Which term describes antibiotic therapy tailored to treat an identified organism? quizlet

Aminoglycosides
• The aminoglycosides are a group of natural and semisynthetic antibiotics that are classified as bactericidal drugs.
• Aminoglycosides include amikacin, gentamicin, and tobramycin.
• Serum levels of aminoglycosides are routinely monitored and dosages are adjusted to maintain optimal levels that maximize drug efficacy and minimize the risk for toxicity. This process is called therapeutic drug monitoring. Aminoglycoside therapy is commonly monitored in this way due to the nephrotoxicity and ototoxicity associated with these drugs.
• Dosing is adjusted to the patient's level of renal function based on estimates of creatinine clearance calculated from serum creatinine values.
• The serum level needs to be at least eight times higher than the minimum inhibitory concentration (MIC), which is a measure of the lowest concentration of drug needed to kill a certain standard amount of bacteria. This value is determined in vitro for each drug.
• Beta-lactams act through time-dependent killing; the amount of time the drug is above the MIC is critical for maximal bacterial kill. Aminoglycosides work primarily through concentration-dependent killing; achieving a drug plasma concentration that is a certain level above the MIC, even for a brief period of time, results in the most effective bacterial kill.
• Once-daily dosing provides a sufficient plasma drug concentration for bacterial kill, along with equal or lower risk for toxicity compared with multiple daily dosing regimens. Use of a once-daily regimen also reduces the nursing care time required and often allows for outpatient or even home-based aminoglycoside drug therapy.
• Trough (lowest) levels are measured to ensure adequate renal clearance and avoid toxicity.
• The therapeutic goal is a trough concentration at or below 1 mcg/mL. Trough levels above 2 mcg/mL are associated with a greater risk for both ototoxicity and nephrotoxicity.
• Aminoglycosides work in a manner similar to that of the tetracyclines in that they bind to ribosomes, specifically the 30S ribosome, and prevent protein synthesis in bacteria.
• Aminoglycosides are most often used in combination with other antibiotics such as beta-lactams or vancomycin because the combined effect of the two antibiotics is greater than the sum of the effects of each drug acting separately. This is known as a synergistic effect.
• Aminoglycosides also have a property known as the postantibiotic effect; continued bacterial growth suppression occurs after short-term antibiotic exposure, as in once-daily dosing.
• Toxicity associated with aminoglycosides limits their use to treatment of serious gram-negative infections and specific conditions involving gram-positive cocci, in which case gentamicin is usually given in combination with a penicillin.
• Gram-negative infections treated with aminoglycosides include those caused by Pseudomonas species and several organisms belonging to the Enterobacteriaceae family, including Escherichia coli, Proteus spp., Klebsiella spp., and Serratia spp.
• Aminoglycosides are also used for prophylaxis in procedures involving the gastrointestinal (GI) or genitourinary (GU) tract because such procedures carry a high risk for enterococcal bacteremia.
• Aminoglycosides are to be administered with caution in premature and full-term neonates because of their renal immaturity.
• Aminoglycosides are very potent antibiotics and are capable of potentially serious toxicities, especially to the kidneys and to the ears, in which they can affect hearing and balance functions. Duration of drug therapy needs to be as short as possible, based on sound clinical judgment and monitoring of the patient's progress.

Antibiotics are used for empiric, definitive therapy, and prophylactic or preventative therapy.
• Antibiotics are either bacteriostatic or bactericidal. Bacteriostatic antibiotics inhibit the growth of bacteria but do not kill them. Bactericidal antibiotics directly kill the bacteria.
• Most antibiotics work by inhibiting bacterial cell wall synthesis in some way. Over time, bacteria can mutate to survive an attack by the antibiotic. The production of beta-lactamases is one way in which bacteria can fend off the effects of antibiotics.
• Signs and symptoms of an infection may appear before a causative organism can be identified. When the risk of life-threatening or severe complications is high, an antibiotic that can best kill the microorganisms known to be the most common causes of the infection is given immediately. This is called empiric therapy.
• Specimens are obtained from the suspected areas of infection to be cultured to identify a causative organism before drug therapy is initiated, whenever possible.
