Document Type : Original Article
DEPARTMENT OF MICROBIOLOGY, BAGHYATOLLAH MEDICAL SCIENCES UNIVERSITY, TEHRAN, IRAN
Introduction: The suspected water samples contaminated with Legionella were enriched with Acanthamoebae. Small numbers of bacteria (not detectable by culture) can be multiplied in Amoebae up to culturable level in co-culture condition. The conventional culture method for legionnaires' disease bacterium always suffers from low sensitivity. This co-culture method can significantly improve culture sensitivity.
Materials and Methods: Legionella spp. generally benefits from interacting with free living amoebae in an aquatic environment. Acanthamoebae (the natural host of the legionella) was used for enrichment of preliminary culture-negative samples. The enriched samples were then cultured again on a supplemented selective media, then were confirmed with the agglutination test, direct immunofluorescence and restriction fragment length polymorphism.
Results: L. Pneumophila were isolated from 15% of the samples and confirmed by biochemical tests as well as legionella latex agglutination test and then grouped by direct fluorescent antibody and restriction fragment length ploymorphism.
Conclusion: In fact, this method have enhanced the bacterial multiplication (in original sample prior to culturing). We assume that all negative samples encountered in legionella laboratories should be submitted for additional culture after preliminary enrichment with Acanthamoebae castellanii.