7.2. Explain how antimicrobial resistance occurs

This guide will help you answer 7.2. Explain how antimicrobial resistance occurs.

Antimicrobial resistance (AMR) is when microorganisms such as bacteria, viruses, fungi, and parasites change in ways that make the medicines used to treat them less effective. This means that infections become harder to treat. AMR is one of the biggest health threats facing people worldwide. It can lead to longer illnesses, higher medical costs, and a greater risk of death.

In health and social care settings, AMR is a serious concern. Many individuals in care services have weaker immune systems. This makes them more vulnerable to infections. Medicines like antibiotics are used regularly. If these medicines lose their effectiveness, it can have severe consequences for patients and the public.

It is important to look at how microorganisms adapt, and how certain practices create conditions for resistance to develop and spread.

Microorganisms and How They Work

A microorganism is a living organism too small to be seen without a microscope. Examples include:

• Bacteria
• Viruses
• Fungi
• Parasites

Some microorganisms are harmless or even helpful. Others cause disease. Antimicrobials such as antibiotics, antivirals, antifungals, and antiparasitic drugs target harmful microorganisms. Each type of antimicrobial works on a particular class of pathogen.

Antibiotics target bacteria by attacking their structure or stopping them from multiplying. Antivirals prevent viruses from reproducing inside human cells. Antifungal medicines kill or stop the growth of fungi.

When an antimicrobial is used, it aims to kill the harmful organism or stop it from spreading. But microorganisms can adapt to survive. This ability to adapt is the root of antimicrobial resistance.

The Process of Developing Resistance

Microorganisms reproduce quickly. Some bacteria can multiply in minutes. Each time they reproduce, small changes can happen in their genetic material. These changes are called mutations.

Some mutations give the microorganism a survival advantage. For example:

• Producing enzymes that break down the antimicrobial drug
• Changing the target site so the drug no longer attaches effectively
• Pumping the drug out of the cell before it can act

If an antimicrobial is present, most of the sensitive microorganisms will die. If by chance some have a mutation that makes them resistant, they will survive. Those resistant microorganisms then multiply. Over time, the population of microorganisms becomes dominated by resistant strains.

This process is called selection pressure. The antimicrobial acts as a pressure that selects for resistant organisms. The more a particular drug is used, the more this pressure builds, and the more likely resistant strains are to survive and spread.

Spread of Resistant Strains

Once resistant microorganisms are present, they can spread between people, animals, and the environment. In health and social care settings, resistant strains can pass from patient to patient in several ways:

• Direct contact with infected individuals
• Touching contaminated surfaces or equipment
• Poor hand hygiene practices among staff
• Inadequate cleaning of shared spaces

Resistant strains can also spread in the wider community through:

• Consumption of contaminated food or water
• Contact with animals carrying resistant bacteria
• Travel between areas with high and low resistance rates

Causes Linked to Human Practices

The rise in AMR is strongly linked to the way antimicrobials are used. Key factors include:

• Overuse of antibiotics: Prescribing antibiotics for viral infections, such as colds or flu, when they are not effective.
• Incomplete courses: Stopping medication early when symptoms improve, allowing surviving bacteria to multiply.
• Inappropriate prescribing: Using broad-spectrum antibiotics unnecessarily instead of targeted ones.
• Use of antibiotics in farming: Giving antibiotics to livestock to promote growth or prevent disease in healthy animals can lead to resistant bacteria in the food chain.
• Lack of infection control: Poor hygiene and sanitation allow resistant organisms to spread more easily.

Bacterial Resistance Mechanisms

Bacteria have several ways of resisting antimicrobials:

• Enzyme production: Some bacteria produce enzymes like beta-lactamase that break down antibiotics before they can act.
• Target modification: Antibiotics often attach to a specific site on a bacterial cell. If the bacteria alter this site, the antibiotic cannot bind properly.
• Efflux pumps: Proteins in the bacterial cell wall that pump out antimicrobial drugs before they can cause harm.
• Reduced permeability: Bacteria can change their cell walls to make it harder for drugs to enter.

