FAQ

The N-Light™ L.monocytogenes test is a qualitative test for rapidly detecting the foodborne bacterial pathogen Listeria monocytogenes. It is intended for use in food processing areas and equipment as part of an environmental monitoring program. Being intuitive, rapid, cost-effective, and lab-free, it offers an affordable solution to scale testing and empowers your quality management process.

AquaSpark™ are dioxetane derivatives bearing substrates that specifically react with targeted enzymes. Being fully synthetic molecules, the platform offers a wide array of variations that allow rapid detection of enzymatic activities, amongst other applications.

RLU stands for Relative Light Units and is the unit of measure used in the NEMIS luminometer. RLU values are proportional to the amount of AquaSpark™ light emission induced by the specific enzyme. For each NEMIS test, a certain threshold for presumptive positive and presumptive negative results has been defined. In the case of the N-Light™ L.monocytogenes test, a sample is considered presumptive positive when the signal is above 20’000 RLU.

The test combines two core technologies: NEMIS bacteriophages (selective enrichment) and AquaSpark™, an ultrasensitive chemiluminescent molecule that reacts with an enzyme (PI-PLC) produced specifically by Listeria monocytogenes. In practice, the user follows a simple protocol:

• Collect the sample using a swab.
• Transfer it to the enrichment tube.
• Incubate it for 24 hours.
• Release the AquaSpark™ tablet into the tube.
• Incubate the activated tube at 37 ˚C for 5 minutes
• Measure results

If Listeria monocytogenes is present in your sample, they will initiate a reaction that generates light which the Luminometer measures, thus yielding a presumptive positive result. Figure 1 shows what happens when the AquaSpark™ tablet is released into a sample containing L.monocytogenes.

Results can be obtained after 24 hours of incubation at 37 °C. A shorter incubation time than 23 hours is not AOAC-validated and not encouraged if minimal contamination should be uncovered. On the other hand, tubes can be incubated for up to 72 h yielding the same results.

The N-Light™ L.monocytogenes test broth contains a mixture of nutrients (for bacterial growth) combined with selective factors (limiting the growth of non-target bacteria) such as antibiotics and NEMIS proprietary combination of bacteriophages. This combination creates an ideal culture medium for Listeria monocytogenes leading to superior sensitivity and specificity of the test. Its unique formulation inhibits the growth of competing bacteria and makes the test more reliable in challenging environments. Additional data about the N-Light™ enrichment broth can be found here.

The only required equipment is the NEMIS dry block heater and the NEMIS Luminometer. They can be used on-site without any laboratory infrastructure. It is recommended to perform the test in a separate room, distant from the production environment.

Yes, the N-Light™ L.monocytogenes has been certified in the AOAC® Performance Tested Methods SM Program and validated against the reference method ISO 11290-1:2017.

Any deviation from the N-Light™ L.monocytogenes test IFU can lead to FP or FN results.
The growth of certain Bacilli, S.aureus, and L.ivanovii could theoretically cause positive signals as they produce the same enzyme PI-PLC which cleaves the AquaSpark™ molecule and leads to the expression of chemiluminescent light. However, the proprietary NEMIS enrichment broth contains both antibiotics and bacteriophages that specifically eliminate these microorganisms.

The test is specific for Listeria monocytogenes, which is the only pathogenic species for humans. Negative results will be obtained for other Listeria species if they are present in the sample.

The test is sensitive to detect L.monocytogenes starting from single-digit bacteria in the sample. Good swabbing practice and accurate compliance with the test IFU are required.

No, it does not. The detection mechanism relies on the hydrolysis of AquaSpark™ by an enzyme (PI- PLC) that is only expressed by viable Listeria monocytogenes. Therefore, negative results will be obtained for dead bacteria.

Yes, VBNC bacteria may be detected. Unlike conventional plating methods, the test detects Listeria monocytogenes as long as they are metabolically active. Preliminary research has demonstrated that VBNC cells cleave the AquaSpark™ and can be distinguished from dead cells in an assay format in the laboratory. Further research is ongoing.

It is possible to collect samples from production lines or sites that have not been recently cleaned. Sample location and application of N-Light™ L.monocytogenes should be categorized as follows:

• Clean Surfaces
  The AOAC has validated the full performance of N-Light™ L.monocytogenes.
• Food or dirt residue exposed surfaces within the production or before cleaning
  Samples taken from production lines (both during and after production) and other places in the facility that are regularly cleaned are well within the capacity of our test. Make sure not to overload the sample with food residues. Rather go into niches and cavities of machines and apply pressure on surfaces. Sampling more “dirt” is not necessarily useful as persistent Listeria on equipment or infrastructure should be detected.
• Direct sampling of food or in places of high dirt / food residue concentration
  Meticulous sampling is required to ensure no test tube overload. Do not directly collect food residues. Examples of high load sampling spots are uncleaned drains, smeared water tanks, or the inside of uncleaned food residue collection containers.

We recommend that sample locations with overload potential should be either avoided or alternative sampling spots in close vicinity be taken. In case of doubt, do not hesitate to reach out to techsupport@nemistech.com

Hot spots that accurately indicate potential product contamination should be preferentially sampled. Please refer to your Hazard Analysis and Critical Control Points (HACCP) plan.

