Recent Issues on Superbug and MDR & XDR

SUPERBUG

British dictionary for definition of superbug:-

“An infective microorganism that has become resistant to antibiotics”.

In 1928, when Alexander Fleming first discovered penicillin, a fungal spore capable of killing bacteria, a new age of medicine began. This was the beginning of the age of antibiotics. Its significance was confirmed in 1945 when Fleming received the Nobel Prize for medicine, along with Howard Florey and Ernst Chain, who had proven penicillin’s potential as a therapeutic drug.

By screening soil samples for substances that kill bacteria—the way in which most of these drugs were first developed—scientists created an arsenal of antibiotics to use in the fight against infection.

By 1960, because of the wide variety of antibiotics available, many thought the war against bacteria had been won. From the beginning, however, bacteria were already fighting back. A strain of Staphylococcus aureus (S. aureus) became resistant to penicillin shortly after it began to be widely used in the 1940s. Random genetic mutation is the reason that bacteria become resistant.

Some bacteria can and have developed resistance to most, if not all, the antibiotics that are used against them. The biggest current menaces in hospitals, especially to surgery patients, are strains of none other than S. aureus that have become resistant to methicillin and many other antibiotics (MRSA – methicillin resistant Staphylococcus aureus).

Recently, some strains of MRSA have even developed a resistance to vancomycin, a powerful antibiotic with frequent unpleasant side effects. Vancomycin was used for over 30 years as an antibiotic of last resort before resistance to it emerged.

One major reason for the development of antibiotic-resistant bacteria is the over-prescription of antibiotics, often for ailments they are powerless to fight. Patients see them as “miracle drugs” and demand them from physicians. Under pressure, physicians prescribe them, knowing full well that they will have no beneficial effect.

A second major reason is that patients fail to take the full dose prescribed, which is necessary to totally clear up the infection. Instead, they stop as soon as they begin to feel better.

When improperly used, antibiotics can have three major negative effects. They can:• Lower the body’s immunity • Destroy “good” bacteria in the body that help with digestion • Lead to the development of antibiotic- resistant bacterial strains

1. Staphylococcus aureus(S. aureus, Staph)Staphylococcus aureus is a bacterium that is found on the skin and on mucous membranes, especially in the nose. If it has an opportunity to enter the body it can cause a variety of infections—skin, wound, urinary tract, and blood stream infections, and pneumonia. It can also cause food poisoning. Methicillin is the most commonly used antibiotic to treat staphylococcus infections. However, S. aureus has rapidly developed a strain that is resistant to methicillin. It is known as methicillin-resistant Staphylococcus aureus (MRSA).

Hospital-acquired MRSA can often only be treated with vancomycin, the drug that doctors often call the “antibiotic of last resort.” Cases of MRSA resistant to vancomycin are beginning to appear.

2. EnterococcusEnterococcus is a bacterium that lives in the human digestive tract. Normally benign, it does not cause problems for healthy individuals. It can, however, cause infections in those with compromised immune systems if it enters the bloodstream or urinary tract through a wound. It is a common hospital problem.

Especially dangerous is VRE, or vancomycin-resistant Enterococcus. It causes life-threatening illnesses in the very young, the very old, and the seriously ill. It also readily transfers its resistance gene to both Staphylococcus and Streptococcus bacteria.

3. Streptococcus pneumoniae (Strep) Streptococcus pneumoniae is the leading cause of inner ear infections, sinusitis, pneumonia, and meningitis. Strep was once easily treated with penicillin, but many strains have developed a resistance to it and other antibiotics. In fact, the resistance rate continues to climb rapidly. The routine dosage of antibiotics required to treat childhood ear infections from strep doubled between 1996 and 2001.

4. CampylobacterCampylobacter bacteria cause diarrhea, cramping, abdominal pain, and fever within two to five days after exposure to the organism. The diarrhea may be bloody and can be accompanied by nausea and vomiting. The illness typically lasts one week. In persons with compromised immune systems, Campylobacter occasionally spreads to the bloodstream and causes a serious life-threatening infection. This is the disease that is most commonly a result of handling uncooked or improperly prepared chicken.

The antibiotics most commonly used to treat severe cases of Campylobacter are erythromycin and quinolones like fluoroquinolone. Campylobacter in North America is beginning to show resistance to quinolones, which are a class of antibiotic given to both humans and animals.

