What are superbacteria? |

Definition

Superbacteria are organisms that have developed resistance to many antibiotic
drugs. Infections caused by these bacteria can be extremely difficult to treat, as
some have become resistant to all antibiotics that were once effective
against them. Because resistance can spread from one bacterium to another,
resistant strains of many different types of bacteria have emerged.

Superbacteria have become a serious health threat worldwide; antibiotic-resistant strains are present on every continent,
including Antarctica. The incidence of illness caused by drug-resistant bacteria
is increasing dramatically around the world. Resistant strains of disease-causing
bacteria, originally found primarily in hospitals, have now moved beyond health
care facilities and into communities.

Emergence and Spread of Superbacteria

When bacteria are exposed to an antibiotic, most of them will die. However, a
few bacteria may acquire changes in their DNA
(deoxyribonucleic acid) that allow them to survive in the presence of the drug.
These bacteria will multiply, creating a drug-resistant group. This vertical
transmission (that is, the method of passing resistance genes) requires time for
resistance-causing mutations to arise and stays within the same type of
bacteria.

The rapid spread of multiple resistance genes among species of bacteria occurs
through a second method of gene transfer: horizontal transmission. Bacteria often
carry their antibiotic resistance genes on bits of DNA called plasmids,
which are commonly passed between bacteria. One plasmid can contain genes for
resistance to numerous different antibiotics. Bacteria that receive such a plasmid
will become resistant to multiple antibiotics in one rapid event. They can then
spread this resistance even further when they multiply.

The widespread use of antibiotics in medicine and agriculture has led to the emergence and spread of superbacteria. Frequent exposure of bacteria to antibiotics increases the likelihood that they will develop resistance. Hospitals provide ideal conditions for bacteria to acquire resistance, because antibiotics are often used liberally and because many species of disease-causing bacteria are present.

Drug-resistant bacteria also arise on farms that produce meat and poultry,
where antibiotics are routinely given to healthy animals to prevent disease and to
promote growth. Incomplete treatment of pathogens with antibiotics can also
promote resistance. When a person stops taking prescribed antibiotics before all
bacteria are eliminated, the remaining bacteria may become resistant.

Associated Diseases and Pathogens

Staph infections. Methicillin-resistant Staphylococcus
aureus (MRSA) causes skin and soft tissue infections, which can be
invasive and life-threatening. MRSA is usually resistant to aminoglycosides,
macrolides, tetracycline, chloramphenicol, lincosamides, and methicillin. MRSA
infection is a major public health problem. According to the Centers for Disease Control and
Prevention (CDC), MRSA infection in 2008 caused
life-threatening illness in 90,000 people and 15,250 deaths in the United States
alone.

Tuberculosis. Nearly one-third of the world’s population is
infected with Mycobacterium tuberculosis, the bacterium that
causes the lung disease tuberculosis (TB). About ten percent of
those infected will develop TB. The rise of antibiotic resistance now threatens
the only treatment for TB, which is antibiotic therapy. Strains of M.
tuberculosis that are resistant to a minimum of one antibiotic have
been documented in every country surveyed by the World Health
Organization. Multidrug-resistant TB (MDR TB) is caused by
strains of M. tuberculosis that are resistant to both isoniazid
and rifampicine, the two most effective anti-TB drugs.

Opportunistic infections. Persons with compromised
immune
systems are vulnerable to infection by organisms that are
normally harmless in healthy people. Acquired in hospitals, opportunistic
infections can be life-threatening without appropriate antibiotic treatment.
Drug-resistant strains of the bacteria responsible for these infections pose a
growing threat to hospitalized persons. The CDC estimates that annually, two
million persons in the United States get some sort of infection while in the
hospital; 70 percent of the bacteria that cause these infections are resistant to
a minimum of one antibiotic typically used to treat them.

Strains of Klebsiella pneumoniae have developed resistance to
carbapenems, one of the few classes of antibiotics effective against these
gram-negative bacteria. Enterobacter variants are also
carbapenem-resistant, and they are resistant to all penicillin derivatives and
cephalosporins. Enterococcus faecium has
developed strains that are resistant to both ampicillin and vancomycin.
Pan-resistant strains of Pseudomonas aeruginosa and
Acinetobacter baumannii are no longer treatable with any known antibiotics.

Impact

Superbacteria present a serious global threat to human health. The worldwide
spread of antibiotic resistance jeopardizes the usefulness of antibiotics in the
treatment of bacterial diseases. Health care providers increasingly face
the challenge of treating infections for which few or no effective antibiotics
exist. People with resistant infections face longer hospital stays, more severe
illness, and an increased chance of death from certain diseases. The resulting
costs are high, both in terms of health care dollars and human lives. Solutions
will require global efforts to reduce overuse and misuse of antibiotics, to
prevent the spread of resistant organisms, and to develop new antibiotic
agents.

Bibliography

Groopman, Jerome. “Superbugs.” The New Yorker 84 (2008): 46-55. Recounts outbreaks of drug-resistant bacteria and discusses the causes and economic impact of multidrug resistance.

Klevens, R. M., et al. “Invasive Methicillin-Resistant Staphylococcus aureus Infections in the United States.” Journal of the American Medical Association 298 (2007): 1761-1763. A study that examines the prevalence of MRSA infection in the United States.

Muto, C. A., et al. “SHEA Guideline for Preventing Nosocomial Transmission of Staphylococcus aureus and Enterococcus.” Infection Control and Hospital Epidemiology 24 (2003): 362-386. Presents evidence-based recommendations for preventing the spread of antibiotic-resistant bacteria in hospitals.

Nikaido, Hiroshi. “Multidrug Resistance in Bacteria.” Annual Review of Biochemistry 78 (2009): 119-146. Review article describes the molecular mechanisms of antibiotic resistance in bacteria.

Sachs, Jessica Snyder. Good Germs, Bad Germs: Health and Survival in a Bacterial World. New York: Hill and Wang, 2008. Describes for general readers the nature and scope of antibiotic resistance and discusses the practices that have led to drug-resistant bacteria.

Sharma, Surendra, and Alladi Mohan. “Multidrug-Resistant Tuberculosis: A Menace that Threatens to Destabilize Tuberculosis Control.” Chest 130 (2006): 261-272. A comprehensive review of drug-resistant tuberculosis worldwide, including its epidemiology, molecular mechanisms, diagnosis, and treatment.