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   The challenge with pseudomonas     aeruginosa     

Figure 1  Wounds colonized with pseudomonas aeroginosa often have a characteristic greenish exudate with a distinctive sweetish smell. As with all rules, there are always some exceptions, and sometimes we will not see the tell-tale color of this bacteria or register any particular smell. Often, however, there is a slimish layer covering the wound, which is also very typical for this bacterial strain. Pseudomonas is very good at making biofilms within short periods, making eradicating the bacteria harder. The image below shows the result of using a less appropriate dressing or too long shift intervals. The dressing has not managed the exudate problem well enough, and the inflammation around the lower end of the ulcer is a result of irritating exudate collecting here.

Pseudomonas aeruginosa is a classical opportunistic bacteria that likes moist and warm environments. It is not rare to encounter them in chronic wounds and most often they are only present in small concentrations and do not always pose a problem. When Pseudomonas, however, gets out of control like in the images above you will not achieve wound healing until the bacteria is again under control. Pseudomonas produces toxins that irritate the skin - the resulting inflammation causes further skin breakdown and usually leads to increased amounts of exudate. In this manner, Pseudomonas creates the perfect environment for itself. Typically we see a slimy layer covering these wounds  - this is biofilm - and many antibacterial products have difficulty penetrating the slime. It is therefore important to debride these wounds particularly to remove the biofilm. Do this gently as these inflamed wounds typically are very painful.

Pseudomonas likes to establish itself in wounds with a lot of exudate like large venous ulcers and burns wounds and can really cause havoc here.   However, it can cause issues in any type of chronic wound. As we mentioned earlier it is easy to spot a Pseudomonas problem when you have large amounts of greenish exudate. At other times there may not be tell-tale signs of Pseudomonas presence. Be aware that if you find Pseudomonas in a bacterial swab from a wound it does not necessarily mean that this strain is causing problems in the wound. In general, however, the presence of Pseudomonas in a wound is not preferred and you should try to eradicate it by applying topical antibacterial products. 

If you are planning to do a split skin graft it is essential that you do not have Pseudomonas on the recipient wound. Pseudomonas will lead to graft failure! For this reason many do routine swabs of the recipient wound a few days before the graft is done to ensure that this bacterial strain is not present there. 

Wounds with Pseudomonas are not a specific entity but we have decided to have our own separate chapter about this as Pseudomonas quite often can be encountered in wounds in Africa, particularly those which are extensive and have a lot of exudate. 

Only very rarely do we need to use antibiotics to fight off Pseudomonas aeruginosa. Most often this bacteria is quite happy to simply live on the surface of the wound and only seldomly decides to wander off into the depths of the tissues or spread to other areas of the body. This is not to say that you cannot get life-threatening septicemia from Pseudomonas. Of course, you can - all we are saying is that this is not too common. In most cases, we can control and eradicate Pseudomonas from the wound by using topical antibacterial solutions. 

One of the challenges with Pseudomonas is that it often shows resistance to several types of antibiotics and is also quite resistant to several topical antimicrobial agents. For example, using topical solutions like super-oxidized water or PHMB solutions will usually not be sufficient- at least not in cases as shown in figure 1. These agents will neutralize some of the Pseudomonas, yes, but their mode of action is too short to be effective. Most topical antibacterial rinsing solutions only have an effect for a few hours after the wound has been irrigated and then the bacteria are back to multiplying and enjoying themselves. 

Using vinegar against Pseudomonas aeruginosa

Globally, the standard treatment of Pseudomonas in wounds is using 3,5%-5% vinegar ( acetic acid). It seems that you need at least a 3,5% concentration for this to be effective. Over 5% concentration can cause unnecessary pain to the patient and may also irritate the wound. Acetic acid is a well-known and documented remedy against this bacterial strain ( and against most types of pathogenic bacteria). In addition, it is important to try to debride most of the slimy layer on the wound and it is essential that we have excellent control over the exudate. This is achieved by using the best absorbable dressing you can get/afford and by changing the dressing very often at the start. 

The problem with vinegar is that its effect is also not long-lasting. A few hours after application the effect is gone. Usually, we soak cotton gauze with the diluted vinegar and apply this to the wound- leaving it in place for at least twenty minutes. This has to be done at minimum once daily, preferably even twice daily if that is practically possible. Understandably it is ideal if a spouse, other family, or relatives can help the patient with the procedure at home. Note that we wrote earlier that we use a 3,5%-5% vinegar solution for this purpose. The reason that we have a choice of concentrations is simply that vinegar can give a burning sensation in the wound when applied. Ideally, we should use 5% vinegar as this is more effective but if the patient complains of pain when using this concentration try 3,5% instead. Note that we use regular clear household vinegar for this purpose. Some pharmacies sell sterile medical-grade vinegar but this is unnecessary for this purpose. Other types of household vinegar like apple-cider vinegar etc. should not be used as they may contain other irritating substances. 

