Legionellosis is an environment-related, acute gram negative bacterial respiratory infection and is caused primarily by the species Legionella pneumophila, an atypical pulmonary pathogen, in the likes of mycoplasma and chlamydia species. Potentially all Legionella spp. may cause human disease, however, the majority (92%) of clinical cases are caused by L. pneumophila and the predominant serogroup is serogroup 1.