Detection of legionella bacteria in sewage by polymerase chain reaction and standard culture method

Abstract

Legionella bacteria are ubiquitous in environmental waters. Only a few species of Legionella , especially, L. pneumophila are pathogenic to humans and cause a sometimes fatal Legionnaires disease as well as a less fatal disease called Pontiac fever. The presence of Legionella in sewage and aerosolized sewage is the subject of this investigation because reuse of sewage may involve the exposure of people to aerosolization, the mode of transmission of Legionella bacteria. The objective of this study was to determine the prevalence of Legionella species and L. pneumophila in wastewater and their fate after various stages of treatment. The polymerase chain reaction (PCR) and standard culture method were utilized to detect Legionella species and L. pneumophila. PCR results indicated that Legionella species were present at levels > 10³ cells / ml during all phases of sewage treatment including chlorinated effluents. Culture results indicated levels at least one log lower than seen with PCR. Legionella species were also recovered from air samples collected from secondary aeration basins at levels < 10³ cells/ml. PCR was shown to be the most rapid and sensitive method for detecting Legionella in sewage.