title: Molecular analysis of Mycobacterium tuberculosis strains with an intact pks15/1 gene in a rural community of Mexico.
abstract: BACKGROUND
  Mycobacterium tuberculosis (MTB) is one of the leading causes of morbidity and mortality worldwide and infects approximately 1/3 of the human population, but only 10% of all infected individuals will ever develop the disease and half of these may result in a rapid progression to disease during the first 2 years after being infected. On the other hand, some phenotypic differences among mycobacterial strains contribute to variations in the outcome of the infection, e.g., the hypervirulent phenotype described in the Beijing family has been associated with the production of a phenolic glycolipid, which reduces the production of Th1 cytokines in the experimental model and requires the activity of a polyketide synthase enzyme encoded by the pks15/1 gene.
  
  
  METHODS
  We analyzed clinical isolates characterized by recent transmission and rapid progression to disease to identify factors that may influence such behavior from a rural and semi-urban community in eastern Mexico.
  
  
  RESULTS
  Using various typing tools, we were able to identify intrafamilial clusters which belonged to the East Asian lineage of MTB isolates (Beijing family) and another that belonged to the Indo-Oceanic lineage (Manila family). All isolates within these two clusters showed an intact pks15/1 gene sequence. Additionally, we identified three more family clusters that belonged to the Euro-American lineage and showed the typical 7-bp deletion of the pks15/1 gene. This 7-bp deletion was also found in the remaining 23 cases from non-family clusters.
  
  
  CONCLUSIONS
  This is the first report of cases caused by strains with an intact pks15/1 gene in Mexico. Interestingly, we identified the three main mycobacterial lineages described so far: East-Asian, Indo-Oceanic, and Euro-American in a human population with almost no present-day migration.
authors.affiliation: Laboratory of Clinical Microbiology, Salvador Zubiran National Institute for Medical Sciences and Nutrition, Mexico, D.F., Mexico.
authors.forename: Areli
authors.initials: A
authors.lastname: Martinez-Gamboa
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ponce-de-Leon
authors.forename: Arturo
authors.initials: A
authors.lastname: Galindo-Fraga
authors.forename: Miriam
authors.initials: M
authors.lastname: Bobadilla-del-Valle
authors.forename: Midori
authors.initials: M
authors.lastname: Kato-Maeda
authors.forename: Brian D
authors.initials: BD
authors.lastname: Robertson
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Young
authors.forename: Peter M
authors.initials: PM
authors.lastname: Small
authors.forename: José
authors.initials: J
authors.lastname: Sifuentes-Osornio
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001426:Bacterial Proteins / Q000145:classification / Q000235:genetics*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000235:genetics*; D010641:Phenotype; D011446:Prospective Studies; D012424:Rural Population; D014376:Tuberculosis / Q000453:epidemiology* / Q000382:microbiology* / Q000503:physiopathology; D055815:Young Adult
chemical_list: D001426:Bacterial Proteins