mesh_terms: D000818:Animals; D054312:Buruli Ulcer / Q000188:drug therapy* / Q000382:microbiology*; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D005260:Female; D035002:Lower Extremity / Q000382:microbiology; D008163:Luminescent Measurements; D051379:Mice; D008807:Mice, Inbred BALB C; D019911:Mycobacterium ulcerans / Q000187:drug effects* / Q000235:genetics; D013194:Staining and Labeling / Q000379:methods; D013997:Time Factors