Antibiotic resistance

1. Antibiotic
Resistance
AKASH KANNAN P
I. M.SC. MICROBIOLOGY
SRI PARAMAKALYANI COLLEGE

2. INTRODUCTION
• Antibiotic resistance refers to the ability of bacteria to resist the
effects of antibiotics. This happens when bacteria develop
mechanisms to prevent antibiotics from killing them, either by
modifying the antibiotic's target site, pumping the antibiotic out
of the cell, or producing enzymes that break down the antibiotic.
• Cellular stress results in selective pressures on a microorganism
leading to the development of resistance within a population
• Three possible outcomes when antibiotics are introduced:
1. Death (Bacteriocidal)
2. Growth Inhibition (Bacteriostatic)
3. Resistance

3. • Antibiotic resistance is a growing problem
worldwide and is considered a major threat
to public health, as it makes bacterial
infections more difficult to treat and can
lead to increased morbidity, mortality, and
healthcare costs.
• The overuse and misuse of antibiotics in
both human and animal populations are the
primary drivers of antibiotic resistance.

4. History of antibiotics
• 1928: Penicillin first discovered by
Alexander Fleming
• The first antibiotic was penicillin,
discovered accidentally from a mold
culture.
• Chain and Florey, helped develop
penicillin into a widely available
medical product
• 1943- Drug companies begin mass
production of penicillin
• 1944 - U.S. Military takes Penicillin to
the battlefield
• Today, over 100 different antibiotics are
available to cure minor, and life-
threatening infections.

5. Mechanism of resistance gene
transfer
• Transfer of r-genes from one bacterium to another
1. Conjugation
2. Transduction
3. Transformation
• Transfer of r-genes between plasmids within the
bacterium
1. By transposons
2. By Integrons

6. Transfer of r-genes from one
bacterium to another
• Conjugation : Main mechanism for spread of
resistanceThe conjugative plasmids make a connecting
tube between the 2 bacteria through which plasmid
itself can pass.
• Transduction : Less common methodThe plasmid DNA
enclosed in a bacteriophage is transferred to another
bacterium of same species.Seen in Staphylococci ,
Streptococco
• Transformation : least clinical problem.Free DNA is
picked up from the environment (i.e .. From a cell
belonging to closely related or same strain.

9. Mechanisms of Resistance gene transfer
Transposons
• Transposons are sequences of
DNA that can move around
different positions within the
genome of single cell.
• " The donor plasmid containing
the Transposons, co-integrate
with acceptor plasmid. They can
replicate during cointegration
• "Both plasmids then separate
and each contains the r-gene
carrying the transposon.
• "Eg ; Staphylococci, Enterococci

10. Mechanisms of Resistance Gene Transfer
Integrons
• "Integron is a large mobile DNA can spread Multidrug resistance
• "Each Integron ispacked with multiple gene casettes, each consisting
of a resistance gene attached to a small recognition site.
• "These genes encode several bacterial functions including resistance
and virulence.
• "They cannot promote self transfer

12. Biochemical mechanism of antibiotic
resistance
• Antibiotic resistance is the ability of bacteria to resist the effects of
antibiotics. This occurs due to various mechanisms, including:
• Modification of the target site: Bacteria may modify the target site of
antibiotics, such as penicillin-binding proteins (PBPs), which are responsible
for cell wall synthesis. This modification makes it difficult for the antibiotic
to bind to the target site, leading to antibiotic resistance.
• Enzymatic degradation of antibiotics: Bacteria may produce enzymes that
can degrade antibiotics, such as β-lactamases, which can hydrolyze the β-
lactam ring of penicillins and cephalosporins, rendering them ineffective.
• Efflux pumps: Bacteria may produce efflux pumps, which are membrane
proteins that can actively pump antibiotics out of the cell. This reduces the
concentration of antibiotics inside the cell, making it difficult for the
antibiotic to exert its effect.
• Decreased permeability: Bacteria may also reduce the permeability of their
cell membranes, making it difficult for antibiotics to enter the cell.
• Alternative metabolic pathways: Bacteria may also develop alternative
metabolic pathways that bypass the antibiotic target, rendering the
antibiotic ineffective.

15. Person to person
• Bacteria are everywhere, and we are exposed to them all the time. We all have our
own unique bacterial “makeup”; some types of bacteria may be the same across
populations while others differ, or the abundance of different types may vary. Bacteria
can spread from one person to another through direct contacts between people.
Transmission can also occur indirectly, for example when someone coughs. If a person
contaminates a surface (such as a doorknob) with bacteria, these bacteria can be
transferred to another person who touches the surface. That does not necessarily
mean that this person will be infected or colonized by these bacteria. Good hand
hygiene is important to limit the spread of pathogens and the risk of becoming a
carrier of resistant bacteria. Still, even with good hygiene practices, bacteria are a
normal part of our surroundings that we will be continuously exposed to.

16. Animals to humans and vice versa
• Bacteria can spread from animals to humans, but also the other way around –
from humans to animals. When animal pathogens become resistant to first line
antibiotics, diseases become more difficult to treat, just as in humans. Many
people come in close contact with animals in their daily life as we keep them as
pets in our homes or raise animals for food. Wildlife encounters are also possible.
Zoonotic diseases are infections that can be passed from animals to humans,
either directly or by vectors such as ticks and mosquitoes.
• Resistant bacteria can be common in livestock and there are several examples
where farmers and their families carry the same resistant bacteria as their
animals .Likewise, livestock veterinarians are at risk of carrying livestock-
associated resistant bacteria. The bacteria may then spread further in society.

17. Food
• All animals have bacteria living in and on their bodies. In many animal
farms, antibiotics are used to prevent and treat infections as well as for
growth promotion. The animals on the farm can then become colonized
with antibiotic resistant bacteria, that can spread among the animals.
During slaughter or when processing the meat, these bacteria may also
be transferred to the product. Crops that come in contact with animal
manure may also be contaminated.
• Eating food contaminated with bacteria may directly cause an infection,
such as diarrhea caused by Salmonella, Campylobacter and
enterohaemorrhagic E. coli (EHEC). Resistant bacterial strains, or genes
encoding resistance, may also be transferred to the normal gut flora of
the consumer without causing an infection. The resistant bacteria can
potentially cause infections later on and spread to other people.

18. • Resistant bacteria are frequently detected in chicken and meat and
other produce. However, the exact impact of this is for human health
is currently not known and may differ in different parts of the world.
Some studies demonstrate similarities between the antibiotic
resistance genes found in meat and those found in human pathogens,
while other studies have not seen this connection.
• Measures to reduce the risk of spreading antibiotic resistance via food
includes the whole food chain such as disease prevention at farm, and
appropriate hygiene from farm to fork. Proper cooking and handling of
food helps to decrease the spread of infections as well as resistant
bacteria.

19. Water
• Bacteria can spread via drinking water or water
supplies that are used for example for irrigation,
washing cooking utensils or for hygienic purposes.
Resistant bacteria have been found in many water
sources such as drinking wells, rivers and effluents
from wastewater treatment plants. Several
bacterial diseases can spread via contaminated
water, including typhoid fever and cholera. There
are many ways resistant bacteria can end up in the
water; release of untreated waste from animals
and humans is one important source.

20. Travel
• International travelers spread resistant bacteria across the
world. Any given day several million people will catch a flight,
and if someone carries a resistant bacterium they will bring it
along. Many studies have demonstrated that a large
proportion of international travelers acquire resistant bacteria
during visits in areas with a high prevalence of resistant
bacteria .The risk is even higher for hospitalized patients, who
are exposed to additional risk factors. Several hospital
outbreaks have originated from patients transferred from
another hospital with high prevalence of resistance

21. Trade
• Meat, fruits, vegetables, seeds,
grain, and animals… the list of goods
that are being imported and
exported to and from different
countries all over the world can be
made long. Bacteria can potentially
spread with any.

22. Factors of antibiotic resistance
• Overuse and misuse of antibiotics: Overprescribing
antibiotics, not finishing a full course of antibiotics, and
using antibiotics inappropriately (such as for viral infections)
can all contribute to the development of antibiotic
resistance.
• Poor infection control: Inadequate hygiene, such as not
washing hands properly or not using gloves, can lead to the
spread of resistant bacteria.
• Agricultural use of antibiotics: Antibiotics are often used in
livestock to promote growth and prevent disease, and this
can contribute to the development of antibiotic-resistant
bacteria that can spread to humans through the food chain.
• Lack of development of new antibiotics: The development
of new antibiotics has slowed down in recent years, which
means that we have fewer options to treat infections caused
by antibiotic-resistant bacteria.

23. Thank you