microbiology flashcards

8 — MICROBIOLOGY

Nursing Study Notes

1. What is Microbiology?

Microbiology = the study of very small organisms and infectious agents.

Why is microbiology important in nursing?

Nurses need to understand microbiology because it helps us:

Understand how infections develop.
Recognise how infections are spread.
Prevent infection transmission.
Use infection-control precautions correctly.
Protect patients, whānau and healthcare workers.
Understand why hand hygiene and PPE are important.
Understand antimicrobial resistance.
Recognise patients who are at higher risk of infection.

Learning outcomes

You should be able to:

Describe bacteria, fungi, protozoa and prions.
Give examples of diseases caused by microbes.
Describe conditions that allow microbes to grow.
Explain how infectious agents are transmitted.
Explain the chain of infection.
Explain the basics of infection control.

2. Microbes and Pathogens

Microbe

A microbe is a very small organism.

Examples:

Bacteria
Fungi
Viruses

Important: Not all microbes are harmful.

Microbiome

The microbiome = all the naturally occurring microbes living on and inside our body.

Examples:

Gut microbiome

Helps maintain healthy digestion.
Supports other aspects of health.

Skin microbiome

Helps protect the skin.

Pathogen

A pathogen = a disease-causing microbe.

Infectious/causative agent

The infectious agent or causative agent = the microbe responsible for causing a particular disease.

Easy way to remember:

Microbe → may be harmless

Pathogen → causes disease

3. Disease Names vs Microorganism Names

The disease and the organism causing it often have different names.

Disease	Causative organism
Whooping cough	Bordetella pertussis
Candidiasis/thrush	Candida albicans
Tinea pedis/Athlete's foot	Several fungi including Trichophyton rubrum

4. Naming Microorganisms

Scientific names have two parts:

Genus + species

Example:

Escherichia coli

Escherichia = genus → capital letter
coli = species → lower case
Written in italics

It can be shortened to:

E. coli

sp.

If the genus is known but the exact species isn't:

Aspergillus sp.

spp.

If referring to multiple species within a genus:

Plasmodium spp.

5. Five Major Groups of Microorganisms

You need to know these:

1. Bacteria

Prokaryotes
Single cells
Can cause many infections

2. Fungi

Eukaryotes
Can be single-celled or multicellular

3. Viruses

Infectious particles
Not living cells
Need a living cell to reproduce

4. Protozoa

Single-celled eukaryotes

5. Prions

Misfolded infectious proteins

Parasitic worms may also be included in microbiology.

🦠 6. BACTERIA

What are bacteria?

Bacteria are:

Very small: approximately 0.2–5 micrometres
Prokaryotes
Simple cells
Do not have membrane-bound organelles.
Do not have a nucleus.

Prokaryote vs Eukaryote

Prokaryote
→ no nucleus
→ bacteria

Eukaryote
→ has a nucleus and membrane-bound organelles
→ humans, fungi and protozoa

7. Structure of a Bacterial Cell

Know the main structures:

Nucleoid

The area containing the bacterial DNA.

No nucleus.

Plasmids

Small pieces of extra DNA.

They can contain genes for:

Antibiotic resistance
Virulence/disease-producing ability

Plasmids can also be exchanged between bacteria.

Ribosomes

Make proteins.

Cytoplasm

The internal fluid/material of the cell.

Plasma membrane

Controls what enters and leaves the cell.

Cell wall

Provides:

Shape
Strength
Protection

It also helps prevent the bacterial cell from taking in too much water and bursting.

Glycocalyx

A protective outer coating.

Can be:

Capsule
Slime layer

Pili/fimbriae

Help bacteria attach to surfaces or exchange genetic material.

8. Plasmids

Plasmids are particularly important in nursing because they can contain genes for:

Antibiotic resistance

A bacterium can acquire resistance genes and pass them to other bacteria.

This contributes to antimicrobial resistance.

Plasmids are also used in genetic engineering.

Example from the slides:

Human insulin genes can be inserted into bacterial plasmids, allowing bacteria to produce human insulin used as medication.

9. Bacterial Cell Wall and Membrane

Cell wall

The bacterial cell wall:

Is rigid and strong.
Gives the bacterium its shape.
Prevents the cell from bursting when water enters.

Bacteria can be classified as:

Gram-positive

→ purple when Gram stained.

Gram-negative

→ pink/red when Gram stained.

Gram-negative bacteria have:

A thinner peptidoglycan layer.
An additional membrane layer.

10. Glycocalyx

Glycocalyx literally means "sugar case."

Two forms:

Capsule

Firm
Rigid

Slime layer

Loose
Flimsy

What does glycocalyx do?

