Epidemiology and Infection

Does using potting mix make you sick? Results from a Legionella longbeachae case-control study in South Australia

B. A. O'CONNOR a1a2, J. CARMAN a3, K. ECKERT a4, G. TUCKER a5, R. GIVNEY a1c1 and S. CAMERON a2a3
a1 Communicable Disease Control Branch, Department of Health South Australia
a2 Master of Applied Epidemiology Program, National Centre for Epidemiology and Population Health, Australian National University, Australia
a3 Department of Public Health, University of Adelaide, Australia
a4 Division of Health Sciences, University of South Australia, Australia
a5 Epidemiology Branch, Department of Health South Australia, Australia

Article author query
o'connor ba   [PubMed][Google Scholar] 
carman j   [PubMed][Google Scholar] 
eckert k   [PubMed][Google Scholar] 
tucker g   [PubMed][Google Scholar] 
givney r   [PubMed][Google Scholar] 
cameron s   [PubMed][Google Scholar] 


A case-control study was performed in South Australia to determine if L. longbeachae infection was associated with recent handling of commercial potting mix and to examine possible modes of transmission. Twenty-five laboratory-confirmed cases and 75 matched controls were enrolled between April 1997 and March 1999. Information on underlying illness, smoking, gardening exposures and behaviours was obtained by telephone interviews. Recent use of potting mix was associated with illness (OR 4·74, 95% CI 1·65–13·55, P=0·004) in bivariate analysis only. Better predictors of illness in multivariate analysis included poor hand-washing practices after gardening, long-term smoking and being near dripping hanging flower pots. Awareness of a possible health risk with potting mix protected against illness. Results are consistent with inhalation and ingestion as possible modes of transmission. Exposure to aerosolized organisms and poor gardening hygiene may be important predisposing factors to L. longbeachae infection.

(Accepted March 31 2006)
(Published Online June 19 2006)

c1 Communicable Disease Control Branch, Department of Health South Australia, PO Box 6, Rundle Mall, Adelaide SA 5000, Australia. (Email: rod.givney@health.sa.gov.au)