Commonly, clear household vinegar is sold at concentrations around 7%. This will be clearly stated on the label. Be aware that some shops also sell clear vinegar concentrate which may have a concentration of about 35%! You must obviously never use this strong vinegar in a wound! Also, regular household vinegar at 7% needs to be diluted to achieve a concentration of between 3,5-5%. See Table 1 for recommended dilutions. 

The vinegar treatment should be continued for at least 7-10 days to eliminate Pseudomonas. You have to be patient because in the first days you will see no improvement at all. Again, it is very important that the vinegar treatment is done daily otherwise the treatment will be ineffective in our experience. Even applying the vinegar every second day is not often enough. The very best is to apply it twice daily. When starting with the vinegar treatment we recommend you try the 3,5% solution first to check that the patient tolerates this well. If the patient does not complain about any strong pain you may try the 5% solution next time. 

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Figure 2 Regular clear household vinegar is appropriate for chronic wounds and is cheaply available anywhere in Africa. Be aware that this comes at different concentrations, often at around 7%, and it needs to be diluted to achieve the desired 3.5-5% solutions we use in wound care. Note that some shops even sell vinegar as a 35% concentrate - this will have to be diluted a lot! Always read the label first!

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Table 1 Examples of how to dilute household vinegar to achieve the concentrations we use in wound care. For example - if we want to use the 3,5% solution and have bought 7% vinegar, we need to dilute this with a ratio of five parts of vinegar with two parts of water. If you have purchased a vinegar concentrate at 35%, you will need to dilute it much more. Use regular medical saline water of 0,9%  to dilute the vinegar.

Ideally, we should try to make a gel product of vinegar that can be left on the wound, hopefully giving a longer-lasting antibacterial effect. There have been some efforts to make this sort of gel. Arne Langøen, assistant professor at the Western University of Norway, has produced a promising vinegar-zinc gel that we tested for over a year with good results. The product is currently used at the wound center at Kisubi Hospital in Uganda, and we are awaiting the latest results from their experiences. As this is not available to most healthcare professionals in Africa, you can try to make your own vinegar gel by mixing either 3% or 5% vinegar solution with methyl-cellulose, a thickening powder. Methyl-cellulose is considered a safe product used widely in pharmaceuticals, cosmetics, and the food industry. It can be cheaply obtained also in Africa, for example, from pharmacies. You will have to experiment with the formula- only a little methylcellulose is needed to thicken the vinegar solution. In the future, we will post a more detailed recipe here.

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Figure 3   There are commercially available vinegar-based gels available today. An example is the Optima pH product range. It has a gel-like consistency and can be left on the wound between dressing changes. This product has to be applied at least once daily for optimal antimicrobial effect. We have recently done an in-vitro evaluation of this product, and our results show that it does not necessarily eliminate all strains of bacteria since it only contains 1% vinegar. However, this type of product is helpful for gently cleaning wounds. Since the vinegar concentration is relatively low, most patients do not feel any discomfort from the product. Note that this product is currently only available in Europe. However, it is the sort of product that has good potential for the African wound care sector. It is cheap, easily stored at room temperature, and a bottle will last you a long time. Incidentally, it is also used a lot in the agricultural/veterinary sector in the hope of reducing the amount of antibiotics used here. 

10% Povidone-Iodine (PI) against Pseudomonas

Vinegar does work against Pseudomonas- but it has some disadvantages.  For one, many patients experience pain during the application of vinegar, even when we are using a 3,5% concentration. Secondly, the effect of vinegar is short-lived. Several studies show that the pH-lowering effect of vinegar lasts at most one hour after the vinegar has been applied. To be effective the vinegar dressing should be applied often, preferably twice daily at the start. Since the vinegar-soaked gauze needs to stay in place for at least twenty minutes this is a time-consuming procedure.

There is a fair amount of documentation about using 10% PI against Pseudomonas. Its effectiveness seems to be equal to that of vinegar. The PI has several advantages. Gauze soaked in PI can be left in place during the entire treatment thus delivering antimicrobial activity over a longer time. We also find that PI cleans up the wound faster than the vinegar treatments - especially during the first days of treatment PI seems to work more rapidly. More important though, most patients do not feel any discomfort when PI is applied. 

As with vinegar, for PI to be effective against Pseudomonas the PI-soaked gauze should be changed frequently- at least daily, preferably twice daily at the start. The treatment time is the same - at least 7-10 days are required to eliminate most of the bacteria. Note that we write " most of the bacteria."  Usually, some Pseudomonas bacteria will manage to hide in areas with slime and dead tissue where the PI does not penetrate well enough. the same applies to the vinegar treatment. However, after 7-10 days of treatment, the Pseudomonas should be under control and a more favorable microbiological balance should appear in the wound.  At this point you could go over to another type of antimicrobial like a silver-based product for example, just to make sure that bacterial numbers are kept low.  Usually, however, at this point, it is sufficient to keep the wound dry and thus remove the environment which Pseudomonas likes. 

Pseudomonas is a rather tricky bacteria and sometimes the vinegar or PI treatment does not work sufficiently well. We have had a few cases where povidone-iodine treatment was not successful while it worked superbly on other patients. This is one of the mysteries of wound care - sometimes established dressings do not perform as expected. If you have used vinegar without success try PI and vice-versa. If these treatments do not work as effectively as expected this is usually due to the high amount of exudates that dilute the antibacterial effect or due to dressings being left on for too long. 

Other remedies against pseudomonas aeroginosa


Silver-based antimicrobials

We have also had good results with using silver products against Pseudomonas- particularly Silverlon products, which have a higher concentration of silver ions. Over a day, Pseudomonas will have produced a slimy layer, making it more difficult for the silver to reach the wound bed. As with all products we use to eradicate Pseudomonas, you should change the silver dressings daily for the first ten days. After that period, you can usually extend the dressing change intervals.


Honey has been documented to have a good effect on Pseudomonas. While we use vinegar ( or iodine) as our first treatment choice against Pseudomonas, you may face a situation where your patient does not tolerate the vinegar treatment because the wound is too painful. Then we have to look at alternatives. 

Honey does work, but the main issue is that the osmotic effect increases the amount of exudate from the wound. In a larger ulcer that already has much exudate, honey may double the exudate amount, particularly at the start of the treatment. You will have to accommodate that by changing your dressing very frequently, maybe several times a day. Apply new honey at each dressing change. 

Wood ash, charcoal and activated charcoal

In very challenging cases, we have sometimes sprinkled a 1-centimeter layer of activated charcoal powder on ulcers heavily colonized with Pseudomonas where other topical treatments had failed. We have occasionally used this treatment variant in the last twenty years with good results. It seems that Pseudomonas does not like activated charcoal at all. The charcoal itself does not eradicate the Pseudomonas - you will also need the vinegar or Povidone-Iodine treatment. Still, it speeds things up, and we use it when the vinegar/PI method does not show encouraging results within about a week.


The activated charcoal is thought to neutralize toxins and other unfavorable substances that Pseudomonas produces in the wound. You have most likely heard before that special dressings containing activated charcoal can help reduce foul odor coming from wounds. But with the method described above, we are taking it one step further - we actually deposit the activated charcoal directly onto the wound bed. This is not something that we have come about by ourselves. Using charcoal ash to treat wounds is probably a method that dates a long time back in history.  And we are not alone - we continuously receive reports where healthcare workers, especially in the most rural areas, use charcoal ash directly on the wound bed.

What is the difference between regular charcoal ashes and activated charcoal? Ordinary charcoal is made by burning wood without oxygen. Activated carbon is a similar process but uses much higher temperatures and often with the addition of substances like chloride. This makes the active charcoal particles more porous and increases their absorptive properties. In cosmetics and healthcare products, activated carbon is preferred. Also, regular charcoal ash is not as pure, and depending on the type of wood that was used as a source, it may cause allergic reactions.

Activated charcoal is usually available in Africa also- you may find it in pharmacies, beauty - or nutritional health shops.   It may go under the name of activated carbon, which is the same thing. Ideally, you want to use a powder that is not too fine, as this will be more difficult to rinse away ( the fine powder adheres more to the wound). We find that a somewhat coarser powder is better suited for this purpose as it rinses off easier. Also, in our experience, we find that the coarser powders have a slightly abrasive effect which gently and painlessly aids in the debridement of the wound bed. 


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Figure 4  Activated charcoal is usually cheaply available in most cities in Africa and can also be obtained from online stores. We prefer the slightly coarse powder to be more easily rinsed off the wound bed at dressing changes.  

The drawback to using charcoal is that a) it is not adequately documented, and b) it is a messy method with small grains of charcoal ending up on the floor of your workplace. Also, the method is not suitable for undermined ulcers with fistulas or other deep channels as you may not be able to retrieve the charcoal again. The method is best for large ulcers with a flat surface.


After applying the vinegar-soaked gauze we sprinkle a liberal layer of activated charcoal onto the entire wound area. If you are using Povidone- Iodine you need to use less charcoal so that the iodine can actually reach the wound bed too. Note that charcoal actually has fairly little absorption capabilities- exudate will just flow past it so you still need a good absorptive dressing on the outside. At each session irrigate away and gently remove most of the charcoal grains ( for example with a curette) and repeat the vinegar/ PI process followed by a new application of charcoal.


You need not be hysterical about removing all charcoal at each session - some charcoal residues are no problem and the surface of the wound will slowly expel them from the wound over time. Usually, a week of charcoal treatment is sufficient. As always when we tell you about some improvised treatment method: we are not telling you that you should go about sprinkling activated charcoal on the wounds of your patients from now on. We simply want to share our experiences and leave it up to your own discrimination whether you would like to use the method on your own responsibility.  

Be aware that sometimes activated charcoal can interact with the exudate to form a tough, crusty layer. This may firmly adhere to the wound bed and cause pain upon removal. This is an undesirable effect. In our experience, we see this phenomenon more often when the exudate is thick and protein-rich and less frequently when the exudate is watery. Therefore, we advise you to test the charcoal on a smaller area of the ulcer first and inspect the wound already the following day. 

In a separate chapter on what to use as wound care dressings in settings with extremely limited resources, we will discuss the topic of charcoal further. You can for example also use a poultice mixture of honey and activated carbon in a 50:50 ratio on chronic wounds with pseudomonas. Again, there is little scientific documentation for this and we simply report on what other healthcare workers in Africa have tried.

Other alternatives are silver-coated dressings or iodine-impregnated dressings if these are available to you. There are also some contact-layer dressings that contain a combination of activated charcoal and silver.


If you do not have access to activated charcoal you can try regular wood ash from a fireplace.  Sieve the grey ash through a fine sieve and sprinkle the ash directly into the wound. Repeat this daily and rinse away the ash from the previous day using water. 

Video 1  A video filmed in a rural area in Uganda where dry activated charcoal is applied to a chronic leg ulcer using only very simple remedies like cotton gauze and a sheet of plastic bag on the front side.  copyright: charcoalhouse

Antibiotic treatment of Pseudomonas

In most cases with Pseudomonas, we do not need to use antibiotics. Mostly the Pseudomonas is present on the wound's surface and can be eradicated using the products mentioned earlier and a dose of patience. However, sometimes there may be signs of deeper infection suggesting that the Pseudomonas has entered the subcutaneous layers and will not be accessible to topical products. In these cases, we need to use a course of antibiotics.


Be aware that antibiotic treatment of Pseudomonas often is tricky. There are only a few good antibiotics available for eradicating Pseudomonas, and many of them can only be administered intravenously or intramuscularly. One exception is Ciprofloxacin - which can be given orally. Unfortunately, many strains of Pseudomonas are resistant to this drug already. If you have a strain that isn't resistant, you can almost be sure that it will become resistant in the course of latest two weeks of treatment. It is crucial that you take a bacterial swab at the start of the treatment to determine the resistance of the strain- otherwise, you will end up wasting the patient's time with an antibiotic that may be useless and only cause side effects. 

Dressing choice when pseudomonas is a problem

Pseudomonas aeruginosa thrives best in warm and moist environments. We can use this to our benefit. If we keep the wound area dry, the bacteria will not thrive as well anymore.   To achieve this, we use superabsorbent dressings. These modern dressings absorb the exudate and lock it into the core of the dressing, keeping the wound area dry. They basically work like a very good diaper from a reputable brand. But even the best super absorbable dressing is not a resting pillow - you may have to change even these more often than you like- especially at the start. This can make the treatment costly. Some workarounds with heavy exudate are actually to use diapers! As the amount of exudate gradually decreases, you will be able to use cheaper, less absorbent dressings over time.

In settings with minimal resources, you may only have cotton gauze available. Then you have to make this work. You will succeed with simple cotton gauze if you change it very often.   Contrary to modern dressings, cotton gauze gets dripping wet when saturated with exudate. A wet gauze on the skin will quickly cause skin breakdown, and the ulcer can increase rapidly in size over a short time. So if you only have gauze at hand, you may have to change the dressing many times a day if there is much exudate. Do not despair - within a few days of very frequent dressing changes, the exudate amount will gradually be reduced, and you can increase the dressing change intervals accordingly.

Remember- leg wounds with high exudate will respond better if compression therapy is used! We know that many people in Africa cannot afford compression bandages or stockings, which is a real challenge as there are few real alternatives to this. Please also refer to our chapter on compression under "Tools" in the menu. 

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