It can protect bacteria from:

Drying out.
Chemicals such as disinfectants.
Phagocytosis by immune cells.

It also helps bacteria stick to surfaces, including:

Mucous membranes
Teeth
Medical devices
Other bacteria

This can help bacteria establish infections.

11. Flagella

Some bacteria have flagella.

A flagellum is a tail-like structure.

Function:

Movement

It allows bacteria to swim.

Examples:

E. coli
Helicobacter pylori
Campylobacter jejuni

12. Pili and Fimbriae

Fimbriae

Help bacteria attach/ad here to host cells.

Think:

Fimbriae = fastening

Pili

Longer
Fewer in number
Can help bacteria attach.
Can also be involved in conjugation.

Conjugation

Bacteria exchange genetic material.

This can contribute to the spread of antibiotic resistance.

13. Bacterial Shapes

Shape can help identify bacteria.

Cocci

Round/spherical

Bacilli

Rod-shaped

Other shapes include:

Vibrio → curved rods
Spirochaetes → tightly coiled

14. Cocci

Coccus = singular

Cocci = plural

Diplococci

Round bacteria in pairs.

Example:
Neisseria gonorrhoeae

→ gonorrhoea

Streptococci

Round bacteria in chains.

Example:
Streptococcus pyogenes

→ strep throat

Staphylococci

Round bacteria in groups/clusters.

Example:
Staphylococcus aureus

→ skin infections and MRSA

Easy memory trick:

Strep = strings/chains

Staph = stacks/clusters

15. Bacilli

Bacilli = rod-shaped bacteria

Examples:

Straight rods

Bacillus anthracis
→ anthrax

Coccobacilli

Short, round rods.

Bordetella pertussis
→ whooping cough

Streptobacilli

Rods arranged in chains.

Streptobacillus moniliformis
→ rat-bite fever

16. Other Bacterial Shapes

Vibrio

Curved rods.

Example:

Vibrio cholerae
→ cholera

Spirochaetes

Tightly coiled bacteria that move using a spinning motion.

Examples:

Leptospira
→ leptospirosis

Treponema pallidum
→ syphilis

17. Bacterial Reproduction

Bacteria reproduce through:

Binary fission

This is asexual reproduction.

Basically:

1 bacterium → 2 bacteria → 4 → 8 → 16...

Bacteria can reproduce extremely quickly under favourable conditions.

Mutations and plasmid exchange can result in changes to bacterial DNA, including antibiotic resistance.

18. Bacterial Growth

Generation time

The generation time = the time needed for a cell to divide into two, or for the microbial population to double.

Examples:

E. coli → approximately 20 minutes
Staphylococcus aureus → approximately 30 minutes
Streptococcus spp. → approximately 20 minutes
Mycobacterium tuberculosis → approximately 18 hours

This rapid reproduction explains why some bacterial diseases can develop quickly.

19. Examples of Bacterial Diseases

Know some important examples:

MRSA
Cellulitis
Impetigo
Boils
Strep throat
Rheumatic fever
Meningococcal disease
Whooping cough
Diphtheria
Gonorrhoea
Chlamydia
Syphilis
Tetanus
C. diff
Botulism
Gas gangrene
Necrotising fasciitis

🍄 20. FUNGI

Fungi are:

Eukaryotes
Have membrane-bound organelles.
Can be unicellular or multicellular.
Can reproduce sexually or asexually.
Obtain nutrients from other living things.

Two broad types:

Yeasts

Moulds

A fungal infection is called a:

Mycosis

Plural = mycoses.

21. Yeasts vs Moulds

Yeasts	Moulds
Unicellular	Multicellular
Slimy colonies	Thread-like structures
Reproduce by budding	Reproduce by spores
Example: Candida	Example: Trichophyton

Hyphae

Moulds have thread-like structures called hyphae.

Candida

Candida is a yeast.

It can sometimes be described as dimorphic, meaning it can exist as both round and filamentous cells.

22. Types of Fungal Infections

Superficial mycosis

Fungus grows on the outer layers of the stratum corneum.

The stratum corneum consists of dead cells.

Usually does not cause inflammation.

Example:
Tinea versicolor

Cutaneous mycosis

Fungus grows in:

Skin
Hair
Nails

Example:
Tinea/ringworm and fungal nail infections

Subcutaneous mycosis

Fungus enters the subcutaneous tissue.

Usually causes an inflammatory response.

A common portal of entry is:

A wound in the skin

Example:
Sporotrichosis

Systemic/deep mycosis

Can involve:

Lungs
Abdominal organs
Bones
CNS

More likely in immunocompromised people.

