Highlights
- •Copper-Silver water ionization disinfection systems can be overcome resulting in nosocomial Legionella outbreaks.
- •Routine monitoring and enhanced monitoring of potable water systems after structural disruptions should be encouraged.
- •In hospital showering activity is identified as a statistically significant risk factor for contracting Legionella during an outbreak.
- •Showering restriction and point of use water filters can help mitigate outbreaks related to potable water.
- •Multidisciplinary collaboration is encouraged to anticipate and assess for vulnerabilities to Legionella outbreaks.
Abstract
Background
An outbreak of Legionella pneumonia occurred at a university hospital using copper-silver ionization for potable
water disinfection. We present the epidemiological and laboratory investigation of
the outbreak, and associated case-control study.
Methods
Cases were defined by syndrome compatible with Legionella pneumonia with laboratory-confirmed Legionella infection. The water circuit and disinfection system were assessed, and water samples
collected for Legionella culture. Whole genome multi-locus sequence typing (wgMLST) was used to compare the
genetic similarity of patient and environmental isolates. A case-control study was
conducted to identify risk factors for Legionella pneumonia.
Results
We identified 13 cases of hospital-acquired Legionella. wgMLST revealed >99.9% shared allele content among strains isolated from clinical
and water samples. Smoking (P= .008), steroid use (P= .007), and documented shower during hospitalization (P= .03) were risk factors for Legionella pneumonia on multivariable analysis. Environmental assessment identified modifications
to the hospital water system had occurred in the month preceding the outbreak. Multiple
mitigation efforts and application of point of use water filters stopped the outbreak.
Conclusions
Potable water system Legionella colonization occurs despite existing copper-silver ionization systems, particularly
after structural disruptions. Multidisciplinary collaboration and direct monitoring
for Legionella are important for outbreak prevention. Showering is a modifiable risk factor for
nosocomial Legionella pneumonia. Shower restriction and point-of-use filters merit consideration during
an outbreak.
Key Words
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Article info
Publication history
Published online: February 22, 2021
Footnotes
Funding: No additional funding was received in order to prepare this manuscript.
Conflicts of interest: The authors report no conflict of interest.
Identification
Copyright
© 2021 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.
