Presentation Type: Poster
Abstract: Background and Aim : Legionella are gram-negative bacteria which found in both natural aquatic and manmade water systems. Some of Legionella species are important causes of severe pneumonia (Legionnaires‘disease ). The prevalence of Legionnaires‘diseases due to Legionella pneumophila is high (approximately 90% ). Although Legionella are known as fastidious bacteria, but isolation of them from respiratory secretions by culture is considered as a gold standard for diagnosis of legionellosis. The aim of this study was isolation of Legionella in clinical specimens of patients with respiratory symptoms refering to Ahvaz teaching hospitals.
Methods : In this study a total of 100 respiratory specimens ( 94 sputum and 6 pleural fluid specimens ) were collected from the patients with respiratory symptoms and examined. The sputum specimens were decontaminated by heat treatment (56°C for 30 min) but the pleural fluid specimens were concentrated by centrifugation without heat treatment. These samples were inoculated to the culture media such as Buffered Charcoal Yeast Extract ( BCYE ) Agar and Modify Wodowsky and Yee ( MWY ) Agar.The plates were incubated for up to 2 weeks at 37°C and about 90% humidity in 3-5% CO2. The grown colonies were examined by Gram staining, catalase and oxidase tests and also in oculation to blood agar and Eosin Methylene Blue ( EMB ) Agar. The colonies which grew on MWY agar but not on blood agar and EMB agar were identified as possible Legionella spp.
Results : In our study, out of 100 examined clinical specimens from the patients with respiratory symptoms, 1% were positive for Legionella spp. by culture on BCYE and MWY agar media.
Conclusion : The low number isolates in our study, might be related to low sensitivity of culture method for isolation of these bacteria and also usage of antibiotics by the patients. Although, some of the reports have been generally shown that isolation Legionella from clinical specimens such as sputum is difficult. So, molecular methods such as PCR, beside the culture method is recommended for detection of these bacteria.