Volume 24, Number 10—October 2018
Dispatch
Two Community Clusters of Legionnaires’ Disease Directly Linked to a Biologic Wastewater Treatment Plant, the Netherlands
Table 2
Location of samples | Sampling date, wk/y | CFU/L | Legionella pneumophila serogroup | ST |
---|---|---|---|---|
Water samples† | ||||
BWTP | ||||
Pond 1 (low aeration) | 48/2017 | 2.0 × 106 | sg1 | ‡ |
50/2017 | 5.6 × 107 | sg1 | ST1646 | |
Pond 2 (no aeration) | 48/2017 | 7.1 × 108 | sg1 | ST1646 |
50/2017 | 19.2 × 108 | sg1 | ST1646 | |
Pond 3 (high aeration) | 48/2017 | 15.0 × 108 | sg1 | ST1646 |
50/2017 | 22.6 × 108 | sg1 | ‡ | |
Municipal waste water treatment plant | ||||
Influent | 39/2017 | 1.0 × 105 | sg1 | ST1646 |
Pond | 39/2017 | 2 × 103 | sg1 | ST1646 |
River midstream | 39/2017 | 2 × 103 | sg1 | ST1646 |
Riverside | 39/2017 | 2 × 104 | sg1 | ST1646 |
Fountain, city center | 50/2016 | Negative | ||
39/2017 | Negative | |||
WCTs and air scrubbers next to BWTP, industrial area | ||||
50/2016 | Negative | |||
39/2017 | Negative | |||
48/2017 | Negative | |||
4 WCTs, industrial area | 50/2016 | Negative | ||
5 WCTs, industrial area | 39/2017 | Negative | ||
Misting device, industrial area |
39/2017 |
Negative |
||
Other environmental samples† | ||||
Biologic waste water treatment plant | ||||
Air sample inside pond 3 tent | 50/2017 | Positive | sg1 | ‡ |
Swab inner surface pond 3 tent | 50/2017 | Positive | sg1 | ST1646 |
*Source: Database National Reference Laboratory for Legionella, Haarlem, the Netherlands. BWTP, biologic wastewater treatment plant; sg, serogroup; ST, sequence type; WCT, wet cooling tower.
†Water samples were analyzed with an accredited in-house developed method based on ISO 11731:2017, with an additional step of acid treatment. Air samples were collected using a SASS 2300 air sampler (Research International, Seattle, WA, USA), and analyzed in with an accredited in-house developed method based on ISO 11731:2017.
‡Sequence type profile was incomplete because of technical problems experienced during mompS typing; however, for all 6 available alleles, results were in accordance with the ST1646 profile (flaA, 2; pile, 10; asd, 14; Mip, 10; mompS, not available; proA, 4; neuA, 11).