Chapter 83 - Basic Principles of Antimicrobial Therapy
What is an antimicrobial agent?
Any agent (or chemical) that can kill or suppress microorganisms.
____ drugs are directly lethal to bacteria at clinically achievable concentrations
Bacteriocidal
____ are drugs that can slow bacterial growth but do not cause cell death
Bacteriostatic
Why are antibiotics selectively toxic?
Because mammals and microbes have differing cellular structure.
____ is the ability of a drug to injure a target cell or target organism without injuring other cells or organisms that are in intimate contact with the target.
Selective toxicity
A patient has acquired an infection while in the hospital. The nurse identifies this type of infection as what? A) Superinfection B) Suprainfection C) Nosocomial infection D) Resistant infection
The answer is C, Nosocomial infections are acquired by patients while in the hospital. Superinfection and suprainfection are terms used to describe the emergence of drug resistance.
True or false: The more that antibiotics are used, the faster drug-resistant organisms emerge.
True.
What are the four basic actions of the microbial mechanisms of drug resistance? (how does the bacteria demonstrate resistance)
-decrease the concentration of a drug at its site of action -inactive a drug -alter the structure of drug target molecules -Produce a drug antagonist
What are some host factors to take into consideration when finding an antibiotic to use?
-host's defenses (do they have an intact immune system?) -Where is the site of infection? -Age of patient -Pregnant or nursing? -Any previous allergic reactions? -Look at genetic factors
Which antibiotics promote the most resistance: Broad-spectrum or Narrow-spectrum?
Broad-spectrum agents do the most to facilitate the emergence of resistance.
The development of a new infection as a result of the elimination of normal flora by an antibiotic is referred to as what? A) Resistant infection B) Superinfection C) Nosocomial infection D) Allergic reaction
The answer is B, Antibiotic therapy can destroy the normal flora of the body, which normally would inhibit the overgrowth of fungi and yeast. When the normal flora is decreased, these organisms can overgrow and cause a new infection, or superinfection.
Which test is the most widely used method for assessing drug sensitivity? A) Minimum inhibitory concentration (MIC) B) Minimum bacterial concentration (MBC) C) Broth dilution D) Disk diffusion
The answer is D, The most widely used method for assessing drug sensitivity is the disk diffusion test, also known as the Kirby-Bauer test. Through diffusion, an antibiotic-containing zone becomes established around each disk. As the bacteria proliferate, growth is inhibited around the disks that contain an antibiotic to which the bacteria are sensitive.
A nurse is assessing the effects of antimicrobial therapy in a patient with pneumonia. The nurse should establish which outcomes when planning care? (Select all that apply.) A) Potassium level of 4 mEq/dL B) Reduction of fever C) Sterile sputum cultures D) Oxygen saturation of 98% E) Elastic skin turgor
The answers are B, C, and D. Antimicrobial therapy is assessed by monitoring clinical and laboratory responses. Clinical indicators of success in a patient with pneumonia may include afebrile status and resolution of an infectious infiltrate, resulting in an oxygen saturation above 95%. The disappearance of infectious organisms from post-treatment cultures also indicates resolution of infection. Potassium levels and elastic skin turgor are not assessment parameters for clinical infections, including pneumonia.
What are the two classification systems used to classify antimicrobial drugs in this book?
-classification by susceptible organism -Classification by mechanism of action
How do we select an antibiotic?
-identify the invading organism -Check for drug sensitivity of the organism -Look at host factors. -Rule out drugs that cause allergic reactions or are unable to penetrate the site of infection.
How do we delay emergence of drug resistance?
-promote adherence to appropriate prescribing guidelines -Reduce demand for antibiotics among healthy adults and parents of young children -Emphasize adherence to prescribed antibiotic regimens -treat infection, not contamination -Treat infection, not colonization -Know when to say no to vanco -Stop treatment when infection i cured or unlikely -Isolate the pathogen -break the chain of contagion
Strictly speaking, what is an antibiotic?
An antibiotic is a chemical produced by one microbe that can harm other microbes
What is empiric therapy and when is it used?
Empiric therapy is antibiotic therapy for patients before the causative organism is positively identified. We treat with empiric therapy if the patient's infection is too extreme.
A patient is prescribed an antibiotic to treat a urinary tract infection. What statement by the patient indicates a need for further teaching? A. "I can stop the medication as soon as the symptoms have disappeared." B. "I will drink more fluids to help clear up the infection." C. "I will stop the medication and contact the doctor if I develop a rash." D. "I should immediately report vaginal itching or discharge."
The answer is A, Patients should be taught not to discontinue antibiotics prematurely, but rather to complete the entire course of therapy, even if symptoms improve or resolve. The other responses are appropriate
Which statement about superinfections does the nurse identify as true? A. Superinfections are more common in patients treated with narrow-spectrum drugs. B. Superinfection is defined as a new infection that appears during the course of treatment for a primary infection. C. Superinfections are caused by viruses. D. Superinfections are easy to treat.
The answer is B, Because broad-spectrum antibiotics kill off more normal flora than do narrow-spectrum drugs, superinfections are more likely in patients receiving broad-spectrum agents. Suprainfections are caused by drug-resistant microbes; these infections are often difficult to treat.
Which patient should receive prophylactic antibiotic therapy? A. A patient who is to have his teeth cleaned B. A patient who is scheduled for a hysterectomy C. A patient with a white blood cell count of 8000 cells/mm3 D. A patient with a high fever without an identifiable cause
The answer is B, Patients who undergo a hysterectomy (and other specific surgeries) may have a decreased incidence of infection if antibiotics are administered before or during surgery. Use of prophylactic antibiotics are not indicated for the other conditions.
What is the minimum bactericidal concentration (MBC)? A) The lowest concentration of an antibiotic needed to suppress bacterial growth completely B) The lowest concentration of an antibiotic needed to reduce the number of bacterial colonies by 99.9% C) The lowest concentration of an antibiotic needed to produce effects D) The lowest dose of an antibiotic needed to eradicate bacteria
The answer is B, The MBC is the lowest concentration of drug that produces a 99.9% decline in the number of bacterial colonies (indicating bacterial kill). The lowest antibiotic concentration needed to suppress bacterial growth or to produce effects and the lowest antibiotic dose needed to eradicate bacteria are incorrect descriptions of MBC.
The nurse identifies which host factor as the most important when choosing an antimicrobial drug? A) Age B) Competent immune function C) Genetic heritage D) Previous medication reactions
The answer is B, Two factors—host defenses and the site of infection—are unique to the selection of antibiotics. It is critical for success that antibiotics act synergistically with the immune system to subdue infection. Other host factors, such as age, genetic heritage, and previous drug reactions, are the same factors that must be considered when choosing any other medication.
An antimicrobial medication that has selective toxicity has which characteristic? A) Ability to transfer DNA coding B) Ability to suppress bacterial resistance C) Ability to avoid injuring host cells D) Ability to act against a specific microbe
The answer is C, Selective toxicity refers to an antibiotic that has the ability to injure only invading microbes, not the host. Conjugation is the process through which DNA coding for drug resistance is transferred from one bacterium to another. Antibiotics do not suppress bacterial resistance, but rather promote the emergence of drug-resistant microbes. Antibiotics that are narrow spectrum are active against only a few microbes.
A nurse removes a central line access device once the patient no longer requires intravenous (IV) antibiotics. This action is an example of which strategy to prevent antimicrobial resistance established by the Centers for Disease Control and Prevention (CDC)? A) Preventing transmission B) Proper diagnosis C) Preventing infection D) Prudent antibiotic use
The answer is C, The CDC's campaign to prevent the development of antimicrobial resistance in hospitals focuses on four approaches: (1) prevent infection, (2) diagnose and treat infection effectively, (3) use antimicrobials wisely, and (4) prevent transmission. Expeditious removal of invasive devices, such as IV catheters, and restricting these devices to essential use are examples of the CDC's strategy to prevent infection.
A microbe acquires antibiotic resistance by which means? A) Development of medication resistance in the host B) Overriding of the minimum bactericidal concentration C) Incorrect dosing, which contributes to ribosome mutations D) Transfer of DNA coding to other bacteria
The answer is D, All alterations in structure and function result from changes in the microbial genome. The microbe, not the host, becomes medication resistant. Genetic changes in a microbe result either from spontaneous mutation or from acquisition of DNA from conjugation with other bacteria. The minimum bacterial concentration (MBC) is used in testing for drug sensitivity. Incorrect dosing does not lead to microbe mutations.
A nurse should recognize that antibiotic prophylaxis is appropriate in patients with which medical conditions? (Select all that apply.) A) Aortic valve replacement B) Ruptured appendix C) Bronchitis D) Neutropenia E) Chickenpox
The answers are A and D, Antibiotic prophylaxis is appropriate and effective in certain situations. These include patients who have prosthetic valves and are at risk for bacterial endocarditis. The use of antibiotics in "dirty" surgeries, such as those for ruptured organs, is considered treatment, not prophylaxis. Severe neutropenia can put patients at risk for severe infection, and antibiotics can reduce infections but may encourage fungal invasion. Antibiotics are not prescribed preventively for bronchitis or chickenpox.
The nurse identifies appropriate use of antimicrobials to prevent infection in which situations? (Select all that apply.) A) Cardiac surgery B) Recurrent urinary tract infections in women C) Anemia D) Treatment of fever of unknown origin E) Hysterectomy
The answers are A, B, and E. Prophylactic use of antibiotics can reduce the incidence of infection in certain kinds of surgery. Procedures in which prophylactic efficacy has been documented include cardiac surgery, peripheral vascular surgery, orthopedic surgery, and surgery on the gastrointestinal (GI) tract (stomach, duodenum, colon, rectum, and appendix). Prophylaxis is also beneficial for women undergoing a hysterectomy or an emergency cesarean section. Severe neutropenia, not anemia, puts individuals at high risk of infection. In young women with recurrent urinary tract infection, prophylaxis with trimethoprim/sulfamethoxazole may be helpful. Unless the cause of a fever is a proven infection, antibiotics should not be used. Fever by itself constitutes a legitimate indication for antibiotic use only when the fever occurs in a severely immunocompromised person. Because fever may indicate infection and because infection can be lethal to immunocompromised individuals, these patients should be given antibiotics when fever occurs, even if fever is the only indication that an infection may be present.
Which are examples of the improper use of antibiotic therapy? (Select all that apply.) A) Using surgical drainage as an adjunct to antibiotic therapy B) Treating a viral infection C) Basing treatment on sensitivity reports D) Treating fever in an immunodeficient patient E) Using dosing that results in a superinfection
The answers are B and E, Common misuses of antibiotics include (1) treatment of a viral infection, which results in exposure of the patient to the risks of the medication without providing any benefits; and (2) improper dosing (dosing that is too high results in superinfection). The other answers are examples of the proper use of antimicrobial therapy.
