145. CCA Study Note: Microorganisms, Normal Flora, and Multidrug-Resistant Organisms

The Big Picture

Tiny living things exist almost everywhere, including on and inside the human body. Most do not cause disease. Some are harmful and lead to infection.

You need to understand the difference between helpful microbes and harmful ones. You also need to know why some bacteria resist antibiotics and why careful infection precautions matter when caring for clients.

Look for Nova Scotia CCA Notes throughout this page for current provincial guidance.

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Course Notes: Key Ideas You Need to Know

What Is a Microorganism?

A microorganism, also called a microbe, is an organism so small that it is visible only with a microscope. Microbes live in water, air, food, soil, plants, animals, and nonliving objects.

They also live on and inside people. Common locations include the skin, mouth, nose, respiratory tract, stomach, and intestines.

Most microbes usually do not cause infection or disease. These harmless microbes are called nonpathogens.

A pathogen is a harmful microbe with the ability to cause infection or disease.

Four Main Types of Microorganisms

Bacteria

Bacteria are single-celled microbes found on living things, dead matter, and nonliving objects.

Bacteria reproduce quickly when conditions suit them. Some bacteria enter a dormant, inactive state and form a protective covering called an endospore. Bacillus and Clostridium species are examples of bacteria that form endospores.

The endospore protects the bacterium from harsh conditions and makes it difficult to kill. When suitable conditions return, the bacterium becomes active and starts multiplying again.

Some bacteria are harmless. Others cause serious infections in different body systems. Bacterial infections are usually treated with antibiotics.

Examples include:

• Salmonella enteritidis
• Helicobacter pylori
• Staphylococcus epidermidis
• Staphylococcus aureus

Viruses

Viruses are infectious particles much smaller than bacteria. They need living cells to grow and multiply.

A virus takes over the machinery inside a host cell to make new virus particles. Two patterns described in viral growth are:

• Lytic cycle: The virus produces new virus particles and kills the host cell.
• Lysogenic cycle: The virus becomes part of the host cell’s DNA and remains dormant for a period.

Examples of viral infections include AIDS ⓘ, hepatitis, influenza, herpes, and the common cold.

Antibiotics do not work against viruses. Specific antiviral medications exist for some viruses.

Some viral diseases are preventable through vaccination, including measles, mumps, rubella, polio, and influenza. A vaccine contains a live or killed bacterium or virus and is given to produce active immunity against a specific infectious disease.

Examples of viruses include:

• varicella zoster, which causes chicken pox
• hepatitis A, B, and C
• herpes simplex
• influenza
• COVID-19

Fungi

Fungi live on organic matter such as plants and animals. Yeasts and moulds are types of fungi, and some are pathogenic.

Fungal infections occur in areas such as the mouth, vagina, skin, and feet. Many fungal infections are mild, while some become life-threatening, especially in susceptible ⓘ people.

Examples include:

• athlete’s foot, or tinea pedis
• ringworm, or tinea corporis
• scalp fungus, or tinea capitis
• Candida, including thrush in the mouth

Parasites

Parasites obtain nourishment and protection from another living organism, called a host.

Transmission occurs between animals and humans, between people, or from humans to animals. Contaminated food or water is one route of transmission.

Parasites range from microscopic, single-celled organisms to worms visible without a microscope. Illness ranges from mild discomfort to severe illness and possibly death.

Parasites are more common in developing countries. Examples found in Canada include lice, mites, pinworms, Giardia, and Trichomonas ⓘ.

What Microbes Need to Grow

A reservoir is the environment where a microbe lives and grows. It is also called a host.

Microbes grow well in warm, dark reservoirs with water and nourishment. Most also need oxygen, although some live without it.

Microbes that infect humans grow best around body temperature. Heat and light destroy them.

Understanding Normal Flora

Normal flora are microorganisms that naturally live in specific areas on or inside the human body.

They are found in places such as:

• the skin
• respiratory tract
• digestive system
• eyes
• ears
• vagina

Normal flora are harmless nonpathogens and provide important benefits. Normal-flora bacteria help with digestion, produce some vitamins, and help protect against infection from pathogens.

Location matters. A bacterium that belongs to the normal flora in one body area can cause serious disease if it enters another body site.