Optimally, high-risk spots should be swabbed on a daily basis after each cleaning or production shift. In case of a positive result, immediate corrective action should be taken with re-cleaning and re-testing until a passing result can be measured. Lower-risk control points may be tested less frequently.

The N-Light™ Listeria spp. test is a qualitative test for rapidly detecting the Listeria spp. group of bacteria which indicate the potential presence of the foodborne bacterial pathogen Listeria monocytogenes. It is intended for use in food processing areas and on food manufacturing equipment as part of an environmental monitoring program.

The only required instruments are the NEMIS dry block heater and the NEMIS Luminometer. They can be used on-site without any laboratory infrastructure. It is recommended to perform the test in a separate room, distant from the production environment.

The N-Light™ Listeria spp. test will undergo the certification process for AOAC® Performance Tested Methods until end of 2025. Please contact sales@nemistech.com or techsupport@nemistech.com for a summary of internal validation data generated by NEMIS.

AquaSpark™ substrates are dioxetane compounds bearing molecular structures that are specifically recognized by target enzymes. When cleaved by an enzyme, AquaSpark™ substrates emit light by a process called chemiluminescence. The N-Light™ Listeria spp. test uses an AquaSpark™ substrate with high specificity for Listeria sensu strict species.

The N-Light™ Listeria spp. broth contains a mixture of nutrients for bacterial growth combined with selective agents limiting the growth of non-target bacteria. These are antibiotics, salts and
a proprietary mix of bacteriophages for suppression of closely related bacteria.

RLU stands for Relative Light Units and is the unit of measure used in the NEMIS luminometer. RLU values are proportional to the amount of AquaSpark™ light emission induced by a specific enzyme.
For each NEMIS test, a certain RLU threshold for presumptive positive tests has been validated in extensive experimental studies at NEMIS. Below the threshold, the test result is considered negative. In the case of the N-Light™ Listeria spp., a sample is considered presumptive positive when the signal is above 4’000 RLU.

Results can be obtained after 24 hours of incubation at 37°C. A reduction of the incubation time by one hour (23 h) is also ok, but incubation times shorter than that will decrease the sensitivity of the N-Light™ Listeria spp. test. Likewise, up to six hours longer incubation time (30 h) will not affect the test, but longer incubation times have not yet been validated and may lead to unreliable results.

Developed N-Light™ Listeria spp. test tubes, safely closed with the biosafety cap, can be sent to a biosafety level 2 lab for follow-up analysis. NEMIS offers a tube cutter for opening of the biosafety cap. Presence of Listeria spp. and/or Listeria monocytogenes in the broth can be analyzed by molecular methods (PCR, real-time PCR, immunoassays) or by cultural methods such as ISO 11290-1.

The test detects Listeria innocua, Listeria welshimeri, Listeria ivanovii and all serotypes of Listeria monocytogenes. In field trials, NEMIS isolated mainly L. innocua and L. monocytogenes strains (confirmed by molecular methods). These species are known to be the most frequently occurring Listeria spp. strains in food factories.

In field trials conducted in food factories, the positivity rate of the N-Light™ Listeria spp. test was 21% to 39%, when sampling was done during production and the selection of sampling sites was focused on locations with a high likelihood of Listeria spp. being present. NEMIS considers the observed positivity rate as being in a useful range for guiding corrective actions and verifying proper cleaning.

The N-Light™ Listeria spp. test is based on the detection of an enzyme which may also occur in some other bacteria which can grow in the NEMIS broth. Therefore, there is a certain likelihood of false positive test results. In field trials conducted in food factories, 30 to 60% of the positive N-Light™ Listeria spp. tests could be confirmed in follow-up analyses by cultural and molecular methods as Listeria spp. Other species found in positive tests were Vagococcus fluvialis, Bacillus saprophyticus, Niallia circulans, Mammalicoccus sciuri and Enterococcus thailandicus. The fraction of false positives obtained with the N-Light™ Listeria spp. test is lower than that of other rapid on-site tests which mostly detect beta-glucosidase activity, an enzyme frequently occurring in a broad range Gram positive bacteria. For a screening assay intended for fast and easy monitoring of the Listeria risk in a factory, the accuracy is considered as good.

The test is capable of detecting Listeria spp. starting from single-digit numbers of bacteria on sampled surfaces. Good swabbing practice and accurate compliance with the test IFU are required for achieving highest sensitivity.

As the detection mechanism relies on active enzymes which are only produced by viable bacterial cells, dead Listeria are not detected.

It is possible to collect samples from production lines or sites that have not been recently cleaned. Sample location and application of N-Light™ Listeria spp. should be categorized as follows:

• Food or dirt residue exposed surfaces within the production or before cleaning
  Samples taken from production lines (both during and after production) and other places in the facility that are regularly cleaned are well within the capacity of our test. Make sure not to overload the sample with food residues. Rather go into niches and cavities of machines and apply pressure on surfaces. Sampling more “dirt” is not necessarily useful as persistent Listeria on equipment or infrastructure should be detected.
• Direct sampling of food or in places of high dirt / food residue concentration
  Meticulous sampling is required to ensure no test tube overload. Do not directly collect food residues. Examples of high load sampling spots are uncleaned drains, smeared water tanks, or the inside of uncleaned food residue collection containers.

Hot spots that accurately indicate potential product contamination should be preferentially sampled. Please refer to your Hazard Analysis and Critical Control Points (HACCP) plan.

Optimally, high-risk spots should be swabbed on a daily basis after each cleaning or production shift. In case of a positive result, immediate corrective action should be taken with re-cleaning and re-testing until a passing result can be measured. Lower-risk control points may be tested less frequently.

The N-Light™ Salmonella Risk test is a qualitative test for rapidly detecting the foodborne bacterial pathogen Salmonella spp. and closely related bacteria. It is intended for use in food processing areas and equipment as part of an environmental monitoring program. Being intuitive, rapid, cost-effective, and lab-free, it offers an affordable solution to enhance testing and empower your quality management process. Given the low prevalence of Salmonella spp. on environmental surfaces, N-Light™ Salmonella Risk not only detect Salmonella spp. but also a small selection of closely related bacteria. Certain strains of Klebsiella, Citrobacter and Enterobacter share the metabolic marker alpha- galactosidase activity with Salmonella spp. Based on NEMIS’ research, we suggest that the persistent presence of alpha-galactosidase-positive bacteria growing in our selective broth can be used as an indicator of the risk of the presence of Salmonella spp.

The low prevalence of Salmonella spp. on environmental surfaces makes its detection difficult. Therefore, the use of specific tests for Salmonella spp. usually gives a meagre rate of positive results, giving quality managers a false sense of security. The N-Light™ Salmonella Risk test allows quality managers to be in control, taking prompt preventive and corrective actions when the risk of the presence of Salmonella spp. is detected.

N-Light™ Salmonella Risk is not an Enterobacteriaceae test as the combined selectivity of the AquaSpark™ detection molecule and the selectivity of the enrichment broth (phages and antibiotics) inhibits the growth of most Enterobacteriaceae strains phylogenetically distant from Salmonella spp.
Please read the Salmonella Risk supporting document for more information

AquaSpark™ enzyme substrates are dioxetane derivatives bearing a chemical structure that specifically reacts with a target enzyme. After the reaction with the enzyme, light is emitted in chemiluminescence. Being fully synthetic molecules, the platform offers a wide choice array of compounds that allow rapid detection of enzymatic activities, amongst other applications.

RLU stands for Relative Light Units and is the unit of measure used in the NEMIS luminometer. RLU values are proportional to the amount of AquaSpark™ light emission triggered by the specific enzyme. For each NEMIS test, a certain threshold for presumptive positive and presumptive negative results has been defined. In the case of the N-Light™ Salmonella Risk test, when the signal is above 20’000 RLU, the enzyme alpha-galactosidase has been detected, indicating that there is a risk of the presence of Salmonella spp.

The test combines two core technologies: NEMIS bacteriophages (selective enrichment) and AquaSpark™, an ultrasensitive chemiluminescent molecule that reacts with the alpha-D-galactosidase enzyme produced by almost all Salmonella spp. and some other Enterobacteriaceae. In practice, the user follows a simple protocol:

• Collect the sample using a swab.
• Transfer it to the enrichment tube.
• Break and leave the swab inside the tube.
• Add the antibiotic tablet.
• Incubate it for 24 hours.
• Release the AquaSpark™ tablet into the tube.
• Incubate the activated tube at 37 ˚C for 3-4 minutes
• Measure results

If there is a risk of having Salmonella spp. that have grown in the selective broth, bacteria will initiate a reaction that generates light which the Luminometer measures, thus yielding a presumptive positive result.

Results can be obtained after 24 hours of incubation at 37 °C. However, a shorter incubation time than 23 hours is not AOAC-validated and not encouraged if minimal contamination levels should be detected. On the other hand, test tubes can be incubated for up to 72 h yielding the same results.

The N-Light™ Salmonella Risk test broth contains a mixture of nutrients (for bacterial growth) combined with selective supplements (limiting the growth of non-target bacteria) such as antibiotics and a proprietary combination of bacteriophages. This combination creates an ideal culture medium for Salmonella spp. leading to superior sensitivity and specificity of the test. Its unique formulation inhibits the growth of competing bacteria and makes the test more reliable in challenging environments.

The only required equipment is the NEMIS dry block heater and the NEMIS luminometer. They can be used on-site without any laboratory infrastructure. However, performing the test in a separate room, distant from the production environment, is recommended.

Yes, the N-Light™ Salmonella Risk has been certified in the AOAC® Performance Tested Methods SM Program and validated against the reference method ISO 11290-1:2017.

Any deviation from the N-Light™ Salmonella Risk test IFU can lead to FP or FN results.

The test can detect all the pathogenic Salmonella spp. Strains. However, N-Light™ Salmonella Risk does not only detect Salmonella spp. but also a small selection of closely related bacteria that share specific metabolic markers, mainly certain strains of Klebsiella, Citrobacter and Enterobacter. Based on NEMIS’ research, we have found that the persistent presence of those strains can be used as indicators for the presence of Salmonella spp.

The test is sensitive to detect Salmonella spp. starting from single-digit bacteria in the sample. Good swabbing practice and accurate compliance with the test IFU are required.

No, it does not. The detection mechanism relies on the hydrolysis of AquaSpark™ by an enzyme (alpha-D-galactosidase) that is only expressed by viable Salmonella spp. Therefore, negative results will be obtained for dead bacteria.

Yes, VBNC bacteria may be detected. Unlike conventional plating methods, the test detects Salmonella spp. as long as they are metabolically active. Preliminary research has demonstrated that VBNC cells cleave the AquaSpark™ and can be distinguished from dead cells in an assay format in the laboratory. Further research is ongoing.

It is possible to collect samples from production lines or sites that have not been recently cleaned. Sample location and application of N-Light™ Salmonella Risk should be categorized as follows:

• Clean Surfaces
  The AOAC has validated the full performance of N-Light™ Salmonella Risk
• Food or dirt residue exposed surfaces within the production or before cleaning
  Samples taken from production lines (both during and after production) and other places in the facility that are regularly cleaned are well within the capacity of our test. Make sure not to overload the sample with food residues. Rather go into niches and cavities of machines and apply pressure on surfaces. Sampling more “dirt” is not necessarily useful as persistent Listeria on equipment or infrastructure should be detected.
• Direct sampling of food or in places of high dirt / food residue concentration
  Meticulous sampling is required to ensure no test tube overload. Do not directly collect food residues. Examples of high load sampling spots are uncleaned drains, smeared water tanks, or the inside of uncleaned food residue collection containers.

We recommend that sample locations with overload potential should be either avoided or alternative sampling spots in close vicinity be taken. In case of doubt, do not hesitate to reach out to techsupport@nemistech.com

Hot spots that accurately indicate potential product contamination should be preferentially sampled. Please refer to your Hazard Analysis and Critical Control Points (HACCP) plan.

Optimally, high-risk spots should be swabbed on a daily basis after each cleaning or production shift. In case of a positive result, immediate corrective action should be taken with re-cleaning and re-testing until a passing result can be measured. Lower-risk control points may be tested less frequently.

The N-Light™ E. coli test is a qualitative test for rapidly detecting Escherichia coli, indicating fecal contamination and the potential presence of pathogenic bacteria and viruses. It is intended for use in food processing areas and on food manufacturing equipment as part of an environmental monitoring program. It can also be used for testing water samples.

The only required instruments are the NEMIS dry block heater and the NEMIS Luminometer. They can be used on-site without any laboratory infrastructure. It is recommended to perform the test in a separate room, distant from the production environment.

The N-Light™ E.coli has no yet been certified by an independent organisation. However, NEMIS rigorously tested the performance of the test together with an academic partner. Please contact sales@nemistech.com or techsupport@nemistech.com for a summary of internal validation data

AquaSpark™ substrates are dioxetane compounds bearing molecular structures that are specifically recognized by target enzymes. When cleaved by an enzyme, AquaSpark™ substrates emit light by a process called chemiluminescence. The N-Light™ E. coli test uses an AquaSpark™ substrate for the enzyme beta-glucuronisdase which is highly specific for Eschrichia coli strains.

The N-Light™ broth contains a mixture of nutrients for optimal growth of E. coli. Suppression of competing microorganisms is achieved by an elevated incubation temperature of 44°C.

RLU stands for Relative Light Units and is the unit of measure used in the NEMIS luminometer. RLU values are proportional to the amount of AquaSpark™ light emission induced by a specific enzyme. For each NEMIS test, a certain RLU threshold for presumptive positive, below the threshold, the test reults is considered as negative. In the case of the N-Light™ E. coli, a sample is considered presumptive positive when the signal is above 10’000 RLU.

Results can be obtained after 16 hours of incubation at 37°C. A reduction of the incubation time by one hour (15 h) is also ok, but incubation times shorter than that will decrease the sensitivity of the N-Light™ E. coli test for stressed cells. In case relatively high numbers of E. coli are expected, incubation time can be reduced to 8 h. It, likewise, up to six hours longer incubation time (30 h) will not affect the test, but longer incubation times have not yet been validated and may lead to unreliable results.

Hot spots that accurately indicate potential product contamination should be preferentially sampled. Please refer to your Hazard Analysis and Critical Control Points (HACCP) plan.

Optimally, high-risk spots should be swabbed on a daily basis after each cleaning or production shift. In case of a positive result, immediate corrective action should be taken with re-cleaning and re-testing until a passing result can be measured. Lower-risk control points may be tested less frequently.

N-Light™ ATP is a rapid and sensitive method developed for hygiene monitoring in the food industry. The test measures the amount of ATP present on surfaces, equipment, or in solution. The amount of ATP indicates the level of contamination with microorganisms and/or food residues.

ATP is the abbreviation for adenosine triphosphate, a biomolecule that provides energy for cellular processes and is present in all animals, plants, fungi and bacteria cells. In the case of microorganisms, metabolically active (living) cells contain the highest levels of ATP, while dead cells contain very little ATP. Foodstuff may also contain ATP, either from fermenting microorganisms or from plant and animal cells (e.g. muscle cells in meat).

Microbial cells, free ATP and food residues are picked up from surfaces or liquids using N-Light™ swabs BP provided together with the test tubes. The swab samples are broken into the assay buffer in the test tubes which contains a lysis agent for efferent release ATP from microbial cells. Then the reagent tablet in the cap is released and luminescence is measured after 10 sec. Light is generated by the reaction of ATP with the enzyme luciferase and the co-substrate D-luciferin.

The N-Light™ swabs BP are not pre-moistened. For sampling of dry surfaces, the swabs should be pre-moistened by dipping them into the assay buffer of the N-Light™ ATP tests. Dry swabs can be used for liquid samples (just stick the swab into the liquid, it will take up approximately 0.2 ml) or for sampling wet surfaces.

RLU stands for Relative Light Units and is the unit of measure used in the NEMIS luminometer and other luminometers. In the N-Light™ ATP test, RLU values are proportional to the amount of ATP present in the sample.

The only required instrument is the NEMIS benchtop luminometer. The test can be used on-site without any laboratory infrastructure.

When the luminometer is close to the sampling site, time-to-result (including sampling) is 2-5 min. When several samples are taken throughout the factory and then analysed together, the time for read-out is approximately 30 sec per test.

A sampled surface is considered very clean N-Light™ ATP test results are below 1000 RLU. Depending on the type of food factory and type of sampling site, higher RLU values of up to 5000 RLU can be defined as upper limit for clean surfaces. Very dirty surfaces can show N-Light™ ATP readings of up to several 100’000 RLU.

ATP tests are usually not certified. However, NEMIS has validated the test extensively in its own laboratory, both with Gram positive and Gram negative bacteria and foodstuff. Please contact sales@nemistech.com or techsupport@nemistech.com for a summary of validation data.

The liquid in N-Light™ ATP tubes contains is an aqueous solution with buffer compound, inorganic salts and low amounts of a detergent for cell lysis. The liquid does not pose any risk to humans or the environment.

Swab samples in transport tubes can be left for a maximum of 2 h at room temperature before analysing them in N-Light™ ATP tests. However, NEMIS recommends analyzing the swabs right after sampling.

The reading should be started in 8 to 12 sec after table release to achieve minimal test to test variability. Shorter or longer times between tablet release and reading will lead to higher variability. Users should never wait for more than 20 sec before starting the read.

Hot spots that accurately indicate potential product contamination should be preferentially sampled. Please refer to your Hazard Analysis and Critical Control Points (HACCP) plan.

Optimally, high-risk spots should be swabbed on a daily basis after each cleaning or production shift. In case of a positive result, immediate corrective action should be taken with re-cleaning and re-testing until a passing result can be measured. Lower-risk control points may be tested less frequently.

Yes, the dry swabs and the NEMIS buffer provided by NEMIS are sterile.

Yes. Commercially available PBS or BPW can be used to moisten N-Light™ swabs if buffer tubes have been stored according to supplier recommendation and their expiration date has not been reached. NEMIS recommends the use of the NEMIS neutralization buffer.

Briefly moisten a swab with the specific sterile buffer (provided with swabs) and rub it over a 10 x 10 cm area while rotating the swab to collect the maximum amount of sample. Apply gentle pressure to penetrate biofilms if present. Ensure the swab does not come into contact with anything other than the area of interest to avoid cross-contamination, e.g., from your hands.

Quantitative studies have demonstrated an increased number of positive samples collected from environmental surfaces if swabs were pre-moistened (https://pubmed.ncbi.nlm.nih.gov/20392914/ ). Only pre-moistened swabs were evaluated by AOAC and validated by NEMIS. Wet area sampling with dry swabs should be re-validated at the factory site. Dry swabbing is allowed in rare cases within the ISO 18593 sampling guideline.

We recommend starting the protocol described in the IFU immediately after sampling. Otherwise, samples can be stored at 4 °C and tested within 24 hours, guided by the ISO 18593:2018 norm. Ensure swabs are brought up to ambient temperature before starting the test, as drastic temperature changes can potentially harm the bacteria collected.

We are currently testing the best combination of neutralizing agents to develop a NEMIS neutralization buffer that does not interfere with the performance of our test. Some commercially available neutralization buffers have been shown to decrease the chemiluminescent intensity slightly. Therefore, we do not recommend any commercially available neutralizer now.

NEMIS uses qualified flocked swabs for improved sample absorption and release. The AOAC certificate has been achieved based on the use of NEMIS’ own sterile dry swabs with separate buffer and test performance can therefore only be guaranteed in accordance with this material and protocol. NEMIS has evaluated different swab materials and models from different suppliers, and we have found significant differences in the capability of those swabs to collect and release microorganisms. We therefore strongly recommend using N-Light™ swabs.

The N-Light™ MaxiSampler is compatible with N-Light™ L. monocytogenes, N-Light™ Listeria spp., N-Light™ Salmonella Risk, and N-Light™ E. coli tests.

Swabbing with the MaxiSampler is as easy as with a normal swab. Wipe across the sampled area two to three times in different directions while inclining the handle to both side. Apply ample pressure to the surface with the robust handle, this helps to remove bacteria firmly attached to the surface.

