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Learning objectives

  • Contrast bacteriostatic versus bactericidal antibacterial activities
  • Contrast broad-spectrum drugs versus narrow-spectrum drugs
  • Explain the significance of superinfections
  • Discuss the significance of dosage and the route of administration of a drug
  • Identify factors and variables that can influence the side effects of a drug
  • Describe the significance of positive and negative interactions between drugs

Several factors are important in choosing the most appropriate antimicrobial drug therapy, including bacteriostatic versus bactericidal mechanisms, spectrum of activity , dosage and route of administration , the potential for side effects , and the potential interactions between drugs. The following discussion will focus primarily on antibacterial drugs , but the concepts translate to other antimicrobial classes.

Bacteriostatic versus bactericidal

Antibacterial drugs can be either bacteriostatic or bactericidal in their interactions with target bacteria. Bacteriostatic drugs cause a reversible inhibition of growth, with bacterial growth restarting after elimination of the drug. By contrast, bactericidal drugs kill their target bacteria. The decision of whether to use a bacteriostatic or bactericidal drugs depends on the type of infection and the immune status of the patient. In a patient with strong immune defenses, bacteriostatic and bactericidal drugs can be effective in achieving clinical cure. However, when a patient is immunocompromised, a bactericidal drug is essential for the successful treatment of infections. Regardless of the immune status of the patient, life-threatening infections such as acute endocarditis require the use of a bactericidal drug.

Spectrum of activity

The spectrum of activity of an antibacterial drug relates to diversity of targeted bacteria. A narrow-spectrum antimicrobial targets only specific subsets of bacterial pathogens. For example, some narrow-spectrum drugs only target gram-positive bacteria , whereas others target only gram-negative bacteria . If the pathogen causing an infection has been identified, it is best to use a narrow-spectrum antimicrobial and minimize collateral damage to the normal microbiota. A broad-spectrum antimicrobial targets a wide variety of bacterial pathogens, including both gram-positive and gram-negative species, and is frequently used as empiric therapy to cover a wide range of potential pathogens while waiting on the laboratory identification of the infecting pathogen. Broad-spectrum antimicrobials are also used for polymicrobic infections (mixed infection with multiple bacterial species), or as prophylactic prevention of infections with surgery/invasive procedures. Finally, broad-spectrum antimicrobials may be selected to treat an infection when a narrow-spectrum drug fails because of development of drug resistance by the target pathogen.

The risk associated with using broad-spectrum antimicrobials is that they will also target a broad spectrum of the normal microbiota, increasing the risk of a superinfection , a secondary infection in a patient having a preexisting infection. A superinfection develops when the antibacterial intended for the preexisting infection kills the protective microbiota , allowing another pathogen resistant to the antibacterial to proliferate and cause a secondary infection ( [link] ). Common examples of superinfections that develop as a result of antimicrobial usage include yeast infections ( candidiasis ) and pseudomembranous colitis caused by Clostridium difficile , which can be fatal.

Questions & Answers

In what way do carriers influence epidemics?
Crizzabarquero Reply
causes of occult blood
Acuc Reply
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need to be sign in online to highlight
Martha
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Zahreen
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Judy
what is anatomy
Suleiman Reply
human anatomy is the study of the structure of the human body
Roja
in Gram staining what is primary stain
Obed Reply
crystal violet
Mounika
Gentian violet
fiftrate
The initial infection with human cytomegalovirus most commonly occurs: A. during early childhood, by exchange of body fluids. B. in utero, by transplacental transmission from a latently infected pregnant woman. C. by transfer of saliva between young adults. D. by sexual intercourse. E. as a result of blood transfusion or organ transplantation.
Zahraa Reply
The initial infection with human cytomegalovirus most commonly occurs: A. during early childhood, by exchange of body fluids. B. in utero, by transplacental transmission from a latently infected pregnant woman. C. by transfer of saliva between young adults. D. by sexual intercourse. E. as a result o
Zahraa
define the most serious disease affects the human affects reproductive organs?
nuur
e. coli is one of the most common infectors of the urinary tract. it can attach to epithelial cell in the urethra and resist the pressure of voiding through____
Simeon Reply
adhesins and pili
Mounika
the product obtained by simplest conventional microbial process is
shridhan Reply
the product obtained by simplest conventional microbial fermentation process is
shridhan
curd
Mounika
beer cheese
Khushi
what is macrobiology
Esther Reply
study in microorganisms
Siva
what is lactose
adekanbi Reply
codomint marker such as RELP are useful for
Nandan Reply
how this process start
Radhika Reply
deffination of staining
Bhavanimangali Reply
It's using dies to differentiate microorganism
shalon
Staining can be defined as a process of using stains or dye to differentiate microorganisms in an environment or habitat.
adeolu
is a dye that imparts colour on an object or a microorganism.
fiftrate
with the aid of a well labeled diagram describe the conducting system
Maridad Reply
what is cellular immunity
namugenyi Reply
Cellular Immunity. -Lymphocytes act against target cell. -Acts directly by killing infected cells.
abdinor
What are NK cells
Peter
Natural killer cells
Rahaba
what are Antigen determinant
mary
cellular immunity is the state where the lymphocytes destroy the infected or targeted cell
cynthia
any examples of oedema
cynthia

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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