A preliminary assessment of the occupational risk of acquiring Legionnaires' disease for people working in telephone manholes, a new workplace environment for Legionella growth

BackgroundTelephone manholes (TMs) are underground wells, used in Italy by the telecommunication companies to locate telephone networks. Following a fatal case of Legionnaires' disease (LD), acquired during working activity in a TM, we investigated whether Legionella was present in TMs and could be a risk for manhole workers (MWs).MethodsThree hundred fifty-three environmental samples were collected from 100 TMs, and serum antibody titer against Legionella pneumophila and Legionella species non-pneumophila was determined from both MWs and control non-manhole workers.ResultsL pneumophila and Legionella species non-pneumophila were detected in 28% of water samples, in 8% of the biofilm, and in 6% of sediment matrices taken in TMs, in a concentration range of 102 to 104 colony-forming units/L. No Legionella was found in TM air samples. Although there was a statistically significant difference (P = .027) in antibody titer to L pneumophila serogroup 1 (Lp1) between MWs and non-manhole workers, a multivariate logistic regression analysis showed a significant association between antibody against Lp1 and both age group and the practice of aquatic sports.ConclusionAlthough further investigations will be performed to quantify the risk of acquiring legionellosis, this preliminary study demonstrates for the first time the presence of Legionella, including human pathogenic species, in a working environment such as TM.