A Tale of Four Danish Cities: Legionella pneumophila Diversity in Domestic Hot Water and Spatial Variations in Disease Incidence

Søren A. Uldum, Lars G. Schjoldager, Sharmin Baig and Kelsie Cassell
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Søren A. Uldum: Department of Bacteria, Parasites and Fungi, Statens Serum Institut, 2300 Copenhagen S, Denmark
Lars G. Schjoldager: CheckPoint World, 8800 Viborg, Denmark
Sharmin Baig: Department of Bacteria, Parasites and Fungi, Statens Serum Institut, 2300 Copenhagen S, Denmark
Kelsie Cassell: Epidemiology of Microbial Diseases, Yale University School of Public Health, New Haven, CT 06510, USA

IJERPH, 2022, vol. 19, issue 5, 1-18

Abstract: Denmark has one of the highest Legionnaires’ disease notification rates within Europe, averaging 4.7 cases per 100,000 population annually (2017 to 2020). The relatively high incidence of disease is not uniform across the country, and approximately 70% of all domestically acquired cases in Denmark are caused by Legionella pneumophila (LP) strains that are considered less virulent. The aim of this study was to investigate if colonization rates, levels of colonization, and/or types of LP present in hot water systems were associated with geographic differences in Legionnaires’ disease incidence. Domestic water systems from four cities in Denmark were analyzed via culture and qPCR. Serogrouping and sequence typing was performed on randomly selected isolates. Single nucleotide polymorphism was used to identify clonal relationship among isolates from the four cities. The results revealed a high LP colonization rate from 68% to 87.5% among systems, composed primarily of non-serogroup 1. LP serogroup 1 reacting with the monoclonal antibody (MAb) 3/1 was not identified in any of the systems tested, while MAb 3/1 negative serogroup 1 strains were isolated from 10 systems (9.6%). We hypothesize that a combination of factors influences the incidence rate of LD in each city, including sequence type and serogroup distribution, colonization rate, concentration of Legionella in Pre-flush and Flush samples, and potentially building characteristics such as water temperature measured at the point of use.

Keywords: domestic hot water; Legionella pneumophila; Legionella colonization; Legionnaires’ disease; serogroup; sequence-type; whole genome sequencing; phylogenetic relatedness (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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