Antibacterial Resistance: What You Don’t Know Can Hurt You

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A mother takes her 7 year-old child to the physician for a sore throat and a runny nose. Those symptoms could be a result of a bacterial infection, in which case antibiotics are necessary. It’s also possible that the child simply has the flu or common cold, both of which are viral infections and cannot be treated with antibiotics. Without definitive testing, it can be difficult to identify the root of these symptoms. Because the mother is concerned and eager to find some relief for her child, the doctor may be tempted to prescribe some antibiotics. They’ll get rid of the bacterial infection, if there is one, and at the very least they’ll give the mother some peace of mind. But at what cost?

Frivolously prescribing antibiotics, particularly when they’re not needed, provides more opportunities for antibiotic-resistant bacteria to grow and reproduce. While the presence of the antibiotic does not necessarily cause resistance, it kills off and inhibits the growth of bacteria that are sensitive to it. This paves the way for resistant organisms, including disease-causing pathogens, to expand their colonies without opposition. The rapid emergence of antimicrobial-resistant bacteria, often referred to as “superbugs,” can be attributed to misuse and overuse of antimicrobial drugs and practices. Examples of such misuse include administration of an antibiotic for a viral infection, stopping or starting an antibiotic regimen when not necessary, supplementing the diet of farm animals with antibiotics to maximize growth, and the overuse of antibacterial soaps and hand sanitizer,

The rapid emergence of superbugs can be attributed to the mechanisms by which bacteria exchange genetic material. Most organisms inherit their genes from their parents in a process called “vertical gene transfer.” Bacteria, on the other hand, can give genes to their neighbors as well as receive them in a process known as “horizontal gene transfer.” This exchange can happen via three different pathways: transformation, conjugation, and transduction (Fig. 1). Transformation occurs when a bacterium absorbs DNA from a dead, or lysed, bacterium nearby. During conjugation, two bacteria exchange small, circular pieces of DNA, known as plasmids, through a protein tube. In transduction, however, viruses that infect bacteria, called bacteriophages, pick up genetic material from one bacterium and inject it into another. Because bacteria have these various mechanisms for horizontal gene transfer, they can evolve rapidly. If one bacterium holds the gene for resistance to a certain antibiotic, the whole colony can develop resistance in anywhere from a few hours to a few days. This viral video recorded by researchers at Harvard Medical School and MIT shows just how quickly E. coli can evolve across a giant petri dish coated in vertical bands of increasing dosage of antibiotic. Within two weeks, the whole colony had evolved resistance to even their strongest antibiotics. What’s more, they found that even the more resistant, slow-growing bacteria were outcompeted by faster-growing, less resistant bacteria, demonstrating the evolutionary trade-offs of antibiotic resistance.

Figure 1. Mechanisms of resistance gene transfer in bacteria.

Figure 1. Mechanisms of resistance gene transfer in bacteria.

Antibacterial resistance is a global health concern that can lead to severe infections, longer and more frequent hospital stays, and increased mortality.  Each year in the United States alone, 2 million people become infected with antibiotic resistant bacteria, and 23,000 people die as a result of those infections. Many resistant strains of bacteria have spread all over the world, including Klebziella pneumoniae, a common intestinal bacteria that can cause life-threatening infections. K. pneuomoniae is responsible for many hospital-acquired infections including pneumonia, infections in the bloodstream, and infections in newborns and patients in the intensive-care unit. This pathogen has developed resistance to its last resort treatment and has spread to all regions of the world. Other urgent threats listed on the CDC website include Clostridium difficile (C. difficile), a bacteria that causes life-threatening diarrhea. More than 250,000 infections per year and approximately 15,000 deaths can be directly attributed to C. difficile. Also listed under “urgent” status is Neisseria gonorrhoeae (N. gonorrhoeae), a bacteria that causes a sexually-transmitted infection (STI) that results in discharge and inflammation of the urethra, cervix, pharynx, or rectum. There are approximately 820,000 gonorrhea infections each year, and around 246,000 of those are from drug-resistant strains, most likely as a result of overuse and misuse of prescribed antibiotics.

There are of course ways to protect oneself from antibacterial-resistant infections and prevent the spread of antibiotic resistance. Simply washing your hands with plain (alcohol-based) soap and water on a regular basis, particularly before and after certain activities, will minimize exposure to disease-causing germs and reduce the spread to others. Filtering your water if possible, avoiding meat supplemented with antibiotics, thoroughly cooking your food, and only taking antibiotics as directed, and only when necessary, can reduce infection from food-borne pathogens and slow down the spread of antibiotic resistance. Antibacterial practices have a place in medical facilities and nursing homes, but it’s important to use them only when necessary. As for everyday usage by regular people, antibacterial soaps and hand sanitizers, especially those containing an antimicrobial agent, such as triclosan, as the active ingredient, should be avoided.

That said, doctors have a decision to make when faced with that mother and her sick child. Until the results of a swab, urine, or blood test confirm the existence of a bacterial infection, the doctor should hold off on the antibiotics and treat the symptoms instead by recommending an over-the-counter medication that targets cold and flu symptoms. This way, no one is contributing to a global epidemic that is a result of antibiotic resistance.


References:

1.    “Antibiotic resistance: The grim prospect.” (2016). The Economist. https://www.economist.com/news/briefing/21699115-evolution-pathogens-making-many-medical-problems-worse-time-take-drug-resistance
2. Centers for Disease Control and Prevention (CDC): Antibiotic/Antimicrobial Resistance. (2017). https://www.cdc.gov/drugresistance/index.html
3. Centers for Disease Control and Prevention (CDC): Antibiotic/Antimicrobial Resistance-- Biggest Threats. (2017). https://www.cdc.gov/drugresistance/biggest_threats.html
4. Centers for Disease Control and Prevention (CDC): Antibiotic/Antimicrobial Resistance-- Protecting Yourself and Your Family. (2017). https://www.cdc.gov/drugresistance/protecting_yourself_family.html
5. Michael Baym, Lieberman, Tami D., Kelsic, Eric D., et al. (2016). Spatiotemporal microbial evolution on antibiotic landscapes. Science. 353(6304): 1147-1151. http://science.sciencemag.org/content/353/6304/1147.full
6.    Microbiology: An Evolving Science. 3rd edit. (2013). Joan Sloncewski & John Foster.  W. W. Norton & Company, New York.
7.  U.S. Food & Drug Administration News Release: FDA issues final rule on safety and effectiveness of antibacterial soaps. (2016). https://www.fda.gov/newsevents/newsroom/pressannouncements/ucm517478.htm
8. U.S. Food & Drug Administration Consumer Updates: Antibacterial Soap? You Can Skip It-- Use Plain Soap and Water. (2017).https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm378393.htm

9. World Health Organization (WHO): Antimicrobial resistance fact sheet. http://www.who.int/mediacentre/factsheets/fs194/en/