Association of shower use with Legionnaires' disease. Possible role of amoebae

Abstract

OUTBREAKS of legionnaires' disease (LD) have been linked to aerosols from evaporative condensers and cooling towers,^1,2whirlpool spas,³respiratory therapy equipment,⁴and humidifiers.⁵An association between shower use and LD has been hypothesized but not epidemiologically demonstrated.^6-11Prevention of LD is limited by a lack of understanding of the ecology of<i>Legionella pneumophila</i>. Monitoring aerosolproducing sites for<i>L pneumophila</i>can be misleading since the bacteria are found often in water sources without a known disease association.¹² Factors essential for<i>Legionella</i>multiplication in water are poorly understood, but the bacteria multiply extracellularly on supplemented culture media.^13,14Nutritional requirements of the genus are unlikely to be met in most water sources; however, these bacteria do multiply inside protozoa,^15-17which are common to aquatic environments.<i>Legionella pneumophila</i>grows in water samples with amoebae but not in those without viable amoebae.¹⁷Recognition of the association