Sometimes bacteria gain resistance genes from other bacteria through horizontal gene transfer. This can happen via:

• Conjugation: Transfer of genetic material through direct contact between bacteria.
• Transformation: Uptake of free DNA from the environment.
• Transduction: Transfer by viruses that infect bacteria.

This means resistance does not only arise from mutations. It can also be acquired from other resistant bacteria.

Impact in Health and Social Care

In health and social care environments, AMR can:

• Limit treatment options for common infections
• Increase the risk of complications
• Require the use of more toxic or less effective drugs
• Lead to longer hospital stays
• Increase the cost of care
• Cause outbreaks of resistant infections within care facilities

Examples of resistant organisms include:

• MRSA (Methicillin-resistant Staphylococcus aureus) – resistant to many antibiotics
• C. difficile (Clostridioides difficile) – resistant to several antibiotics and causes severe diarrhoea
• ESBL-producing bacteria (Extended-spectrum beta-lactamases) – resistant to many beta-lactam antibiotics

The Role of Selection Pressure in Care Settings

In health and social care, antibiotics and other antimicrobials are used more often than in the general community. This creates high selection pressure.

For example, in a care home where residents often receive antibiotics, resistant bacteria are more likely to develop and remain in the environment. If cleaning and hygiene standards slip, resistant bacteria can spread quickly between residents and staff.

Preventing and Slowing Resistance

Workers in health and social care can help reduce AMR by:

• Following correct infection prevention and control procedures
• Using antimicrobials only when prescribed, and as directed
• Completing full courses of treatment
• Avoiding pressure on prescribers to issue antimicrobials unnecessarily
• Practising strict hand hygiene before and after contact with each person in care
• Properly cleaning and disinfecting shared equipment and surfaces
• Wearing appropriate personal protective equipment (PPE) where required

Health professionals must balance the need to treat infections against the risk of encouraging resistance. Prescribers often follow local and national guidelines to choose the correct drug, at the right dose, for the correct length of time.

Factors Contributing to AMR Beyond Healthcare

Antimicrobial resistance is not only created in hospitals and care environments. It is also affected by:

• Agriculture: Use of antibiotics in animals can lead to resistant bacteria in meat, milk, and eggs. These can pass to humans through food handling and consumption.
• Global travel: People can bring resistant strains from one country to another in a short time.
• Water contamination: Antibiotic residues and resistant bacteria from human waste or farming can contaminate water sources.

This means AMR is both a health and environmental problem.

Differences Between Drug Types and Resistance

• Antibiotic resistance: Mainly applies to bacteria. Caused by overuse, misuse, and genetic adaptation.
• Antiviral resistance: Less common, but can occur when viruses mutate, making treatments like those for HIV or influenza less effective.
• Antifungal resistance: Occurs when fungal cells change to survive treatments such as azoles or echinocandins.
• Antiparasitic resistance: Seen in malaria parasites developing resistance to drugs like chloroquine.

The process is similar for all around selection pressure, survival of resistant strains, and spread through individuals and populations.

Why AMR Is a Threat

AMR threatens to make once-treatable infections deadly again. Surgeries, chemotherapy, and medical treatments that depend on effective antimicrobials could become far riskier. Without effective drugs, routine infections could lead to severe illness or death.

It also affects public trust in healthcare and increases anxiety among patients and staff. Families of patients with resistant infections often experience distress and extra worry.

Final Thoughts

Antimicrobial resistance happens because microorganisms adapt to survive drug treatment. This process is driven by overuse and misuse of these medicines. Once resistance appears, it can spread quickly and make infections much harder to treat.

In health and social care, staff play an important role in slowing the spread. This means sticking to infection control practices, supporting correct use of medicines, and raising awareness among colleagues, patients, and families.

Keeping antimicrobials effective for future generations will depend on everyone following best practice now. The decisions made today about medicine use, hygiene, and patient care will have a direct impact on whether these life-saving treatments continue to work in the years ahead.