Legionella are pathogenic gram negative bacteria that were first identified in 1977 to cause disease (1). These bacteria are found globally in aquatic and soil environments (2). Many man-made environments like air-conditioning systems, water distribution systems and potting mix can act as reservoirs and amplifiers of Legionella (2). Humans that are exposed to environments that harbour Legionella are at risk of being infected. Legionella can cause two distinct illnesses: Pontiac fever, a non-pneumonic, self-limiting influenza type illness that typically lasts 2-5 days, and Legionnaire’s disease which causes atypical pneumonia and has a fatality rate of 10-15% in normally healthy individuals (2). Legionnaire’s disease has been reported in all age groups (2), however the large majority of cases are patients who are 50 years or over (WHO).
Legionella infections can be sporadic or epidemic. Globally, numerous Legionella outbreaks are reported each year. Compared to other countries, NZ has a high incidence rate of Legionnaires’ disease (3). Each year more than 200 cases of Legionella are reported in NZ. There are more than 50 known Legionella species, however, the large majority of cases are associated with two prevalent Legionella species: L. longbeachae and L. pneumophila (4). Exposure to compost or gardening potting mix is associated with L. longbeachae infection, while exposure to aquatic environments is associated with L. pneumophila infection (2). Legionella is a notifiable disease in NZ and is one of the three most common causes of severe pneumonia in both the community and in hospitals. There are no distinctive clinical features of pneumonia caused by Legionella spp and a delay in antibiotic treatment has been associated with increased mortality (6). Diagnostic tests available for Legionella detection include urinary antigen testing, PCR, serology and culture. PCR is an effective tool in identifying infections caused by any Legionella species in patient samples. The diagnostic test described below has been designed to detect all Legionella species but not differentiate between species. A secondary speciation PCR has to be carried out to determine if infection is due to L. longbeachae or L. pneumophila.
Amodeo, M. R., Murdoch, D. R., & Pithie, A. D. (2010). Legionnaires’ disease caused by Legionella longbeachae and Legionella pneumophila: comparison of clinical features, host-related risk factors, and outcomes. Clinical microbiology and infection, 16(9), 1405-1407.
2. Graham, F. F., White, P. S., Harte, D. J. G., & Kingham, S. P. (2012). Changing epidemiological trends of legionellosis in New Zealand, 1979–2009. Epidemiology & Infection, 140(8), 1481-1496.
3. Dalton, S. T., Wen, S. C., Murdoch, D. R., Martin, J. F., Wallace, K. N., Vivian, C. A., & Walls, T. M. (2018). Searching for pediatric Legionnaire disease in a population with high adult incidence. The Pediatric infectious disease journal, 37(9), 960-961.
4. The Institute of Environmental Science and Research Ltd. Notifiable Diseases in New Zealand: Annual Report 2017. 2019.
5. WHO. Legionellosis https://www.who.int/news-room/fact-sheets/detail/legionellosis2018
6. Diederen, B. M. W. (2008). Legionella spp. and Legionnaires' disease. Journal of infection, 56(1), 1-12.
7. Benitez AJ, Winchell JM. Clinical application of a multiplex real-time PCR assay for simultaneous detection of Legionella species, Legionella pneumophila, and Legionella pneumophila serogroup 1. J Clin Microbiol. 2013 Jan;51(1):348-51. doi: 10.1128/JCM.02510-12. Epub 2012 Nov 7. Erratum in: J Clin Microbiol. 2014 Feb;52(2):709. PMID: 23135949; PMCID: PMC3536254.
Microbiology - Virology
DLEG
DLEG
Testing is batched daily Monday-Friday at approximately 9.30am, with results available from mid-afternoon.
Add-ons can be made if an appropriate sample has already been received for other testing. Please call Virology to discuss.
Legionnaires disease
3 days
2599