Chapter 38 - Antibiotics Part 1

The four most common mechanisms of antibiotic action are....

1) interference with bacterial cell wall synthesis 2) interference with protein synthesis 3) interference with nucleic acid synthesis 4) anti-metabolite action that disrupts chemical reactions inside the bacterium

To be effective, prophylactic antibiotics need to be given before the procedure, generally ____ minutes before the incision is made to ensure adequate tissue penetration.

30

Culture test results are usually available within ____ to ____ hours.

48 / 72

Penicillins are classified as pregnancy category ____ drugs. They are very safe antibiotics. Their use is contraindicated in patients with known allergy, but because of their relatively good adverse effects profile, there are otherwise very few contraindications to their use.

B

Antibiotic use is strongly associated with the potential for the development of diarrhea. Antibiotic-associated diarrhea is a common adverse effect of antibiotics. However, it becomes serious when it causes ______ infection.

C. difficile

True or False: Patients who are allergic to penicillins do not have an increased risk for allergy to other beta-lactam antibiotics.

False.

Areas of the hospital associated with the greatest risk for HAI include...

ICU transplant units cancer units burn units

Because of this property, it is not unusual to see beta-lactams given via...

IV infusion (also given via intermittent infusion q. 4-6 hours)

Pediatric doses of amoxicillin are sometimes _____ than in the past because of the development of increasingly resistant _____ _____ organisms.

Streptococcus pneumoniae

True or False: Amoxicillin can be given with or without food.

True.

True or False: Generally speaking, only those patients with a history of throat swelling or hives from penicillin should NOT receive cephalosporins.

True.

True or False: It is believed that sulfonamide reactions are immune-mediated and involve the production of reactive drug metabolites in the body.

True.

True or False: Sulfonamides do not affect the metabolism of folic acid in humans.

True.

True or False: Severe allergic reactions are much more common with injected than with oral penicillin.

True. *As is the case with most drugs.

The most common HAIs include...

UTIs surgical site infection bloodstream infections pneumonia

Another type of superinfection occurs when a second infection closely follows the initial infection and comes from an external source (as opposed to normal body flora). A common example is...

a case in which a patient has a viral respiratory infection and develops a secondary bacterial infection

Antibiotic drug therapy begins with...

a clinical assessment of the patient to determine whether he or she has the common signs and symptoms of infection

A therapeutic response to antibiotics is...

a decrease in the specific signs and symptoms of infection compared with the baseline findings (e.g., fever, elevated WBC count, redness, pus, etc.)

antiseptic

a substance used to inhibit the growth of microbes, not necessarily kill them - applied exclusively to LIVING TISSUE

disinfectant

a substance used to kill organisms and is USED ONLY ON NON-LIVING OBJECTS to destroy organisms that may be present

When these bacteria or fungi are killed off by antibiotics, other bacteria or fungi are permitted to take over and cause an infection. An example of a superinfection caused by antibiotics is the development of...

a vaginal yeast infection

Patients who are slow acetylators have a physiologic makeup that causes certain drugs to be metabolized more slowly than usual in a chemical step known as _____. This can lead to toxicity from drug accumulation.

acetylation

Bacterial strains that produce penicillinase were a therapeutic obstacle until drugs were made that inhibit these enzymes (the beta-lactamase inhibitors). One example of a drug that is a combination of penicillin and a beta-lactamase inhibitor is...

amoxicillin (pencillin + clavulanic acid)

health care-associated infection (HAI)

an infection acquired by a patient during the course of receiving treatment for another condition in a health care institution the infection was not present or incubating at the time of admission, but occurs greater than 48 hours after admission

community-acquired infection

an infection acquired by a person who has not recently (within the past year) been hospitalized or had a medical procedure (e.g., dialysis, surgery, catheterization)

The most dangerous reaction is _____ _____, in which a patient can suffocate from drug-induced respiratory arrest.

anaphylactic shock

definitive therapy

antibiotic therapy tailored to treat organism identified with cultures

Antibiotics are also given for prophylaxis. This is oten the case when patients...

are scheduled to undergo a procedure, such as surgery, in which the likelihood of dangerous microbial contamination is high during and/or after the procedure

Why is it important to obtain a culture specimen before initiating antibiotic therapy?

because the presence of antibiotics in the tissues may result in misleading culture results

Before the start of antibiotic therapy, specimens are obtained from the suspected areas of infection to be cultured in an attempt to identify the causative agent. It is important that cultures be obtained when?

before drug therapy is initiated

Some bacterial strains produce the enzyme _____ _____. These enzymes provide an advantage for bacteria, providing resistance to these antibiotics.

beta-lactamase

Because of this, additional drugs known as ____ ____ are added to the several of the penicillin antibiotics to make the drug more powerful against beta-lactamase-producing bacterial strains.