Example: Escherichia coli, or E. coli, normally lives in the colon and assists with food metabolism. If E. coli enters the bloodstream or urinary tract, it causes a serious infection.

Keeping Normal Flora in Balance

The number of microbes in normal flora changes in response to different factors, including infection by pathogens.

Illness and medications such as antibiotics sometimes kill part of the normal flora. This disrupts the balance of beneficial bacteria and leaves the person at risk of a harmful infection.

Probiotic foods such as yogourt, cheeses, and pickled foods can help maintain normal flora, especially while a person takes antibiotics.

Antibacterial soaps are intended for handwashing or for removing contaminated substances from skin. Overusing them for purposes such as bathing destroys part of the normal flora.

Overuse of antimicrobial soaps and alcohol-based sanitizers can damage beneficial bacteria. Normal flora play an important role in helping the immune system protect the body from infection.

How Antibiotic Resistance Develops

Bacteria reproduce rapidly. Past misuse and overprescribing of antibiotics led some bacterial strains to mutate ⓘ and become resistant to antibiotics.

Different resistance methods are described:

• Some bacteria produce membrane proteins that remove antibiotic medication.
• Some produce proteins that neutralize or deactivate antibiotics.
• Some transfer antibiotic-resistant genes to other bacteria through conjugation.

Conjugation allows resistance genes to move between different bacterial species. The result is that some infections resist most antibiotics.

What Is a Multidrug-Resistant Organism?

A multidrug-resistant organism (MRO) is a bacterial strain that resists more than one antibiotic and is difficult to treat with common antibiotics. MROs are sometimes called superbugs.

MRO infections spread easily among people at greater risk of infection, including babies, older people, people with serious medical conditions, and people with weakened immune systems.

Severe MRO infections become fatal in some cases because treatment is difficult. MROs therefore create a serious concern for clients in health care facilities.

The most common MROs in Canada are:

• methicillin-resistant Staphylococcus aureus (MRSA)
• vancomycin-resistant Enterococcus (VRE)
• Clostridium difficile (C. difficile)

Another MRO, extended-spectrum beta-lactamase (ESBL), is increasingly associated with urinary tract infections, wound infections, pneumonia, and bloodstream infections. It is treated in a similar manner to MRSA or VRE.

Carriers and the Spread of MROs

Carriers are people who transfer a pathogen to others without developing an active infection themselves.

Health care workers can become carriers of MROs when proper precautions are not followed. A worker without symptoms then spreads the organism to susceptible clients.

Support workers receive training about special precautions for clients who have an MRO or who are suspected of having one. Workers also need to know the required precautions for new MROs they encounter.

Personal Care Order in a Facility

When providing personal care to several clients, provide care to clients who are not infected with an MRO first. Provide care to clients infected with an MRO afterward.

This order helps reduce the spread of MROs to clients who are not infected.

Hand hygiene means cleaning the hands. Handwashing and glove use are important parts of preventing MRO spread, especially when moving from one infectious client to another.

Clostridium difficile, C. difficile

Clostridium difficile (C. difficile) is a bacterium that causes diarrhea and inflammation of the colon. C. difficile is the most frequent cause of infectious diarrhea in hospitals and long-term care facilities in Canada, as well as in other industrialized countries.

Symptoms include:

• watery diarrhea
• fever
• loss of appetite
• nausea
• abdominal pain and tenderness

Most cases occur in patients who receive certain antibiotics in high doses or for long periods. Antibiotics sometimes destroy normal bacteria in the gut, allowing C. difficile to grow.

C. difficile then produces toxins that damage the bowel and cause diarrhea. Some people have C. difficile bacteria in their bowel without symptoms.

C. difficile and Hand Hygiene

Frequent hand hygiene is the most effective way described for preventing transmission of health care-associated infections.

During a C. difficile outbreak, washing with soap and water is one of the best defenses against further spread.

When soap and water are unavailable, frequent use of alcohol-based hand rub ⓘ is encouraged. Alcohol-based hand rub is less effective than soap and water against C. difficile because it does not destroy C. difficile spores.

C. difficile Treatment Background

People with mild symptoms sometimes require no treatment. More severe cases involve medication and, in some situations, surgery.

Fecal transplantation is also being studied as a treatment for persistent C. difficile infection.

