title: Exogenous reinfection as a cause of recurrent tuberculosis after curative treatment.
abstract: BACKGROUND
  For decades it has been assumed that postprimary tuberculosis is usually caused by reactivation of endogenous infection rather than by a new, exogenous infection.
  
  
  METHODS
  We performed DNA fingerprinting with restriction-fragment-length polymorphism analysis on pairs of isolates of Mycobacterium tuberculosis from 16 compliant patients who had a relapse of pulmonary tuberculosis after curative treatment of postprimary tuberculosis. The patients lived in areas of South Africa where tuberculosis is endemic. Medical records were reviewed for clinical data.
  
  
  RESULTS
  For 12 of the 16 patients, the restriction-fragment-length polymorphism banding patterns for the isolates obtained after the relapse were different from those for the isolates from the initial tuberculous disease. This finding indicates that reinfection was the cause of the recurrence of tuberculosis after curative treatment. Two patients had reinfections with a multidrug-resistant strain. All 15 patients who were tested for the human immunodeficiency virus were seronegative.
  
  
  CONCLUSIONS
  Exogenous reinfection appears to be a major cause of postprimary tuberculosis after a previous cure in an area with a high incidence of this disease. This finding emphasizes the importance of achieving cures and of preventing anyone with infectious tuberculosis from exposing others to the disease.
authors.affiliation: Department of Pediatrics and Child Health, University of Stellenbosch, Tygerberg, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: van Rie
authors.forename: R
authors.initials: R
authors.lastname: Warren
authors.forename: M
authors.initials: M
authors.lastname: Richardson
authors.forename: T C
authors.initials: TC
authors.lastname: Victor
authors.forename: R P
authors.initials: RP
authors.lastname: Gie
authors.forename: D A
authors.initials: DA
authors.lastname: Enarson
authors.forename: N
authors.initials: N
authors.lastname: Beyers
authors.forename: P D
authors.initials: PD
authors.lastname: van Helden
mesh_terms: D000328:Adult; D015373:Bacterial Typing Techniques; D016172:DNA Fingerprinting; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D010349:Patient Compliance; D012150:Polymorphism, Restriction Fragment Length; D012008:Recurrence; D018088:Tuberculosis, Multidrug-Resistant / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy / Q000382:microbiology* / Q000635:transmission