Page 81 - Review of Medical Microbiology and Immunology ( PDFDrive )

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mebooksfree.com mebooksfree.com Role of Antimicrobial Drug Stewardship in Mitigating These Problems mebooksfree.com mebooksfree.com
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PART I Basic Bacteriology
70
TABLE 10–1 Basic Principles of Antimicrobial Drug Stewardship
Current Problems in the Use
of Antibiotics
1. Use antibiotics only when a microbiologic diagnosis indicates effectiveness
Inappropriate use of
2. Empiric therapy should be tailored to the most likely pathogen(s)
antibiotics
3. Send appropriate cultures before starting antibiotics
Overuse of broad-spectrum
1. Use narrow-spectrum antibiotics whenever possible
2. Require approval for the use of advanced generation broad-spectrum antibiotics
antibiotics
High rate of adverse effects
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mebooksfree.com mebooksfree.com 1. Stop antibiotics as soon as appropriate to reduce adverse effects, such as antibiotic-associated colitis caused by mebooksfree.com
Clostridium difficile
2. Be aware of the effect of the patient’s renal function on the dose of antibiotic prescribed
3. Be aware of the patient’s hypersensitivity to specific antibiotics
4. Determine whether the patient’s declared hypersensitivity is correct and clinically significant
5. Warn patients regarding certain idiosyncratic drug reactions, such as photosensitization
reported, they may not always be of significance such as some
or awareness of the physician. Risk avoidance on the part of
alleged hypersensitivity reactions. If optimal treatment requires
the physician is also common. Inadequate microbiologic
information plays a role as well. Patient expectation and direct
a drug such as penicillin to which the patient says they are
allergic, then skin testing can be employed to determine the
In summary, antimicrobial stewardship refers to the effort
accuracy of that claim. In addition, patients should be warned
regarding the possibility that certain drugs may cause adverse
to improve the treatment of infectious diseases by the appro-
effects. For example, certain photosensitizing antibiotics may demands for antibiotics contribute to the problem.
priate use of antibiotics. This is critical in this era of rising
rates of multidrug-resistant pathogens. Targeted therapy with
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cause a rash when the patient is exposed to sunlight.
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the most appropriate single antibiotic will hopefully improve
The reasons that inappropriate use of antibiotics occurs are
varied. Probably the most important is the lack of knowledge
clinical outcomes and reduce the cost of care.
PRINCIPLES OF ANTIMICROBIAL THERAPY
The most important concept underlying antimicrobial
therapy is selective toxicity (i.e., selective inhibition of the
viruses use many of the normal cellular functions of the
growth of the microorganism without damage to the host).
host in their growth, it is not easy to develop a drug that
Selective toxicity is achieved by exploiting the differences
the host cell.
between the metabolism and structure of the microorgan-
Broad-spectrum antibiotics are active against several
ism and the corresponding features of human cells. For
types of microorganisms (e.g., tetracyclines are active
example, penicillins and cephalosporins are effective anti- specifically inhibits viral functions and does not damage
mebooksfree.com mebooksfree.com mebooksfree.com primarily used against certain gram-positive cocci, namely, mebooksfree.com
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against many gram-negative rods, chlamydiae, mycoplas-
bacterial agents because they prevent the synthesis of pep-
tidoglycan, thereby inhibiting the growth of bacterial but
mas, and rickettsiae). Narrow-spectrum antibiotics are
active against one or very few types (e.g., vancomycin is
not human cells.
There are four major sites in the bacterial cell that are
sufficiently different from the human cell that they serve as
staphylococci and enterococci).
Antifungal drugs are included in this chapter because
the basis for the action of clinically effective drugs: cell wall,
they have similar unique sites of action such as cell walls,
ribosomes, nucleic acids, and cell membrane (Table 10–2).
cell membranes, and nucleic acid synthesis. Additional
There are far more antibacterial drugs than antiviral
information on antifungal drugs is given in Chapter 47.
drugs. This is a consequence of the difficulty of designing a
BACTERICIDAL & BACTERIOSTATIC ACTIVITY
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mebooksfree.com mebooksfree.com mebooksfree.com phagocytosis, are required to kill the bacteria. Bactericidal mebooksfree.com
In some clinical situations, it is essential to use a bacteri-
drugs are particularly useful in certain infections (e.g.,
cidal drug rather than a bacteriostatic one. A bactericidal
drug kills bacteria, whereas a bacteriostatic drug inhibits
those that are immediately life-threatening; those in
patients whose polymorphonuclear leukocyte count is
their growth but does not kill them (Figure 10–1). The
below 500/μL; and endocarditis, in which phagocytosis is
salient features of the behavior of bacteriostatic drugs are
limited by the fibrinous network of the vegetations and
that (1) the bacteria can grow again when the drug is with-
bacteriostatic drugs do not effect a cure).
drawn, and (2) host defense mechanisms, such as
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