Comparison of Whole-Genome Sequences ofLegionella pneumophilain Tap Water and in Clinical Strains, Flint, Michigan, USA, 2016

Abstract

During the water crisis in Flint, Michigan, USA (2014–2015), 2 outbreaks of Legionnaires’ disease occurred in Genesee County, Michigan. We compared whole-genome sequences of 10 clinical Legionella pneumophila isolates submitted to a laboratory in Genesee County during the second outbreak with 103 water isolates collected the following year. We documented a genetically diverse range of L. pneumophila strains across clinical and water isolates. Isolates belonging to 1 clade (3 clinical isolates, 3 water isolates from a Flint hospital, 1 water isolate from a Flint residence, and the reference Paris strain) had a high degree of similarity (2–1,062 single-nucleotide polymorphisms), all L. pneumophila sequence type 1, serogroup 1. Serogroup 6 isolates belonging to sequence type 2518 were widespread in Flint hospital water samples but bore no resemblance to available clinical isolates. L. pneumophila strains in Flint tap water after the outbreaks were diverse and similar to some disease-causing strains.

Copper Pipe, Lack of Corrosion Control, and Very Low pH May Have Influenced the Trajectory of the Flint Legionnaires’ Disease Outbreak

“…Other sampling campaigns conducted approximately 5, 8, 10, and 12 months after the switch back to Detroit water, with lower nutrients, more stable disinfectant residuals, and phosphate corrosion inhibitor, did not detect L. pneumophila gene markers and revealed a culture positivity rate in both large and small buildings (hospitals2–58%, residences0–21%) ,− that was comparable to normal background for hot U.S. tap water (20.7 gc/mL, 13% positivity). , While, to our knowledge, comparable widespread water sampling data from Flint during 2014 do not exist, available data to date suggest that there were large differences between L. pneumophila occurrence in large buildings (such as hospitals) and small buildings (such as residences) during summer 2015.…”

“…After determining that the aged SGWH heaters did not have detectable culturable L. pneumophila, each was inoculated in week 0 to achieve a final concentration of 1,000 cfu/mL, using equal proportions of four L. pneumophila strains: two previously isolated from a hospital in Flint (serogroup 6 and serogroup 1), one reference strain similar to 130b (serogroup 1), 26,35 and an uncharacterized strain that had previously grown well in the SGWHs (unknown serogroup).…”

A Legionnaires’ Disease Cluster in a Private Building in Italy

“…In Germany, since 2011, due to the high incidence of LD cases and the mortality rate of 10% for community acquired cases, the mandatory annual Legionella monitoring has been extended not only to public building but also to those for commercial use and apartments [ 12 , 13 ]. In Flint, Michigan, the increased incidence of LD has drawn attention to contamination of domestic plumbing, although an epidemiological correlation with patient isolates has never been found [ 14 , 15 ].…”

Did Municipal Water Distribution System Deficiencies Contribute to a Legionnaires’ Disease Outbreak in Quincy, IL?

“…The fifth community case, which occurred in September, did have potential exposure to a known hotel outbreak in another community, and a different sequence type of Legionella pneumophila was isolated from the patient’s sputum than what was found at the IVHQ. However, it is not uncommon in community outbreak investigations to detect multiple strains of Legionella in environmental and clinical samples, − and this fifth case resided within 1 mile of the IVHQ. Although historical LD occurrence data in Adams County were not available, it is reasonable to consider a cluster of four community-acquired LD cases in a small city (∼40000 people; ∼75000 people in the metro area) in less than a 40 day window as an unusually high LD incidence (i.e., 5–10 times higher than the 2015 national incidence of LD).…”