title: Exogenous reinfection of tuberculosis in a low-burden area.
abstract: OBJECTIVE
  Recurrence of tuberculosis (TB) can be the consequence of relapse or exogenous reinfection. The study aimed to assess the factors associated with exogenous TB reinfection.
  
  
  METHODS
  Prospective cohort study based on the TB database, maintained at the Division of Infectious Diseases, Luigi Sacco Hospital (Milan, Italy). Time period: 1995-2010.
  
  
  METHODS
  (1) ≥2 episodes of culture-confirmed TB; (2) cure of the first episode of TB; (3) availability of one Mycobacterium tuberculosis isolate for each episode. Genotyping of the M. tuberculosis strains to differentiate relapse and exogenous reinfection. Logistic regression analysis was used to assess the influence of risk factors on exogenous reinfections.
  
  
  RESULTS
  Of the 4682 patients with TB, 83 were included. Of these, exogenous reinfection was diagnosed in 19 (23 %). It was independently associated with absence of multidrug resistance at the first episode [0, 10 (0.01-0.95), p = 0.045] and with prolonged interval between the first TB episode and its recurrence [7.38 (1.92-28.32) p = 0.004]. However, TB relapses occurred until 4 years after the first episode. The risk associated with being foreign born, extrapulmonary site of TB, and HIV infection was not statistically significant. In the relapse and re-infection cohort, one-third of the patients showed a worsened drug resistance profile during the recurrent TB episode.
  
  
  CONCLUSIONS
  Exogenous TB reinfections have been documented in low endemic areas, such as Italy. A causal association with HIV infection could not be confirmed. Relapses and exogenous reinfections shared an augmented risk of multidrug resistance development, frequently requiring the use of second-line anti-TB regimens.
authors.affiliation: Department of Infectious Diseases, H. Sacco, Milan, Italy. schiroli.consuelo@gmail.com.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Schiroli
authors.affiliation: Department of Infectious Diseases, H. Sacco, Milan, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Carugati
authors.affiliation: Department of Infectious Diseases, H. Sacco, Milan, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Zanini
authors.affiliation: A. O. San Gerardo, Monza, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bandera
authors.affiliation: Department of Infectious Diseases, H. Sacco, Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Di Nardo Stuppino
authors.affiliation: Department of Infectious Diseases, H. Sacco, Milan, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Monge
authors.affiliation: Department of Infectious Diseases, H. Sacco, Milan, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Morosi
authors.affiliation: A. O. San Gerardo, Monza, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gori
authors.affiliation: A. O. Spedali Civili, Brescia, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Matteelli
authors.affiliation: Centre of Tuberculosis Control of Lombardy, Villa Marelli, Milan, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Codecasa
authors.affiliation: Department of Infectious Diseases, H. Sacco, Milan, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Franzetti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000995:Antitubercular Agents / Q000494:pharmacology; D018562:Disease Transmission, Infectious; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D011446:Prospective Studies; D012008:Recurrence; D014376:Tuberculosis / Q000453:epidemiology*; D055815:Young Adult
chemical_list: D000995:Antitubercular Agents
keywords: Exogenous reinfection; Fingerprinting; Relapse; Tuberculosis