McKenna's Pharmacology for Nursing, 2e

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P A R T 2  Chemotherapeutic agents

BACTERIA AND RESISTANCE TO ANTIBIOTICS

pathogens, such as bacteria, fungi or yeasts, because antibiotics (particularly broad-spectrum agents) destroy bacteria in the flora that normally work to keep these opportunistic invaders in check. When “normal” bacteria are destroyed or greatly reduced in number, there is nothing to prevent the invaders from occupying the host. In most cases the superinfection is an irritating adverse effect (e.g. vaginal yeast infection, candidiasis, diarrhoea), but in some cases, the superinfection can be more severe than the infection that was originally being treated. Treat- ment of the superinfection leads to new adverse effects and the potential for different superinfections. A vicious cycle of treatment and resistance is the result. ■■ The goal of antibiotic therapy is to reduce the population of invading bacteria to a size that the human immune response can deal with. ■■ Bacteria can be classified as gram-positive (frequently found in respiratory infections) or gram-negative (frequently found in GI and GU infections). They can also be classified as anaerobic (not needing oxygen) or aerobic (dependent on oxygen). ■■ Culture and sensitivity testing ensures that the correct antibiotic is chosen for each infection, a practice that may help to decrease the number of emerging resistant-strain bacteria. KEY POINTS KEY POINTS

Bacteria have survived for hundreds of years because they can adapt to their environment. They do this by altering their cell wall or enzyme systems to become resistant to (i.e. protect themselves from) unfavourable conditions or situations. Many species of bacteria have developed resistance to certain antibiotics. For example, bacteria that were once very sensitive to penicillin have developed an enzyme called penicillinase, which effec- tively inactivates many of the penicillin-type drugs. New drugs have had to be developed to effectively treat infec- tions involving these once-controlled bacteria. It is very important to use these drugs only when the identity and sensitivity of the offending bacterium have been estab- lished. Indiscriminate use of these new drugs can lead to the development of more resistant strains for which there is no effective antibiotic (see later discussion of new antibiotics for additional information on linezolid). The longer an antibiotic has been in use, the greater is the chance that the bacteria will develop into a resist- ant strain. Efforts to control the emergence of resistant strains involve intensive educational programs that advocate the use of antibiotics only when necessary and effective and not for the treatment of viral infections such as the common cold (Box 9.3). In addition, the use of antibiotics may result in the development of superinfections or overgrowth of resistant Using antibiotics properly In 2003, the US Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) joined efforts to educate the public and healthcare providers about the dangers of inappropriate use of antibiotics. The evidence-based practice guidelines combine data from many studies to outline the most efficacious use of antibiotics.To review some of the studies, review the references listed in the Bibliography. Nurses and midwives should include some of the following points about the risks and dangers of antibiotic abuse in each person’s education plan: • Explain clearly that a particular antibiotic is effective against only certain bacteria and that a culture needs to be taken to identify the bacteria. • Explain that bacteria can develop resistant strains that will not be affected by antibiotics in the future, so use of antibiotics now may make them less effective in situations in which they are really necessary. • Ensure that people understand the importance of taking the full course of medication as prescribed, even if they feel better. Stopping an antibiotic midway through a The evidence BOX 9.3

regimen often leads to the development of resistant bacteria. Using all of the medication will also prevent people saving unused medication to self-treat future infections or to share with other family members. • Tell people that allergies may develop with repeated exposures to certain antibiotics. In addition, explain to people that saving antibiotics to take later, when they think they need them again, may lead to earlier development of an allergy, which will negate important tests that could identify the bacteria making them sick. • Offer other medications, such as antihistamines, decongestants, or even chicken soup, to people who request antibiotics; this may satisfy their need for something to take. Explaining that viral infections do not respond to antibiotics usually offers little consolation to people who are suffering from a cold or the flu. The publicity that many emergent, resistant strains of bacteria have received in recent years may help to get the message across to people about the need to take the full course of an antibiotic and to use antibiotics only when they are appropriate.