Antimicrobial agent

Consider the categories of antimicrobial agents.

  • Think about differences between viral and bacterial infections.
  • Reflect on why proper identification of the infection is key to selecting the proper
    antimicrobial agent.
    ** Write a 3- page paper that addresses the following:
    Describe the categories of antimicrobial agents.
    Describe differences between viral and bacterial infections.
    Explain why proper identification of viral and bacterial infections is key to selecting the
    proper antimicrobial agent.
    Use current resources of less than 5 years old.
    Arcangelo, V. P., & Peterson, A. M. (Eds.). (2013). Pharmacotherapeutics for advanced
    practice: A practical approach (3rd ed.). Ambler, PA: Lippincott Williams & Wilkins.
    Chapter 8, “Principles of Antimicrobial Therapy” (pp. 96-117)

Antimicrobial agent


Antimicrobial agents are synthetic or natural compounds that are designed to either
inhibit or kill infectious microorganisms. They are chemical compounds that are able to prevent
the multiplication of microorganisms (bacteriostatic) so as to enable the immune system of the
host to overcome them or completely kill them (bactericidal). Antibiotics that are taken with the
aim of improving the symptoms caused by a particular disease are referred to as
chemotherapeutic drugs. These drugs are produced by a microbe, such as bacteria or fungus and
are the derivative chemical compounds produced by the microbes. Specific microbial gents are

Antimicrobial agent 2

used to treat systemic infections. These agents usually have no significant effects on the

Bacterial and viral infection

Bacterial infections are caused by bacteria, while viral infections are caused by viruses.
Example of bacterial infection includes urinary tract infection, throat and tuberculosis just to
mention a few. Viral diseases are caused by viruses and they include such diseases as common
cold, chickenpox and AIDS among many others. Bacteria refer to single-celled microorganisms
that live in various types of environments ranging from extremely cold to extremely hot
environment. Many strains of bacteria inhabit the intestines of living organism such as humans.
Most bacteria are usually harmless and play a symbiotic role in their environment. Some species
of bacteria assists in the digestion of food (Navid, 2012).

Viruses are pseudo micro-organism that cannot exist on their own. Viruses require a
living host in order to replicate. Viruses are much smaller than bacteria and depend on living
hosts like plants and animals. When a virus gains entry into a human body, it invades certain
human cells and takes over the cellular mechanism by redirecting it to produce the virus. The
most essential distinction between viruses and bacteria is that antibiotic drugs are able to kill
bacteria, but are ineffective against viruses (Navid, 2012).

There are various criteria of categorizing antimicrobial agents. Generally, antimicrobial
agents can be categorized into biological/natural, that is, antibiotic or synthetic.

Antibiotics can be categorized into two main classes based on their mechanism of action.
The two classes are bactericidal and bacteriostatic. Bactericidal antibiotics act by killing bacteria,

Antimicrobial agent 3

while bacteriostatic simply inhibits the growth and reproduction of bacteria. Bactericidal
antibiotics kill bacteria by inhibiting the synthesis of cell wall. Example of bactericidal
antibiotics includes cephalosporin, Beta-lactam antibiotics such as the derivatives of penicillin,
metronidazole, daptomycin and fluoroquinolones just to mention a few. Antibiotics that are
bactericidal in some organisms may be bacteriostatic in other microorganisms. The least
concentration of a drug that is capable of killing microorganism is referred to as the minimum
bactericidal concentration (MBC) (Arcangelo & Peterson, 2013).

Bacteriostatic antibiotics inhibit the growth and multiplication of bacteria by interfering
with the replication of DNA, production of bacterial protein as well as other aspects of cellular
metabolism of bacteria. Both bactericidal and bacteriostatic antibiotics must work together with
the immune system to eliminate the microorganisms from the body. At a high concentration,
bacteriostatic agents can become bactericidal. On the other hand, low concentration of
bactericidal agents is bacteriostatic. The least concentration of a drug that is capable of inhibiting
the growth of the microorganism is referred to as the minimum inhibitory concentration (MIC).

Antibiotics can be categorized based on the structure and function. This type of
classification produces five functional groups which cover most antibiotics. These groups
include: antibiotics that inhibit the synthesis of cell wall; inhibitors of synthesis of protein;
membrane function inhibitors; Inhibitors of nucleic acid synthesis; and anti-metabolites
(Arcangelo & Peterson, 2013).

The classification of antimicrobial agents is based on the following factors:

 The spectrum of activity

Antimicrobial agent 4

 Where they have been obtained from.

 Mechanism of action.

 Type of action.

 Chemical structure

 The organism in which they are active against.

The classification based on the primary organism in which an antimicrobial agent is active
against produces the following types of antimicrobial agents:

 Antibacterial/antibiotics; these drugs are active against both gram positive and gram
negative bacteria, for instance, penicillin and erythromycin.

 Antifungal agents such as amphotericin B which are active against fungal infection.

 Antihelmintic agents such as Mebendazole are active against Helminthic infestation.

 Antiprozoal agents such as chloroquine works against protozoan infections.

 Antiviral agents like acyclovir are active against viral infection.

Based on the spectrum of activity, antimicrobial can be classified into two categories.
The first category is the narrow spectrum antibiotic such as penicillin, which targets one type of
microbes. The second category is the spectrum antibiotic such as tetracyclin which is active
against a wide variety of microbes (Arcangelo & Peterson, 2013).

Antimicrobial agent 5

Antimicrobial agents can also be categorized based on the level of importance in human
medicine. This mode of categorization gives four main categories which are as follows
(Arcangelo & Peterson, 2013):

 Very high importance: comprises of Therapeutic agents for tuberculosis like
 High importance: Penicillins and Quinolones
 Medium importance: Bacitracin and Fosfomycin
 Low importance: Flavophosholipids

Proper diagnosis that is able to identify the causative agents or the etiology of an
infectious disease is necessary so as to come up with the most efficient antimicrobial agents. The
type of infection has to be identified based on the type of symptoms and the laboratory test to
determine the correct treatment.


Arcangelo, V. P., & Peterson, A. M. (2013). Pharmacotherapeutics for advanced practice: A
practical approach (3rd ed.). Ambler, PA: Lippincott Williams & Wilkins. 
Navid, A. (2012). Microbial systems biology methods and protocols. New York: Humana Press.