Methicillin-Resistant Staphylococcus aureus, MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is a common bacterium that is not killed by most antibiotics. It is an MRO that is resistant to methicillin.

Symptoms depend on which body system is infected. MRSA is associated with:

• pneumonia
• sepsis
• toxic shock syndrome
• necrotizing fasciitis ⓘ

Many people with MRSA have no signs or symptoms of infection. Instead, they carry the bacteria on their skin, in their nose, or in their gastrointestinal tract.

These people are carriers.

A person does not always remain an MRSA carrier permanently. Certain antibiotics treat the bacteria in some cases, and in other cases the problem resolves on its own.

Staphylococcus aureus is also part of normal flora and normally grows in the nostrils and respiratory tract.

MRSA Risk and Spread in Care Settings

Hospital inpatients with incisions, wounds, or tubes are prone to MRSA infection because these openings provide routes for germs to enter the body.

MRSA infections are most likely spread in hospitals and long-term care settings through:

• person-to-person contact
• infected wound drainage
• infected urine
• poor hand hygiene by health care workers
• failure to wear proper gloves

A test confirms the presence of MRSA. When the test is positive, multiple strong intravenous, or IV, antibiotics are prescribed.

Vancomycin-Resistant Enterococcus, VRE

Enterococci are bacteria normally found in the digestive tract. In healthy people with strong immune systems, healthy flora help keep these bacteria under control.

Overuse of antibiotics led to a resistant strain called vancomycin-resistant Enterococcus (VRE). VRE is resistant to all antibiotics, including vancomycin.

VRE most often spreads on the hands of health care workers after contact with clients who carry or have the bacteria. It also spreads after workers handle contaminated materials or equipment.

VRE causes life-threatening infections in people with weakened immune systems, including clients who are very young, very old, or very ill.

VRE can also pass its resistance gene to other bacteria, including Staphylococcus and Streptococcus.

Contaminated Surfaces and VRE

VRE also spreads through contaminated surfaces and equipment, including:

• call bells
• bed rails
• blood pressure cuffs
• other contaminated equipment

Environmental contamination with VRE occurs more often when a client has diarrhea.

Preventing the Spread of MRSA and VRE

MRSA and VRE both cause serious infections.

Careful handwashing with antibacterial soap is described as the best way to stop their spread. When gloves are required, health care workers should always change them between clients.

For a very sick person, the number of visitors should be limited to one. Visitors should wash their hands well.

Residents of long-term care facilities who recently stayed in a large hospital are usually tested for MROs before returning to their facility. Residents with drug-resistant bacteria are isolated from other residents.

Caring for a Client With an MRO at Home

Some clients with MROs remain at home while receiving care. Clients who remain in their own homes and familiar surroundings are unlikely to spread the MRO infection to other clients. Caregivers remain at risk if precautions are not taken or required PPE is unavailable.

PPE is special clothing and equipment that forms a barrier between microbes and a person’s hands, eyes, nose, mouth, and clothing. Examples include gloves, gowns, masks, and eye protection.

Follow these steps in order:

1. Review the client’s care plan and identify the required personal protective equipment.
2. When you enter the home, remove your coat and outdoor footwear. Put on duty shoes. Follow agency directions for folding and storing outerwear.
3. Apply a waterless, alcohol-based hand rub and let it air-dry completely.
4. Put on the required PPE. The supplies should be located near the client’s front door.
5. If required PPE listed in the care plan is unavailable, report the problem to your supervisor immediately.
6. Without the required PPE, you are not allowed to enter the home to provide care. Explain this to the client.

Common Mix-Ups

Wrong Idea	Better Idea
All microbes cause disease.	Most microbes usually do not cause disease.
A nonpathogen is harmful.	A nonpathogen usually does not cause infection or disease.
Antibiotics work against viruses.	Antibiotics do not work against viruses.
Normal flora are always harmful.	Normal flora normally provide important benefits.
Normal flora stay harmless anywhere in the body.	A normal-flora bacterium causes disease if it enters certain other body sites.
Everyone carrying MRSA has symptoms.	Many MRSA carriers have no signs or symptoms.
Alcohol-based hand rub destroys C. difficile spores.	Soap and water works better because alcohol-based rub does not destroy the spores.