Gangrene

(Gas Gangrene)

In this factsheet:
• The Facts on Gangrene
• Causes of Gangrene
• Symptoms and Complications of Gangrene
• Diagnosing Gangrene
• Treating and Preventing Gangrene

The Facts on Gangrene

Gangrene is defined as the destruction of tissue and develops when the blood supply to an affected body part is cut off because of various factors such as infection, vascular disease, or trauma. Gangrene can involve any body part, but the most commonly affected areas are the extremities (feet, lower, legs, hands).

Causes of Gangrene

Gas gangrene is the most life threatening form of gangrene. It occurs in wounds that are infected by a family of bacteria called Clostridium. At least 20 kinds of Clostridium can cause gas gangrene. What makes the clostridia special is that they are anaerobic - that is, they grow best in the absence of oxygen. Because healthy human tissue is full of oxygen, it's rarely bothered by this bacterium. However, when they do grow, clostridia release gas and poisons into the body. This form of gangrene spreads very quickly, and can cause a rapid death.

Injuries that leave a portion of muscle tissue deprived of oxygen make an ideal home for clostridia. Some of the cells in a wound are already dead, and the infection starts in these. "Crush" injuries are most likely to cut off blood supply to a large amount of tissue, and are most prone to gangrene. The infection usually strikes the extremities, where blood supply is most easily cut off. Car accidents, for instance, often cause crush injuries to the lower legs - exactly the sort of wound that clostridia find most suitable.

Surgery can also produce areas of vulnerable tissue. Conditions favourable to clostridia are most common in people who have pre-existing vascular problems, or who have many of the risk factors for heart disease. For example, high cholesterol can make blood more likely to clot. A person with high cholesterol is more likely to have more clotted blood vessels after surgery. The tissue that's normally fed by those blood vessels can run out of oxygen, allowing bacteria to multiply.

There are other causes of gangrene that aren't associated with clostridia. Serious diseases that interfere with blood flow can cut off oxygen supply to the extremities even when there's no trauma or injury. For example, peripheral vascular disease in which blood flow to the legs is poor can lead to a severely ischemic foot or leg (deprived of blood or oxygen) resulting in gangrene. People with diabetes, for instance, are prone to gangrene in the foot. Diabetes-related infections are the most common reason for foot amputation. Severe frostbite (due to over-exposure to the cold) can also lead to gangrene due to lack of proper blood flow to the tissues.

Symptoms and Complications of Gangrene

Areas affected by gangrene are usually warm and swollen. The skin may be pale at first, but soon turns red or brown and finally greenish-black. Sometimes, a brown fluid forms under the skin, causing large skin bubbles to rise. If clostridia are the cause of the gangrene, the gas produced by the bacteria can be seen bubbling in these pockets. It often smells foul.

The substances produced by the bacteria are highly toxic to human tissue and kill cells ahead of the infection, keeping the oxygen supply low. Unless the infection is stopped, these bacterial toxins soon reach the bloodstream and begin to poison the vital organs (see Toxic Shock), with the kidneys failing first.

Blood poisoning; Bacteremia with sepsis

Blood poisoning; Bacteremia with sepsis

Causes:
Septicemia is a serious, life-threatening infection that gets worse very quickly. It can arise from infections throughout the body, including infections in the lungs, abdomen, and urinary tract. It may come before or at the same time as infections of the bone (osteomyelitis), central nervous system (meningitis), or other tissues.

Symptoms

Septicemia can begin with spiking fevers, chills, rapid breathing, and rapid heart rate. The person looks very ill.The symptoms rapidly progress to shock with decreased body temperature (hypothermia), falling blood pressure, confusion or other changes in mental status, and blood clotting problems that lead to a specific type of red spots on the skin (petechiae There may be decreased or no urine output. and ecchymosis).

Exams and Tests

Physical examination may show:

• Low blood pressure
• Low body temperature or fever
• Signs of associated disease (such as meningitis, epiglottitis, pneumonia, or cellulitis)

Tests that can confirm infection include:

• Blood culture
• Urine culture
• CSF culture
• Culture of any suspect skin lesion
• CBC
• Platelet count
• Clotting studies
  • PT
  • PTT
  • Fibrinogen levels
• Blood gases

Treatment

Septicemia is a serious condition that requires a hospital stay. You may be admitted to an intensive care unit (ICU).
Fluids and medicines are given by an IV to maintain the blood pressure.
Oxygen will be given. Antibiotics are used to treat the infection.
Plasma or other blood products may be given to correct any clotting abnormalities.

