Ch 8 Anti Infectives - Read

Immunocompromised client - difficult to treat any infections in such patients for two reasons:

- Anti-infective drugs cannot totally eliminate the pathogen without causing severe toxicity in the host, and - these patients do not have the inflammatory or immune response in place to deal with even a few invading organisms

Acquired Resistance - Microorganisms develop resistance in a number of ways, including the following

- Producing an enzyme that deactivates the antimicrobial drug. For example, some strains of bacteria that were once controlled by penicillin now produce an enzyme called penicillinase, which inactivates penicillin before it can affect the bacteria. This occurrence led to the development of new drugs that are resistant to penicillinase. - Changing cellular permeability to prevent the drug from entering the cell or altering transport systems to exclude the drug from active transport into the cell. - Altering binding sites on the membranes or ribosomes, which then no longer accept the drug. Producing a chemical that acts as an antagonist to the drug.

Combination therapy may be used for several reasons:

- The health care provider may be encouraged to use a smaller dose of each drug, leading to fewer adverse effects but still having a therapeutic impact on the pathogen. - Some drugs are SYNERGISTIC, which means that they are more powerful when given in combination. - Many microbial infections are CAUSED BY MORE THAN ONE ORGANISM, and each pathogen may react to a different anti-infective agent. - Sometimes, the combined effects of the different drugs DELAY the emergence of resistant strains. This is important in the treatment of tuberculosis (a mycobacterial infection), malaria (a protozoal infection), HIV infection (a viral infection), and some bacterial infections. Resistant strains may be more likely to emerge when fixed combinations are used over time; however, this may be prevented by individualizing the combination.

INTERFERE with DNA SYNTHESIS in the cell, leading to inability to divide and cell death.

FLOURQUINOLONES

Bacterial resistance to an anti-infective could be the result of which of the following?

Natural or intrinsic properties of the bacteria The production of chemicals that antagonize the drug Changes in cellular permeability or cellular transport systems

Bacteriostatic/fungastatic

Some anti-infectives are not as aggressive against invading organisms; they interfere with the ability of the cells to reproduce or divide. These drugs are said to be

bactericidal or fungicidal,

Some anti-infectives are so active against the infective microorganisms that they actually cause the death of the cells they affec

ALTER the PERMEABILITY of the cell membrane to allow essential cellular components to leak out, causing cell death.

Some antibiotics, antifungals, and antiprotozoal drugs

Anti-infective drugs destroy cells that have invaded the body. They do not specifically destroy only the cell of the invader, and because of this many adverse effects can be anticipated when an anti-infective is used. Which of the following adverse effects are often associated with anti-infective use?

Superinfections Renal toxicity Diarrhea

Anti-infective agents may act on the cells of invading organisms in several different ways, but the goal?

The goal is interference with the normal function of the invading organism to prevent it from reproducing and to cause cell death without affecting host cells.

Polymyxin B (generic) - available in

This drug is available for IM, IV, or intrathecal use, as well as an ophthalmic agent for the treatment of infections caused by susceptible bacteria.

Anti-Infective Agents - in Children - General Principles

Use anti-infectives with caution; early exposure can lead to early sensitivity. Controversy is widespread regarding the use of antibiotics to treat ear infections, a common pediatric problem. Some believe that the habitual use of antibiotics for what might well be a viral infection has contributed greatly to the development of resistant strains. May have increased susceptibility to the gastrointestinal (GI) and nervous system effects of anti-infectives, monitor hydration and nutritional status carefully.

Antibiotics are not effective in the treatment of

Viral infection and common cold

Meropenem - causes

almost always causes very uncomfortable GI effects; in fact, use of this drug has been associated with potentially fatal pseudomembranous colitis. It also results in headache, dizziness, rash, and superinfections

INTERFERE with the steps involved in PROTEIN SYNTHESIS, a function necessary to maintain the cell and allow for cell division.

aminoglycosides, the macrolides, and chloramphenicol (see the section on adverse effects for a box on chloramphenicol)

An example of an anti-infective used as a means of prophylaxis would be

an antibiotic used before dental surgery

Polymyxin B (generic)

an older antibiotic, uses a surfactant-like reaction to enter the bacterial cell membrane and disrupt it, leading to cell death in susceptible gram-negative bacteria.

AMINOGLYCOSIDE antibiotics collect in the eighth cranial nerve and can cause

can cause dizziness, vertigo, and loss of hearing

Sensitivity testing of a culture shows

drugs that are capable of controlling that particular microorganism.

Several factors should be considered before beginning one of these chemotherapeutic regimens (greatest benefit and fewest adverse effect) -

identification of the correct pathogen and selection of a drug that is most likely to (1) cause the least complications for that patient and (2) be most effective against the pathogen involved.

penicillins work by doing what to the cell wall

interfere with BIOSYNTHESIS of the pathogen cell wall, this is an effective way to destroy the bacteria without interfering with the host

Bacitracin is available in (prep)

intramuscular, ophthalmic, and topical preparations.

Meopenem - Because of the toxic effect on the GI cells - it is used

it is used only in those infections with proven sensitivity to meropenem and reduced sensitivity to less toxic antibiotics

The emergence of resistant strains of microbes is a serious public health problem. Health care providers can work to prevent the emergence of resistant strains by

limiting the use of antimicrobial agents to the treatment of specific pathogens known to be sensitive to the drug being used.

immunocompromised for any reason e.g

malnutrition, age, acquired immune deficiency syndrome, use of immunosuppressant drugs

Because of the actions of polymyxin B on cell membranes, however, it can be toxic to the human host, leading to

nephrotoxicity, neurotoxicity (facial flushing, dizziness, ataxia, paresthesias, and drowsiness), and drug fever and rashes. Therefore, it is reserved for use in acute situations when the invading bacterium has been proven to be sensitive to polymyxin B and less sensitive to other, less toxic antibiotics

A broad-spectrum antibiotic would be the drug of choice when

one is waiting for culture and sensitivity results.

*The goal of anti-infective therapy is

reduction of the population of the invading organism to a point at which the human immune response can take care of the infection

BACITRACIN is now indicated ONLY for the treatment of

respiratory infections in infants caused by susceptible staphylococci, treatment of eye infections, prevention of infections in minor skin wounds, and treatment of minor skin infections caused by susceptible strains of staphylococci

CHLOROQUINE, which is used to treat malaria and some other rheumatoid disorders, can accumulate in the

retina and optic nerve and cause blindness.

PREVENT the cells of the invading organism from USING SUBSTANCES essential to their GROWTH and DEVELOPMENT, leading to an inability to divide and eventually to cell death.

sulfonamides, the antimycobacterial drugs, and trimethoprim-sulfamethoxazole (a combination drug frequently used to treat urinary tract infections) work in this way.

Meropenem (Merrem IV), an IV antibiotic, inhibits

synthesis of bacterial cell walls in susceptible bacteria

Many infections that once led to lengthy, organ-damaging, or even fatal illnesses are now managed quickly and efficiently with the use

systemic anti-infective agents

The spectrum of activity of an anti-infective indicates

the anti-infective's effectiveness against different invading organisms.

Bacitracin (Baci-IM, AK-Tracin, Baciguent) is an antibiotic that interferes with

the cell wall synthesis of susceptible staphylococcal bacteria

Combination therapy is often used in treating infections. An important consideration for using combination therapy would be that

the combination of drugs can delay the emergence of resistant strains.

Prophylaxis

to prevent infections before they occur.

The most commonly encountered adverse effects associated with the use of anti-infective agents are direct

toxic effects on the kidney, GI tract, and nervous system. Hypersensitivity reactions and superinfections also can occur.

Meropenem (Merrem IV), an IV antibiotic - used to

used to treat intra-abdominal infections and some cases of meningitis caused by susceptible bacteria.

Superinfections can occur when anti-infective agents destroy the normal flora of the body. Candida infections are commonly associated with antibiotic use. A patient with this type of superinfection would exhibit

vaginal discharge or white patches in the mouth