• Once the results of culture and sensitivity testing are available (usually within 48 to 72 hours), the antibiotic therapy is then tailored to treat the identified organism by using the most narrow-spectrum, least toxic drug based on sensitivity results. This is known as definitive therapy.
• Broad-spectrum antibiotics are those that are active against numerous organisms (gram-positive, gram-negative, and anaerobic).
• Narrow-spectrum antibiotics are effective against only a few organisms.
• Overuse of broad-spectrum antibiotics contributes to resistance. The goal of therapy is to use the most narrow-spectrum drug when possible based on sensitivity results.
• Antibiotics are also given for prophylaxis when patients are scheduled to undergo a procedure in which the likelihood of dangerous microbial contamination is high during or after the procedure. Prophylactic antibiotic therapy is used to prevent an infection.
• To optimize antibiotic therapy, the patient is continuously monitored for both therapeutic efficacy and adverse drug effects. A therapeutic response to antibiotics is one in which there is a decrease in the specific signs and symptoms of infection compared with the baseline findings. Antibiotic therapy is said to be subtherapeutic when these do not improve.
• Superinfection can occur when antibiotics reduce or completely eliminate the normal bacterial flora—bacteria and fungi that are needed to maintain normal function in various organs. When killed by antibiotics, other bacteria or fungi take over and cause infection.
• Host-specific factors pertain specifically to a given patient and can affect the success or failure of antibiotic therapy. These factors include age, allergy history, kidney and liver function, pregnancy status, genetic characteristics, site of infection, and host defenses.

Quinolones
• Quinolones are very potent bactericidal broad-spectrum antibiotics and include norfloxacin, ciprofloxacin, levofloxacin, and moxifloxacin. With the exception of norfloxacin, these antibiotics have excellent oral absorption.
• Quinolone antibiotics destroy bacteria by altering their DNA.
• Quinolones are active against a wide variety of gram-negative and selected gram-positive bacteria. Most are excreted by the kidneys as unchanged drug. This, together with the extensive gram-negative coverage, makes them suitable for treating complicated urinary tract infections, as well as respiratory, skin, GI, and bone and joint infections.
• The use of quinolones in prepubescent children is not generally recommended because these drugs have been shown to affect cartilage development in laboratory animals. However, judicious use in children might be less of a risk than previously thought, and these drugs are used commonly in children with cystic fibrosis.
• Bacterial overgrowth is a complication of quinolones but is more commonly associated with long-term use. More worrisome is a cardiac effect that involves prolongation of the QT interval on the electrocardiogram (ECG).
• Concurrent use of quinolones with antacids, calcium, magnesium, iron, zinc preparations, or sucralfate causes a reduction in the oral absorption of the quinolone.
• Probenecid can reduce the renal excretion of quinolones. Nitrofurantoin can antagonize the antibacterial activity of the quinolones, and oral anticoagulants are to be used with caution because of the antibiotic-induced alteration of intestinal flora, affecting vitamin K synthesis.

Miscellaneous Antibiotics
• Clindamycin (Cleocin) is a semisynthetic antibiotic. Clindamycin can be either bactericidal or bacteriostatic depending on the concentration of the drug at the site of infection and on the infecting bacteria. It inhibits protein synthesis in bacteria and is indicated for the treatment of chronic bone infections, GU tract infections, intraabdominal infections, anaerobic pneumonia, septicemia caused by streptococci and staphylococci, and serious skin and soft tissue infections caused by susceptible bacteria.
• Clindamycin is contraindicated in patients with a known hypersensitivity to it, those with ulcerative colitis or enteritis, and infants younger than 1 month of age.
• With clindamycin, GI tract adverse effects are the most common and include nausea, vomiting, abdominal pain, diarrhea, pseudomembranous colitis, and anorexia.
• Clindamycin is also known to have some neuromuscular-blocking properties that may enhance the actions of neuromuscular drugs used in perioperative and intensive care settings.
• Linezolid (Zyvox) is the first antibacterial drug in a new class of antibiotics known as oxazolidinones. This drug works by inhibiting bacterial protein synthesis.