If you sample dry surfaces, moistening the MaxiSampler with N-Light™ Neutralizer or N-Light™ BPW is essential. Wet surfaces can be sampled with the dry MaxiSampler.

Maximum 4 hours at room temperature.

The N-Light™ MaxiSampler can be used to sample surface areas up to 0.3 m² (e.g. 30×30 cm or 50 x 50 cm, making it ideal for sampling large surfaces for environmental monitoring.

It is best used for large, flat surfaces such as conyeyor belts, tables,carts, doors, plastic curtains, floors, machine covers and casings, walls, and countertops. It can be applied on all types of surface materials (stainless steel, plastic, ceramics).

Best is to place the MaxiSampler back in its pouch after sampling. Avoid touching the swab part with your hands or other sources of contamination. Then transfer the sample as soon as possible to the N-Light™ test tube.

Open cap of the test tube, then insert the swab part of the MaxiSampler in the tube with the tip pointing down, then turn the handle upwards to unlock the click mechanism, then let the swab part slip down into the test tube and screw the cap back on the tube.

Rising of the MaxiSampler surface with the enrichment broth in the N-Light™ test tubes is very important. By this, bacteria are washed to the bottom of the tube where growth in the right medium and at the right temperature takes place. For rinsing, move the closed N-Light™ tube in horizontal position, with the coated part of the MaxiSampler facing down. Then incline the tube upwards and downwards at least ten times, which will cause the liquid in the tube to flow back and forth over the fiber coating.

In case of N-Light™ Listeria spp. and N-Light™ Salmonella Risk tests, remove the MaxiSampler swab from the tube after rinsing. This is done by sticking the upper end of the disassembled handle into the upper end of the MaxiSampler swab inside the tube and then drawing the swab out. While doing this, leave as much enrichment broth as possible in the tube by sloughing off liquid from the swab at the tube wall. Discard handle and swab in a waste bin. Follow instructions for use of N-Light™ Listeria spp. and N-Light™ Salmonella Risk tests for further steps.
In case of N-Light™ Listeria monocytogenes and N-Light™ Escherichia coli, the swab part of the MaxiSampler is left in the test tube. Before starting incubation, don’t forget to press the cap of the N-Light™ test tubes down for locking the biosafety mechanism.

There is no need to reuse the MaxiSampler as each MaxiSampler comes with a swab attached to a handle.

Our dry incubator was specifically designed to heat up only the lower part of the test tube (enrichment broth) while the upper part (biosafety cap with the AquaSpark™ tablet) remains at ambient temperature. Using a microbiological incubator (whole racks of tubes incubated, compare Figure 2 below) will expose the tablet to higher temperatures and might alter the accuracy of your test. Therefore, NEMIS only guarantees accurate test performance for the use of the NEMIS dry bath incubator.

According to the manufacturer’s specifications, temperature stability at 37 °C is +/- 0.2 °C while uniformity within the block at 37 °C lies at +/- 0.2 °C.

Incubating at higher or lower temperatures than 37°C will significantly affect the performance of the test and increase the risk of false negatives. Higher temperatures could negatively affect Listeria monocytogenes survival rate and growth properties and, lower temperatures slow down growth rate. Further, it has been demonstrated that Listeria monocytogenes can optimally express the trigger factor (PI-PLC) at 37°C and is significantly reduced at temperatures below 37°C. NEMIS can only guarantee reliable test performance at incubating at a constant temperature of 37°C.

Shorter: Incubating for less than 24h might not be enough to grow Listeria monocytogenes, especially if the contamination level is expected to be low. Performance, according to AOAC PTM has only been validated for a minimum of 23h. NEMIS recommends 24h or up to 72h incubation.
Longer: NEMIS has validated that a total incubation time up to 72h maintains the assay performance.

The Dry Block Heater is built for long, maintenance-free service. No lubrication or other technical user maintenance is required, and the only requirement is to keep the surfaces and incubation wells clean. For any warranty claims, please contact your local distributor or NEMIS if you have purchased the instrument directly.

The broth contains no hazardous or otherwise dangerous components.
Wipe up spills using absorbent pads or paper towels, then disinfect the surfaces using household bleach or 70% ethanol, or any other disinfectant that you commonly use in your location.

Yes, increased turbidity of the tube is a normal result of the growth of Listeria monocytogenes in the broth. Thus, this effect is typical and will not interfere with the functioning of the test. To be noted, turbidity can also arise from environmental bacteria growth. Therefore, the turbidity is not a sufficient indication of Listeria monocytogenes growth. Further, due to the test’s sensitivity, non- turbid tubes may be Listeria monocytogenes positives after 24h. Hence, only the N-Light™ reaction induced by the drop of the detection tablet can reliably indicate the presence of Listeria monocytogenes.

Yes, components collected in the factory environment can get the broth turbid (dust, food residues, etc.). Pitch black substances such as machine oil should be avoided. See question 19 for more information about the sampling spots.

The NEMIS BTL1 Luminometer is a highly sensitive instrument designed to measure light emissions, specifically luminescence. It plays a key role in detecting bacteria using NEMIS tests. These tests operate on a simple yet effective mechanism: if a bacterial-specific enzyme is present in the sample, it reacts with AquaSpark®, a proprietary substrate. This reaction generates light, and the BTL1 Luminometer precisely measures the intensity of this emitted light.

