WATER HYGIENE AND SAFETY
of L. anisa reach around 1,000 CFU/L, the mixed colonies disappear, and L. pneumophila is the victim. This poses a range of microbiological questions, including: n Is annual testing of sites that have no record of a loss of control sufficient given this example?
n Is ‘plumber’s putty’ a high nutrient source for bacteria?
n Some samples have only L. anisa positives; does this mean that L. pneumophila is not present in the pipework, or is its presence being masked by other species on the culture plate? What is the real microbiological situation in the pipework itself?10
n Is the L. pneumophila a concern if it’s being masked by another species?
n Would L. pneumophila be found by rapid tests that target specifically L. pneumophila SG1 where the culture method failed to detect?
n How big a problem is L. anisa in the water industry?11
n How much more does the culture test support growth of one L. spp over another?
n Does the incubation temperature for the culture test encourage certain species to grow over others?12
n Are the counts an error by the laboratory in selecting too few colonies to confirm the type of Legionella present, i.e. would a wider spread of colonies or more colony picks confirmed by MALDI-ToF give a wider spread of species?
n Should we consider testing Legionella at the current temperature (36 °C), and also undertake a test at ‘system’ temperature (conditions)? What impact would this make, and what would it show?
‘‘
It is clear to see from the full dataset on this site that L. anisa and L. pneumophila can co-exist in low numbers. However, when the counts of L. anisa reach around 1,000 CFU/L the mixed colonies disappear, and L. pneumophila is the victim
n Should the AE be involved in the purchasing process to ensure correct specification of equipment?
n Should all major plumbing works undertaken in healthcare settings that could have an impact on the microbiological load be completed by LCA-registered member companies?
Conclusions The prominence of L. anisa in the ‘challenging’ ward appears to have been supported by poor system conditions over an elongated period of time. There were several factors that exacerbated this issue, including: n No flow or return temperatures being taken on the calorifiers.
n Incorrect specification issued to the Trust for calorifiers by primary contractors.
n Over-reliance on contractor specification by Estates teams, instead of referring uncertain specifications for major plant equipment back to Authorising Engineers for approval and sign-off.
n No audits/checks on the original PPM tasks being completed.
n Calorifiers unable to reach pasteurisation temperatures.
n Budget being spent on calorifiers (originally) rather than the tank re- location to aid PPM works access. n Access and working at height issues
for installing the Chlorine Dioxide permanent dosing plant to storage tanks.
n Impact of the excessive use of ‘plumbers’ putty’ as a food source for bacteria.
n Use of incorrect components in plumbing this system.
Impact of individual issues unknown What is unknown is the impact of each individual issue, any certainty being around the combined effects. Questions should therefore be asked about how much Legionella growth, of any species, would be encouraged by each of these issues on their own. Further research is required regarding the ability, or not, of L. anisa and L. pneumophila to be able to co-exist on an ISO11731 culture plate.13
The preliminary
data of 13,500 samples held by Lakeside Water suggests that co-existence is not possible with counts over 6,000CFU/L of L. anisa, but this could be impacted by a range of factors, including the number of colonies selected for identification via MALDI-ToF among others. The data suggests that, given the right
conditions, Legionella can continue to thrive even with a range of treatments in place, and the only protection to patients, staff, and visitors in this instance was point-of-use filtration.14
How many other
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