Ten-Year Retrospective Analysis of Legionella Diffusion in Hospital Water Systems and Its Serogroup Seasonal Variation

The Detection Limits of Legionella According to the EU Directive 2020/2184. Could That Be Too Permissive?

INTRODUCTION

The problem of detecting legionella after a case of legionellosis from the source of environmental contamination has been known since a long time ago. Legionella is a bacterium present in various natural and artificial habitats and especially in surface fresh waters. It is found in greater concentration in warm waters, at temperatures between 20 °C and 42 °C. The greatest risk factor for humans is represented by the presence of Legionella in water distribution systems in hospitals, medical equipment (e.g. respirators, dialyzers, inhalers, humidifiers, water, massage equipment used in balneotherapy) and turbines used in dental practices, especially for hospitalized individuals. In the EU directive 2020/2184, issued by the European parliament on 16/12/2020, the concentration of Legionella was added to the parameters to be determined in assessing the quality of drinking water intended for human consumption. The objectives were to improve the quality standard of drinking water, reduce the consumption of bottled water and consequently reduce plastic waste. The WHO notes that Legionella causes the greatest burden from a health point of view and it is included among the parameters that require careful monitoring with a limit of less than 1000 CFU/L. The aim of this report was to evaluate the new EU directive 2020/2184 on the light of our laboratory experience.

MATERIALS AND METHODS

A total of 459 samples were processed at our Hygiene of food Laboratory - Department of Medical Sciences and Public Health. All statistical analyses were conducted using the SPSS statistical package (version 23 for Windows. SPSS, Inc. Chicago, Ill).

RESULTS AND DISCUSSION

Of the 67 structures examined where the cases occurred, 35 showed samples with at least one over-threshold value considering the reference value of 100 CFU/L, whereas using the new limit of 1000 CFU/L, only 25 structures resulted as having at least one sample above the threshold. In our experience as a regional reference laboratory for Legionella research, the increase from 100 CFU/L to 1,000 CFU/L could lead to a lower alert level. In fact, in the period between October 2017 and October 2021, the median value of CFU/L in presence of a case was 0 (0-100). Despite the large amount of studies on Legionella only a few relate the withdrawals and the consequent CFU/L with the confirmed cases of legionellosis, as in our analysis. The 75° percentile values of the Legionella concentration equal to 100 CFU/L in all samples associated with cases and clusters leads us to hypothesize that the limit equal to 1000 CFU/L that will be introduced for environmental monitoring as per recent European regulations may not be sufficiently protective for minimizing risk in the population, especially in healthcare facilities where fragile patients are assisted.

Legionella spp. Monitoring in the Water Supply Systems of Accommodation Facilities in Sardinia, Italy: A Two-Year Retrospective Analysis

Travel-associated Legionnaires' disease is a significant public health concern worldwide. A high number of cases are reported every year among travellers who stay at guest houses, hotels, and spas. Indeed, hot water systems, showers, and air-conditioning systems can be contaminated by Legionella, which grows at 25-42 °C. Studies have shown that in Sardinia, especially during the summer months, the water circulation in the hotels' pipes is exposed to extremely high temperatures. As a result, this study was conducted to assess the colonization of hotel water systems by Legionella in Sardinia, concerning a recent EU directive 2020/2184 for drinking water with a limit of 1000 CFU /L. Methods. A total of 112 accommodation facilities were analyzed, of which 61.3% were found to be colonized with Legionella, and out of a total of 807 samples, 32.5% were positive for Legionella presence. The results showed a higher number of positive samples in the summer season. This was also associated with the higher concentration presence of >1000 CFU/L in the samples. Consequently, this study confirms that local hotel operators should improve their water safety and prevention plans, especially in spring and summer.

Overview of the Clinical and Molecular Features of Legionella Pneumophila: Focus on Novel Surveillance and Diagnostic Strategies

Legionella pneumophila (L. pneumophila) is one of the most threatening nosocomial pathogens. The implementation of novel and more effective surveillance and diagnostic strategies is mandatory to prevent the occurrence of legionellosis outbreaks in hospital environments. On these bases, the present review is aimed to describe the main clinical and molecular features of L. pneumophila focusing attention on the latest findings on drug resistance mechanisms. In addition, a detailed description of the current guidelines for the disinfection and surveillance of the water systems is also provided. Finally, the diagnostic strategies available for the detection of Legionella spp. were critically reviewed, paying the attention to the description of the culture, serological and molecular methods as well as on the novel high-sensitive nucleic acid amplification systems, such as droplet digital PCR.

Environmental Surveillance of Legionella spp. in an Italian University Hospital Results of 10 Years of Analysis

The occurrence of Legionella spp. in the water distribution systems of large hospitals and other healthcare facilities is considered particularly dangerous, due to the critical nature of the hospitalized patients. The aim of this study is to present a pluri-annual environmental surveillance in a large university hospital assessing the prevalence of Legionella spp. and underlining its variability over the years. The samples of water were collected in accordance with the Italian National Guidelines and the sampling sites considered in this study were selected favoring wards with very high-risk patients and with patients at increased risk. The laboratory analyzed a total of 305 water samples deriving from 24 different sampling points. Legionella spp. were detected in 39.4% of samples, the majority of which were contaminated by Legionella pneumophila serogroups 2–14 (68.7%). Statistically significant differences were found among different seasons with a linear trend in positive proportion from summer to spring. Several experimental interventions to prevent and reduce Legionella colonization were attempted, but there is no a definitive method for the complete eradication of this microorganism. The permanent monitoring of hospital water distribution systems is fundamental to preventing the potential risk of nosocomial Legionellosis and to implementing procedures to minimize the risk of Legionella spp. colonization.