Microbes are living organisms that reproduce, thrive, and spread
quickly and efficiently increasing their numbers. Microbes include bacteria
(Staphylococcus aureus), viruses (colds and influenza, which causes the "flu"),
fungi (e.g., Candida albicans, which causes some
yeast infections), and
parasites (e.g., Plasmodium falciparum, which causes malaria).
Antimicrobial is a general term given to medicines that kill or slow the
growth of microbes.
Antimicrobial drug resistance is the ability of a microbe to grow in the
presence of a chemical that would normally kill it or limit its growth.
History
In 1928 while working with Staphylococcus bacteria, Scottish scientist
Alexander Fleming noticed that a type of
mold growing by
accident on a laboratory plate was protected from, and even repelled, the
bacteria. The active substance, which Fleming called
penicillin, was literally an antibiotic
- it
killed living organisms.
Thus began the age of using natural and, later, synthetic drugs to treat
people with bacterial infections. Though not widely popular until the 1940s,
antibiotics and other antimicrobials (medicines that kill or slow growth of a
microbe) have saved countless lives and blunted serious complications of many
feared diseases and infections. The success of antimicrobials against
disease-causing microbes is among modern medicine's great achievements.
The Problem
After more than 50 years of widespread use, evolution of disease-causing
microbes has resulted in many antimicrobials losing their effectiveness.
As microbes evolve, they adapt to their environment. If
something stops them from growing and spreading-such as an antimicrobial-they
evolve new mechanisms to resist the antimicrobials by changing their genetic
structure. Changing the genetic structure ensures that the offspring of the resistant microbes are also
resistant.
Antimicrobial resistance makes it harder to eliminate infections from the
body. As a result of a microbe's ability to survive in spite of antimicrobials,
some infectious diseases are now more difficult to treat than they were just a
few decades ago. In fact, antimicrobials have helped people so effectively that
humans are hurting the protective value of medicines through overuse and misuse.
More prudent use of antimicrobials will help to slow the development of
resistance.
Causes of antimicrobial drug resistance
Microbes, such as bacteria, viruses, fungi, and parasites, are living
organisms that evolve over time. Their primary function is to reproduce, thrive,
and spread, quickly and efficiently. Therefore, microbes adapt to their
environment and change in ways that ensure their survival. If something stops
their ability to spread, such as an antimicrobial, genetic changes can occur
that enable the microbe to survive. There are several ways this happens.
Natural [Biological] Causes
Mutation
Microbes reproduce by dividing every few hours, allowing
them to evolve rapidly and adapt quickly to new environmental conditions. With
each replication, mutations arise, and some of these mutations may help an individual
microbe survive exposure to an antimicrobial.
Picture of Mutation Causes of Drug Resistance
Gene Transfer
Microbes may also acquire genes from each other, including genes that make
the microbe drug resistant.
Picture of Gene Transfer Facilitates Drug Resistance
Selective Pressure
In the presence of an antimicrobial, microbes are either killed or, if they
carry resistance genes, survive. These survivors will replicate and their
progeny will quickly become the dominant type throughout the microbial
population.
Societal Pressures
The use of antibiotics, even when used appropriately, creates a selective
pressure for resistant organisms. However, there are additional societal
pressures that act to accelerate the increase of antimicrobial resistance.
Inappropriate Use
Selection of resistant microorganisms is exacerbated by inappropriate use of
antimicrobials. Sometimes physicians will prescribe inappropriate antimicrobials
wishing to placate an insistent patient who has a viral infection or an as-yet
undiagnosed condition.
Inadequate Diagnostics
More often, physicians must use incomplete or imperfect information to
diagnose an infection and thus prescribe an antimicrobial just-in-case or
prescribe a broad-spectrum antimicrobial when a specific antibiotic might be
better. These situations contribute to selective pressure and accelerate
antimicrobial resistance.
Hospital Use
Critically ill patients are more susceptible to
infections and, thus, often require the aid of antimicrobials. However, the
heavier use of antimicrobials in these patients can worsen the problem by
selecting for antimicrobial-resistant microorganisms. The extensive use of
antimicrobials and close contact among sick patients creates a fertile
environment for the spread of antimicrobial-resistant
germs.