Outlook (Prognosis)

Septic shock has a high death rate, exceeding 50%, depending on the type of organism involved. The organism involved and how quickly the patient is hospitalized will determine the outcome.

Possible Complications

Septicemia can rapidly lead to adult respiratory distress syndrome (ARDS), septic shock, and death.
Septicemia associated with meningococci can lead to shock, adrenal collapse, and Waterhouse-Friderichsen syndrome.

When to Contact a Medical Professional

Septicemia is not common but is devastating. Early recognition may prevent progression to shock.
Seek immediate care if:
- A person has a fever, shaking chills, and looks acutely ill

- There are signs of bleeding into the skin

- Any person who has been ill has changes in mental status

Call your health care provider if your child is not current on vaccinations.

Prevention

Appropriate treatment of localized infections can prevent septicemia. The Haemophilus influenza B (HIB) vaccine has already reduced the number of cases of Haemophilus septicemia and is a routine part of the recommended childhood immunization schedule.

Children who have had their spleen removed or who have diseases that damage the spleen (such as sickle cell anemia) should receive pneumococcal vaccine. Pneumococcal vaccine is not part of the routine childhood immunization schedule.

Persons who are in close contact with someone with septicemia may be prescribed preventative antibiotics.

PSEUDOMONAS INFECTION

A pseudomonas infection is caused by a bacterium, Pseudomonas aeruginosa, and may affect any part of the body. In most cases, however, pseudomonas infections strike only persons who are very ill, usually hospitalized.

Description

P. aeruginosa is a rod-shaped organism that can be found in soil, water, plants, and animals. Because it rarely causes disease in healthy persons, but infects those who are already sick or who have weakened immune systems, it is called an opportunistic pathogen. Opportunistic pathogens are organisms that do not ordinarily cause disease, but multiply freely in persons whose immune systems are weakened by illness or medication. Such persons are said to be immunocompromised. Patients with AIDS have an increased risk of developing serious pseudomonas infections. Hospitalized patients are another high-risk group, because P. aeruginosa is often found in hospitals. Infections that can be acquired in the hospital are sometimes called nosocomial diseases.

Of the two million nosocomial infections each year, 10% are caused by P. aeruginosa. The bacterium is the second most common cause of nosocomial pneumonia and the most common cause of intensive care unit (ICU) pneumonia. Pseudomonas infections can be spread within hospitals by health care workers, medical equipment, sinks, disinfectant solutions, and food. These infections are a very serious problem in hospitals for two reasons. First, patients who are critically ill can die from a pseudomonas infection. Second, many Pseudomonas bacteria are resistant to certain antibiotics, which makes them difficult to treat.

P. aeruginosa is able to infect many different parts of the body. Several factors make it a strong opponent. These factors include:

• the ability to stick to cells
• minimal food requirements
• resistance to many antibiotics
• production of proteins that damage tissue
• a protective outer coat

Infections that can occur in specific body sites include:

• Heart and blood. P. aeruginosa is the fourth most common cause of bacterial infections of the blood (bacteremia). Bacteremia is common in patients with blood cancer and patients who have pseudomonas infections elsewhere in the body. P. aeruginosa infects the heart valves of intravenous drug abusers and persons with artificial heart valves.
• Bones and joints. Pseudomonas infections in these parts of the body can result from injury, the spread of infection from other body tissues, or bacteremia. Persons at risk for pseudomonas infections of the bones and joints include diabetics, intravenous drug abusers, and bone surgery patients.
• Central nervous system. P. aeruginosa can cause inflammation of the tissues covering the brain and spinal cord (meningitis) and brain abscesses. These infections may result from brain injury or surgery, the spread of infection from other parts of the body, or bacteremia.
• Eye and ear. P. aeruginosa can cause infections in the external ear canal--so-called "swimmer's ear"-- that usually disappear without treatment. The bacterium can cause a more serious ear infection in elderly patients, possibly leading to hearing problems, facial paralysis, or even death. Pseudomonas infections of the eye usually follow an injury. They can cause ulcers of the cornea that may cause rapid tissue destruction and eventual blindness. The risk factors for pseudomonas eye infections include: wearing soft extended-wear contact lenses; using topical corticosteroid eye medications; being in a coma; having extensive burns; undergoing treatment in an ICU; and having a tracheostomy or endotracheal tube.
• Urinary tract. Urinary tract infections can be caused by catheterization, medical instruments, and surgery.
• Lung. Risk factors for P. aeruginosapneumonia include: cystic fibrosis; chronic lung disease; immunocompromised condition; being on antibiotic therapy or a respirator; and congestive heart failure. Patients with cystic fibrosis often develop pseudomonas infections as children and suffer recurrent attacks of pneumonia.
• Skin and soft tissue. Even healthy persons can develop a pseudomonas skin rash following exposure to the bacterium in contaminated hot tubs, water parks, whirlpools, or spas. This skin disorder is called pseudomonas or "hot tub" folliculitis, and is often confused with chickenpox. Severe skin infection may occur in patients with P. aeruginosa bacteremia. The bacterium is the second most common cause of burn wound infections in hospitalized patients.

Causes and symptoms

P. aeruginosa can be sudden and severe, or slow in onset and cause little pain. Risk factors for acquiring a pseudomonas infection include: having a serious illness; being hospitalized; undergoing an invasive procedure such as surgery; having a weakened immune system; and being treated with antibiotics that kill many different kinds of bacteria (broad-spectrum antibiotics).

Each of the infections listed above has its own set of symptoms. Pseudomonas bacteremia resembles other bacteremias, producing fever, tiredness, muscle pains, joint pains, and chills. Bone infections are marked by swelling, redness, and pain at the infected site and possibly fever. Pseudomonas meningitis causes fever, headache, irritability, and clouded consciousness. Ear infection is associated with pain, ear drainage, facial paralysis, and reduced hearing. Pseudomonas infections of the eye cause ulcers that may spread to cover the entire eye, pain, reduced vision, swelling of the eyelids, and pus accumulation within the eye.

P. aeruginosa pneumonia is marked by chills, fever, productive cough, difficult breathing, and blue-tinted skin. Patients with cystic fibrosis with pseudomonas lung infections experience coughing, decreased appetite, weight loss, tiredness, wheezing, rapid breathing, fever, blue-tinted skin, and abdominal enlargement. Skin infections can cause a range of symptoms from a mild rash to large bleeding ulcers. Symptoms of pseudomonas folliculitis include a red itchy rash, headache, dizziness, earache, sore eyes, nose, and throat, breast tenderness, and stomach pain. Pseudomonas wound infections may secrete a blue-green colored fluid and have a fruity smell. Burn wound infections usually occur one to two weeks after the burn and cause discoloration of the burn scab, destruction of the tissue below the scab, early scab loss, bleeding, swelling, and a blue-green drainage.

Diagnosis

Diagnosis and treatment of pseudomonas infections can be performed by specialists in infectious disease. Because P. aeruginosa is commonly found in hospitals, many patients carry the bacterium without having a full-blown infection. Consequently, the mere presence of P. aeruginosa in patients does not constitute a diagnostic finding. Cultures, however, can be easily done for test purposes. The organism grows readily in laboratory media; results are usually available in two to three days. Depending on the location of the infection, body fluids that can be tested for P. aeruginosa include blood, urine, cerebrospinal fluid, sputum, pus, and drainage from an infected ear or eye. X rays and other imaging techniques can be used to assess infections in deep organ tissues.

Treatment

Medications

Because P. aeruginosa is commonly resistant to antibiotics, infections are usually treated with two antibiotics at once. Pseudomonas infections may be treated with combinations of ceftazidime (Ceftaz, Fortraz, Tazicef), ciprofloxacin (Cipro), imipenem (Primaxin), gentamicin (Garamycin), tobramycin (Nebcin), ticarcillin-clavulanate (Timentin), or piperacillin-tazobactam (Zosyn). Most antibiotics are administered intravenously or orally for two to six weeks. Treatment of an eye infection requires local application of antibiotic drops.

Surgery

Surgical treatment of pseudomonas infections is sometimes necessary to remove infected and damaged tissue. Surgery may be required for brain abscesses, eye infections, bone and joint infections, ear infections, heart infections, and wound infections. Infected wounds and burns may cause permanent damage requiring arm or leg amputation.

Prognosis

Most pseudomonas infections can be successfully treated with antibiotics and surgery. In immunocompromised persons, however, P. aeruginosa infections have a high mortality rate, particularly following bacteremia or infections of the lower lung. Mortality rates range from 15 to 20% of patients with severe ear infections to 89% of patients with infections of the left side of the heart.

Prevention

Most hospitals have programs for the prevention of nosocomial infections. Patients with cystic fibrosis may be given periodic doses of antibiotics to prevent episodes of pseudomonas pneumonia.

Minor skin infections can be prevented by avoiding hot tubs with cloudy water; avoiding public swimming pools at the end of the day; removing wet swimsuits as soon as possible; bathing after sharing a hot tub or using a public pool; cleaning hot tub filters every six weeks; and using appropriate amounts of chlorine in the water.

Key Terms

Bacteremia

Bacterial infection of the blood.

"Hot tub" folliculitis

A skin infection caused by that often follows bathing in a hot tub or public swimming pool.

Immunocompromised

Having a weak immune system due to disease or the use of certain medications.

Nosocomial infection

An infection that is acquired in the hospital.

Opportunistic

Causing disease only under certain conditions, as when a person is already sick or has a weak immune system.

Pathogen

Any microorganism that produces disease.

MRSA stands for methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infection

Written by Dr Alan Johnson, clinical scientist

What is MRSA? Staphylococcus aureus is a species of bacterium commonly found on the skin and/or in the noses of healthy people. Although it is usually harmless at these sites, it may occasionally get into the body (eg through breaks in the skin such as abrasions, cuts, wounds, surgical incisions or indwelling catheters) and cause infections. These infections may be mild (eg pimples or boils) or serious (eg infection of the bloodstream, bones or joints). MRSA stands for methicillin-resistant Staphylococcus aureus, which is a type of Staphylococcus aureus that is resistant to the antibacterial activity of methicillin and other related antibiotics of the penicillin class. The treatment of infections due to Staphylococcus aureus was revolutionised in the 1940s by the introduction of the antibiotic penicillin. However,, most strains of Staphylococcus aureus are now resistant to penicillin. This is because Staphylococcus aureus can make a substance called ß-lactamase (pronounced beta-lactamase), that degrades penicillin, destroying its antibacterial activity. In the early 1960s, a new type of penicillin antibiotic called methicillin was developed. Methicillin was not degraded by ß-lactamase and so could be used to treat infections due to ß-lactamase-producing strains of Staphylococcus aureus. Subsequently, methicillin was replaced by newer and better penicillin-type antibiotics (such as flucloxacillin) that were also not affected by ß-lactamase. Unfortunately, shortly after the introduction of methicillin, certain strains of Staphylococcus aureus emerged that were resistant to methicillin (and also to the newer drugs such as flucloxacillin) These methicillin-resistant Staphylococcus aureus became known as 'MRSA' for short, and although methicillin is no longer prescribed, having been replaced by flucloxacillin, the term MRSA continues to be used. Although other types of antibiotics can still be used to treat infections caused by MRSA, these alternative drugs are mostly not available in tablet form and must be administered through a drip inserted into a vein or by injection. MRSA infections in hospital MRSA infections are a particular problem in hospitals. As with ordinary strains of Staphylococcus aureus, some patients harbour MRSA on their skin or nose without harm (such patients are said to be 'colonised'). However, these patients may develop infections if the MRSA spread to other parts of the body (eg if MRSA spread from the colonised nose to a wound). When this happens the resulting infection is described as 'endogenous'. Some patients are at increased risk of developing infection. They include those with breaks in their skin due to wounds or indwelling catheters which allow MRSA to enter the body, and those with certain types of deficiency in their immune system, such as low numbers of white cells in their blood. Individuals colonised with MRSA may also serve as a 'reservoir' of MRSA that may spread to other patients. This may happen, for example, if hospital staff attending to a colonised or infected patient become contaminated or colonised with MRSA themselves (often only briefly) and spread the bacteria to other patients with whom they subsequently have contact. These patients may in turn become colonised and/or infected. The spread of MRSA (or for that matter other bacteria) between patients is called cross-infection. In addition, MRSA may be spread via contaminated equipment or through the environment. Some strains of MRSA are particularly successful at spreading between patients and may also spread between hospitals, presumably when colonised patients or staff move from one hospital to another. These strains are known as epidemic MRSA (or EMRSA for short). During the 1990s there was a marked increase in infections caused by MRSA in hospitals in the UK due to the emergence and spread of two particular stains of EMRSA known as EMRSA-15 and EMRSA-16. MRSA infections in the community Patients may be colonised with MRSA when they leave hospital, and there has long been concern that MRSA might spread from hospitals into the community. In recent years increasing numbers of cases of MRSA infection in the community have been seen in many countries around the world, particularly the USA. However, investigations of these cases have shown that in many instances, the strains of MRSA found in patients in the community are distinct from those strains seen in hospitals and it now appears that these so called 'community-associated MRSA' have evolved independently of hospital MRSA. Although infections with 'community-associated MRSA' occur frequently in some countries, they are uncommon in the UK. Studies in the USA and other countries have shown that the 'community-associated MRSA' often cause infections in previously healthy individuals who lack the risk factors seen in hospitalised patients. Many of these strains have a toxin called the Panton-Valentine leucocidin (usually referred to as 'PVL') which may contribute to their increased ability to cause infections. Luckily, 'community-associated MRSA' are frequently susceptibility to a wide range of antibiotics (apart from those belonging to the penicillin class). As further evidence of their independent evolution, 'community-associated MRSA' are generally susceptible to a wider range of antibiotics than are hospital strains. Can the spread of MRSA be controlled? There are several steps that may be undertaken to minimise the spread of MRSA between patients. Hospital staff should wash their hands scrupulously before and after having physical contact with patients, using soap or rapidly acting antibacterial alcohol solutions. Patients colonised or infected with MRSA may be kept away from other patients by being placed in separate rooms, either alone or with other patients who also have MRSA. Access to such rooms should be restricted to essential personnel. Hospital staff should wear gloves and disposable gowns prior to having physical contact with MRSA patients. Before leaving the room, they should discard these safely, and wash their hands. Visitors and carers likely to have a lot of physical contact with patients should also wear disposable gloves and gowns. All visitors should wash their hands before leaving the room. MRSA can survive on inanimate objects or surfaces such as linen, sinks, floors and even mops used for cleaning. For this reason, areas where MRSA patients are nursed should be thoroughly cleaned using disinfectants. How is infection or colonisation with MRSA diagnosed? To diagnose MRSA infection, specimens such as a swab of an infected wound or a sample of blood are taken from the patient. These are sent to a microbiology laboratory, where bacteria present in the specimen are cultured and identified. This process may take several days. In addition, sometimes more rapid tests which detect the DNA (the genetic material) typically found in MRSA may be undertaken. Colonisation with MRSA is detected similarly, using swabs of a person's skin or from the inside of the nose. How is MRSA treated? Patients colonised with MRSA Patients colonised with MRSA may have a special antibiotic called mupirocin applied onto their skin (Bactroban) or the inside of their nose (Bactroban nasal). This helps to eliminate the MRSA and reduces the risk of the bacteria spreading either to other sites on the patient's body, where they might cause infection, or to other patients. Some strains of MRSA are, however, resistant to mupirocin. Individuals colonised with MRSA may also wash their skin and hair with suitable disinfectants, such as chlorhexidine. Patients infected with MRSA Patients with infections due to Staphylococcus aureus often need antibiotics. Infections due to normal strains of Staphylococcus aureus are often treated with flucloxacillin (eg Floxapen), but this is ineffective against MRSA. To make matters worse, MRSA are often also resistant to other types of antibiotics such as erythromycin (eg Erythroped) and ciprofloxacin (eg Ciproxin). Although MRSA are resistant to many drugs, most remain susceptible to the antibiotics vancomycin and teicoplanin (Targocid). Infections due to MRSA are therefore often treated with one or other of these drugs. Both must be administered by infusion or injection, and for this reason, they are used for treatment only in hospitalised patients. Injection of vancomycin into muscle is painful and thus not used, while rapid administration into a vein may produce an allergic-type reaction (the so-called 'red man' syndrome). To overcome these problems, vancomycin must be given by slow infusion into a vein. In contrast, teicoplanin may be safely administered by injection into muscle or rapid infusion into a vein. A very few MRSA resistant to vancomycin and/or teicoplanin have been found in the USA and although there is concern that they may become more common, there is no evidence of this happening to date. Fortunately, in the last few years further antibiotics that are active against MRSA have been developed and licensed for clinical use. One such drug, called linezolid (Zyvox) may be given either by intravenous infusion (in severely ill patients) or in tablet form. Clinical trials have so far shown it is useful (either alone or in combination with other antibiotics) for the treatment of pneumonia and skin and soft tissue infections. More recently, another drug called daptomycin (Cubicin) has been licensed for the treatment of skin, soft tissue, heart and blood infections including those caused by MRSA.