Unfortunately, that is not possible. The NEMIS BTL1 Luminometer is specifically designed for compatibility with NEMIS tests. The test tubes are uniquely shaped to fit inside the NEMIS device, ensuring accurate measurements. Additionally, the BTL1 Luminometer comes with predefined protocols that automatically interpret results, providing a clear indication of whether a sample is a presumptive positive or negative.
The NEMIS BTL1 Luminometer, like most luminometers, output results in Relative Light Units (RLU), which lack qualification to a consistent international standard. As a result, the thresholds used by NEMIS tests cannot be easily translated to other devices, making the BTL1 Luminometer essential for accurate and reliable results.

Currently, NEMIS does not offer a handheld Luminometer. However, the NEMIS BTL1 Luminometer is designed with portability in mind. It can be powered using any USB power bank, making it possible to use the device on a trolley for mobile applications. This setup provides flexibility for on-site testing while maintaining the precision and functionality of the device.

The BTL1 can accommodate up to 50 users, 100 test protocols, and 1000 test results (up to 30000 kinetic data points). The oldest data will be automatically overwritten when the maximum capacity has been reached. We, therefore, recommend transferring data from time to time to a personal computer or laptop to avoid data loss. Complementary instructions can be found in the luminometer user manual.

The luminometer does not need any scheduled maintenance service. However, on page 72, section 9.1 in the luminometer manual, you will find the recommendations for good maintenance the user should perform.

Data is automatically saved on the Luminometer after each measurement. Therefore, the data can be saved at any point in time. The only limitation to be aware of is the max storage capacity of 1000 test results (see question 45.). During synchronization of the luminometer with the NEMIS app, all the results will be transferred to the NEMIS data app and automatically removed from the luminometer. Data can be stored in the NEMIS data app and/or exported in excel/LIMS compatible format (.csv). There is no limit on the storage capacity within the PC app.

If you encounter issues accessing test protocols, NEMIS provides the latest versions of all test protocols through the NEMIS Data App. Please ensure you have the most up-to-date version of the app by downloading it from the following link: https://lp.nemistech.com/luminometer-pc-app-versions
This link also includes instructions for installing the app. Once installed, synchronize your luminometer as described in the instructions to access the required protocols.

You can reinsert the spring into the back of the measurement chamber by placing it in position with one finger and pressing it in securely using a pen or screwdriver. If the problem persists, please contact techsupport@nemistech.com, and NEMIS will provide a reworked spring that fits more securely.

To export your measurement results, first synchronize your Luminometer with the NEMIS Data App. If you haven’t installed the app yet, you can find the installation instructions and download the latest version here:
https://lp.nemistech.com/luminometer-pc-app-versions.
Once your results are synced to the app, select the desired measurement(s) and click the “Export” button. This will generate a .csv file, which can be easily opened and edited in Excel.

Currently, it is not possible for your Luminometer to communicate with your laptop via WLAN. However, NEMIS is actively working on a solution to offer this functionality in the future.

Yes, please follow the following link:
https://www.nemistech.com/technical-documents/

The minimal RLU is depending on your firmware version either -300 RLU (old firmware) or 0 RLU. The maximal RLU that is displayed is 9’999’999 RLU.

Please follow this link to download the latest version of the NEMIS Data App:
https://lp.nemistech.com/luminometer-pc-app-versions
This link also includes instructions for installing the app. Once installed, synchronize your luminometer as described in the instructions to update your firmware.

To ensure that the measured RLU values are accurate, NEMIS provides the L-Check device. This device verifies whether the measured signals are within the acceptable range. For more information or to request a quote, please contact sales@nemistech.com.

The Luminometer automatically calibrates itself every time it is turned on, so manual calibration is not necessary. However, to ensure that the measured RLU values are accurate, NEMIS provides the L-Check device. This device verifies whether the measured signals are within the acceptable range. For more information or to request a quote, please contact sales@nemistech.com.

The NEMIS L-Check is a device resembling the test tubes used in the NEMIS test system, designed for compatibility with the NEMIS BTL1 Luminometer. Inside the L-Check device is a temperature-stabilized LED probe. Once charged, this LED emits light at a consistent intensity.

The NEMIS L-Check is a reference tool for verifying the accuracy of the NEMIS Benchtop Luminometer (BTL1). It features a temperature-stabilized LED probe that emits light at a fixed intensity, allowing users to check if the luminometer measures correctly.
Each L-Check comes with a Certificate of Analysis, specifying the expected measurement range. By comparing readings to this range, users can ensure the instrument’s accuracy, troubleshoot discrepancies, and maintain reliable performance for quality control.

No, the BTL1 Luminometer does not require manual calibration, as it automatically calibrates itself each time it is powered on. As a result, the NEMIS L-Check is not intended for calibration purposes.
Instead, the L-Check is used for verification or qualification of the luminometer. It ensures the device is functioning correctly by providing a stable reference light source to check against the expected measurement range specified in the Certificate of Analysis.