Examples of people at risk:

People with HIV/AIDS
Transplant recipients
People receiving cancer treatment

These infections can be fatal.

23. Opportunistic Pathogens

An opportunistic pathogen is an organism that is normally harmless but causes infection when:

The person's health changes, or
The organism moves to a different location in the body.

Example:

Candida albicans

Another example:

Cryptococcus

It can be found in bird droppings and enter the lungs when contaminated dust is inhaled.

People with HIV/AIDS are particularly vulnerable.

Easy definition:

Opportunistic = takes advantage of a weakened opportunity/host.

24. Examples of Fungal Infections

Know these:

Candidiasis
- Oral thrush
- Vaginal thrush
- UTIs
- Skin infections
Tinea pedis
- Athlete's foot
- Fungal nail infections
Tinea versicolor
Tinea nigra
Tinea capitis → scalp infection
Tinea cruris → jock itch
Tinea corporis → ringworm
Sporotrichosis
Aspergillosis
Cryptococcosis

🦠 25. PROTOZOA

A protozoan is:

A single-celled eukaryote.
Commonly found in water.
Many are harmless.
Some cause disease.

They can reproduce in different ways, including:

Budding
Multiple fission/schizogony
Sexual reproduction

Some, such as Giardia, can form cysts.

Cysts can survive in the environment for long periods.

26. Protozoan Diseases

Giardiasis

Cause:
Giardia duodenalis

Symptoms include:

Diarrhoea
Abdominal pain

Cryptosporidiosis

Cause:

Cryptosporidium hominis
Cryptosporidium parvum

→ diarrhoea

Toxoplasmosis

Cause:
Toxoplasma gondii

Can cause flu-like symptoms.

⚠ Pregnancy

Toxoplasmosis can be dangerous during pregnancy because it can damage the developing baby, including causing problems with vision and hearing.

27. Other Protozoan Diseases

Trichomoniasis

Cause:
Trichomonas vaginalis

→ STI

Amoebic meningitis

Cause:
Naegleria spp.

Rare but usually fatal.

The slides specifically emphasise avoiding putting your head underwater in geothermal pools.

Malaria

Cause:
Plasmodium spp.

Spread by:
Anopheles mosquitoes

Malaria is not found in New Zealand.

🧬 28. VIRUSES

Viruses are infectious particles.

They consist of:

Nucleic acid + protein coat

The nucleic acid can be:

Important:

Viruses are not living cells.

They:

Don't require nutrition like cells do.
Cannot reproduce independently.
Must enter a living cell to replicate.

Viruses can survive on surfaces for varying lengths of time.

29. Structure of a Virus

Nucleic acid

Contains:

DNA or
RNA

Capsid

A protein shell surrounding the genetic material.

Envelope

Some viruses have an envelope.

It is a phospholipid bilayer taken from the host cell.

Spike/envelope proteins

Allow viruses to:

Attach to host cells.
Bind to receptors on the cell.

Not all viruses have envelopes.

30. Viral Replication

The key idea:

Virus enters a host cell → uses the host cell's machinery → makes new viral components → new viruses are produced.

Viruses need a living cell because they cannot reproduce independently.

31. Latent Viral Infections

A latent infection occurs when a virus remains dormant inside a host cell.

It can become active again without the person becoming reinfected.

Examples:

Herpes simplex virus 1 and 2

→ cold sores
→ genital herpes

Varicella-zoster virus

→ chickenpox
→ shingles

The virus can remain latent for a person's lifetime.

Important nursing concept:

Chickenpox → virus remains latent → can reactivate later → shingles.

32. Retroviruses

Normally:

DNA → RNA → protein

A retrovirus can:

RNA → DNA

It does this inside the host cell.

Example:

HIV

33. Oncogenic Viruses

Onco = cancer

Genic = generating

Therefore:

Oncogenic viruses = viruses that can contribute to cancer.

Examples include:

Hepatitis B
Hepatitis C
HPV
Epstein-Barr virus
HIV-1
Human T-cell lymphotropic virus type 1
Kaposi sarcoma-associated herpesvirus

The slides state that approximately 12% of human cancers are associated with infectious agents, most of which are viruses.

34. Examples of Viral Diseases

Know:

Common cold → Coronavirus
Influenza/flu → Orthomyxovirus
COVID-19 → Coronavirus
RSV
Measles
Mumps
Hepatitis A, B and C
Oral herpes
Genital herpes
Chickenpox
Warts → HPV
Norovirus
Rotavirus
HIV

🧠 35. PRIONS

A prion is:

A self-replicating misfolded infectious protein.

Prions cause unusual transmissible neurodegenerative diseases.

