Investigation of Legionella pneumophila seropositivity in the professional long distance drivers as a risky occupation

Abstract

Contaminated water sources, reservoirs and systems such as evaporative condensers of air-conditioners are known to be the main transmission routes of Legionella spp. which are ubiquitous aquatic bacteria. By virtue of this point the aim of this study was to investigate the rate of Legionella pneumophila seropositivity in a profession considered as risky due to the direct and prolonged exposure to air-conditioning and air-circulating systems. For this purpose, in the period of February-August 2004 a total of 79 male subjects (63 were bus drivers and 16 were driver assistants) who were continously travelling to two different route (South part as hot climate and Middle/North parts as cold climate of Turkey) from Denizli province coach station (a province located in internal Aegian where accepted as crossroads), were included to the study. The mean age and mean working duration of bus drivers were 43.0±1.1 years and 20.0±1.1 years, respectively, while these values were 22.5±0.9 years and 4.0±0.6 years, respectively, for the drivers' assistants. The serum samples collected from the subjects were screened by a commercial indirect immunofluorescence method (Euroimmun, Germany) using L.pneumophila serogrup 1-14 antigens for the presence of specific antibodies. Additionally, air-conditioners' moisture exhaust samples of the busses in which seropositive subjects travelling with have been examined by culture and 5S rRNA gene targeted polymerase chain reaction (PCR) methods, for the presence of Legionella spp. The overall L.pneumophila seropositivity rate was detected as 15.2% (12/79). This rate was 19% (12 /63) for bus drivers while all of the drivers' assistants were found seronegative. The seropositivity rate was found statistically higher in the personnel who were travelling to the hot climates (10/36, 27.8%) than those who travel to cold climates (2/43, 4.6%), (p<0.05). The culture and PCR yielded negative results for Legionella spp. in the exhaust samples collected from the air-conditioners of the busses in which seropositive drivers travel. Our data indicated that long distance bus drivers were chronically exposed to this pathogen and this may be considered as an occupational risk factor for legionellosis especially for drivers who travel to the west and south parts of our country (mean temperature in August 2004: 30-35°C), since the bus air-conditioning and air-circulating systems are active during the travel. Further studies on air spreading of Legionella in intercity busses can reveal how the exposure occurs for bus drivers.