LEGIONELLA - World Health Organization

8.5.2 Verification
Microbial parameters for hot tubs commonly include the heterotrophic plate count (HPC)
at 37 °C, coliforms, Escherichia coli, Pseudomonas aeruginosa, and sometimes also Legionella. For
Legionella, WHO recommends the following routine sampling frequencies during normal
operation (WHO, 2006):
• disinfected pools, public and heavily used — quarterly
• disinfected pools, semi-public — quarterly
• natural spas — monthly
• hot tubs — monthly.
Table 8.4 gives examples of national standards in a selection of countries (Broadbent, 1996). 13
Well-maintained pools regularly achieve no detectable counts of pseudomonas, aerobic colony
counts, Legionella, coliforms or E. coli, and this should be the goal. Failures should be investigated
and the effectiveness of any remedial work should be monitored.
Special attention should be paid to microbial sampling for hot tubs linked to cases of legionellosis.
In such cases, water samples must be supplemented with swabs from air jets, dismantled
shower heads, hoses and taps, including water outlets and inlets. Water samples of 1 litre should
be collected from the pool, filter housing and balance tank, where fitted. Balance tank samples
are more likely to yield legionellae than hot tub samples; filter material and biofilm from inside
the pipes may also contain large numbers of legionellae and should be sampled by swabbing.
Often, sections of pipe will have to be cut into to achieve this, but sometimes it is possible to
gain access to the insides of pipes by removing the water jets in the base or sides of the spa pool.
8.6 Surveillance
In some jurisdictions, health authorities may periodically inspect facilities (e.g. sports facilities,
such as gymnasia); this may include both physical inspections and inspections of records of
activities such as cleaning and disinfection. The competency of staff may also be checked; for
example, there may be checks to determine whether staff hold appropriate pool maintenance
qualifications.
13 http://www.dh.sa.gov.au/pehs/publications/monograph-heated-spas.pdf (accessed 12 July 2005)
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS