Unit 7 Antimicrobial agents: General characteristics and
mode of action
Amphotericin B is a polyene
antifungal drug. It binds to ergosterol, a key component of fungal cell
membranes, and forms channels or pores. These pores disrupt the integrity of
the cell membrane, leading to leakage of cellular contents and ultimately
causing cell death.
Griseofulvin, on the other hand,
is an antifungal medication that belongs to the class of drugs known as
antifungal antibiotics. It works by inhibiting the synthesis of fungal cell
walls. Specifically, it interferes with the assembly of microtubules, which are
essential for the growth and replication of fungal cells. By disrupting this
process, griseofulvin prevents the fungus from spreading and helps to eliminate
the infection.
Amphotericin B can have some side
effects. The most common ones include fever, chills, nausea, vomiting, and
headache. It can also cause kidney damage, so it's important to monitor kidney
function during treatment. Some people may experience allergic reactions or
have issues with their blood cells. It's always best to talk to a healthcare
professional if you have any concerns or questions about specific side effects.
Amantadine is primarily used
to treat influenza A virus infections. It works by blocking a protein called
M2 ion channel in the viral envelope. By inhibiting this protein, Amantadine
prevents the release of viral genetic material into the host cell, ultimately
stopping the replication of the virus.
Acyclovir, on the other hand, is
commonly used to treat herpes virus infections, including genital herpes, cold
sores, and shingles. It is a nucleoside analogue that gets incorporated into
the viral DNA during replication. Once incorporated, Acyclovir disrupts the
viral DNA synthesis, preventing the virus from replicating and spreading.
Amantadine blocks the M2 ion
channel by binding to it and preventing the flow of ions, like protons, into
the viral particle. This disruption of ion flow inhibits the release of viral
genetic material into the host cell, which is necessary for the virus to
replicate. By blocking the M2 ion channel, Amantadine helps to stop the spread
of the influenza A virus.
Amantadine typically starts
working within a few hours to a couple of days after starting treatment.
However, it's important to note that the exact timeframe can vary depending on
the individual and the specific condition being treated. It's always best to
follow the instructions provided by your healthcare professional and give the
medication some time to take effect.
Amantadine can interact with
certain medications, so it's important to let your healthcare provider know
about all the medications you're taking. Some medications that may interact
with Amantadine include anticholinergic drugs, such as certain medications for
Parkinson's disease or certain antihistamines. Additionally, Amantadine may
enhance the effects of certain medications that affect the central nervous
system, like sedatives or alcohol.
Different terms related to
antibiotic resistance. Let's break them down:
1. Azidothymidine (AZT): While
AZT is not an antibiotic, it is an antiviral medication used to treat HIV/AIDS.
It works by inhibiting the reverse transcriptase enzyme, which is crucial for
the replication of the virus. By blocking this enzyme, AZT helps to slow down
the progression of HIV infection.
2. Antibiotic resistance: This
refers to the ability of bacteria or other microorganisms to resist the effects
of antibiotics. Over time, bacteria can develop mechanisms to survive and grow
in the presence of antibiotics, making the medications less effective in
treating infections.
3. MDR (Multi-Drug Resistant):
MDR bacteria are those that have become resistant to multiple antibiotics,
making them more challenging to treat. These bacteria have developed mechanisms
to withstand the effects of multiple drugs, limiting treatment options.
4. XDR (Extensively Drug
Resistant): XDR bacteria are even more concerning as they are resistant to a
wide range of antibiotics, including those considered to be the last line of
defense. This makes infections caused by XDR bacteria extremely difficult to
treat.
5. MRSA (Methicillin-Resistant
Staphylococcus aureus): MRSA is a type of bacteria that has developed
resistance to many antibiotics, including methicillin and other
penicillin-related antibiotics. It can cause difficult-to-treat infections,
particularly in healthcare settings.
6. NDM-1 (New Delhi
metallo-beta-lactamase-1): NDM-1 is an enzyme produced by certain bacteria that
confers resistance to a broad range of antibiotics, including carbapenems,
which are often considered the last resort for treating severe infections.
1. Azidothymidine (AZT): While
AZT is not an antibiotic, it is an antiviral medication used to treat
HIV/AIDS. It works by inhibiting the reverse transcriptase enzyme, which is
crucial for the replication of the virus. By blocking this enzyme, AZT helps to
slow down the progression of HIV infection.
2. Antibiotic resistance: This
refers to the ability of bacteria or other microorganisms to resist the effects
of antibiotics. Over time, bacteria can develop mechanisms to survive and grow
in the presence of antibiotics, making the medications less effective in
treating infections.
3. MDR (Multi-Drug Resistant):
MDR bacteria are those that have become resistant to multiple antibiotics,
making them more challenging to treat. These bacteria have developed mechanisms
to withstand the effects of multiple drugs, limiting treatment options.
4. XDR (Extensively Drug
Resistant): XDR bacteria are even more concerning as they are resistant to a
wide range of antibiotics, including those considered to be the last line of
defense. This makes infections caused by XDR bacteria extremely difficult to
treat.
5. MRSA (Methicillin-Resistant
Staphylococcus aureus): MRSA is a type of bacteria that has developed
resistance to many antibiotics, including methicillin and other
penicillin-related antibiotics. It can cause difficult-to-treat infections,
particularly in healthcare settings.
6. NDM-1 (New Delhi
metallo-beta-lactamase-1): NDM-1 is an enzyme produced by certain bacteria that
confers resistance to a broad range of antibiotics, including carbapenems,
which are often considered the last resort for treating severe infections.
AZT, also known as zidovudine,
is an antiretroviral drug used in the treatment of HIV/AIDS. It belongs to
a class of medications called nucleoside reverse transcriptase inhibitors
(NRTIs). AZT works by inhibiting the reverse transcriptase enzyme, which is
necessary for the replication of the HIV virus.
When HIV infects a person, it
enters their immune cells and uses the reverse transcriptase enzyme to convert
its RNA into DNA. This DNA is then integrated into the host cell's DNA,
allowing the virus to reproduce. AZT works by blocking the reverse transcriptase
enzyme, preventing the virus from replicating and slowing down the progression
of the disease.
AZT is typically used in
combination with other antiretroviral drugs to form a highly active
antiretroviral therapy (HAART) regimen. This combination approach helps to
reduce the viral load in the body, improve the immune system, and prolong the
lifespan of individuals living with HIV/AIDS.
It's important to note that AZT,
like any medication, can have side effects. Common side effects may include
nausea, vomiting, headache, fatigue, and anemia. However, the benefits of AZT
in managing HIV/AIDS often outweigh the potential side effects.
They can develop antibiotic
resistance through a few different ways:
1. Mutation: Bacteria can undergo
genetic mutations that give them the ability to withstand the effects of
certain antibiotics. These mutations can occur naturally over time or be
acquired from other resistant bacteria.
2. Horizontal gene transfer:
Bacteria can share their genetic material with other bacteria through processes
like conjugation, transformation, or transduction. This means that a bacterium
that is already resistant to an antibiotic can pass on its resistance genes to
other bacteria, allowing them to become resistant as well.
3. Overuse and misuse of
antibiotics: When antibiotics are used too often or not used properly, it can
create an environment where bacteria are exposed to the drugs frequently. This
selective pressure can favor the survival and growth of resistant bacteria,
leading to the development of antibiotic resistance.
4. Evolutionary pressure:
Bacteria have a remarkable ability to adapt and evolve. When exposed to
antibiotics, the bacteria that are naturally resistant or acquire resistance
genes have a survival advantage. Over time, these resistant bacteria become more
prevalent in a population.
There are a few key factors
that contribute to the development of antibiotic resistance:
1. Natural selection: Bacteria
reproduce rapidly, and with each generation, there is a chance for genetic
mutations to occur. Sometimes, these mutations can provide bacteria with the
ability to resist the effects of antibiotics. When antibiotics are used, they
kill the susceptible bacteria, but the resistant ones survive and multiply,
passing on their resistance genes to future generations.
2. Overuse and misuse of
antibiotics: When antibiotics are used too frequently or inappropriately, it
puts selective pressure on bacteria. This means that the bacteria that have
natural or acquired resistance to antibiotics have a survival advantage. Over
time, these resistant bacteria become more prevalent in a population, making
the antibiotics less effective.
3. Transmission of resistance
genes: Bacteria can also acquire resistance genes from other bacteria through a
process called horizontal gene transfer. This can happen through mechanisms
like conjugation, where genetic material is exchanged between bacteria, or
through the uptake of DNA from the environment. This transfer of resistance
genes allows bacteria to quickly develop resistance to multiple antibiotics.
Multi-Drug Resistant, refers
to bacteria or other microorganisms that have developed resistance to
multiple types of antibiotics. This means that they are not affected by the
usual medications that would normally be used to treat infections caused by
those bacteria.
MDR can occur due to several
reasons:
1. Overuse and misuse of
antibiotics: Similar to antibiotic resistance, the inappropriate use of
antibiotics can contribute to the development of MDR. When antibiotics are used
excessively or not taken as prescribed, it provides an opportunity for bacteria
to adapt and become resistant to multiple drugs.
2. Poor infection control: In
settings such as hospitals, clinics, or long-term care facilities, the spread
of MDR organisms can occur if proper infection control practices are not
followed. This can lead to the transmission of resistant bacteria between
patients, making it more challenging to treat infections effectively.
3. Global travel and migration:
With increased global travel and migration, MDR organisms can spread across
different regions and countries. This can result in the introduction of
resistant strains into new populations, making it difficult to control their
spread.
XDR stands for Extensively Drug
Resistant, and it's even more serious than MDR. When bacteria or other
microorganisms are classified as XDR, it means they are resistant to a wide
range of antibiotics, including those considered as last-resort treatments.
XDR bacteria have developed
resistance not only to multiple classes of antibiotics but also to some of the
most potent ones available. This makes them extremely difficult to treat and
can lead to severe infections that are challenging to control.
Similar to MDR, the causes of XDR
include overuse and misuse of antibiotics, poor infection control practices,
and global spread. However, XDR organisms have acquired additional resistance
mechanisms, making them even more formidable.
The consequences of XDR
infections can be devastating, as they limit treatment options and increase the
risk of complications and mortality. In some cases, infections caused by XDR
bacteria may require specialized antibiotics or combination therapies that have
more potential side effects or are less effective.
MRSA stands for
Methicillin-Resistant Staphylococcus aureus. Staphylococcus aureus is a type of
bacteria commonly found on the skin or in the nose of healthy individuals.
However, when it becomes resistant to methicillin and other antibiotics, it can
cause serious infections that are difficult to treat.
MRSA infections can occur in both
healthcare settings (HA-MRSA) and in the community (CA-MRSA). In healthcare
settings, MRSA can spread through contact with contaminated surfaces, medical
equipment, or from person to person. In the community, MRSA can be transmitted
through close skin-to-skin contact or by sharing personal items like towels or
razors.
Symptoms of MRSA infections can
vary depending on the site of infection, but they often include skin infections
such as boils, abscesses, or cellulitis. In more severe cases, MRSA can cause
bloodstream infections, pneumonia, or surgical site infections.
Treating MRSA can be challenging
because it is resistant to many commonly used antibiotics. However, there are
still effective treatment options available, such as certain antibiotics or a
combination of medications. In some cases, drainage of abscesses or surgical
intervention may be necessary.
Preventing MRSA infections
involves practicing good hygiene, such as regular handwashing, keeping wounds
clean and covered, and avoiding sharing personal items. In healthcare settings,
infection control measures like proper hand hygiene, isolation precautions, and
environmental cleaning are crucial in preventing the spread of MRSA.