• The most commonly reported adverse effects attributed to linezolid are headache, nausea, diarrhea, and vomiting. It has also been shown to decrease platelet count. Tyramine-containing foods such as aged cheese or wine, soy sauce, smoked meats or fish, and sauerkraut can interact with linezolid to raise blood pressure.
• Metronidazole (Flagyl) is an antimicrobial drug of the class nitroimidazole that has especially good activity against anaerobic organisms and is widely used to treat intraabdominal and gynecologic infections that are caused by such organisms.
• Adverse effects of metronidazole include dizziness, headache, GI discomfort, nasal congestion, and reversible neutropenia and thrombocytopenia. Drug interactions include acute alcohol intolerance when it is taken with alcoholic beverages.
• Metronidazole may also increase the toxicity of lithium, benzodiazepines, cyclosporine, calcium channel blockers, various antidepressants (e.g., venlafaxine), warfarin, and other drugs. In contrast, phenytoin and phenobarbital may reduce the effects of metronidazole.
• Nitrofurantoin (Macrodantin) is an antibiotic drug of the class nitrofuran used primarily for urinary tract infections caused by E. coli, S. aureus, Klebsiella spp., and Enterobacter spp.
• Adverse effects include GI discomfort, dizziness, headache, skin reactions (mild to severe reported), blood dyscrasias, ECG changes, possibly irreversible peripheral neuropathy, and hepatotoxicity. Although hepatotoxicity is rare, it is often fatal.
• Quinupristin and dalfopristin (Synercid) are two streptogramin antibacterials marketed in a 30:70 fixed combination approved for intravenous treatment of bacteremia and life-threatening infection caused by VRE and for treatment of complicated skin and skin structure infections caused by S. pyogenes and S. aureus, including MRSA.
• Common adverse effects are arthralgias and myalgias, which may become severe. Adverse effects at the infusion site, including pain, inflammation, edema, and thrombophlebitis, have developed in approximately 75% of patients treated through a peripheral intravenous line.
• Vancomycin is a natural bactericidal antibiotic that destroys bacteria by binding to the cell wall. It is the antibiotic of choice for treatment of MRSA infection and infections caused by other gram-positive bacteria. It is not active against gram-negative bacteria, fungi, or yeast.
• Vancomycin is similar to the aminoglycosides in that there are very specific drug levels in the blood that are safe.
• Nephrotoxicity is more likely to occur with concurrent therapy with other nephrotoxic drugs such as aminoglycosides, cyclosporine, and contrast media used for computed tomography scans. Vancomycin can cause additive neuromuscular-blocking effects in those taking neuromuscular blockers.
• Daptomycin (Cubicin) is currently the only drug of the new class known as lipopeptides. It binds to gram-positive cells in a calcium-dependent process and disrupts the cell membrane potential. It is used to treat complicated skin and soft-tissue infections caused by susceptible gram-positive bacteria, including MRSA and VRE.
• Telavancin (Vibativ) is a new drug and the only one in the class called the lipoglycopeptides. It is indicated for the treatment of skin and skin structure infections caused by susceptible gram-positive organisms.

Assess for history of or current symptoms indicative of hypersensitivity or allergic reactions, with symptoms from mild reactions with rash, pruritus, or hives to severe reactions with laryngeal edema, bronchospasm, and hypotension to possible cardiac arrest.
• With any antibiotic, assess for superinfection, or a secondary infection that occurs with the destruction of normal flora during antibiotic therapy.
• Antibiotic resistance is a concern, especially in pediatrics and in large health care institutions and long-term care facilities. You must consider this possibility of resistance to certain antibiotics when assessing patients for symptoms of infection and superinfection.
• Aminoglycosides, as well as any antibiotics, are given exactly as ordered and with hydration.
• Instruct the patient to report to the prescriber any changes in hearing, ringing in the ears, full feeling in the ears, nausea, vomiting with motion, ataxia, nystagmus, and dizziness.
• Quinolones are to be taken exactly as prescribed and for the full course of treatment. Instruct the patient not to take these medications with antacids, iron, zinc preparations, multivitamins, or sucralfate because the absorption of the antibiotic will be decreased. If the patient needs to take calcium or magnesium, instruct the patient to take it 1 hour before or after the quinolone. Forcing of fluids is recommended unless contraindicated.
