Legionella pneumophila contamination of hospital dishwashers

Rapid Detection of Legionella pneumophila in Drinking Water, Based on Filter Immunoassay and Chronoamperometric Measurement

Legionella is a pathogenic bacterium, ubiquitous in freshwater environments and able to colonise man-made water systems from which it can be transmitted to humans during outbreaks. The prevention of such outbreaks requires a fast, low cost, automated and often portable detection system. In this work, we present a combination of sample concentration, immunoassay detection, and measurement by chronoamperometry. A nitrocellulose microfiltration membrane is used as support for both the water sample concentration and the Legionella immunodetection. The horseradish peroxidase enzymatic label of the antibodies permits using the redox substrate 3,3′,5,5′-Tetramethylbenzidine to generate current changes proportional to the bacterial concentration present in drinking water. Carbon screen-printed electrodes are employed in the chronoamperometric measurements. Our system reduces the detection time: from the 10 days required by the conventional culture-based methods, to 2–3 h, which could be crucial to avoid outbreaks. Additionally, the system shows a linear response (R² value of 0.99), being able to detect a range of Legionella concentrations between 10¹ and 10⁴ cfu·mL⁻¹ with a detection limit (LoD) of 4 cfu·mL⁻¹.

Air-conditioner cooling towers as complex reservoirs and continuous source of Legionella pneumophila infection evidenced by a genomic analysis study in 2017, Switzerland

Introduction

Water supply and air-conditioner cooling towers (ACCT) are potential sources of Legionella pneumophila infection in people. During outbreaks, traditional typing methods cannot sufficiently segregate L. pneumophila strains to reliably trace back transmissions to these artificial water systems. Moreover, because multiple L. pneumophila strains may be present within these systems, methods to adequately distinguish strains are needed. Whole genome sequencing (WGS) and core genome multilocus sequence typing (cgMLST), with their higher resolution are helpful in this respect. In summer 2017, the health administration of the city of Basel detected an increase of L. pneumophila infections compared with previous months, signalling an outbreak.

Aim

We aimed to identify L. pneumophila strains populating suspected environmental sources of the outbreak, and to assess the relations between these strains and clinical outbreak strains.

Methods

An epidemiological and WGS-based microbiological investigation was performed, involving isolates from the local water supply and two ACCTs (n = 60), clinical outbreak and non-outbreak related isolates from 2017 (n = 8) and historic isolates from 2003–2016 (n = 26).

Results

In both ACCTs, multiple strains were found. Phylogenetic analysis of the ACCT isolates showed a diversity of a few hundred allelic differences in cgMLST. Furthermore, two isolates from one ACCT showed no allelic differences to three clinical isolates from 2017. Five clinical isolates collected in the Basel area in the last decade were also identical in cgMLST to recent isolates from the two ACCTs.

Conclusion

Current outbreak-related and historic isolates were linked to ACCTs, which form a complex environmental habitat where strains are conserved over years.

Epidemiologic Survey of Legionella Urine Antigen Testing Within a Large Wisconsin-Based Health Care System

Purpose

Legionella pneumophila pneumonia is a life-threatening, environmentally acquired infection identifiable via Legionella urine antigen tests (LUAT). We aimed to identify cumulative incidence, demographic distribution, and undetected disease outbreaks of Legionella pneumonia via positive LUAT in a single eastern Wisconsin health system, with a focus on urban Milwaukee County.

Methods

A multilevel descriptive ecologic study was conducted utilizing electronic medical record data from a large integrated health care system of patients who underwent LUAT from 2013 to 2017. A random sample inclusive of all positive tests was reviewed to investigate geodemographic differences among patients testing positive versus negative. Statistical comparisons used chi-squared or 2-sample t-tests; stepwise regression followed by binary logistic regression was used for multivariable analysis. Positive cases identified by LUAT were mapped to locate hotspots; positive cases versus total tests performed also were mapped by zip code.

Results

Of all LUAT performed (n=21,599), 0.68% were positive. Among those in the random sample (n=11,652), positive cases by LUAT were more prevalent in the June-November time period (86.2%) and younger patients (59.4 vs 67.7 years) and were disproportionately male (70.3% vs 29.7%) (P<0.0001 for each). Cumulative incidence was higher among nonwhite race/ethnicity (1.91% vs 1.01%, P<0.0001) but did not remain significant on multivariable analysis. Overall, 5507 tests were performed in Milwaukee County zip codes, yielding 82 positive cases by LUAT (60.7% of all positive cases in the random sample). A potential small 2016 outbreak was identified.

Conclusions

Cumulative incidence of a positive LUAT was less than 1%. LUAT testing, if done in real time by cooperative health systems, may complement public health detection of Legionella pneumonia outbreaks.

Persistent Legionella contamination of water faucets in a tertiary hospital in Japan

OBJECTIVE

The feasibility of the decontamination procedure for Legionella pneumophila of water systems in healthcare facilities varies by water purification and disinfection methods in each country. We evaluated the efficacy of feasible decontamination strategies in Japan.

METHODS

This study was conducted at Tokyo Medical University Hospital (1015 beds) between 2015 and 2018. Samples from the water system and cooling tower were cultured periodically. Hyper-chlorination of cool tap water (>0.2 ppm), increases in the temperature of hot water (>55 °C), and flushing were used as decontamination strategies. The case of healthcare-associated legionellosis was surveyed. Environmental and clinical isolates were genotyped.

RESULTS

1439 environmental samples were collected; 19 (1.3%) samples tested positive for L. pneumophila from water faucets of patient rooms, toilets, waste rooms, and water sourced from wells. Genotyping of 12 isolates confirmed that the same strains were present in eight environmental isolates and two isolates from patients over three years. Although the environmental contamination of the water system was persistent, the number of positive locations of hospital environments gradually decreased; eight in 2015, four in 2016, three in 2017, and four in 2018, respectively.

CONCLUSIONS

Monitoring contamination, hyper-chlorination, controlling temperature, and flushing were effective as a Legionella decontamination strategy.

Can incorporation of UVC LEDs into showerheads prevent opportunistic respiratory pathogens? - Microbial behavior and device design considerations

Respiratory infections from opportunistic bacterial pathogens (OBPs) have heightened research interests in drinking water distribution systems, premise plumbing, and point-of-use technologies. In particular, biofilm growth in showerheads increases OBP content, and inhalation of shower aerosols is a major exposure route for Legionellae and Mycobacteria infections. Incorporation of UVC LEDs into showerheads has thus been proposed as a point-of-use option for healthcare facilities. Herein we have examined incongruities between the nature of OBP contamination in shower water and the hypothetical application of conventional UV disinfection engineering concepts. Effective UV dosing within showerheads must overcome significant shielding effects imparted by the biological matrices in which common OBPs reside, including biofilm particles and protozoan hosts. Furthermore, prevention of biofilm growth in showerhead interiors requires a different UV irradiation approach and is lacking in established design parameters. Development of showerhead devices is also likely to face a trade-off between bathing functionality and simpler form factors that are more conducive to internal UV irradiation.