Antimicrobial Resistance

The rise and increase in drug-resistant infectious bacteria which can no longer be controlled, inhibited or killed by currently available antimicrobial compounds have increasingly become a major public health concern. As a result of the emergence of drug-resistant bacteria and pathogens, diseases such as childhood ear infections, gonorrhea, tuberculosis and malaria have become increasingly more difficult to treat and control. Antimicrobial/antibiotic resistance pathogens such as Methicillin-resistant Staphylococcus aureus or MRSA are becoming a concern in virtually every hospital-acquired infection. There is a rising concern among medical health professionals and several strains of bacterial infections and diseases soon may be untreatable.

Not only has antimicrobial resistance become a public health concern but it also contributes to increasingly higher medical care expenses. Treating drug resistant infections also results in extended hospital stays, the use of more toxic drugs. The cost of treating MRSA and other antibiotic resistant strains of infectious diseases has become a $30 billion industry in the United States alone.

Antimicrobial resistance infectious organisms are unicellular microbes that, unlike multicellular organisms, have a small number of genes. This provides them with the ability to mutate and adapt quickly to their environment. Since microbes reproduce and replicate rapidly, even a single genetic mutation can quickly affect their disease-causing molecular makeup. As they mutate to survive and adapt they easily render an antibiotic medication ineffective. As the microbes find and produce a genetic marker that is resistant to the antibiotic, they will quickly encode and pass on the genetic trait between their own species of bacteria as well as pass it on to other unrelated bacteria.

The adaptability of bacteria to reproduce immunity to antibiotics is added by the widespread use, abuse and inappropriate distribution of antibiotics. Antimicrobials have been routinely prescribed for viral infections, simple colds, and the treatment of acne pimples, rosacea and numerous other conditions for which they are not intended. Compound this problem with the fact that often times the patients will not finish the full course of the prescription, allowing for genetic mutations as the bacteria adapt. We also have the problem of antibiotics routinely being added into the food supply through meats and farming methods.

Understanding the Far-Reaching Scope of the Problem

Shortly after the introduction of penicillin, penicillin-resistant infections caused by Staphylococcus aureus began appearing rapidly.  Medical science has been aware of antimicrobial resistance for over 6o years and today we face an unprecedented crises caused by the rapid mutation, emergence and dissemination of many other microbes growing resistant to one or more antimicrobial drugs.

Newly developed strains and varieties of Staphylococcus aureus resistant to methicillin and other antibiotics are reaching epidemic size proportions. Infection with methicillin-resistant Staphylococcus aureus or MRSA strains are also replicating in non-hospital settings- and is now present in community-acquired infections. The terms HA-MRSA or healthcare-associated MRSA and CA-MRSA or community-associated MRSA reflect how this one antimicrobial has mutated. Only a very limited number of drugs still remain effective against these strains of infections. Vancomycin once the last resort against MRSA strains of infections is no longer as effective as it once was.

Streptococcus pneumoniae the bacteria responsible for meningitis and pneumonia, and ear infections are becoming resistant to penicillin about 30% of the time. Through mutation penicillin-resistant strains of bacteria are also growing resistant to additional antimicrobial drugs.

More than 35% of gonorrhea cases have become resistant to the standards of treatment – tetracycline or penicillin, sometimes both.

In many under-developed countries, anywhere from 300 to 500 million people become infected with the parasites responsible for malaria. Resistance to chloroquine and other antimalarial drugs is becoming a widespread and growing concern.

Over the last ten years, strains of tuberculosis are becoming multidrug-resistant known as MDR-TB. This is a very serious threat particularly for those infected with HIV. Drug-resistant MDR-TB strains are very contagious, more expensive to treat and difficult to control leaving patients infectious for longer periods of time due to inadequate treatment options, thus allowing for additional mutation of the infection.

In under developed countries, highly  resistant strains of Diarrheal diseases caused by pathogenic bacteria such as Campylobacter, Shigella dysenteriae, Escherichia coli, Vibrio cholerae, and Salmonella are causing up to 3 million deaths per year. Salmonella food poisoning is becoming more common and widespread in the United States. A potentially dangerous train of salmonella known as Salmonella typhimurium, has become resistant to the antibiotics chloramphenicol, sulfa, ampicillin, tetracycline, and streptomycin which is traditionally used to treat it.

Fungal pathogens are the cause of a growing number of nosocomial related infections, that is to say  these are infections acquired or resulting from a hospital or healthcare facility in which the patient was been admitted for reasons other than the infection. Fungal infections such as Pneumocystis carinii pneumonia and candidiasis are among the more common affecting AIDS patients, and in isolated incidences there have been outbreaks of these and other fungal diseases occurring even in people with uncompromised immune systems. Concern is rising as some types of fungi in particular Candida species has shown documented resistance to fluconazole which is antifungal drug used widely to treat systemic fungal diseases.

Health care professionals and medical research scientists are coordinating efforts to better understand and track the biological processes in the evolution of pathogens that leads to their emerging antimicrobial resistance to our current arsenal of agree that decreasing the incidence of antibiotic/antimicrobial drugs. Studying the microbial physiology of microbial and fungi pathogens help scientists understand the process that engage to resist drug treatments.

This knowledge will ultimately lead to the development of new strategies and methods to reverse or overcome these processes. This process must be a global organized effort to be successful. Most countries are not prepared with a comprehensive strategy to control, monitor, and limit or prevent the misuse of antimicrobial drugs and a plan to reduce or limit the spread of antimicrobial and fungal resistance.

Ongoing research in biochemistry and molecular genetics is giving us new insight into the manner in which microbes replicate. Advances in gene sequencing technology help us identify the actual molecules responsible for these genetic changes, and will hopefully give us new methods of targeted antimicrobial drugs. This research has already made it possible to identify molecular tools or markers to identify drug-resistant parasites. We now have a better understanding of the alterations in the genetic genome of several of the parasite species. Research will enable us to use this knowledge to find ways to reverse the antimicrobial resistance and create new drugs that are effective against current drug-resistant strains.

News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at http://www.niaid.nih.gov/.