Abstract
SUMMARYResearch backgroundLegionella are Gram-negative bacteria that are ubiquitous in the natural environment. Contaminated water in man-made water systems is a potential source of transmission of legionnaires’ disease. The aim of this study is to explore the prevalence of Legionella pneumophila in the drinking water distribution system (DWDS) of Primorje-Gorski Kotar (PGK) County, Croatia, for the period 2013-2019, coupled with the incidence of legionnaires’ disease. A number of L. pneumophila-positive samples (>100 CFU/L), serogroup distribution and the degree of contamination of specific facilities (health and aged care, tourism, and sports) were assessed. Based on the obtained results, the reasoning for the implementation of a mandatory Legionella environmental surveillance program was assessed.Experimental approachSample testing for Legionella was carried out according to the standard method for enumeration of this bacterium. A heterotrophic plate count (HPC) and Pseudomonas aeruginosa number were analysed along with the basic physicochemical indicators of drinking water quality. The research period was divided into two parts, namely, the 2013-2018 period (before implementation of the prevention program, after the outbreak of legionnaires’ disease), and the year 2019 (proactive approach, no disease cases recorded).Results and conclusionDuring the 7-year observation period in PGK County, an increase in the number of samples tested for Legionella was found. An increase in Legionella-positive samples (particularly pronounced during the warmer part of the year) was recorded, along with a growing trend in the number of reported legionnaires’ disease cases. In addition to hot water systems, the risk of Legionella colonisation also applies to cold water systems. Health and aged care facilities appear to be at highest risk. In addition to the higher proportion of positive samples and a higher degree of microbiological load in these facilities, the highest proportion of L. pneumophila SGs 2-14 was identified. Due to the diagnostic limitations of the applied tests, the number of legionnaires’ disease cases is underdiagnosed.Novelty and scientific contributionThe introduction of a mandatory preventive approach to monitoring Legionella in DWDS water samples, along with the definition of national criteria for the interpretation of the results will create the preconditions for diagnosis and adequate treatment of larger numbers of legionnaires’ disease cases.
Highlights
Legionnaires’ disease emerged in 1976 in the city of Philadelphia, PA, USA, during a convention of 4400 U.S Army veterans; it affected 182 participants, and proved fatal for 34 people [1]
The aim of this study is to explore the prevalence of Legionella pneumophila in the drinking water distribution system (DWDS) of Primorje-Gorski Kotar (PGK) County, Croatia, for the period 2013–2019, coupled with the incidence of legionnaires’ disease
The number of samples tested for Legionella, the fraction of L. pneumophila-positive samples, and the number of recorded legionnaires’ disease cases are increasing
Summary
Legionnaires’ disease emerged in 1976 in the city of Philadelphia, PA, USA, during a convention of 4400 U.S Army veterans (legionnaires); it affected 182 participants, and proved fatal for 34 people [1]. McDade and his collaborators isolated the pathogen, a bacterium that was named after the legionnaires, namely Legionella. It belongs to the Legionellaceae family, and to date, at least 65 species and 70 serological groups L. pneumophila is the most pathogenic species; it causes more than 90 % of the infections worldwide [2]. Legionella can cause legionnaires’ disease (potentially fatal atypical pneumonia) or Pontiac fever (short-term flu-like febrile illness). According to the latest epidemiological report published by the European Centre for Disease Prevention and Control (ECDC), 8 % of legionellosis cases in European Union and European Economic Area (EU/EAA) countries ended fatally [5]
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