• Clindamycin oral dosage forms should be taken with 8 oz of water or other fluid. With topical forms, advise patients to avoid the simultaneous use of peeling or abrasive acne products, soaps, or alcohol-containing cosmetics to prevent cumulative effects.
• Linezolid is generally given orally or intravenously. Oral doses are to be evenly spaced around the clock, as ordered, and given with food or milk to decrease the possibility of GI upset. Oral suspension forms must be used within 21 days of reconstitution. Protect intravenous doses from light and infuse over 30 to 120 minutes; do not mix with any other medication. Monitor platelet counts closely (e.g., weekly) during therapy.
• Nitrofurantoin is available in oral forms and should be given with plenty of fluids, food, or milk to decrease GI upset. Do not crush tablets to help prevent tooth staining and GI upset. Because of the risk for superinfection, hepatotoxicity, and peripheral neuropathy, constantly monitor for signs and symptoms of these adverse effects and document the findings.
• Too rapid an infusion of vancomycin or administration by intravenous push may lead to severe hypotension and red man syndrome. Extravasation may cause local skin irritation and damage, so frequently monitor the infusion, particularly the intravenous site.
• Because of the significant issue of multidrug-resistant organisms, encourage patients and family members not to abuse or overuse antibiotics and always to report immediately to the prescriber any signs and symptoms of an infection that is not resolving or responding to antibiotic therapy.
• Therapeutic goals include all those previously mentioned as well as a return to normal of all blood counts and vital sign values, negative results on culture and sensitivity testing, as well as improved appetite, energy level, and sense of well-being. Signs and symptoms of the infection will begin to resolve once therapeutic levels are achieved.
• Another aspect of evaluation is monitoring for adverse effects of therapy such as superinfections, antibiotic-associated colitis, nephrotoxicity, ototoxicity, neurotoxicity, hepatotoxicity, and other drug-specific adverse effects.
• Superinfection is a secondary infection that occurs because of the destruction of normal flora during antibiotic therapy. Superinfections may occur in the mouth, respiratory tract, GI and GU tracts, and on the skin. Fungal infections are evidenced by fever, lethargy, perineal itching, and other anatomically related symptoms.

Gather data regarding a history of or symptoms indicative of hypersensitivity or allergy.
• For patients taking sulfonamides, a careful assessment for drug allergies to sulfa-type drugs or sulfites, such as oral sulfonylureas and thiazide diuretics, is important to patient safety.
• With penicillins, check for drug allergies. Potential drug interactions include concurrent use with aminoglycosides, clavulanic acid, nonsteroidal anti-inflammatory drugs, oral contraceptives, and warfarin.
• With cephalosporins, conduct a thorough assessment of allergies, including allergy to penicillins, because of possible cross-sensitivity.
• Carbapenems are used when there are complicated connective tissue infections in acutely ill patients who are hospitalized. Assess patients for a history of seizure activity.
• With macrolides, assess baseline cardiac function and hearing status because these drugs may lead to palpitations, chest pain, electrocardiogram changes, and hearing loss and tinnitus.
• With tetracyclines, there is concern regarding the use of these drugs in patients younger than 8 years of age because of the problem of permanent mottling and discoloration of the teeth. Use of these drugs in pregnancy may also pose problems for the fetus.
• Common adverse effects of antibiotics include nausea, vomiting, and diarrhea.
• Inform patients that antibiotics should be taken for the prescribed length of time.
• Normally occurring bacteria are killed by antibiotic therapy; superinfections may arise, noted by fever, perineal itching, oral lesions, vaginal irritation/discharge, cough, and lethargy.
• Give oral antibiotics within the recommended time frames and fluids/foods as indicated.
• All medications should be taken as ordered and in full and around the clock to maintain effective blood levels unless otherwise instructed by the prescriber.
• Doses should not be omitted or doubled up.
• Oral antibiotics are not to be given at the same time as antacids, calcium supplements, iron products, laxatives containing magnesium, or some of the antilipemic drugs.
• Herbal products/dietary supplements are used only if they do not interact with the antibiotic.
