Molecular analysis of Mycobacterium tuberculosis strains with an intact pks15/1 gene in a rural community of Mexico.
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.
Martinez-Gamboa
Areli
A
Laboratory of Clinical Microbiology, Salvador Zubiran National Institute for Medical Sciences and Nutrition, Mexico, D.F., Mexico.
Ponce-de-Leon
Alfredo
A
Galindo-Fraga
Arturo
A
Bobadilla-del-Valle
Miriam
M
Kato-Maeda
Midori
M
Robertson
Brian D
BD
Young
Douglas B
DB
Small
Peter M
PM
Sifuentes-Osornio
José
J
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
D001426:Bacterial Proteins