beta-lactamase inhibitors

Beta-lactamase works by...

breaking the chemical bond between the carbon and nitrogen atoms in the structure of the beta-lactam ring and all beta-lactam drugs use their antibacterial efficacy

Patients who report a penicillin allergy need to describe their prior allergic reaction. It is very important for you to document the type of reaction. The decision to treat with ______ therapy in such cases is often a matter of clinical judgement, based on the severity of reported prior reactions to penicillin drugs, the nature of the infection, the drug susceptibility of the causative agent if known, and the availability and patient tolerance of other alternative antibiotics.

cephalosporin

Sulfonamide drugs are a common cause of allergic reaction. Patients will sometimes refer to this as "sulfa allergy" or even "sulfur allergy." Although immediate reactions can occur, sulfonamides typically cause delayed _____ reactions.

cutaneous

The most common severe reactions to any medication that need to be noted in the patient's chart are...

difficulty breathing significant rash/hives/other skin reaction severe GI intolerance

Trimethoprim, although not a sulfonamide, works via a similar mechanism, inhibiting _____ _____ reduction to _____, which results in inhibition of the enzymes of the folic acid pathway.

dihydrofolic acid / tetrahydrofolate

The most common mode of transmission for HAIs is...

direct contact

What are the main differences between disinfectants and antiseptics?

disinfectants: used on non-living objects/higher potency/bactericidal antiseptics: used on living tissue/lower potency/bacteriostatic

Amoxicillin is commonly used for...

ear infections

Antibiotics have three general uses. What are these three uses?

empiric therapy definitive therapy prophylactic therapy

What are the classic signs and symptoms of infection?

fever pain swelling chills sweats weight loss fatigue redness increased WBC count formation of pus

These reactions frequently begin with...

fever followed by a rash

Symptoms of anaphylaxis include...

flushing itching hives anxiety irregular, fast pulse throat and tongue swelling

Some patients have certain genetic abnormalities that result in various enzyme deficiencies. These conditions can adversely affect drug actions in the body. Two of the most common examples of such genetic host factors are...

glucose-6-phosphate dehydrogenase (G6PD) deficiency slow acetylation

The presence of colored sputum (e.g., _____ or _____) may or may not be a sign of a bacterial superinfection during a viral respiratory illness.

green / yellow

Although some antibiotics are ideally taken on an empty stomach, eating a small amount of food with the medication may be sufficient to....

help the patient tolerate the drug and realize its therapeutic benefits

The administration of antibiotics such as sulfonamides to a person with G6PD deficiency may result in...

hemolysis of red blood cells

Other reactions to sulfonamides include...

hepatotoxicty hematologic complications nephrotoxicity nausea/vomiting

Often the signs and symptoms of an infection appear long before a causative organism can be identified. When this happens and the risk for life-threatening or severe complications is high (e.g., suspected acute meningitis), when is an antibiotic given to the patient?

immediately

Sulfonamide MOA

inhibit growth of bacteria by preventing folic acid synthesis by bacterium *do so by preventing step in process of making folic acid (a biosynthetic pathway) so they are also considered an ANTIMETABOLITE

Sulfonamides achieve a very high concentration in the ______, through which they are eliminated. Therefore, sulfamethoxazole/trimethoprim is often used to treat ______.

kidneys / UTIs

As people age, there is a gradual decline in the function of the _____ and _____, the organs primarily responsible for metabolizing and eliminating antibiotics.

kidneys / liver

The anatomical site of hte infection is a very important host factor to consider when deciding not only which antibiotic to use but also the dosage, route of administration, and duration of therapy. Some antibiotics do not penetrate into the site of infection, such as...

lungs / bone / abscesses

Often HAIs are acquired from various devices, such as...

mechanical ventilators IV infusion lines dialysis equipment catheters

The particular organisms that cause HAIs have changed over time. What is currently the common organism causing HAIs?

methicillin-resistant staphylococcus aureus (MRSA)

Most antimicrobials have activity against only one type of microbe (e.g., bacteria, viruses, fungi, protozoans). However, a few drugs have activity against...

more than one class of organisms

Relatively minor adverse effect to antibiotic use include...

nausea/vomiting/diarrhea *these are quite common with antibiotic therapy and are usually not severe enough to require drug discontinuation

Oftentimes patients will become colonized with bacteria. Although bacteria are present in open wounds, in secretions, on mucous membranes, or on the skin, these patients do not have any overt signs of infection. Does colonization require antibiotic treatment?

no (however it is not uncommon for it to be treated - contributes to antibiotic resistance)

Some beta-lactamases produced by bacteria that specifically inactivate PENICILLIN are called...

penicillinases

Two major types of beta-lactams are...

