title: Pharmacodynamic Modeling of Bacillary Elimination Rates and Detection of Bacterial Lipid Bodies in Sputum to Predict and Understand Outcomes in Treatment of Pulmonary Tuberculosis.
abstract: BACKGROUND
  Antibiotic-tolerant bacterial persistence prevents treatment shortening in drug-susceptible tuberculosis, and accumulation of intracellular lipid bodies has been proposed to identify a persister phenotype of Mycobacterium tuberculosis cells. In Malawi, we modeled bacillary elimination rates (BERs) from sputum cultures and calculated the percentage of lipid body-positive acid-fast bacilli (%LB + AFB) on sputum smears. We assessed whether these putative measurements of persistence predict unfavorable outcomes (treatment failure/relapse).
  
  
  METHODS
  Adults with pulmonary tuberculosis received standard 6-month therapy. Sputum samples were collected during the first 8 weeks for serial sputum colony counting (SSCC) on agar and time-to positivity (TTP) measurement in mycobacterial growth indicator tubes. BERs were extracted from nonlinear and linear mixed-effects models, respectively, fitted to these datasets. The %LB + AFB counts were assessed by fluorescence microscopy. Patients were followed until 1 year posttreatment. Individual BERs and %LB + AFB counts were related to final outcomes.
  
  
  RESULTS
  One hundred and thirty-three patients (56% HIV coinfected) participated, and 15 unfavorable outcomes were reported. These were inversely associated with faster sterilization phase bacillary elimination from the SSCC model (odds ratio [OR], 0.39; 95% confidence interval [CI], .22-.70) and a faster BER from the TTP model (OR, 0.71; 95% CI, .55-.94). Higher %LB + AFB counts on day 21-28 were recorded in patients who suffered unfavorable final outcomes compared with those who achieved stable cure (P = .008).
  
  
  CONCLUSIONS
  Modeling BERs predicts final outcome, and high %LB + AFB counts 3-4 weeks into therapy may identify a persister bacterial phenotype. These methods deserve further evaluation as surrogate endpoints for clinical trials.
authors.affiliation: Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre Liverpool Heart and Chest Hospital Liverpool School of Tropical Medicine, United Kingdom Department of Microbiology Department of Medicine, College of Medicine, University of Malawi, Blantyre.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Sloan
authors.affiliation: Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre Department of Microbiology Department of Medicine, College of Medicine, University of Malawi, Blantyre.
authors.forename: Henry C
authors.initials: HC
authors.lastname: Mwandumba
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester.
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Garton
authors.affiliation: Department of Pharmacology, University of Liverpool.
authors.forename: Saye H
authors.initials: SH
authors.lastname: Khoo
authors.affiliation: Department of Microbiology London School of Hygiene and Tropical Medicine.
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Butterworth
authors.affiliation: Department of Medicine, College of Medicine, University of Malawi, Blantyre.
authors.forename: Theresa J
authors.initials: TJ
authors.lastname: Allain
authors.affiliation: Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre Department of Medicine, College of Medicine, University of Malawi, Blantyre.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Heyderman
authors.affiliation: Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre Department of Microbiology London School of Hygiene and Tropical Medicine.
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Corbett
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester.
authors.forename: Mike R
authors.initials: MR
authors.lastname: Barer
authors.affiliation: Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre Department of Medicine, College of Medicine, University of Malawi, Blantyre Institute of Infection and Global Health, University of Liverpool, United Kingdom.
authors.forename: Geraint R
authors.initials: GR
authors.lastname: Davies
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015169:Colony Count, Microbial; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D006801:Humans; D066292:Lipid Droplets; D008295:Malawi; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification* / Q000648:ultrastructure*; D011446:Prospective Studies; D013183:Sputum / Q000166:cytology* / Q000382:microbiology*; D016896:Treatment Outcome; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy*; D055815:Young Adult
keywords: clinical trials; lipid bodies; persistence; sterilizing activity; tuberculosis