title: Rapid impact of effective treatment on transmission of multidrug-resistant tuberculosis.
abstract: BACKGROUND
  Effective treatment for drug-susceptible tuberculosis (TB) rapidly renders patients non-infectious, long before conversion of sputum acid-fast smear or culture to negative. Multidrug-resistant TB (MDR-TB) patients on treatment are currently assumed to remain infectious for months. While the resources required for prolonged hospitalization are a barrier to the scale-up of MDR-TB treatment, the safety of community treatment is clear.
  
  
  OBJECTIVE
  To estimate the impact of treatment on infectiousness among MDR-TB patients.
  
  
  METHODS
  A series of five human-to-guinea pig TB transmission studies was conducted to test various interventions for infection control. Guinea pigs in adjacent chambers were exposed to exhaust air from a hospital ward occupied by mostly sputum smear- and culture-positive MDR-TB patients. The guinea pigs then underwent tuberculin skin testing for infection. Only the control groups of guinea pigs from each study (no interventions used) provide the data for this analysis. The number of guinea pigs infected in each study is reported and correlated with Mycobacterium tuberculosis drug susceptibility relative to treatment.
  
  
  RESULTS
  Despite exposure to presumably infectious MDR-TB patients, infection percentages among guinea pigs ranged from 1% to 77% in the five experiments conducted. In one experiment in which guinea pigs were exposed to 27 MDR-TB patients newly started on effective treatment for 3 months, there was minimal transmission. In four other experiments with greater transmission, guinea pigs had been exposed to patients with unsuspected extensively drug-resistant tuberculosis who were not on effective treatment.
  
  
  CONCLUSIONS
  In this model, effective treatment appears to render MDR-TB patients rapidly non-infectious. Further prospective studies on this subject are needed.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Dharmadhikari
authors.affiliation: South African Medical Research Council, Pretoria, South Africa.
authors.forename: M
authors.initials: M
authors.lastname: Mphahlele
authors.affiliation: South African Medical Research Council, Pretoria, South Africa.
authors.forename: K
authors.initials: K
authors.lastname: Venter
authors.affiliation: University of Pretoria, Pretoria, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Stoltz
authors.affiliation: South African Medical Research Council, Pretoria, South Africa.
authors.forename: R
authors.initials: R
authors.lastname: Mathebula
authors.affiliation: South African Medical Research Council, Pretoria, South Africa.
authors.forename: T
authors.initials: T
authors.lastname: Masotla
authors.affiliation: South African Medical Research Council, Pretoria, South Africa.
authors.forename: M
authors.initials: M
authors.lastname: van der Walt
authors.affiliation: Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: M
authors.initials: M
authors.lastname: Pagano
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: P
authors.initials: P
authors.lastname: Jensen
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: E
authors.initials: E
authors.lastname: Nardell
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000391:Air Microbiology; D000818:Animals; D000995:Antitubercular Agents / Q000627:therapeutic use*; D003428:Cross Infection / Q000175:diagnosis / Q000382:microbiology / Q000517:prevention & control* / Q000635:transmission*; D054908:Extensively Drug-Resistant Tuberculosis / Q000188:drug therapy / Q000382:microbiology / Q000635:transmission; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D017053:Infection Control / Q000379:methods*; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000302:isolation & purification; D012189:Retrospective Studies; D013183:Sputum / Q000382:microbiology; D013997:Time Factors; D016896:Treatment Outcome; D014374:Tuberculin Test; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis / Q000188:drug therapy* / Q000382:microbiology / Q000635:transmission*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000188:drug therapy* / Q000382:microbiology / Q000635:transmission; D055815:Young Adult
chemical_list: D000995:Antitubercular Agents