[Evaluation of tuberculosis transmission routes in an outbreak among young adults for developing an effective method for contact investigations].
OBJECTIVE
To evaluate the various transmission routes of tuberculosis in an outbreak among young adults in order to develop an effective method for contact investigations.


METHODS
We reviewed the records of 21 tuberculosis patients involved in an outbreak of tuberculosis; the records were collected by conventional epidemiological studies. Mycobacterium tuberculosis isolates were genotyped using IS6110-based restriction fragment length polymorphism (RFLP).


RESULTS
The index patient was a 26-year-old man whose 32-year-old brother was identified as the source patient of tuberculosis through a contact investigation. Investigation of their contacts led to the identification of 10 tuberculosis patients. Further, 5 more patients with only casual contact with the index or source patients developed tuberculosis 18-25 months after identification of the index patient. The RFLP analysis of strains obtained from these 5 patients as well as the index and source patients revealed an identical pattern. Further, 4 persons, among those who had epidemiological links with some of the above-mentioned 5 patients, developed tuberculosis 22-34 months after identification of the index patient. All 21 patients were relatively young. In total, 15 strains obtained from these patients were sent for the RFLP analysis, all of which showed an identical pattern. The epidemiological links were categorized into a household environment, an entertainment area, a university, a music band, and a construction site.


CONCLUSIONS
Molecular epidemiology can provide insights into the process of tuberculosis transmission, which may otherwise go unrecognized by conventional contact investigations. Additionally, it can play an important role in identifying places of tuberculosis outbreaks and routes of transmission in a contact investigation.
Kochi City Public Health Center, 1-7-45, Marunouchi, Kochi-shi, Kochi 780-0850 Japan. kc-140200@city.kochi.lg.jp
Makoto
M
Toyota
D000293:Adolescent; D000328:Adult; D000368:Aged; D002675:Child, Preschool; D016358:Contact Tracing / Q000379:methods*; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D009169:Mycobacterium tuberculosis / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D014376:Tuberculosis / Q000382:microbiology / Q000635:transmission*; D055815:Young Adult