• Continually monitor for hypersensitivity reactions past the initial assessment phase because immediate reactions may not occur for up to 30 minutes; accelerated reactions may occur within 1 to 72 hours, and delayed responses may occur after 72 hours. These are noted by wheezing; shortness of breath; swelling of the face, tongue, or hands; itching; or rash.
• If there are signs of a possible hypersensitivity reaction, the first thing to do is stop the dosage form immediately, contact the prescriber, and monitor the patient closely
• The natural flora in the GI tract may be killed; unaffected GI bacteria such as C. difficile may overgrow. This may be prevented by probiotics, such as products containing Lactobacillus, supplements, or cultured dairy products such as yogurt, buttermilk, and kefir.
• Therapeutic effects of antibiotics include a decrease in the signs and symptoms of the infection; a return to normal vital signs, including temperature; negative results on culture and sensitivity tests; normal results for complete blood cell counts; and improved appetite, energy level, and sense of well-being.

are semisynthetic antibiotics structurally and pharmacologically related to the penicillins. They are bactericidal and interfere with bacterial cell wall synthesis.
• Cephalosporins can destroy a broad spectrum of bacteria, and this ability is directly related to the chemical changes that have been made to their basic cephalosporin structure.
• Modifications have given rise to five generations of cephalosporins that are active against gram-positive, gram-negative, or anaerobic bacteria.
• First-generation cephalosporins are usually active against gram-positive bacteria and have limited activity against gram-negative bacteria.
• Like the first-generation cephalosporins, second-generation cephalosporins have coverage against gram-positive organisms but have enhanced coverage against gram-negative bacteria.
• The available third-generation cephalosporins include cefotaxime, cefpodoxime, ceftazidime, ceftibuten, cefdinir, ceftizoxime, and ceftriaxone. They are the most potent of the first three generations of cephalosporins in fighting gram-negative bacteria, but they generally have less activity than first- and second-generation drugs against gram-positive organisms.
• Cefepime (Maxipime) is the prototypical fourth-generation cephalosporin. It has increased activity against many Enterobacter spp. (gram-negative) as well as gram-positive organisms.
• Cefepime is indicated for the treatment of uncomplicated and complicated UTIs, uncomplicated skin and skin structure infections, and pneumonia.
• Ceftaroline (Teflaro) is a fifth-generation cephalosporin. It has a broader spectrum of activity than the current cephalosporins. It is effective against a wide variety of organisms, including methicillin-resistant Staphylococcus aureus (MRSA), making it the only cephalosporin that treats MRSA.
• Commonly reported adverse effects with cephalosporins are mild diarrhea, abdominal cramps, rash, pruritus, redness, and edema. A person allergic to penicillin may also be allergic to cephalosporin. This is referred to as cross-sensitivity.

The penicillins can be divided into four subgroups based on their structure and the spectrum of bacteria they are active against; these subgroups are natural penicillins, penicillinase-resistant penicillins, aminopenicillins, and extended-spectrum penicillins.
• Penicillins kill a wide variety of gram-positive and some gram-negative bacteria. Some bacteria have acquired the capacity to produce enzymes capable of destroying penicillins. Called beta-lactamases, they can inactivate the penicillin.
• Combinations of penicillin and beta-lactamase inhibitors are available and include ampicillin/sulbactam (Unasyn), amoxicillin/clavulanic acid (Augmentin), ticarcillin/clavulanic acid (Timentin), and piperacillin/tazobactam (Zosyn).
• Penicillins are indicated for the prevention and treatment of infections caused by gram-positive bacteria, including Streptococcus spp., Enterococcus spp., and Staphylococcus spp.
• Most natural penicillins have little, if any, ability to kill gram-negative bacteria.
• Allergic reactions may occur with penicillins. Common adverse effects include urticaria, pruritus, and angioedema.
• Idiosyncratic drug reactions can also occur, such as maculopapular eruptions, eosinophilia, Stevens-Johnson syndrome, and exfoliative dermatitis.
• Three extended-spectrum penicillins, with a wider spectrum of activity, are currently available: carbenicillin, piperacillin, and ticarcillin. Both ticarcillin and piperacillin are available in fixed-combination products that include beta-lactamase inhibitors.