For the last half-century, antibiotic drugs have been prescribed as the common treatment against bacterial infection and illness. As the medical popularity of antibiotics was climbing, so is the rate at which bacteria and other microorganisms are developing methods to withstand the effects of these drugs. Researchers explain that the excessive prescribing of antibiotics has significantly contributed to antibiotic resistance in microorganisms, as well as gene transfer between resistant and non-resistant bacterial stands. The World Health Organization reports that 444,000 new cases of multidrug-resistant tuberculosis surface every year, and are responsible for 150,000 deaths. The prevalence and threat of antibiotic resistance bacteria places the global population at risk returning to a rate of bacterial infection that has not been seen since the discovery of antibiotics.
Antibiotic Resistant Bacteria
The Prevalence and Threat of Antibiotic Resistance Bacteria
The rate at which bacteria are becoming resistant to drug treatments that are intended to eliminate or weaken them is growing rapidly. For over half a century, antibiotic drugs have been prescribed to treat bacterial infections, and as their medical popularity was mounting, bacteria and microorganisms developed ways to withstand the effects of antibiotic drugs. The increasing amount of antibiotic resistant bacteria poses a severe threat to global health as it compromises the effectiveness of antibacterial treatment, contributing to greater incidence of bacterial infection, fatalities, and health care expenses (1). According to the World Health Organization (WHO), 444,000 new cases of multidrug-resistant tuberculosis alone surface every year, and are responsible for causing at least 150,000 deaths (2). Researchers explain that the excessive use and misuse of antibiotics has been the major contributor in causing drug resistance, as disproportionate exposure to antibiotics forced microorganisms to evolve to evade harsh environments (1, 2). The prevalence and the threat of antibiotic resistance is so severe, the WHO explains the global population is at risk of returning to a pre-antibiotic era in terms of incidence of illness (2). In addition to vulnerable immune systems, antibiotic resistance has implications on health care costs, trade, and economies (2). Rational use of antibiotics, infection prevention and control, and patient safety are all required measures to combat the current threat of antibiotic resistant bacteria.
Mechanism of Resistance
Antibiotic resistant bacteria emerged as an evolutionary response to natural selection. As bacteria are exposed to recurrent, low doses of antibiotics, that are not potent enough to kill all of the bacteria, some bacteria develop ways to survive the intended effects of the drug (1, 3, 4). The misuse and overuse of antibiotics have intensified the problem by giving bacteria the opportunity to evolve. Inappropriate doses and treatment lengths can leave bacteria in the body, even if the patient no longer has symptoms, and allows for the remaining bacteria to pass on their resistant traits to future bacteria generations (3). Bacteria are able to fight the effects of antibiotic drugs is by altering their biochemistry. Bacteria can prevent antibiotics from reaching their target cells by changing the structure of their cell walls, and keep the antibiotic drug from entering the cell (3). Bacteria can also develop biochemical methods to pump drugs outside of the cell, or produce enzymes that destroy the antibiotics (3).
Bacteria gain these drug resistance properties by receiving resistance DNA genes from other bacteria (3). Bacteria DNA evolves in order to give bacteria the biological tools to escape the affects of antibiotic drugs. Once bacteria have antibiotic-resistant DNA, they are able to pass these resistance genes to other bacteria in various ways: bacteria can join together and transfer DNA to each other; free-floating pieces of DNA, called plasmids, which carry resistance genes are taken-in by bacteria; or pieces of DNA from one bacterium are incorporated into another (3). The mechanism by which resistant and non-resistant bacteria transfer genes is depicted in Figure 1.
Figure 1. Drug resistant bacteria transfer genes to non-resistant bacteria, causing drug resistant bacteria to dominate and multiply (4).
The ability for bacteria to multiply quickly is conducive to rapid evolution (in comparison to other species), which causes several generations of antibiotic resistant bacteria to be introduced into the population.
Incidence of Antibiotic Resistant Bacteria
Antibiotic resistance is acknowledged as one of the most significant threats to human health worldwide, and does not discriminate between First World or Third World nations (5). Antibiotic resistance enables bacteria and microorganisms to escape being killed or weakened by antibacterial, antiviral, and antifungal drugs (5). This compromises physicians' ability to treat life-threatening infections, and leads to increased incidence of infection and fatalities. The emergence of drug resistant bacteria is increasing across the globe. The WHO reports 440,000 new cases of multidrug-resistant tuberculosis (MDR-TB) are reported annually, and cause at least 150,000 deaths (2). Studies published from the developing world suggested the risks of drug resistance decades ago; however, it was not until MDR-TB surfaced in the United States in the 1990s that the problem of drug resistant bacteria received its due attention (6).
Multidrug-resistant tuberculosis is only the beginning of a long list of infection-causing bacteria that are now resistant to conventional medical treatment. One organism, Methicillin-resistant Staphylococcus aureus (MRSA), kills approximately 19,000 Americans annually, which is more than HIV / AIDS, Parkinson's disease, emphysema, and homicide combined (5). In the mid-1980s, the incidence of MRSA isolates was close to zero, and by 1998 the incidence of MRSA was approximately 70% in Japan, 40% in Belgium, 30% in the United Kingdom, and 28% in the United States (1). Every year, 2 million Americans obtain hospital-acquired infections, most of which are caused by antibiotic resistant microorganisms, and result in 99,000 deaths (5). In malaria-endemic countries, resistance to earlier anti-malaria medications such as chloroquine and sulfadoxine-pyrimethamine is widespread, which sustains malaria as a significant health threat (2). Antibiotic resistance is relevant in every country, and has the potential to affect all strands of bacteria that are responsible for human infection.
Threat of Antibiotic Resistance
The prevalence of antibiotic resistant bacteria is not only a threat to global health, but also poses dangers for health expenditures, trade, and economy. In 2002, the cost of health care expenditures caused by antibiotic resistant microbes in the United States was estimated at $7 billion (1). Antibiotic resistance not only proves fatal to many patients, but it inhibits the control of infection diseases. This reduces the effectiveness of antibiotic treatments, causing patients to need medical care longer, and increases the risk of antibiotic resistant bacteria spreading to other patients. The WHO explains antibiotic resistance threatens to return global health to the pre-antibiotic era as many infectious diseases have the potential to become uncontrollable (2). Since conventional antibiotics can not be used on resistant bacteria, more expensive treatments are required, again causing longer hospital stays, and escalates the cost of healthcare. Growing costs of healthcare can weaken economies, both domestic and global. As antibiotic resistant bacteria continue to spread, and treatments become less effective, the growth of global trade and travel only intensifies the problem by allowing bacteria to travel the globe faster (2). Combating the threat of antibiotic resistant bacteria requires rational use of antibiotics, infection prevention and control, and patient safety at the very least.
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