A case of Legionnaires’ Disease in Italy, associated with a Dental Practice has renewed interest from dentists worldwide in protecting their patients from infection.
FAQ’s
Only one sample point is supplied in the industrial Legionella test kit. Can this be used to sample from different points?
The Industrial Legionella test kit was designed with one sampling outlet in mind where the sample point is fitted and left in place at that location. The test kit consisting of 5 tests would then be used for monthly testing at that site. If there are circumstances whereby this is not convenient and you want to test multiple locations in a short period of time for example then you can either purchase additional sample points for these locations or move the sample point.
Will contamination be an issue if I move the sample point to different locations?
Contamination will only be a potential issue if the test result from a previous outlet was positive. Even then, if the instructions for use are followed and the sample point flushed, then it is very unlikely that any residual antigen on the sample point would cause a false positive. However, if you are concerned about cross contamination then the sample point can be cleaned between uses.
How can I clean the sample point to remove any residual antigen?
Flushing the sample point should be sufficient to remove any residual antigen from a previous sample. However, the sample point can be sterilised by rinsing it in >50ppm free Chlorine solution (e.g. baby bottle sterilising fluid) for 1 minute (50ppm Chlorine will completely destroy the antigen in this time at room temperature).
The pipework adapter does not fit all of the sites that I need to test. How can I test from these sites using the Industrial Legionella test kit?
The pipework adapter is designed to fit standard ½” and ¾” BSP and NPT pipe fittings and whilst these are common in the industry, they are not universal. It is often possible however to find adapters which will convert from most pipe fittings to one of these sizes. Although we do not supply these adapters they can often be sourced locally very easily and would allow you to use the Industrial Legionella test kit as instructed. Alternatively, there are several methods of sampling from sinks in clean water systems which can be used. (a) Collect the sample in a collection bottle and then use a 50mL syringe with luer end (five times) to pass the water through the filter and then resuspend as per the instructions. (b) Collect the sample in a collection bottle and then use a vacuum pump to draw the water through the filter and resuspend as per instructions. Neither (a) nor (b) are likely to be suitable for cooling water. A peristaltic pump could be used to pump cooling water through the filter but this will have cost implications.
The detection limit for the Legionella Field Test is 100,000 cfu/L (100 cfu/ml) which is too insensitive for our needs.
Although the detection limit for the Legionella Field test is 100,000 cfu/L or 100 cfu/ml, we also offer a number of kits which reduce this detection limit by the addition of a concentration step. This makes the test 1000x more sensitive – i.e reduces the detection limit to 100 cfu/L or 0.1 cfu/ml. This process uses either hollow fibre filters or flat bed membrane filters (dependant on water type to be filtered) and takes < 30 minutes in the field and so a much greater sensitivity is achieved whilst not compromising on the rapidity of the test. We also offer the potential to detect L. pneumophila sg1 existing in biofilms where they might otherwise be missed, and therefore offer the potential to identify problematic areas for treatment.
Can the Legionella Field Test detect any Legionella pneumophila serotypes or species?
No, the rapid Legionella field test has been developed to detect L. pneumophila sg1 only and does not detect other serotypes or species. Over 80% of recorded Legionnaires Disease cases are caused by L. pneumophila sg1 and thus this form of the bacterium poses the greatest risk to human health. Other L. pneumophila serotypes and Legionella species do not pose such a threat to human health and therefore it may be more acceptable to wait up to 10 days for laboratory culture results. However, the ability to detect L. pneumophila sg1 rapidly is most beneficial in the prevention of an outbreak of disease and the Legionella field test provides “early warning” information on this high risk organism. This means that steps can be taken to control the Legionella bacteria and thus reduce the threat to human life, days before the laboratory would even have a preliminary positive.
Is the Legionella Field Test designed for routine monitoring or in outbreak response?
The Legionella Field test was originally designed for routine monitoring of water systems where L. pneumophila sg1 may be present and, with its many formats, is a useful tool in helping to prevent outbreaks occurring. However, it can also be a useful tool in outbreak response as it may help to identify problematic areas of a system following an outbreak where a positive test result can allow immediate intervention to help prevent further infection. Another time when the hydrosense Legionella field test may be beneficial is when another problem arises in the system e.g. if the chlorine, TVC (or HCC), temperature, or other parameters have gone “out of specification”. This deviation from the acceptable may be enough to give Legionella the opportunity to proliferate in the system and therefore the hydrosense test can be used to check for this instead of having to wait 2 weeks for results from the lab.
Does the hydrosense Legionella test conform to any British Standards?
There are currently no standards for Legionella field tests to which to conform. The comparative testing on the product carried out by Nalco (IWC paper) was to ISO1173:1998. The KWR report compares it to a number of “standard” Legionella tests (NEN standards).
Are there any regulatory documents which specifically recommend the use of the hydrosense test?
There are currently no standards in the EU/UK which specifically mention the use of rapid tests such as the Legionella Field Test. However, the UK regulations (L8) actively encourage the use of “additional measures” when there are particular high risk situations. The Health and Safety Executive (HSE, who regulate Legionella management in the UK), have confirmed that the hydrosense test is considered an additional measure.
The regulations on Legionella testing only require me to perform laboratory culture tests therefore why should I carry out additional testing such as the hydrosense test?
Compliance with regulations of Legionella testing is the minimum testing that should be carried out on your system. The Legionella field test can provide you with an early warning of a potential problem and allow a fast response to such problems. If L. pneumophila sg1 is present in your system, do you really want to wait 2 weeks to find out if you are exposing people to a potentially fatal infection? Whilst you may be complying with the regulations by only carrying out laboratory culture tests, it can also be argued that you have not taken all reasonable measures to prevent an outbreak given the availability of a fast test. If someone dies following infection by L. pneumophila sg1 from your system, it could be seen as negligence for not using a fast test where available even if the law does not require it.
Why not just use DFA instead of the hydrosense test for faster preliminary testing?
DFA (or Direct Fluorescence Antibody) is a laboratory process which involves using fluorescence stained antibodies to label Legionella in a sample and then using a microscope to detect the fluorescence and thus Legionella. This process requires a skilled operator and the correct reagents and although generally fast (i.e. 1 day), it is rather insensitive and labour intensive. The water sample must also still be transported to a lab before testing can occur which will add time to the overall process. The hydrosense test on the other hand is much quicker to carry out, can be applied at the site of sampling and will give more sensitive and specific results for L. pneumophila sg1.
A positive result on a hydrosense test might be the result of dead bacteria and therefore give a false impression of risk.
Whilst it is true that the hydrosense test does detect antigen on dead as well as live bacteria, the reality is that any dead bacteria detected by antigen tests were “recently alive” and so are an indicator of risk. Presence of dead bacteria in a system most likely suggests a problem somewhere in the system which will need to be dealt with.
The regulations on Legionella in our country do not require me to test to a level as low as the detection limit for the hydrosense test. How will I know if a positive result is the result of L. pneumophila sg1 at an action level.
If you are concerned that the detection limit is “too sensitive” for your requirements, then the volume of sample to be filtered can be reduced to raise the detection level to the standard you require. However, by using the test at its maximum sensitivity you will be giving the greatest warning of a problem if it exists. A positive result by hydrosense test could be followed up by a laboratory culture test to confirm the levels of legionella alongside the cleaning and disinfection of the system. It must be remembered that under ideal conditions, Legionella bacteria can double in concentration in 90 minutes and so the population could become much greater from the time of sampling. Ignoring any level of Legionella in a sample could be potentially fatal and therefore it should be addressed immediately to prevent risk of outbreak.