Cytotoxicity, Intracellular Replication, and Contact-Dependent Pore Formation of Genotyped Environmental Legionella pneumophila Isolates from HospitalWater Systems in the West Bank, Palestine
Date
2021-04-01
Authors
Zayed, Ashraf R.
Pecellin, Marina
Jaber, Lina
Butmeh, Suha
Bahader, Shereen A.
Steinert, Michael
Höfle, Manfred G.
Brettar, Ingrid
Bitar, Dina M.
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
Legionella pneumophila is the causative agent of Legionnaires’ disease. Due to the hot climate
and intermittent water supply, the West Bank, Palestine, can be considered a high-risk area for
this often fatal atypical pneumonia. L. pneumophila occurs in biofilms of natural and man-made
freshwater environments, where it infects and replicates intracellularly within protozoa. To correlate
the genetic diversity of the bacteria in the environment with their virulence properties for protozoan
and mammalian host cells, 60 genotyped isolates from hospital water systems in the West Bank were
analyzed. The L. pneumophila isolates were previously genotyped by high resolution Multi Locus
Variable Number of Tandem Repeat Analysis (MLVA-8(12)) and sorted according to their relationship
in clonal complexes (VACC). Strains of relevant genotypes and VACCs were compared according
to their capacity to infect Acanthamoeba castellanii and THP-1 macrophages, and to mediate poreforming
cytotoxicity in sheep red blood cells (sRBCs). Based on a previous detailed analysis of the
biogeographic distribution and abundance of the MLVA-8(12)-genotypes, the focus of the study was
on the most abundant L. pneumophila- genotypes Gt4(17), Gt6 (18) and Gt10(93) and the four relevant
clonal complexes [VACC1, VACC2, VACC5 and VACC11]. The highly abundant genotypes Gt4(17)
and Gt6(18) are affiliated with VACC1 and sequence type (ST)1 (comprising L. pneumophila str. Paris),
and displayed seroroup (Sg)1. Isolates of these two genotypes exhibited significantly higher virulence
potentials compared to other genotypes and clonal complexes in theWest Bank. Endemic for theWest
Bank was the clonal complex VACC11 (affiliated with ST461) represented by three relevant genotypes
that all displayed Sg6. These genotypes unique for the West Bank showed a lower infectivity and
cytotoxicity compared to all other clonal complexes and their affiliated genotypes. Interestingly, the
L. pneumophila serotypes ST1 and ST461 were previously identified by in situ-sequence based typing
(SBT) as main causative agents of Legionnaires’ disease (LD) in the West Bank at a comparable level.
Overall, this study demonstrates the site-specific regional diversity of L. pneumophila genotypes in
theWest Bank and suggests that a combination of MLVA, cellular infection assays and hierarchical
agglomerative cluster analysis allows an improved genotype-based risk assessment.
Description
Keywords
Legionella pneumophila , genotype , MLVA , clonal complex , Gt10(93 , VACC11 , virulence