If the signal measured with your L-Check is below the specified range, consider the following steps to address potential issues:
1. Ensure Proper Insertion
Verify that the L-Check is fully inserted into the measurement chamber of the BTL1 Luminometer. A common issue is incomplete insertion, often caused by the black clamp on the L-Check not being fully secured in the measurement chamber. This can lead to reduced RLU (Relative Light Unit) readouts.
2. Inspect the White Tip
Check the white tip of the L-Check for black residues, which can absorb light and lower the signal. If residues are present, clean the tip using a dry or slightly damp cosmetic towel. For damp cleaning, use water or 70 % ethanol as a wetting agent.
If the signal remains low after performing these checks, please contact techsupport@nemistech.com for further assistance.

Please contact techsupport@nemistech.com for further assistance.

The recommended temperature for the enzymatic hydrolysis of AquaSpark™ by Listeria monocytogenes is 37 °C (see IFUs for other tests). The tubes should be placed back (after tablet dissolution) in the incubator and removed only just before taking the measurement. Please follow the instructions according to the instructions for use (IFU) provided with the test.

The tablet can be released subsequently to incubation. There is no need to bring the test tube back to ambient temperature. It is mandatory to place the tubes back in the incubator just after tablet release and perform the measurement at a broth temperature of 37°C.

The tablet will be completely dissolved in less than 1 min. For optimal dissolution, follow the N-Light™ IFU. However, not all components in the tablet are water soluble, some of the insoluble components will remain at the bottom of the tube as fine particles.

The analytical tablet is white and relatively small. If you observe additional white particles in the broth, the tablet might have been released without notice.
In case you cannot identify the tablet, you can:

• Invert and shake the tube until you see the tablet inside the broth (before shaking, make sure that your tube has been sealed. For how to seal the tube, please follow the IFU). The humidity inside the tube can keep the tablet stuck on the tube’s wall. Make sure to hold the tube vertically while pushing the release button to avoid this.
• Press again the button on top of the cap, until the tablet is released inside the broth. It can rarely happen that the aluminum sealing layer in the cap does not entirely rupture keeping the tablet inside the cap.
• Gently beat the tube on a flat surface until the tablet drops into the broth.
• In the very rare instance that the tablet cannot be released and is stuck but the sealing foil has been ruptured, you may invert the tube to dissolve the tablet manually. In case of doubt, it is recommended to discard the test and repeat the test at the sampling location.
• Start the timer for the measurement only when the tablet is released inside the broth. If your timer is already running for different samples, start another timer, or consider performing the above procedures separately after measuring the other samples.

The tablets are made of different components, and not all of them are water soluble. Therefore, it is normal to observe fine particles at the bottom of the tube. The complete dissolution of AquaSpark™ in the broth should happen in within the first 20 seconds after the release if the tubes have been stored accordingly.

Generally, small residues of sanitizers and soap should not interfere with the test performance. However, sampling directly after cleaning without water rinsing may make the test invalid.
For detailed information on your specific use case contact techsupport@nemistech.com.

In case of a presumptive positive, you can either run a cultural confirmation or send the tube to an external laboratory (please handle the sample as a dangerous good of type UN3373 and follow the
required packaging and labeling instructions). In principle, the N-Light™ tests can also be confirmed via PCR or immunogenic reactions. Contact us at techsupport@nemistech.com for details regarding a list of validated confirmation methods. In case you are confirming with a service laboratory, please make sure that the laboratory contacts NEMIS for a valid confirmation procedure.

Generation of the chemiluminescence is an active process, which happens when the AquaSpark™ molecules are cut by the enzyme produced. Due to that, the signal builds for 5 to 15 minutes. After that time, fewer AquaSpark™ molecules are available in the solution and thus less light is generated. As a result, the signal starts decaying. To obtain the most reproducible results, ensure you measure chemiluminescent 5 minutes after the release of the AquaSpark™ tablet as detailed in our IFU.

You have an old version of the luminometer software. Please contact us at techsupport@nemistech.com to remove the negative values from your device. However, negative values usually, from -1 to –50 RLU, are given by the N-Light™ luminometer only when there is no chemiluminescence light emission. There is no difference between 0 RLU and slightly negative values.

Please check your local regulatory requirements for the proper disposal of biohazard materials. Used N-Light™ tests can be inactivated by autoclaving in an autoclavable bag or by incineration. NEMIS recommends disposing of all N-Light™ tests by a specialized service provider for biohazardous waste. CAUTION: Do not dispose of enrichment broth using the sink, as it contains antibiotics.

N-Light™ sterile dry swabs with separate PBS buffer can be stored at room temperature or in a fridge (+2 – 30 °C). Do not freeze and check the expiration date on the label. Opened buffer tubes must be stored in a fridge at +2-8 °C, and NEMIS recommends using open buffer tubes only on the same day of opening.

Dispose of N-Light™ swabs and PBS buffer with your regular household waste and in accordance with local regulations.

Some components in the N-Light™ tests are thermolabile. Therefore, performance and shelf life are assured only when the test is stored at 2-8 °C. The test can be exposed to higher temperatures for a short period of time as required for transport and handling. NEMIS has validated the anticipated worst-case storage conditions and confirms that the test performance will remain within the specifications for the times and temperatures listed below: