Description of organisms

Knowledge is power and with this in mind we have constructed fact sheets for all the test organisms stated in the standards we test against. We have also created these sheets for other popular organisms and have tried to keep up to date with topical organisms such as hospital required infections and food poisoning organisms.

Aspergillus brasilensis, which was formally known as Aspergillus niger, is one of the most common species of Aspergillus.  When grown in the lab on a petri dish they form very large colonies, with black centres and a white ring around them.  They are fluffy on top where the spores form.    

Aspergillus brasilensis is widespread in a range of different environments.  One of the most common places it is found in is in soil. Due to this it commonly causes food contamination and can result in visible mould. Aspergillus brasilensis is also found in factories and industrial plants.  This can be picked up on through regular hygiene monitoring, such as surface swabbing.  If mould is found through hygiene monitoring, a deep clean may be necessary, but due to its hardiness not all disinfectants will kill it. You would need to look for a disinfectant with a specific ‘fungicidal claim’.

Aspergillus brasilensis is the most used mould in both cosmetics and biocides microbiology testing.  It is the only mould used in the preservative efficacy testing but the pass rate for this organism is a lot lower than any other organism. This is due to its resistance and tolerance to stressors.  Even in biocidal testing the log reduction required is lower than most bacteria and yeasts.

Although testing against mould isn’t required by ECHA like bacteria and yeasts are, it is common for a biocide to test against both the mould and yeast which in combination gives you a fungicidal claim.  Common tests that Aspergillus brasilensis is used in are the EN 13624, the EN 1650 and the EN 13697.

Aspergillus brasilensis can cause multiple different health conditions but is usually harmless.  Most people breath in some sort of Aspergillus spore every single day and it does not affect them.  Even though anyone can get ill from Aspergillus, people who are elderly and immunocompromised are at a much higher risk.  Aspergillus infections cause an illness called Aspergillosis.  While this can present differently in different people, the infection is always in or around the respiratory system and often presents as the common cold.  The most severe forms of Aspergillosis can cause coughing up blood and weight loss.  Most Aspergillus infections clear on their own, but for persistent or severe causes, you may need anti-fungal medication.

Interestingly, Aspergillus brasilensis is the most common organism found on the international space station and this is partly due to the fact it is resistant to space radiation!

Bacillus cereus is a Gram-positive, spore forming, rod-shaped bacteria.  Its name ‘cereus’ comes from the Latin word for ‘waxy’, due to its appearance when grown on agar.  When grown in a lab on a petri dish, the colonies are usually, large, pale and non-uniform.  As the name suggests they can often look like spilled candle wax.

Like other types of Bacilli, Bacillus cereus is common in the environment and can be found in soil and plants.  It originates from decaying, organic matter but can be found in both plants and insects as well as food.  Bacillus cereus is commonly known as the organism that affects rice.  It is also often present in the digestive system of mammals, including humans.  Again, like other bacilli, Bacillus cereus survives in extreme environments, making it harder to eliminate once infection starts.  As with other types of spores, if disturbed, they can become airborne, and if breathed in by humans or animals they can cause infections.

There is only one standard that Bacillus cereus is an obligatory organism in, and this is the EN 17126, which is the medical step 2 phase 1 test for sporicidal activity.  You must also have Bacillus subtilis tested on the EN 17126.  It is also commonplace to have Bacillus cereus tested against EN 13704.  Although this organism is not obligatory for the EN 13704 it is becoming increasingly popular to test against it.  Although Bacillus cereus isn’t specified in cosmetics testing, different types of Bacilli are one of the most common contaminants found in cosmetics, due to their hardiness and prevalence in society.

The most common place found, where we can get ill from Bacillus cereus, is rice.  This is when rice isn’t cooked properly.  Usually, when you get ill after an Indian takeaway, it’s the rice to blame, not the curry!  It is also common to find Bacillus cereus in reheated rice, which is why you should never reheat it.  As the spores are so hardy when the rice is being reheated, it does not kill them. This means it is still infectious.  Bacillus cereus food poisoning causes nausea, vomiting and diarrhoea.  A healthy person would have to ingest food that has at least 10000 colonies per gram (1.0 x 104) to get food poisoning from contaminated food.  Although illness from Bacillus cereus isn’t usually dangerous, it can become serious for the elderly who have low stomach acidity and it can even fatal in extreme cases.

Bacillus subtilis is a Gram-positive, rod-shaped bacterium.  It is often referred to as grass or hay Bacillus due to its prevalence in grassy areas.  When grown in petri dishes in a lab environment, Bacillus subtilis form large, pale colonies often present on the surface of the agar.  Around the centre of the colony a root like formation can occur which looks like frost on a window.  Bacillus is the most regularly studied, spore forming bacteria.

Bacillus subtilis is extremely prevalent in soil, which then transmits to grass and hay.  Due to its pervasiveness in grass and hay, many herbivores carry it in their gastrointestinal tract; including cattle, goats, sheep and deer, to name just a few.  Though the optimal growth temperature for Bacillus subtilis is between 25oC and 35oC, they are particularly versatile, and can survive in temperatures above boiling point, as well as below freezing.  Due to this, if you get a biofilm forming or a contamination of Bacillus subtilis, it can be very difficult to remove.

Bacillus subtilis is used to prove sporicidal activity in biocides.  The two standards that have this as a named organism are: the EN 13704 and the EN 17126.  The EN 13704 is for the industrial and food industry and only has Bacillus subtilis as an obligatory test organism.  The EN 17126 is for the medical industry, and this has both Bacillus subtilis and Bacillus cereus as obligatory organisms.  In both standards you also have the option to test against Clostridium difficile to make a claim against it.  This is often expected in healthcare disinfection.   

Bacillus subtilis is considered ‘non-pathogenic’ and rarely causes illness or infection in humans.  There have been cases of it infecting the immunocompromised through food poisoning, causing diarrhoea and vomiting but occurrences are rare, and it is generally considered to be harmless. It is also very rare is for Bacillus subtilis to cause illness in animals. This is because it is commonly found in animal feed, and they have built up immunity to it over time.

Campylobacter jejuni is a Gram-negative bacterium.  The bacteria cells are curved rods, which enable them to infiltrate gastrointestinal mucus by twisting themselves through. When grown in a laboratory environment on petri dishes, they appear as dark red or white colonies and are usually small.

Campylobacter jejuni often comes from the digestive tract of birds, including poultry.  It is also commonly found in cattle, but it rarely affects birds or cattle in a negative way.  Most of the time when humans come into contact Campylobacter jejuni, it is from contaminated food and drink, and this is mostly found in the meats of poultry and beef.  When it is found in meat it, is usually because of poor hygiene in slaughterhouses and indicates that faeces has come into contact with the meat at some point.  Along with meat often unpasteurised milk will carry Campylobacter jejuni and some unchlorinated water.  When proper hygiene is put in place Campylobacter jejuni can be killed and avoid it contaminating food and drink.

Campylobacter jejuni isn’t specified in any of the biocidal standards but it is a common ‘add on’ organism.  Campylobacter jejuni is particularly relevant for disinfectants that are to be used in food preparation areas as well as places that handle raw meat, such as abattoirs.  Sometimes Campylobacter jejuni is also added onto the veterinary tests such as the EN 1656, when the disinfectant is needed in areas where livestock is kept.

Campylobacter jejuni is the most common cause of food poisoning in the developed world and results in millions of people getting ill every year.  It is estimated that 0.02% of the population will get ill with Campylobacter jejuni each year.  Usually, symptoms start about 2-5 days after encountering the organism.  When infected with Campylobacter jejuni, the most common symptom is diarrhoea, that can often become bloody.  Campylobacter jejuni infections usually clear up without intervention, but occasionally complications can occur such as IBS and even temporary paralysis.  The immunocompromised, such as people with AIDS or those going through chemotherapy are at higher risk of complications.

Candida auris is a common species of “multiple drug resistant yeast”.  When this organism is grown in the lab on petri dishes, it appears as a creamy white, large colony with. It has a stereotypical yeast smell, like the smell of beer and bread.

Candida auris is a reasonably new discovery in the microbiology world, in comparison to some other organisms.  It was first isolated by scientists in 2009 from the ear canal of a 70-year-old Japanese woman. However, the first reported illness caused by Candida auris wasn’t until 2011 in South Korea, which then spread throughout Asia and Europe.  The name ‘auris’ actually comes from the Latin for ear, as this is where it was first discovered.  Nowadays it is mostly found in hospitals where it spreads between patients.

Although Candida auris isn’t yet specified in any biocidal testing it is becoming more popular to test against, due to a worrying increase in cases seen in hospitals.  Some of the standards which people add Candida auris on to are, the EN 1650, the EN 13624 and the EN 16615.  At Melbec, Candida auris can be added to most fungicidal standards upon request.

Candida auris infections are often misdiagnosed due to its similarity to other Candida infections.  This can be very dangerous as Candida auris is resistant to multiple different antifungal medications that are usually used to treat a Candida infection. The only way to establish if the infection is Candida auris is through blood samples tested in a lab.  Almost all known cases of Candida auris infections have been passed through hospitals and other healthcare institutes.  Although there is limited data on Candida auris infections, some common symptoms seem to be wounds that form puss, high temperatures and generally feeling under-the-weather.  The only wany to treat Candida auris is through antifungal medication but the amount that have any action against this resistant organism, is limited.  It is believed that as many as 60% of people with diagnosed Candida auris infections die.

Candida albicans is a very common pathogenic yeast.  When grown in a lab environment they form large, white colonies which often resemble stars; this is due to the spikes they grow.  They also have a very distinctive yeast smell which is common of bread and beer.

Candida albicans can be found in lots of different environments and is reasonably resilient to different conditions.  Most commonly it is found in the gastrointestinal tract and the mouth of humans but is also found in the vagina.  Around 50% of people carry this organism. Once outside the body the yeast can also survive, meaning it is found in a range of different environments.  Candida albicans is the most common yeast to cause a biofilm.  Once a biofilm forms, the slime is secreted defending it, making it hard to remove. It is essential to have good hygiene practices in place to prevent this, especially in pipework.

Candida albicans is used in both cosmetic and biocidal microbiology testing.  In cosmetics testing, it is usually the only yeast that is tested against.  It is also used in preservative efficacy testing but has a lower pass rate than the bacteria used.  It is specified in ‘Cosmetic Regulation ISO 17516’ that this organism must be absent from a cosmetic before each batch can be released to the market.  At Melbec the testing that is used to determine if all the specified organisms are absent is called ‘The QC with specifics test’ or ‘The QC with specified and non-specified organisms test’.

Additionally, Candida albicans is the most popular yeast used in biocidal testing.  The most common standards that you will find this yeast in, are the EN 1650, the EN 13624 and the EN 16615.  It is by far the most widely used organism used to substantiate yeasticidal claims.

Although a lot of people do carry Candida albicans, it can still cause illness through infection.  Candida albicans is in fact the most common cause of fungal disease in humans.  It is also generally the cause of thrush, which around 75% of all women will experience in their lifetime.  Candida albicans is often found in hospitals, due to its ability to grow on different surfaces, including medical devices.  In the immunocompromised this can lead to ‘disseminated candidiasis’, which can be fatal.

Clostridium difficile is a Gram-positive, spore forming, rod shaped bacterium.  Also, they usually have little nodules at the end of the bacteria, making them look like spindles.  When grown in a laboratory on a petri dish in blood agar, they come up as a yellowish colony.

Clostridium difficile is found in about 1 in 30 adults and lives in the digestive system.  Normally, this causes no harm, as the other organisms found in the digestive system keep it under control and in low numbers.  Clostridium difficile is often found in the faeces of infected people and is usually spread through oral digestion.  Commonly, this happens when an infected person has poor hygiene procedures during food preparation or in food preparation areas.  Once the spores are released, they can stay in the area for weeks at a time and infect people as they walk through.  The spores can stay in the air, as well as settle on surfaces and therefore are difficult to get rid of once they are there.  Again, as with other spores, they can survive in harsh environments, meaning they can be difficult to kill, especially once airborne.

There aren’t any biocidal standards that Clostridium difficile is an obligatory requirement for.  The two standards that Clostridium difficile is most often tested against are the EN 17126 and the EN 13704.  As none of these standards have Clostridium difficile as a requirement, you will only need it tested if you want to make a Clostridium difficile claim.  It is becoming increasingly popular to add Clostridium difficile when the EN 17126 test is required, due to the growing number of C. diff. infections occurring in healthcare settings.  Often, when the NHS are looking for sporicidal disinfection, a Clostridium difficile claim is required, so this is something to bear in mind if you are going through tender. Clostridium difficile is also popular among UV testing, as they also tend to be used in healthcare.

Clostridium difficile commonly infects people who have recently been on antibiotics. This is due to the antibiotics interfering with the microbes in the digestive system, allowing Clostridium difficile to increase in numbers high enough to cause an infection.  Usually, people who are infected have either been in hospital for a long period of time or are aged over 65.  Immunocompromised people are at a higher risk as well.  Clostridium difficile causes diarrhoea, fever and sickness.  Another symptom is a tummy ache that can become very painful.  There are a few ways in which Clostridium difficile can be treated.  Normally, swapping the antibiotics that caused the infection will be stopped and replaced with a specialist antibiotic which targets Clostridium difficile.  In extreme cases surgery may be required to remove the infected parts of the bowel.

Enterococcus hirae is a Gram-positive round bacterium.  When grown in a lab environment Enterococcus hirae form very small, white colonies.

Enterococcus hirae is commonly found in the digestive system and faecal matter of mammals (including humans).  Enterococcus hirae is uncommon in other places in the environment and therefore remains a reasonably rare organism.

Unlike a lot of the other bacteria in the common standards, Enterococcus hirae is not as prevalent.  Enterococcus hirae is not used in cosmetics testing at all, as it very unlikely to be found in a cosmetic.  Here at Melbec we can check for the presence of Enterococcus hirae, but it would usually show up in a normal TVC test anyway.  Enterococcus hirae is very common in biocidal testing and is present in most bacterial standards, including the most common one’s like the EN 1276, EN 13727 and EN 13697 and tends to be an easier organism to kill than the Staphylococcus aureus (which is the other Gram-positive bacteria included in most of the tests).

Although Enterococcus hirae can cause infection and illness in humans, it is exceptionally rare.  It is thought there have been less than 100 infections cause by this bacterium ever recorded! However, the real number could much be higher, even though it is not prevalent like other bacteria we test against.  While Enterococcus hirae doesn’t cause many issues for humans, other mammals and especially birds can suffer badly from getting infected with it.  If Enterococcus hirae does infect humans, it usually causes sepsis and UTIs.

Escherichia coli, more commonly known as E. coli is a Gram-negative bacterial rod. When grown in a lab environment it appears as large, beige colonies, which can look generic.

E. coli is an extremely common bacteria and can be found in most people’s digestive systems. It usually accounts for around 0.15% of the gut’s microbiome. E. coli is one of the fastest multiplying bacteria, reproducing every 20 minutes. Due to this, even small amounts can grow and overrun a large entity. E. coli is found in animal products where poor hygiene regimes have been in place during food preparation. Although most E. coli is harmless and lives alongside humans and animals, it can cause illness when found in the wrong place.

In cosmetics, E. coli is a “specified organism”, which means you must prove that your product is absent from E. coli. E. coli is used in both biocidal efficacy testing, such as the EN 1276 and the EN 13697, as well as preservative efficacy testing; this is to ensure the product can withstand E. coli being introduced into the cosmetics. E. coli is excluded from most medical biocidal standards, like the EN 13727 and the EN 16615, but is present in biocidal standards for the food and industrial markets.

E. coli is the most common cause of food poisoning and results in vomiting and diarrhoea. Another ailment caused by E. coli are urinary tract infections. Over 75% of all UTI’s are caused by E. coli which is transferred in faecal matter.  Although most E. coli infections are not serious to a healthy person, the exception to this would be an ‘E. coli 0157:H7 infection’.  This can cause more serious symptoms including bloody stools and kidney failure.  At Melbec we can test against 0157:H7 and is popular requirement among biocidal manufacturers.            

Legionella pneumophila is a Gram-negative, rice shaped bacterium, which is best known for being the cause of Legionnaire’s disease.  When we grow Legionella pneumophila in the lab we use specialist agar with charcoal added which makes it look black and translucent.  The colonies grow as small, round and white which contrast well against the agar.

Legionella pneumophila is mostly found in unpreserved bodies of waters.  This includes rivers, reservoirs and ponds.  When found in these places they are usually in low numbers.  Because of the cold temperature of outdoor water, it is uncommon for people to pick up an infection from these types of places.  Almost all outbreaks of Legionella pneumophila originate in manmade places.  Legionella pneumophila grows well from condensation, so it is common to find it in cooling towers and other places where trapped heat causes condensation.  Spa pools are also a common place where outbreaks occur.  Not only can you become infected from encountering contaminated water, but you can also become infected by breathing in tiny droplets of condensation.

Legionella pneumophila can also form hardy biofilms, which when trapped in pipework can be almost impossible to get rid of.  In areas where conditions stimulate the growth of Legionella pneumophila, extra care should be taken with pipework to ensure biofilms do form.  More regular disinfection with a high current flow can be a good place to start.

Legionella pneumophila is the obligatory test organism in the EN 13623, and the EN 13623 is a biocidal standard test against Legionella pneumophila, used to determine the effectiveness of a biocide in treating aqueous systems.  You can also opt to have the product tested for either general purpose use or as a product for cooling water. Your test temperature and the diluent used will differ depending on which you pick.  There are also two different contact times you can go with, depending on the use of the product.  This depends on whether the product is fast-acting or a slower acting product.  If it is a fast-acting product then you would require a 1-hour contact and if the product is a slow acting, then you would require a 15-hour contact time.

Most healthy, young people who are exposed to Legionella pneumophila do not get sick.  People are at a higher risk of getting Legionnaires’ disease if they are older, have a lung disease or have experienced damage to the lungs (such as smokers) or have a suppressed immune system.  Legionnaires’ disease is commonly misdiagnosed as pneumonia due to its almost identical symptoms.  These symptoms include fever, struggling for breath, coughs, and aches.  Legionnaires’ can still be misdiagnosed as pneumonia, even after using a chest x-ray, so the only way to get a definitive answer is to take a culture, which is then grown and tested in a lab.  Even healthy people that get Legionnaires’ disease often need hospitalising for treatment, but they usually make a full recovery. Unfortunately, about 10% of all people who get Legionnaires’ disease die and about 25% that contract it whilst in hospital will die.

MRSA, whose full name is Methicillin-resistant Staphylococcus aureus is a Gram-positive, round bacterium.  It is a type of Staphylococcus aureus but is a different strain to those that are specified in the biocidal standards.  When grown in the lab on a petri dish, it forms medium sized colonies which appear in a grey colour on blood agar.  MRSA is known as a superbug due to its antibiotic resistant properties.

MRSA is very common in hospitals and other healthcare facilities.  MRSA originates from normal Staphylococcus aureus that are not antibiotic resistant.  These strains are usually commonly referred to as methicillin-susceptible Staphylococcus aureus or MSSA for short.  MRSA can develop from a Staphylococcus aureus infection that a person has or can be caught as MRSA from someone else.  MRSA can also infect livestock and can be passed to humans this way.  Around 25% of the population carries MRSA but don’t usually become ill from it.

MRSA isn’t specified in any biocidal standard as an obligatory organism.  It is commonly added on to help support claims.  Testing against MRSA would be particularly relevant when supplying to the NHS or healthcare sector.  Other places known to have had MRSA outbreaks are schools and prisons.  The most common standard that an MRSA claim can be added to is the EN 14561.  The EN 14561 is a medical standard for disinfection by emersion.  This can be used for medical devices to ensure sterilisation in between patients.

MRSA can infect all different places in the body from the skin to the chest.  If MRSA infects the skin, the individual will come out in boils and abscesses. Usually, the skin infections are mild in themselves, but complications can arise when MRSA enters the blood stream via the skin, causing much more serious infections.  When MRSA gets into the bloodstream it can result in sepsis and pneumonia.  MRSA can also cause respiratory infections.  The symptoms of these are fevers, cough, chest pain and aches and presents similarly to the common cold and flu.  MRSA can affect any part of the body, but other common infections caused by MRSA are UTI’s and digestive tract infections.  Although MRSA is resistant to many antibiotics, there are still some that can treat it. These are administered orally or intravenously.

Mycobacterium avium is a Gram-positive, rod-shaped bacterium.  When grown in a lab environment in a petri dish it forms small, white colonies.  Mycobacterium avium is a very slow growing organism meaning it must be incubated for at least 21 days to be able to get a reliable count.

Mycobacterium avium is a very common organism that can be found in many different places in human environments.  Nearly everyone has Mycobacterium avium in their body, even in small numbers.  This is due to the prevalence of the organisms in both our drinking water and our food.  Despite its prevalence, Mycobacterium avium does not affect most healthy people because of the strength of their immune systems. Another common source of Mycobacterium avium is in household dust.  Almost every household will have Mycobacterium avium in their home, making it virtually impossible to avoid.  In addition to this, most soil will have some amount of Mycobacterium avium in.

