Legionella Species Isolated in the Water Systems of Ships and Their Molecular Characterization

Legionella species are generally found in nature and in water resources, and they are gram negative bacilli that can cause pneumonia by being transmitted from water systems to humans via aerosol or aspiration. Legionnaires' disease caused by this agent continues to be a public health problem in cruise ships. In this study, it was aimed to determine the prevalence of the colonization of Legionella species by culture method and to determine the molecular characterization of the isolated Legionella in water samples taken from the water systems of the ships docking in Mersin International Port. A total of 158 cold water samples were taken from 18 ferry and/or cargo ships docking in Mersin International Port between December 2014 and June 2015. Fifty-four of the samples were obtained from tanks, 68 from taps and 36 from shower heads. All samples were centrifuged and inoculated from the pellet onto "Buffered Coal Yeast Extract" (BCYE) (Oxoid, CM0655, UK) agar medium supplemented with iron pyrophosphate, L-cysteine and alpha-ketoglutarate (Oxoid, SR0110, UK). The culture plates were incubated for 10-15 days in microaerophilic environment in a desiccator at 37 degrees C. The suspicious colonies grown in cultures were serogrouped by latex agglutination test (Oxoid, DR0800M, UK) and fluorescent antibody method (m-Tech Monoclonal Technologies, Inc., USA). For the molecular analysis of Legionella species grown in culture, DNA isolation was made from Legionella colonies and then polymerase chain reaction amplification was performed using specific primer sequences targeting the rpoB gene region of the Legionella genome. Direct DNA sequencing of rpoB gene products was performed in the "ABI PRISM 3130XL Genetic Analyzer" (Applied Biosystems, USA). The DNA sequences were typed by BLAST analysis and the determined types, and NCBI (National Center for Biotechnology Information) reference Legionella sequences were phylogenetically compared with the Neighbor-joining comparison method by using the Mega 7 program. Legionella spp. was isolated in 18 (11.4%) of 158 samples. Of these, four (7.4%, 4/54) were detected from the tank, 11 (16.2%, 11/68) from the tap and three (8.33%, 3/36) from the shower head. After the latex agglutination test performed from the growing bacterial colonies, five (27.8%) were serogrouped as Legionella spp., four (22.2%) as Legionella pneumophila sg 5, two (11.1%, each) as L.pneumophila sg 1,L.pneumophila sg 8 and Legionella bozemanii and one (5.6%) as L.pneumophila sg 3. Two (11.1%) of the isolates grown in culture could not be serogrouped. Molecular characterization of 12 Legionella isolates could be performed. One of them was serologically serogrouped as L.bozemanii, and it was found to be 99% similar to Legionella rubrilucens when compared with NCBI Legionella sequence data in the BLAST program. One isolate that could not be differentiated by serogrouping was identified as Legionella erytra in the BLAST program after DNA sequence analysis. The remaining 10 isolates (55.6%, n= 18) were confirmed as L.pneumophilia after the comparison with reference NCBI sequences. In this study, it was determined that 11.4% of the water samples collected from the water systems of the ships docking in Mersin International Port were contaminated with Legio nell a species. The detected Legio nell a species have an important potential source of infection for the captain, ship workers and passengers travelling on the ships. In this respect, this study reveals the necessity of establishing studies to improve the risk management of Legionella in the water systems of ships.