APA News

  • Edinburgh Scientific Services Involved In Legionella Outbreak Investigation and Expansion of Microbiology Related Real Time–PCR


    In autumn 2013 a cluster of seven cases of Legionella longbeachae were reported in the community. Five of the cases were in NHS Lothian and two in NHS Tayside. Robbie Beattie, Public Analyst and Food Examiner in Edinburgh, sat on a national Incident Management Team which was set up due to the unprecedented nature of the cluster. During the investigation Edinburgh Scientific Services isolated Legionella longbeachae from environmental soil and compost samples, as did Tayside Scientific Services who were investigating the two NHS Tayside case. The final report of the Incident Management Team into the outbreak, which was one of the largest of its kind reported in the world, was published on 30th June 2014.

    The investigation was challenging due to the matrix which in the normal course of events carries a high and mixed bacterial load. The traditional culture method and confirmation method is based on detection from water so the latex agglutination testing only confirms Legionella species or Legionella pneumophila. As a result confirmation to species identification level had to be done by the national Legionella Reference laboratory in Glasgow.

    Work by the Incident Management Team trying to link environmental bacterial isolates with clinical isolates using whole genome sequencing (WGS) gave a glimpse of the problems of the future. What if the bacteria is a mixed strain and have minimally different genetic profiles and one preferentially grows on the environmental matrix and the other grows preferentially in the clinical setting e.g. the lungs. Whereas in the past on the basis of testing available it would have been possible to say the two were linked it may now become impossible in some cases to say the bacteria are linked to identify unequivocally the source.

    Edinburgh Scientific Services has now developed a Real-Time PCR assay specifically for Legionella longbeachae which augments its UKAS accredited Legionella species and Legionella pneumophila assays. Surprisingly in the most recent four year period only one case of Legionnaires disease linked to Legionella longbeachae was found in England and Wales compared to nine cases in Scotland with one tenth of the population. This may be due to more advanced clinical screening tools such as PCR being used in some parts of Scotland.

    Edinburgh Scientific Services provided Public Health England with positive compost to help develop their own RT PCR assays to begin monitoring in England.