LEGIONELLA - World Health Organization

acteria, and that they are aware of the risk to themselves and to others from potentially
positive sites. In some circumstances, it may be necessary to use respiratory protective equipment,
although in most cases cooling systems can be turned off to allow safe sample collection. An
exception may be where a wet cooling system is being used to cool a potentially explosive
industrial process. In that situation, a risk assessment must be made before sampling. If it is
not safe to take samples, the system should be rendered safe as soon as possible.
Several countries or regions produce guidelines on sampling. Advice on methods that comply
with the European and United Kingdom guidelines has recently been published and is freely
available from the Internet (Standing Committee of Analysts, 2005). 26
11.4 Legionella speciation and serology typing
11.4.1 Identifying different Legionella species
Methods used to identify and differentiate Legionella species include (Benson & Fields, 1998;
Ratcliff et al., 2003):
• phenotypic characteristics
• growth requirements
• biochemical characteristics
• fatty acid and carbohydrate analysis
• ubiquinones
• protein profiling
• serology
• monoclonal antibodies reactions
• various molecular techniques (including, recently, the use of sequencing techniques).
The use of biochemical profiles for routine identification of legionellae other than L. pneumophila
is limited. Legionellae test positive for catalase — an enzyme in blood and cells that catalyses
the decomposition of hydrogen peroxide into oxygen and water. The oxidase reaction gives
variable results and is therefore not very useful. Reactions for nitrate reduction, urease and
carbohydrate use are negative. Most species of Legionella produce beta-lactamase, lipase and
phosphatase (Thorpe & Miller, 1981) and liquefy gelatine. Strains belonging to all serogroups
of L. pneumophila, except serogroups 4 and 15, strongly hydrolyse hippurate (Hebert, 1981).
Several laboratories have described methods for identifying putative Legionella isolates to the
genus level, and in some cases to the species level, using only phenotypic characteristics.
26 http://www.environment-agency.gov.uk/commercial/1075004/399393/401849/?version=1&lang=_e
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS