There are many different strains of MRSA, in all about 19 different versions. CA - MRSA (Community Acquired) now represents the greatest threat.
In San Francisco, the USA-300, PVL strain of MRSA, which is a type of 'flesh-eating' bacterial infection, has been reported. However, these bacterium do not 'eat' the flesh, they emit toxins which kill your blood cells and it look like they are being eaten.
Extract from: http://www.mrsamedical.com/
An explanation of how MRSA emerged and ways in which it causes infection.
MRSA
Methicillin Resistant Staphylococcus Aureus - is the medical term for MRSA, also known as "The Superbug." It belongs to the Staphylococcus Aureus family of bacterium. There is no doubt that this bacterium has always been with us. Obviously it was not recognised until advances were made in medical detection of bacterium that cause infections.
Staphylococcus Aureus causes many bacterial infections. These can be: Boils, Carbuncles, Infected Wounds, Deep Abscesses and most worryingly, infection of the Blood Stream, which is medically termed as Bacteraemia.
Blood stream infection is also sometimes called Septicaemia, this is of greater severity and clinical significance. A wide variety of bacterium can cause Bacteraemia but one of the most common is Staphylococcus Aureus. This is a very difficult situation for treatment or cure.
The symptoms though, are not specific to MRSA. They can be the same for other bacterium that cause Septicaemia. Symptoms of Septicaemia can include: high fever, rigors (shaking), a raised white blood cell count and disturbance in clotting of the blood, with a tendency to bleed and ultimate failure of the vital organs. This is the kind of MRSA infection that has the highest death rate in England and Wales and also now in the USA.
MRSA bacterium can be found on the skin, in the nose, in wounds and in blood and urine or any other body site. They are most likely to cause infection when a person has a break in their skin or another opening where bacterium can get inside the body.
Common skin conditions caused by MRSA include infected cuts, boils, infected hair follicles, fluid filled blisters (impetigo), or skin sores that look like infected insect bites. Minor MRSA infection can sometimes develop into more serious complications, such as spread of the staph infection to surrounding tissues, serious abscesses, blood, bone, or heart infection.
First descriptions of Staph aureus came in the 1880's. It came to the attention of Medical Practitioners that this bacterium was the most common cause of infection of wounds following surgical procedures. (Surgery, Tube Insertion, Instruments, etc.):
Although Penicillin was discovered by Sir Alexander Fleming in 1929, Penicillin was not Introduced against S. aureus until the 1940's and most strains of S. aureus were found sensitive to its use. Prior to Penicillin, these infections could cause serious, or sometimes, even fatal infection, as no treatment or cure was available before Penicillin.
Unfortunately, when Penicillin was used for treatment of these staph infections, a few strains of Staph aureus made a protective enzyme called Penicillinase, which broke down the penicillin and protected the Staph aureus bacterium. Beta-lactamase is a type of enzyme produced by some bacterium that is responsible for their resistance to beta-lactam antibiotics like penicillins, cephalosporins, cephamycins and carbapenems. These antibiotics have a common element in their molecular structure: a four-atom ring known as a beta-lactam. The lactamase enzyme breaks that ring open, deactivating the molecule's antibacterial properties.
These strains had become very resistant to Penicillin and in 1959, approximately 90-95% of all Staph aureus strains which were taken from patients with clinical infections, were Penicillin resistant. The bacterium that caused these infections had become evolutionist in nature. Penicillin was therefore no longer effective for the treatment and cure of these resistant Staph aureus strains.
'Methicillin' was the next medical development and was derived from Penicillin, to treat these evolutionist Staph aureus strains. It was manufactured to combat the degradation of the antibiotic by the newly formed enzyme called Penicillinase. This ensured that the previously "Penicillin Resistant Staphylococcus Aureus," would still be treatable by using this new medical drug. About a year after the initial use of Methicillin, MRSA was discovered in England. Staphylococcus Aureus had again become evolutionist in nature and was now resistant to Methicillin.
There are few reports about MRSA in the 1960's and the 1970's. More appeared during the 1980's. It became massive in the mid-1990's. Epidemic levels of certain strains of MRSA became uncontrollable in medical hospitals throughout the United Kingdom. Many believe that the cause of this outbreak was associated with "new comfortable living habits" and as a result, a reduction in our immune system strength.
These new strains are very infectious and transmit easily. Colonisation was taking place between the Medical staff and patients they were treating. The new strains have the ability to cause very serious infections. These new strains now represent about 50% of the Staph aureus bacterium found in patients with blood stream infections in England, Wales and the USA.
The Staphylococcal Family
Staph aureus is just one of a large family of staphylococcal bacterium. Their normal place of residence is on the human skin. The most common non - Staph aureus Staphylococcus on human skin is called S. Epidermidis. Generally harmless and called part of the 'normal communal flora' of the human body, many S. Epidermidis are also resistant to antibiotics, including methicillin. They have the same resistance mechanism as MRSA and are referred to as MRSE.
Although resident on everyone's skin, but normally harmless, S. Epidermidis causes significant infection if it enters wounds upon medical devices. For Example: Artificial hip joints, heart valves, or when medical staff use intravenous catheters to provide access the bloodstream. Severely ill patients, such as those in intensive medical care units, or those undergoing cancer chemotherapy, are at a greater risk of this sort of infection than most others.
MRSA Colonisation
Staphylococcus aureus of the most common kind, including those strains that are MRSA in nature, can cause a very wide range of infection. These range from Asymptomatic Colonisation, where the MRSA is doing no damage but still has the capability of causing clinical infection, to fatal Septicaemia, which is the most severe form of blood stream infection. Trying to treat or cure Septicaemia is nigh on impossible.
Colonisation Areas
About 30% of the worlds population is colonised by Staph aureus. In Medical Hospitals the percentage is greatly increased, due to more contact with cases of infection. Staph aureus carriage is more likely to be MRSA in hospital populations, more amongst patients and Medical staff, than in the general community. This is because antibiotic-resistant bacterium are encouraged to develop by the use of antibiotics to treat ranges of infections in hospitals. That being said, Community Acquired MRSA - CA-MRSA is also on the increase, especially in countries like; The Middle East, Iraq and Africa.
Carriage sites of MRSA are most commonly in the nose and on the skin, especially in folds, such as the Axilla (armpit) or the groin area. A carrier of MRSA can be a source of infection for themselves. Self inflicted infection. Hip replacement and heart surgery are high risk situations and if pre-screening detects MRSA carriage, medical decontamination with skin and nasal treatment in an isolation ward is recommended before they undergo surgery.
MRSA Mimics
There are no specific 'MRSA diseases' like with Maleria, Tuberculosis or Typhoid. Staph aureus infects a broad range of tissues and bodily systems, often giving ambiguous symptoms that are common to many different infections, caused by many other bacterium.
Infections of Wounds
Staph aureus / MRSA is the most common cause of wound infection - either after accidental injury or medical surgery. This shows as a red and inflamed wound, with yellow pus flowing from the site. This wound may break open, or fail to heal and a wound abscess could develop.
Superficial Types of Ulcers
Pressure, varicose and diabetic ulcers, which are all attributable to a poor blood supply with some superficial skin damage, are often sites of MRSA infection.
Intravenous line infections
MRSA may infect the entrance site of an intravenous line, causing localised inflammation with pus from which the MRSA can enter the blood stream to cause a bacteraemia, more commonly known as a blood stream infection.
Deep Abscesses
If MRSA (or any strain of Staph aureus) spreads from a local site into the blood stream it can lodge at various sites in the body, such as the kidneys, lungs, liver, bones or spleen, etc: This can cause one or more deep abscesses but distant from the original site of infection. These can be painful with a high fever, a high white blood cell count with signs of inflammation near the new infection. The patient will be very unwell and may have rigors (shivers) and low blood pressure (shock). Over a period, the body enters a catabolic state with breakdown of tissue, loss of weight and failure of the essential organs. This is usually linked with an associated septicaemia and by this time, treatment or cure has, in most cases, become impossible.
Read more about CAMRSA PVL and USA 300 here:
http://www.mrsamedical.com/hamrsaandcamrsa.htm