Molecular typing of Legionella pneumophila from air-conditioning cooling waters using mip gene, SBT, and FAFLP methods

Whole-genome sequencing of the clinical isolate of Legionella pneumophila ALAW1 from the West Bank allows high-resolution typing and determination of pathogenicity mechanisms

Background

Legionella pneumophila is water-based bacterium causing Legionnaires' disease (LD). We describe the first documented case of nosocomial LD caused by L. pneumophila sequence type (ST) 461 and serogroup 6. The etiology of LD was confirmed by culturing the bronchoalveolar lavage sample retrieving L. pneumophila strain ALAW1. A 7-days treatment of the LD patient with Azithromycin and Levofloxacin allowed complete recovery.

Methods

In details, we sequenced the whole genome of the L. pneumophila ALAW1 using Illumina HiSeq platform. The sequence of ALAW1 was aligned with the genome sequence from the closely related reference strain Alcoy 2300/99 and a whole-genome phylogeny based on single nucleotide polymorphisms (SNPs) was created using Parsnp software. Also, the TYGS web-server was used in order to compare the genome with type strain.

Results

An analysis of the population structure by SNP and TYGS comparison clustered ALAW1 with the reference genome Alcoy 2300/99. Blastp analysis of the type IV secretion Dot/Icm system genes showed that these genes were highly conserved with (≤25%) structural differences at the protein level.

Conclusions

Overall, this study provides insights into detailed genome structure and demonstrated the value of whole-genome sequencing as the ultimate typing tool for Legionella.

Biofilm growth and control in cooling water industrial systems

Matrix-embedded, surface-attached microbial communities, known as biofilms, profusely colonise industrial cooling water systems, where the availability of nutrients and organic matter favours rapid microbial proliferation and their adhesion to surfaces in the evaporative fill material, heat exchangers, water reservoir and cooling water sections and pipelines. The extensive growth of biofilms can promote micro-biofouling and microbially induced corrosion (MIC) as well as pose health problems associated with the presence of pathogens like Legionella pneumophila. This review examines critically biofilm occurrence in cooling water systems and the main factors potentially affecting biofilm growth, biodiversity and structure. A broad evaluation of the most relevant biofilm monitoring and control strategies currently used or potentially useful in cooling water systems is also provided.