Restriction-fragment-length polymorphism (RFLP) analysis was used to study one outbreak of reinfection pulmonary tuberculosis at a day-laborers' facility equipped with a sauna. The results were interpreted in conjunction with clinical and epidemiologic data. The DNA prove was derived from the insertion sequence IS 6110.
A 63-year-old man who stayed at a day-laborers' facility for eight months was found to have advanced cavitary lung disease with sputum smears strongly positive for acid-fast bacilli. One year later a 46-year-old man staying at the same facility for 24 months was also found to have sputum-positive tuberculosis. The 46-year-old man had undergone treatment for tuberculosis 16 years previously and showed radiographic evidence of previous lung damage from tuberculosis. The second man had no tubercule bacilli in sputum when the 63-year-old man was found to have sputum-positive tuberculosis. The organisms isolated from these two men were both drug sensitive and had a similar RFLP pattern which suggests that 63-year-old man was the source of this outbreak and that pulmonary tuberculosis in the 46-year-old man was caused by exogenous reinfection. We conclude that exogenous reinfection may have been one pattern of tuberculosis transmission in this high-risk environment.