Important examples:

Humans

Creutzfeldt-Jakob disease (CJD)
Kuru

Cattle

Bovine spongiform encephalopathy (BSE)

Sheep

Scrapie

Reindeer/elk/moose

Chronic wasting disease

Cats

Feline spongiform encephalopathy

How do prions cause disease?

A misfolded protein causes normally folded proteins to become misfolded.

This leads to:

Major neurological deterioration
Eventually death

🔗 36. CHAIN OF INFECTION

This is VERY important for nursing.

For an infection to develop and spread, several links need to be present.

The slides identify:

Reservoir/source
Portal of exit
Mode of transmission
Portal of entry
Susceptible host

Think:

Where is it? → How does it get out? → How does it travel? → How does it get in? → Who gets infected?

37. Key Infection Terms

Colonisation

An infectious agent is present on or in the body.

It does not necessarily mean the person is sick.

Infection

An infectious agent enters tissues and causes an immune response.

There may or may not be symptoms.

Asymptomatic

The infectious agent causes no injury/signs or symptoms.

Symptomatic

The person develops clinical signs and symptoms.

Communicable/contagious

The infectious agent can be transmitted from person to person.

⭐ Important Difference

Colonisation ≠ infection

A person can carry a microorganism without it causing disease.

For example, meningococcal bacteria can live in the mouth/throat of healthy people without causing meningococcal disease.

This is why sharing items that go into the mouth can increase transmission.

38. Normal Flora

Normal flora = microorganisms that normally live on or inside the body.

Other terms:

Microflora
Microbiota
Microbiome

Important nursing example:

E. coli normally lives in the gut.

But if it enters the urinary tract:

normal flora → wrong location → UTI

39. Transient Flora

Transient flora are microorganisms acquired through contact with:

People
Objects
Surfaces

Example from the slides:

A patient acquires C. difficile from bacteria in a healthcare environment.

40. Reservoir

A reservoir is a place where a pathogen can survive.

It may or may not multiply there.

Examples could include:

Humans
Animals
Environment

Source

The source is the person, object, animal or substance from which the person actually acquired the infection.

Example from the PowerPoint:

John has Staphylococcus aureus boils.

Mark shares John's towel and develops boils.

John = reservoir

Towel = source

🌡 41. Conditions That Help Microbes Grow

Microbes need favourable conditions.

They generally need:

Food/nutrients

Water

Appropriate temperature

Often similar to human body temperature.

Appropriate pH

Usually approximately pH 5–8.

Oxygen

Some microbes need oxygen.

Darkness

Many microbes thrive in darkness because UV light can kill microbes.

🧤 Why is the Skin Under Gloves a Good Environment for Microbes?

Because it provides:

Food → skin/sweat
Moisture
Suitable pH
Darkness
Warmth

This is why hand hygiene is important after removing gloves.

Gloves do not replace hand hygiene.

42. Aerobic vs Anaerobic

Aerobic

Needs/uses oxygen.

Anaerobic

Can survive/grow without oxygen.

Example:

Some Clostridium bacteria are anaerobic.

They can thrive in:

Stab wounds
Compound fractures
Burns

Important:

Viruses don't require food or oxygen because they are not living cells.

🚪 43. PORTALS OF EXIT

A microorganism needs a way to leave the reservoir.

Possible portals of exit include:

Skin
Mucous membranes
Respiratory tract
Urinary tract
Gastrointestinal tract
Reproductive tract
Blood

Examples

Coughing → respiratory tract

Urine → urinary tract

Faeces → gastrointestinal tract

Blood → bloodstream

🔄 44. MODES OF TRANSMISSION

Once a pathogen leaves its reservoir, it needs a way to travel.

1. Direct contact

Touch.

The slides identify this as the most common mode of transmission.

2. Droplet

Body-fluid droplets.

Example:
Coughing/sneezing.

3. Airborne

Tiny infectious particles carried by air currents.

4. Contaminated articles/fomites

Objects that carry microbes.

Examples:

Equipment
Towels
Medical devices
Surfaces

5. Food

6. Water

7. Vectors

Living organisms that transmit infection.

Examples:

Insects
Rodents

🚪 45. PORTALS OF ENTRY

Microbes can enter the body through many of the same portals they exit from.

Examples:

Skin

Can be broken by:

Needles
Surgery
Wounds

Urinary tract

A urinary catheter can provide a portal of entry.

Other portals include:

GI tract
Female reproductive tract
Respiratory tract
Bloodstream

👤 46. SUSCEPTIBLE HOST

A susceptible host is someone who is more likely to acquire an infection.

