Antimicrobial Chemotherapy, DPA 200-2

COLLEGE OF HEALTH – YAMFO
Medical Microbiology 1 (BCOH201), for B.Sc.

Physician Assistants, Level 200
2021/2022 Academic Year, First Semester
Lecture Venue: Hon. Apraku Lartey’s Block, LH 1/2
Tutor: Benjamin Pulle Niriwa

Contacts’ Details: 0242015959, pullebenjamin@gmail.com
Office Hours: 8:00AM-5:00PM
1
OBJECTIVES AND ACTIVITIES
Lecture Objectives: Activities Time
Periods student should have the ability to
7th Week, Antimicrobial 1. Know What 1. Tutor Gives Mon.,
07.03.2022 chemotherapy: Antimicrobial is Didactic 01:30PM
Selective Lectures with to
toxicity, 2. Know the Types of example, 03:40PM
mechanism of Antimicrobials scenarios, &
action and demonstrates
resistance 3. Describe the 2. Tutor Asks
Mechanism of Action Questions to
of Antimicrobials Assess If
Students
4. Explain How Understand
Resistance of 3. Students
Microbes to participate by
Antimicrobial Occurs discussing and
asking
questions
2
Introduction
Any time the word treat or cure comes into your mind, it is
referring mostly to knowing the patient’s condition and managing
it with antimicrobials.
Antimicrobials are substances that have the ability of inhibiting

the action(s) of pathogens or destroying them completely.
Depending on the type of infection or infectious agent that is

inhibited or destroyed, antimicrobials are grouped as:
“Antibacterial, antifungal, antiviral and anti-parasitic drugs”.
3
Terms Describing Antimicrobial Quality
Sensitive: This is the ability of a microbe to response to the
destructive or inhibiting effect(s) of an antimicrobial(s). If a
pathogen is not sensitive to an antimicrobial, it cannot treat it.
If one is infected and is able to recover after taking a particular

antimicrobial, then the infectious agent is sensitive to that drug.
Example if S. aureus infects a wound and Gen is able to help the

wound heal, then it means that S. aureus is sensitive to Gen.
Resistance: This is inability of an infection to be cured after the

patient is given an antimicrobial or some antimicrobials. If a
pathogen is resistant to an antimicrobial, it cannot be used to
treat or cure it.
4
Terms Describing Antimicrobial Quality
It does not also means that because an antimicrobial is
susceptible, it would effectively when used for treating or curing
that condition.
Intermediate: If an antimicrobial susceptibility test result is

saying that an antimicrobial is intermediate, it means that there is
an uncertainty whether it could be effective for treatment or not.
For normal or standard dosage, such antimicrobial would work

poorly but effectively with increasing doses in some situations.
5
What Can Hinder Antimicrobial Effectiveness?
Several conditions determine the success/ability of a particular
antimicrobial for the treatment of an infection, not only because
the pathogen is susceptible to that antimicrobial. These are:
Site of infection – The antimicrobial must be able to invade the

site where the pathogen is causing the infection.
Obstruction(s): There must be nothing like very deep abscess or

abscesses and scars at the infection’s site that obstruct the drug
from reaching the infectious agent.
Severity of the disease, lymphoblastic leukemia
Presence of granulocytopaenia
6
Types/Features of Antimicrobials
Depending on the type of infection or infectious agent that is
inhibited or destroyed, antimicrobials are grouped as: Broad
spectrum and narrow spectrum
Using the infectious agent that is treated or cured, they are:

“Antibacterial, antifungal, antiviral and anti-parasitic drugs”.
Broad-spectrum antibiotics are able to inhibit or destroy

several types of infectious agents; whether they are Gram
positives, Gram negative or both.
But a narrow-spectrum antibiotics, are only effective against

specific families of bacteria. 7
Broad-spectrum antibiotics are properly used in the following
clinical situations:
Empirically, prior to the formal identification of the causative
bacteria, when there is a wide range of possible illnesses and
a potentially serious illness would result if treatment is
delayed
Broad spectrum antibiotics are more likely to disrupt normal

flora of the body while narrow-spectrum antibiotics would
mostly not do that.
8
 Antibiotics are also further divided into two main categories
depending on what they do in the bacteria as demonstrated in
vitro as: “Bactericidal and bacteriostatic”.
Bactericidal antibiotics refer to antimicrobials that are able to

“Kill” or destroy bacteria completely, the bacteriostatic ones
inhibit bacteria’s growths or replication.
The bactericidal antibiotics are to do that using a term selective

toxicity and this is the ability of a chemical substance or drug to
selectively kill a microorganism without harming its host.
9
Therapeutic index or therapeutic ratio is comparing the
quantity of a therapeutic agent that is able to initiate the
therapeutic effect to the quantity that is able cause toxicity.
The larger the Therapeutic Index the safer the drug. Example,
penicillin has a high Therapeutic Index of how it works.
The bacteriostatic drugs also use the same principle, in that

they selectively inhibit the bacteria from replicating without
hurting their host(s).
10
Now, using their sources too, there are three main types of
antibacterial agents:
Antibiotics from natural sources
Garlic, ginger, honey, thyme or oregano essential oils.
Synthetic antibiotics
antimicrobial agents of synthetic origin such as
sulfonamides, nalidixic acid and chloramphenicol.
Semisynthetic antibiotics produced by a microbe that are

subsequently modified to enhance their antimicrobial
properties
11
How Do Antimicrobials Work? (Mechanism)
Using the specific mechanism(s) by which antimicrobials work,
they are again divided into those that:
1. Inhibit cell wall synthesis
2. Inhibit protein synthesis
3. Inhibit nucleic acid synthesis
4. Damage to plasma membrane, and
5. Inhibit synthesis of essential metabolites

12
13
Those That Inhibit Cell Wall Synthesis: b-Lactam Drugs
These are how they are able to do that:
At the final stages where the cell wall synthesis is supposed to
be completed, the antimicrobial(s) permanently stop production
and the activities enzymes needed for those stages.
Formation of peptide bridges between adjacent stands of the

peptidoglycan layer is mediated by these enzymes. Once their
production or activities are inhibited, this is also halted.
 β-lactam drugs have rings that structurally resemble that of

normal enzyme’s substrate. So, it is easy for these drugs to bind
to the enzymes and that affect enzymatic activity 14
Some bacteria produce β-
lactamase-enzyme that destroys
the β-lactam ring, so that the
enzymatic activity can continue.
So, β-lactam drugs like penicillins

and cephalosporins are to inhibit
these enzymatic activities.
Examples are: Cephalosporins

like Cedadroxi, Cefuroxime, or
Ceftazidine, and Vancomycin
15
Antibacterial agents that Inhibit Protein Synthesis
Target ribosomes of bacteria
Aminoglycosides: bind to 30S subunit causing it to distort

and malfunction; blocks initiation of translation
Macrolides: They bind to 50S subunit and prevents protein
synthesis from continuing.
Tetracyclines: bind to 30S subunit blocking attachment of
tRNA.
Chloramphenicol: This binds to 50S and prevent formation
of peptide bond.
16
Those Inhibit Nucleic Acid Synthesis
Target enzymes required for nucleic acid synthesis
Fluoroquinolones: They inhibit enzymes that are used to

maintain the supercoiling of closed circular DNA
Rifamycins: block prokaryotic DNA-dependent RNA

polymerase from initiating transcription
17
Antibacterials – Competitive Inhibitors
Sulfonamides (Sulfa drugs)

Inhibit folic acid synthesis, Mostly Broad spectrum drugs
18
Antibacterial that Destroy or Cause Injury to the Plasma
Membrane
Polymyxin B: binds to membrane of G- bacteria and alters

permeability
This leads to leakage of cellular contents and cell death
These drugs also bind to eukaryotic cells to some extent, which

limits their use to topical applications
19
Antibacterial Drugs that Inhibit Synthesis of

Essential Metabolites
Competitive inhibition by substance that resembles

normal substrate of enzyme
Examples are Sulfa drugs
20
Antimicrobial Resistance
Antimicrobial resistance refers to the ability of pathogens like,
“bacteria” to resist the action(s) or effects that antimicrobials have
on them.
Globally antimicrobial resistance (AMR) keeps on rising and

spreading like bush fires in every nation. It is a public health
threat that negatively affect treatments of most infectious
diseases.
Aside treatment of infections, it is also a serious problem in food

security since never know which food might end up contributing to
AMR.
21
What Causes Antimicrobial Resistance?
There are so many multiple factors that contribute to
antimicrobial resistance! Some of these are:
Self-Medication due to multiple factors like poverty, mistrust,

Avoiding unnecessary prescription,
Poor diagnosis and treatment,
Failure To Complete Treatment,
Failure to Take Drugs at the Times Advised,
Treating TB in co-infected HIV/AIDs patients Poorly,
Poor Identification of contacts (Poor Contact Tracing),
Few Research Into Antimicrobial Resistance.
 When the above are avoided antimicrobial can be prevented.

22
Antimicrobials’ Self-Medication
There have been a global rise in self-medication where people
who do not feel well or are sick. They buy drugs from licensed
chemical sellers without visiting a health facility
There many reasons that people especially who are the

majority involved in self-medications give. The major amongst
all is due to many factors at the hospitals of which mistrust is
one of them
The most commonly self-medicated antimicrobials are

narcotic drugs and aphrodisiac.
In Ghana there was a report of increased abuse of

Tramadol by the youths 23
Summary of Lecture
This lecture covers the following:
1. Students now Know What an Antimicrobial is
2. Students Can tell at least three (3) Types of

Antimicrobials
3. Students Can Now Describe the Mechanism of

Action of Some Antimicrobials
4. They Know What Cause Antimicrobial Resistance

and How They Can Prevent Them. 24
Some References/Reading Materials
• Meir, H., M., Balawi, I., A., Meer, H., M., Nayel, H., & Al-Mobarak, M., F. (2001).
Fever and granulocytopenia in children with acute lymphoblastic leukemia under
induction therapy. Saudi Med J. 22(5): 423–427
• Okwu, M., U., Olley, M., Akpoka, A., O., & Izevbuwa, O., E. (2019). Methicillin-
Resistant Staphylococcus aureus (MRSA) and Anti-MRSA Activities of Extracts of
Some Medicinal Plants: A brief Review. AIMS Microbiol. 5(2): 117-137.
Doi: 10.3934/microbiol.2019.2.117
• WHO., World Health Organization. (2021). Antimicrobial Resistance. Key facts,
Fact sheets. Retrieved from https://www.who.int/news-room/fact-
sheets/detail/antimicrobial-resistanceon 09.03.2022 at 12:51AM
25
Structural Components of Microbes Contribute to Their
Virulence, But They Are Helpful In Vaccine Production!
THANK
YOU!
26

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COLLEGE OF HEALTH – YAMFO

Medical Microbiology 1 (BCOH201), for B.Sc.

2021/2022 Academic Year, First Semester

Lecture Venue: Hon. Apraku Lartey’s Block, LH 1/2

Tutor: Benjamin Pulle Niriwa

Antimicrobials are substances that have the ability of inhibiting

Depending on the type of infection or infectious agent that is

If one is infected and is able to recover after taking a particular

Example if S. aureus infects a wound and Gen is able to help the

Resistance: This is inability of an infection to be cured after the

Intermediate: If an antimicrobial susceptibility test result is

For normal or standard dosage, such antimicrobial would work

Site of infection – The antimicrobial must be able to invade the

Obstruction(s): There must be nothing like very deep abscess or

Severity of the disease, lymphoblastic leukemia

Using the infectious agent that is treated or cured, they are:

Broad-spectrum antibiotics are able to inhibit or destroy

But a narrow-spectrum antibiotics, are only effective against

Broad spectrum antibiotics are more likely to disrupt normal

Bactericidal antibiotics refer to antimicrobials that are able to

The bactericidal antibiotics are to do that using a term selective

The bacteriostatic drugs also use the same principle, in that

Semisynthetic antibiotics produced by a microbe that are

2. Inhibit protein synthesis

3. Inhibit nucleic acid synthesis

4. Damage to plasma membrane, and

5. Inhibit synthesis of essential metabolites

Formation of peptide bridges between adjacent stands of the

 β-lactam drugs have rings that structurally resemble that of

So, β-lactam drugs like penicillins

Examples are: Cephalosporins

Target ribosomes of bacteria

Aminoglycosides: bind to 30S subunit causing it to distort

Target enzymes required for nucleic acid synthesis

Fluoroquinolones: They inhibit enzymes that are used to

Rifamycins: block prokaryotic DNA-dependent RNA

Sulfonamides (Sulfa drugs)

Polymyxin B: binds to membrane of G- bacteria and alters

This leads to leakage of cellular contents and cell death

These drugs also bind to eukaryotic cells to some extent, which

Antibacterial Drugs that Inhibit Synthesis of

Competitive inhibition by substance that resembles

Examples are Sulfa drugs

Globally antimicrobial resistance (AMR) keeps on rising and

Aside treatment of infections, it is also a serious problem in food

Self-Medication due to multiple factors like poverty, mistrust,

 When the above are avoided antimicrobial can be prevented.

There many reasons that people especially who are the

The most commonly self-medicated antimicrobials are

In Ghana there was a report of increased abuse of

1. Students now Know What an Antimicrobial is

2. Students Can tell at least three (3) Types of

3. Students Can Now Describe the Mechanism of

4. They Know What Cause Antimicrobial Resistance

Virulence, But They Are Helpful In Vaccine Production!

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