Microbiology For Dummies
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Since the beginning of their widespread use in 1943, antibiotics have saved countless lives and changed the way medicine is practiced. Before their discovery, people suffered or died from infectious diseases that today are a mere annoyance, like sexually transmitted diseases and post-operative infections. Today antibiotics are essential in treating life-threatening bacterial infections, like pneumonia and sepsis, and are used preventively in a number of medical procedures (like surgery) and treatments (like cystic fibrosis). But when you have a sore throat, cough, or cold, your doctor may opt not to prescribe antibiotics. Here are ten reasons why:

  • Antibiotics do not treat viral infections. Most common ailments (such as the common cold and influenza) are due to viral infections rather than bacterial infections. Antibiotics are designed to treat illnesses caused by bacteria. They don't treat viral infections.

  • Your immune system can usually handle things on its own. Upon being infected with a virus that your body has never seen before, your immune system fights the offending pathogen (disease-causing agent). The first time your body encounters a virus, it takes some time to mount this immune response. But when the virus is eradicated, the body "remembers" the composition of the viral antigen (the part of the virus that stimulates an immune response). So, the next time your body encounters the same virus, your body will be able to mount an immune response much more quickly and effectively in order to stop the virus in its tracks.

  • High doses of antibiotics can cause suppression of your immune system. Antibiotics given in high doses can alter the regular response of your immune system. Initially, when the body recognizes an infection, it elicits an inflammatory response. This response is invaluable to the body's ability to fight infection. Some antibiotics, like erythromycin, have anti-inflammatory properties, so although your symptoms seem to get better initially, ultimately it will take longer for you to get better.

  • Overuse (and misuse) of antibiotics can lead to antibiotic resistance. Antibiotics that are given for an infection that is not caused by bacteria or antibiotics that aren't specific for the bacterial pathogen can contribute to the development of antibiotic-resistant bacteria in that individual. In any population of bacteria, there is always a small number of mutants. Although the mutations are random, at any given time there's a small chance that one is resistant to an antibiotic. Every time you expose the bacteria in your body to antibiotics, the susceptible bacteria are killed but any antibiotic-resistant mutants are spared. These bacteria are then capable of reproducing a new population of bacteria with the mutation that allows them to evade antibiotic therapy.

    This process of creating a situation where some members of a population survive and others die is called selection, and it results in certain traits, like antibiotic resistance, becoming more abundant than they would in the normal course of events. Placing the bacteria in the body under the selection pressure of antibiotics, by using them too often, doesn't select only for antibiotic-resistant members of the pathogenic population but from all species of bacteria in the body. And when any of these become problematic, they're much more difficult to treat. When an individual uses more antibiotics, that leads to more antibiotic exposure by bacteria, creating an even greater selective pressure on bacteria and ultimately leading to more resistant strains overall.

  • Overuse of antibiotics causes the emergence of superbugs. Drug-resistant microorganisms have a large impact on human health. The U.S. Centers for Disease Control (CDC) estimates that over two million people are infected by drug-resistant microorganisms, including bacteria and fungi, in the United States each year, with 23,000 people dying as a direct result and many more dying as an indirect result.

    Superbugs are bacteria that have the ability to evade multiple different antibiotics. As their name suggests, superbugs, or multidrug-resistant bacteria, are very difficult to eradicate. Some, like Clostridium difficile and drug-resistant Neisseria gonorrhoeae, are not widespread, but there is no other treatment for them, making them a big potential threat for the future. Others like, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), are seen more often and can still be managed by a small number of drugs. Currently, there are not many promising new antibiotics being developed. Traditionally, these were thought of as hospital-acquired infections, but as inappropriate antibiotic use continues, these infections are now being seen in the community at large.

  • Antibiotics are far more useful when we use the right ones. Some antibiotics, called broad-spectrum drugs, are general and target a wide range of microbes, whereas others are specific for a smaller group of microbes. Likewise, different bacteria are vulnerable to some antibiotics and unaffected by others. So, it makes sense to treat a bacterial infection with the drug that will be most effective against the pathogen in question. To determine the cause of an infection, it's important to collect a sample from the sick person and send it to be identified by the medical lab.

    Without a culture of the infection, your doctor can't know which organism is causing the symptoms. In the past, doctors used broad-spectrum antibiotics to treat infections, and the majority of people got better. Recently, it has been discovered that this practice has lead to the development of superbugs, as well as contributed to the increasing number of cases of antibiotic-related infections (such as C. diff) and antibiotic-resistant bugs (such as MRSA).

  • Antibiotics can leave you susceptible to opportunistic infections. The use of antibiotics can kill the good bacteria that live in your body. All the surfaces of your body are teeming with bacteria, called the microbiota, that have been there since you were born and protect you from invading pathogens every day. For example, the intestine and, in women, vaginal microbiota contain a balance of good and potentially bad microorganisms. The use of antibiotics can cause the good bacteria to be wiped out, leaving an environment that favors the potentially harmful microorganisms.

  • Antibiotics have nasty side effects. Though the common side effects of antibiotics are mostly just a nuisance, some side effects can be quite dangerous. Diarrhea, nausea, and vomiting are common and are likely due to an inflammatory response in your stomach and intestinal lining. It can be difficult to distinguish these side effects from the more dangerous diarrhea caused by C. diff. Overgrowth of Candida albicans can occur in both the mouth and the vagina. Perhaps the most serious of side effects is allergic reactions. These reactions can range from hypersensitivity reactions (hives, itching, and redness) to a more severe anaphylactic reaction (throat and tongue swelling) that can lead to death.

  • Antibiotics can interact with other prescription and over-the-counter medications. Antibiotics can interact with other medications you're taking and cause potentially serious consequences. Some antibiotics can interact with nonsteroidal anti-inflammatory drugs (NSAIDs) to cause damage to your kidneys, while others can interact with antacids and cause decreased absorption of nutrients from your intestine. Some antibiotics can make birth control pills ineffective. Still others can interfere with anticoagulation medications and cause a substantial increase in the amount of time it takes blood to clot, which can lead to excessive bleeding if you suffer an injury. Hypoglycemia, bone marrow suppression, and drug-related toxicity can also occur with the use of antibiotics combined with some other medications. Your doctor will take into consideration the other medications you're taking before prescribing an antibiotic.

  • Antibiotic use in pregnancy may have effects on the child. There is evidence to suggest that when women use antibiotics inappropriately during pregnancy, their offspring have an increased risk of developing allergies. If you're pregnant, your doctor will keep the health of your baby in mind before prescribing antibiotics.

About This Article

This article is from the book:

About the book authors:

Jennifer C. Stearns, PhD, is an Assistant Professor in the Department of Medicine at McMaster University. She studies how we get our gut microbiome in early life and how it can keep us healthy over time. Michael G. Surette, PhD, is a Professor in the Department of Medicine at McMaster University, where he pushes the boundaries of microbial research. Julienne C. Kaiser, PhD, is a doctoral career educator.

Jennifer C. Stearns, PhD, is an Assistant Professor in the Department of Medicine at McMaster University. She studies how we get our gut microbiome in early life and how it can keep us healthy over time. Michael G. Surette, PhD, is a Professor in the Department of Medicine at McMaster University, where he pushes the boundaries of microbial research. Julienne C. Kaiser, PhD, is a doctoral career educator.

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