penicillins cephalosporins

_______ and ______ are two broad classes of antibiotics that many have allergic anaphylactic reactions to.

penicillins / sulfonamides

Depending on the level of kidney or liver function of a given older adult, dosage adjustments may be necessary. _____ often play a role in evaluating the dosages of antibiotics and other medications to ensure optimal dosing for a given patient's level of organ function.

pharmacists

Adverse effects associated with amoxicillin include...

pruritis angioedema n/v/d

An example of a drug-drug interaction is that between _____ antibiotics and antacids or multivitamins containing iron, leading to decreased absorption of the drug.

quinolone *this is important because quinolone antibiotics are used to treat serious infections

The intravenous formulations of some penicillins contains large amounts of sodium and/or potassium. Therefore, doses must be adjusted for patients with...

renal dysfunction

The use of sulfamethoxazole/trimethoprim is also used to treat...

respiratory tract infections outpatient Staphylococcus aureus infections (community MRSA)

Antibiotic therapy is considered toxic when...

serum levels of the antibiotic are too high or when the patient has an allergic or other major adverse reaction to the drug (these reactions include rash, itching, hives, fever, chills, joint pain, difficulty breathing, or wheezing)

Photosensitivity reactions are another type of skin reaction that is caused by exposure to sunlight during sulfonamdie therapy. In some cases, such reactions can result in...

severe sunburn

However, in some situations, it is not possible to obtain a sample (especially _____) in a reasonable amount of time, and antibiotic therapy is begun without a sample.

sputum

gram-negative

stain pink/red

gram-positive

stain purple

Antibiotic therapy is said to be ______ when these signs and symptoms do not improve.

subtherapeutic

Sulfonamides were one of the first groups of drugs used as antibiotics. Although there are many drugs in the sulfonamide family, only ______ combined with _______ (a nonsulfonamide antibiotic), known as Bactrim, Septra, or co-trimoxazole and often abbreviated as ________ is used commonly in clinical practice.

sulfamethoxazole / trimethoprim

_____ can occur when antibiotics reduce or completely eliminate the normal bacterial flora, which consist of certain bacteria and fungi that are needed to maintain normal function in various organs.

superinfection

If an organism is then identified in the laboratory, it is then tested for...

susceptibility to various antibiotics

The combination of these two drugs allows for a _____ antibacterial effect.

synergistic

Several antibiotics pass through the placenta and can cause harm to the developing fetus. Drugs that cause developmental abnormalities in the fetus are called ______.

teratogens

One of the common food-drug interactions is that between milk or cheese and _____, which results in decreased GI absorption of the drug.

tetracycline

Infants and children may not be able to take certain antibiotics, such as ______, which affect the development of teeth or bones; ______, which may affect bone or cartilage development in children; and ______, which may displace bilirubin from albumin and precipitate kernicterus (hyperbilirubinemia).

tetracycline / quinolones / sulfonamides

The beta-lactams exhibit time-dependent killing. This means...

that their concentration must be above the minimum inhibitory concentration to kill bacteria

Penicillins are generally well-tolerated and associated with very few adverse effects. As with many drugs, the most common adverse effects involve...

the GI system

morphology

the different shapes of bacteria

When a host's defenses are somehow compromised, that person becomes susceptible to infection. The microorganisms invade and multiply in the body tissues, and if the infective process overwhelms the body's immune system, what happens?

the infection becomes clinically apparent

A vaginal yeast infection occurs when...

the normal vaginal bacterial flora is reduced by antibiotic therapy and yeast growth is no longer kept in balance

Whenever a patient who on or was previously treated with antibiotics develops watery diarrhea, what needs to be done?

the patient needs to be tested for C. diff

Antibiotics are most effective when...

their actions are combined with body defense mechanisms

To optimize antibiotic therapy, the patient is continuously monitored for both _____ efficacy and adverse effects of the drug.

therapeutic

Penicillins and cephalosporins share a common mechanism of action. What is it?

they both interfere with the synthesis of the bacterial peptidoglycan cell wall (peptidoglycan = cell wall)

empiric therapy

treatment of an infection before specific culture information has been reported or obtained an antibiotic is given that can best kill the microorganisms known to the be the most common causes of the infection

prophylactic therapy

treatment with antibiotics to PREVENT an infection

Subtherapeutic antibiotic treatment can result from...

use of an incorrect route of administration inadequate drainage of an abscess poor drug penetration to the infected area insufficient serum levels of the drug bacterial resistance to the drug

After the causative agent is identified, the antibiotic therapy is then tailored to treat the identified organism by...

using the most narrow-spectrum, least toxic drug possible

C. diff occurs because antibiotics have disrupted the normal gut flora and can cause an overgrowth of Clostridium difficile. The most common symptoms of C. diff are...

watery diarrhea fever abdominal pain