Mycobacterium avium appears in three biocidal tests which are the EN 14348, the EN 14563 and the EN 14204 which are all suspension tests. It is an optional organism in the EN 17272 standard. The EN 14348 and the EN 14204 are both phase 2 step 1 suspension tests.  The EN 14348 is for medical settings and the EN 14204 is for veterinary settings.  Neither the EN 14348, the EN 14563 nor the EN 14204 are stated by ECHA as obligatory standards to bring a disinfectant to the market, unless you are planning to make a mycobactericidal claim.  The EN 14563 is for instrument disinfection through submersion and the EN 17272 is a room fogging standard.  Although Mycobacterium avium isn’t stated in most of the step 2 tests you can add it into most of them i.e., the EN 16615, so you will then have a surface test in addition to the suspension tests.

Although Mycobacterium avium is harmless to most people and lives alongside us in our everyday lives, there are people who can get very ill from it.  With a Mycobacterium avium infection, the symptoms are usually very similar to a bout of the flu.  These include fever, struggling for breath, weight loss, diarrhoea, anaemia and stomach pain.  Excessive sweating is also reported in some cases.  To diagnose a Mycobacterium avium infection, a culture is grown from the patient’s coughed up mucus.  A chest x-ray and CT scan will also be conducted, to try and speed up the diagnosis process.  Although anyone can contract a Mycobacterium avium infection, people with AIDS are at a much higher risk and are usually become much more ill than those without AIDS.  Mycobacterium avium infections are often long term and only 75% of people survive for 5 years after they are first diagnosed.

Mycobacterium terrae is a Gram-positive, rod-shaped bacterium.  When grown in a lab environment in a petri dish it forms small, white colonies.  Like other types of Mycobacteria, Mycobacterium terrae is a very slow growing organism and takes around three weeks to grow to obtain reliable counts.

Mycobacterium terrae is not as common as other types of Mycobacteria and even less is known about it due to a lack of research.  Mycobacterium terrae was first isolated in 1950, from water used to wash radishes.  Because of this it is often referred to as radish bacillus.  When Mycobacterium terrae was discovered, animal testing was carried out to establish whether the new organism was harmful, but after the guineapigs that were infected with it showed no illness or adverse effects, it was deemed non-pathogenic and not a concern.  The first case of a Mycobacterium terrae infection wasn’t recorded until 1997, when a women developed an infection in her finger.  It is likely that infections were present in individuals prior to this but were not identified as Mycobacterium terrae infection.  Mycobacterium terrae can be treated with certain antibiotics but is resistant to others.

Mycobacterium terrae appears in two biocidal suspension test standards which are the EN 14348 and the EN 14563.  It is also named as an optional organism in the EN 17272, which helps support a mycobactericidal claim.  Neither the EN 14348, the EN 14204 or the EN 14563 are required by ECHA as obligatory standards to bring a disinfectant to the market, unless you are planning to make a specific mycobactericidal claim.  The EN 17272 is obligatory if you are making a fogging disinfection claim but the mycobacteria aren’t essential in this, unless you want to make a mycobactericidal claim.  In the EN 14348 and the EN 14563, Mycobacterium terrae is the organism required to make a tuberculocidal claim.  If you only want to claim tuberculocidal rather than a full mycobactericidal claim you will only need the Mycobacterium terrae testing.                

Mycobacterium terrae can often be misdiagnosed as osteoarthritis, this is due to the similarity of the symptoms.  The symptoms of a Mycobacterium terrae infection in the joints include, swelling or inflammation and lesions that can become filled with puss.  Although Mycobacterium terrae infections are very rare, when they do occur, they are usually found in clinical settings, among immunocompromised individuals.  Although Mycobacterium terrae most commonly infects the joints and bones, it has also been known to cause infections in the lungs, the digestive system and the urinary tract.  Mycobacterium terrae can be antibiotic resistant, and the slow growing nature of the organism can also cause trouble when trying to treat it.  Long courses of antibiotics are usually recommended when a Mycobacterium terrae infection is present in a patient.

Pseudomonas aeruginosa is a Gram-negative bacterial rod.  When grown in petri dishes they form large; yellow, blue or green colonies that are often fluorescent and can be identified by doing an oxidise test on them.  It also has a distinctive sweet smell which some people think is pleasant. The name aeruginosa means “copper rust” in Latin, which describes the blue/green colour when grown on laboratory agar.

Pseudomonas is also one of the common forming biofilms there is and is especially common in water systems.  When a biofilm forms, they secrete a slime which protects them from both being washed away and from chemicals.  This is one of the things that makes them so hard to remove once they are there.  When we test process waters here at Melbec, we include a test to specifically look for Pseudomonas and if you test process water regularly you should hopefully pick up quickly a biofilm starting to form, before it spreads or gets too big.

Pseudomonas aeruginosa is one of the most common test organisms we use here at Melbec due to its prevalence in biocidal efficacy standards.  For example, it is present in both the EN 1276 and the EN 13697 and it can be one of the harder bacteria to achieve a pass against.

Pseudomonas aeruginosa is antibiotic resistant and can cause multiple different infections and conditions such as UTIs, dermatitis, bone and respiratory infections.  It is estimated that Pseudomonas aeruginosa cause 10-20% of infections in hospitals. In the environment it is commonly found in hot tubs and other heated bodies of water.

Staphylococcus aureus is a Gram-positive round bacterium.  When grown in the lab in petri dish, it forms an orange colour.  To identify if an organism is a Staphylococcus or not, we would do a “latex kit”.

Staphylococcus aureus is one of the most common organisms found in humans and around 30% of the population carry it in their nostrils and it is also found in the vagina.  Due to the prevalence of Staphylococcus aureus in humans, it is common to find it on surfaces, especially as it can be sneezed out.

Staphylococcus aureus is used in the Preservative Efficacy Test (PET) for cosmetics because of its prevalence in society.  This is especially relevant for cosmetics that are packed in “open concept” pots meaning regular introduction of fingers.  Staphylococcus aureus is also used in biocidal testing such as the EN 1276 and the EN 13697.  As with Pseudomonas aeruginosa, Staphylococcus aureus is one of the harder of the bacteria to kill on these tests.

Staphylococcus aureus causes a range of different complications in the body, such as skin infections which cause acne and deep tissue infections causing cellulitis.  They can also cause very serious and fatal infections such as toxic shock syndrome and sepsis.  Patients in hospitals (especially ICUs) are at a higher risk from Staphylococcus aureus, this is why disinfectants used in a medical setting are tested against it.

Vancomycin-resistant Enterococcus, more commonly referred to as ‘VRE’ is a Gram-positive, round bacterium.  When grown in the lab environment on selective agar in petri dishes, it will appear blue in colour, making it easy to identify.

VRE is often found in the digestive system of humans.  It can also be found in the female reproductive tract.  VRE is quite common in people, but rarely makes them ill.  VRE develop when an Enterococcus attach to a specific piece of DNA called ‘Plasmid’, this then allows the Enterococcus to become resistant to Vancomycin which is one of the most popular antibiotics used to treat infection.  VRE often spreads through hospitals and especially through invasive medical devices such as catheters.  If hospital staff are caring for people with a known VRE infection, PPE is recommended to reduce the risk of spread the infection from person to person.

VRE itself, is not specified in any biocidal standards, however Enterococcus is.  Many standards such as, the EN 13727, the EN 1276 and the EN 16615 have Enterococcus as a specified test organism.  In microbiological tests, both VRE and other Enterococcus tend to act in similar ways, however, if you do wish to make a specific claim against VRE, then you should also have this tested, as no two organisms will ever act completely alike.  VRE is often added to medical standard tests such as, the EN 13727 and the EN 16615. This is because is it most common in hospitals and acre facilities and having a disinfectant that can kill VRE is vitally important in stopping the spread.

VRE can cause infection almost anywhere in the human body, if it gets in the wrong places, but there are places that it is more common in than others.  Usually, it’s the urinary tract that gets infected from faecal matter, or from a contaminated catheter used whilst in hospital.  VRE also commonly causes blood infection and sepsis.  The symptoms of a VRE infection tend to be quite generic and therefore can be misdiagnosed without a culture being used for identification.  Some of the most common symptoms are fever, sickness, and chills.  VRE can also cause skin rashes and swelling.  If the infection continues to worsen, the sufferer may also experience an increase in heart rate and random palpitations.  Most people need antibiotics to clear a VRE infection, making it sometimes hard to treat, as some of the most common antibiotics will not work against this organism.  It is estimated that around 10% of people who are in hospital with a VRE infection, will die from it.

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