5. Clostridium difficile (C. difficile) Clostridium difficile causes intestinal difficulties ranging from diarrhea to colitis. C. difficile is one of the most common causes of hospital infections, and has become a major problem in hospitals in Quebec, especially in the Montreal area. There were 1 406 cases in 88 Quebec hospitals between August and November 2004 alone

Types of Drug Resistant TB - MDR, MDR plus, XDR, XDR plus

What are the main types of drug resistant TB?There are two main types of drug resistant TB, MDR TB and XDR TB. Another type of drug resistant TB, variously referred to as totally drug resistant TB, XXDR TB or TDR TB has also now been detected.

What is the difference between the types MDR TB and XDR TB?

MDR (multi drug resistant) TB is the name given to TB when the bacteria that are causing it are resistant to at least isoniazid and rifampicin, two of the most effective TB drugs.

XDR TB (extensively drug resistant TB) is defined as strains resistant to at least rifampicin and isoniazid in addition to being resistant to one of the fluoroquinolones, as well as resistant to at least one of the second line injectable TB drugs amikacin, kanamycin or capreomycin.

MDR TB and XDR TB do not respond to the standard six months of TB treatment with “first line” anti TB drugs, and treatment for them can take two years or more and requires treatment with other drugs that are less potent, more toxic and much more expensive. Worldwide only a few thousand patients with MDR TB and XDR TB are treated each year.

Should there be names for more types of drug resistant TB?“MDR plus” TB, another type of TBHaving just two types for all those people who have MDR or XDR TB, is possibly under representing the extent of resistance to the second line TB drugs, as well as causing confusion as people in an adhoc way adopt new names.

A study reported in 2012, showed that of 1,278 patients with MDR TB, some 43.7% had resistance to at least one second line drug. They did not though have the specific resistance to two of the classes of second line drugs, necessary for them to be considered as the XDR TB type, which in this study was at a level of 6.7%

It could be useful to have a new category or type of “MDR plus” TB for people with MDR TB, but who also have some resistance to second line drugs, but not sufficient for them to be categorised as having the type XDR TB.

If monitored by the World Health Organisation (WHO) and others, it could enable more information to be available about the extent to which resistance is developing to the second line drugs.

The adoption by WHO of a new type or category of “MDR plus” TB, would also reduce the confusion caused by the current use by some people of the term “pre XDR-TB”.

Totally drug resistant TB is TB which is believed to be resistant to all the first and second line TB drugs. It is sometimes referred to as extremely drug resistant, or XXDR TB, and it is extremely difficult, although not always totally impossible to treat.

“XDR plus” TB, another type of TB

The World Health Organisation considers all the cases of “totally” drug resistant TB to be the type XDR TB because they all satisfy the criteria for XDR TB.

As there is currently some considerable confusion being caused by all the different names, one possibility would be to refer to these types of drug resistant TB as being “XDR plus” TB, meaning cases of XDR TB with additional unspecified resistance. This would be similar to having “MDR plus” TB for cases of MDR TB where there is additional resistance.

Where does MDR TB occur?The notified cases of MDR TB by World Health Organisation (WHO) region are given below.

Globally just under 60,000 cases of MDR TB were notified to WHO in 2011, mostly by European countries and South Africa. This represented just 19% of the 310,000 cases of MDR TB estimated to exist among the patients with pulmonary TB who were notified to WHO in 2011.

The highest prevalence of MDR TB that had been documented by 2012 was in Minsk, Belarus, with a prevalence of 47.8% being reported in 2011. Among patients with infectious (smear positive) pulmonary disease, MDR TB was seen in 35.3% of newly detected cases, and in a massive 76.5% of previously treated patients.

Where does XDR TB occur?

XDR TB is TB which is resistant to at least rifampicin and isoniazid, in addition to being resistant to one of the fluoroquinolones, and at least one of the second line injectable TB drugs.

By 2012 some 84 countries had reported at least one case of XDR TB. These are not just developing countries, but include countries such as England and the United States of America.

WHO estimate that some 5% of people with MDR TB may actually have XDR TB. So if the actual number of MDR TB cases could be as high as 500,000 people, it means that as many as 25,000 cases of XDR TB could already have occurred.

Thank you