Agricultural Use
Scientists also believe that the practice of adding antibiotics to
agricultural feed promotes drug resistance. More than half of the antibiotics
produced in the United States are used for agricultural purposes. However, there
is still much debate about whether drug-resistant microbes in animals pose a
significant public health burden.
Yeast vaginitis is a yeast infection of the vagina. Symptoms include itching, burning, soreness, pain during intercourse and urination, and vaginal discharge. Yeast infections can be treated with over-the-counter and prescription medications.
Pneumonia is inflammation of one or both lungs with consolidation. Pneumonia is frequently but not always due to infection. The infection may be bacterial, viral, fungal or parasitic. Symptoms may include fever, chills, cough with sputum production, chest pain, and shortness of breath.
Gastroenteritis (viral gastroenteritis, stomach flu) is an infection caused by a variety of viruses that results in vomiting and/or diarrhea. Even though it is often called the "stomach flu," it is not caused by the influenza viruses. Viruses that can cause gastroenteritis (stomach flu) include: rotaviruses, adenoviruses, caliciviruses, astroviruses, Norwalk virus, and a group of Noroviruses. Gastroenteritis is not caused by bacteria. The main symptoms of gastroenteritis include vomiting and watery diarrhea, however, headache, fever, and abdominal cramps (stomach ache) may also be present.
Diarrhea is a change is the frequency and looseness of bowel movements. Cramping, abdominal pain, and the sensation of rectal urgency are all symptoms of diarrhea. Absorbents and anti-motility medications are used to treat diarrhea.
MRSA (methicillin resistant Staphylococcus aureus) bacteria causes skin infections with the following signs and symptoms: cellulitis, abscesses, carbuncles, impetigo, styes, and boils. Normal skin tissue doesn't usually allow MRSA infection to develop. Individuals with depressed immune systems and people with cuts, abrasions, or chronic skin disease are more susceptible to MRSA infection.
Bronchitis is a disease of the respiratory system in which the bronchial passages become inflamed. There are two types of bronchitis, acute and chronic. Symptoms of acute bronchitis include frequent cough with mucus, lack of energy, wheezing, and possible fever. Treatment may require medication such as bronchial inhalers and predinsone. Supportive treatment is focused on relieving the symptoms with fever reducers, cough suppressants, and rest. Treatment may be more aggressive in patients with pre-existing conditions such as empyema, COPD, or cigarette smoking.
HIV (human immunodeficiency virus) is the cause of AIDS (acquired immunodeficiency syndrome). HIV is a type of virus called a retrovirus, which infects humans when it comes in contact with a break in the skin or tissues such as those that line the vagina, anal area, mouth, or eyes.
Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis bacteria. Symptoms include weakness, fever, weight loss, night sweats and in worse cases, chest pain, shortness of breath, and coughing up blood. A person with an active infection (a positive TB skin test, abnormal chest x-ray and TB bacteria in their sputum) requires treatment with izoniazid, rifampin, ethambutol and pyrazinaide.
Sexually transmitted diseases, or STDs,
are infections that are transmitted during any type of sexual exposure,
including intercourse (vaginal or anal), oral sex, and the sharing of sexual
devices, such as vibrators. Women can contract all of the STDs, but may have no symptoms, or have different symptoms than men do.
Whooping cough (pertussis) is highly contagious respiratory infection that is caused by the bacteria Bordetella pertussis. There are an estimated 300,000 plus deaths annually from whooping cough (pertussis). Whopping cough commonly affects infants and young children, but can be prevented with immunization with the vaccine. First stage whooping cough symptoms are a runny nose, sneezing, low-grade fever, a mild cough with the cough gradually becoming more severe. After one to two weeks, the second stage of whooping cough begins.
Malaria is an infectious disease transmitted by the bite of an infected Anopheles mosquito. Symptoms of malaria include chills, pain, fever, and sweating. Though mild cases of malaria can be treated with oral medication, severe cases require intravenous drug treatment and fluids.
Sexually transmitted diseases, or STDs, are infections that are transmitted during any
type of sexual exposure, including intercourse (vaginal or anal), oral sex, and
the sharing of sexual devices, such as vibrators. Although treatment exists for many STDs, others currently are
usually incurable, such as those caused by HIV, HPV, hepatitis B and C, and HHV-8.
Influenza (flu) is a respiratory illness caused by a virus. Flu symptoms include fever, cough, sore throat, runny nose, headache, fatigue, and muscle aches. The flu may be prevented with an annual influenza vaccination.
Salmonella bacteria are known to cause salmonellosis, typhoid fever, and paratyphoid fever in humans. Salmonella infection is usually caused by ingesting large amounts of the bacteria in contaminated food or water.
Gonorrhea is a bacterial infection transmitted during sexual contact. In women, symptoms include a yellow vaginal discharge, burning or frequent urination, and redness, swelling, burning and itching of the vaginal area. Gonorrhea can be treated with injectable (penicillin) or oral medications.
Vancomycin-resistant enterococci (VRE) infection is the most common type of infection acquired by patients while hospitalized. Patients at risk for VRE are those who are already ill, and hospitalized, including individuals with diabetes, elderly, ICU patients, kidney failure patients, or patients requiring catheters. Enterococci can survive for months in the digestive tract and female genital tract. Other risk factors for acquiring VRE include those how have been previously treated with vancomycin and combinations of other antibiotics. Treatment of VRE is generally with other antibiotics other than vancomycin. Prevention of VRE can be achieved by proper hand hygiene.
Middle ear infection or inflammation (otitis media) is inflammation fo the middle ear. There are two types of otitis media, acute and chronic. Acute otitis media is generally short in duration, and chronic otitis media generally lasts several weeks. Seventy-five percent of children in the U.S. suffer from otitis media at some point. Treatment depends upon the type (chronic or acute).
There are many types of E. Coli (Escherichia coli ). Pathogenic E. coli can cause urinary tract and bladder infections, or lead to sepsis. E coli O157:H7 (EHEC) causes bloody diarrhea and colitis. Complications of E. coli infection include hemorrhagic diarrhea, hemolytic-uremic syndrome, and thrombotic thrombocytopenic purpura. Symptoms include severe abdominal pain and bloody diarrhea. E coli O157:H7 commonly is due to eating raw or undercooked hamburger or raw milk or dairy products.
Encephalitis is a brain inflammation that causes sudden fever, vomiting, headache, light sensitivity, stiff neck and back, drowsiness, and irritability. Meningitis is an infection that causes inflammation of the meninges that surround the brain and spinal cord. Symptoms of meningitis include high fever, headache, nausea, vomiting, and stiff neck.
Plague is an infectious disease caused by the Yersinia pestis bacteria, which is primarily found in rodents the fleas that feed off of them. The bacteria are passed to humans through flea or rodent bites. There are three forms of plague: bubonic, septicemic, and pneumonic. The symptoms and method of transmission vary with each form of plague. Plague can be treated with antibiotics.
Travelers' diarrhea is generally contracted by eating contaminated food or drinking contaminated water. Food is the primary source of travelers' diarrhea. Enterotoxigenic E. coli is the cause of up to 70% of all cases of travelers' diarrhea. There are five unique classes of E. coli that causes gastroenteritis. Other bacteria responsible for travelers' diarrhea include
Campylobacter, jejuni, shigella, and salmonella. Viruses such as rotavirus and Norwalk virus (norovirus) and giardia lamblia a parasite may cause travelers' diarrhea. Prevention is careful eating and drinking of water.
NDM-1 (New Delhi metallo-beta-lactamase) is an enzyme produced by certain strains of bacteria that have recently acquired the genetic ability to make this compound. Bacteria that produce NDM-1 are resistant to all commonly used beta-lactam antibiotics. Klebsiella, Escherichia and Acinetobacter are known to possess the gene for NDM-1, which can turn these bacteria into superbugs. Symptoms and signs of NDM-1 infection include fever, fatigue, and shock. Treatment depends upon the NDM-1 strain.
When you are pregnant, many sexually transmitted diseases (STDs) can be especially harmful to you and your baby. These STDs include herpes, HIV/AIDS, genital warts (HPV), hepatitis B, chlamydia, syphilis, gonorrhea, and trichomoniasis. Symptoms include bumps, sores, warts, swelling, itching, or redness in the genital region. Treatment of STDs while pregnant depends on how far along you are in the pregnancy and the progression of the infection.
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