Examples from the slides:

Older adults
Neonates, especially premature babies
People receiving cancer treatment
Transplant patients
People with diabetes
Smokers
People who have long hospital stays
ICU patients
People who have had surgery
Burns patients
People with compromised immunity
People with HIV
People with autoimmune conditions
People who are obese

🏥 47. Healthcare-Associated Infections (HAIs)

Also called:

Nosocomial infections
Hospital-acquired infections

These are infections associated with receiving healthcare.

Examples:

UTIs
Pneumonia
Wound infections
Bloodstream infections
MRSA

A NZ study from 2021 found that 6.6% of surveyed patients had HAIs.

48. Why are healthcare patients at risk?

Healthcare settings can have:

Vulnerable patients.
Virulent organisms.
Antibiotic-resistant organisms.
Invasive devices.
Procedures that break the skin.
Increased antibiotic use.

ICU patients have particularly high risk because they are vulnerable and antibiotics are commonly used.

Nursing responsibility

Nurses need to be particularly careful with:

Aseptic technique

Aseptic = free from contamination.

49. Causes of Healthcare-Associated Infections

Urinary tract

Catheter insertion
Urine travelling back into the bladder

Surgical sites/wounds

Improper skin preparation
Poor surgical hand antisepsis

Respiratory tract

Contaminated equipment
Incorrect disposal of secretions

Bloodstream

Contaminated IV fluids
Poor care of needle insertion sites

🧼 50. Antisepsis

Antisepsis = killing/reducing microbes on living tissue.

This is important in procedures such as:

IV insertion
Wound care
Surgical procedures

The overall goal is to prevent microorganisms from entering vulnerable areas.

💊 51. Antimicrobial Resistance

This is VERY important for nursing.

Microbes can become resistant to:

Antibiotics
Other antimicrobial drugs

How?

Repeated exposure can mean:

Susceptible/weaker microbes die.
Resistant microbes survive.
Resistant microbes reproduce.
Resistance becomes more common.

52. How can we reduce antimicrobial resistance?

1. Complete the prescribed antibiotic course

Use antibiotics as directed.

2. Use narrow-spectrum antibiotics when appropriate

Rather than unnecessarily using broad-spectrum antibiotics.

3. Don't use antimicrobials unnecessarily

Antibiotics do NOT kill viruses.

Therefore, antibiotics should not be used for viral infections unless there is another bacterial indication.

4. Reduce unnecessary antibiotic use in farming.

🦠 53. Multi-Resistant Organisms (MROs)

MROs are microbes that are resistant to multiple classes of antimicrobial drugs.

They can become established as endemic pathogens in hospitals.

Examples:

MRSA

Methicillin-resistant Staphylococcus aureus

VRE

Vancomycin-resistant enterococci

Pseudomonas aeruginosa

54. Preventing MRO Transmission

Important strategies include:

🧼 Hand hygiene

🥼 PPE

🚪 Isolation of patients when required

🧹 Cleaning and disinfecting

🧪 Targeted screening

55. Endemic

Endemic = an infection is consistently present within a particular population, community or healthcare setting.

The slides explain that an endemic infection has a permanent reservoir, meaning there are continually people who have the infection and could potentially transmit it.

🇳🇿 56. Public Health

One role of a public health nurse is:

Communicable disease control

This can involve:

Education
Organising laboratory tests
Supporting disease control.

Notifiable diseases

Some diseases must be reported to the Medical Officer of Health.

Examples in the slides include:

Cryptosporidiosis
Amoebic meningitis
Hepatitis A, B and C
Measles
Tetanus
Tuberculosis

🍓 57. Hepatitis A Example

The PowerPoint discusses a 2022–2023 NZ Hepatitis A outbreak associated with imported frozen berries.

Hepatitis A is spread via:

Faeces → contamination → food/water → ingestion → infection

This is an example of how contamination can occur through the faecal-oral route.

🐮 58. Workplace Safety & Zoonoses

Some workplaces have increased risk of infectious diseases.

Examples:

Farms
Veterinary clinics
Meatworks
Plumbing
Drainlaying

Zoonosis

A zoonosis is a disease transmitted between different species.

Example:

Cow → human

Leptospirosis

Caused by:

Leptospira bacteria.

This is particularly relevant to people working with animals.

⭐ THE BIG THINGS I WOULD MEMORISE FOR YOUR NURSING EXAM

If you're short on time, focus heavily on these:

🦠 Microorganisms

Know the difference between:

Type	Key thing
Bacteria	Prokaryotic cells
Fungi	Eukaryotic organisms
Protozoa	Single-celled eukaryotes
Viruses	Not cells; need host cells to replicate
Prions	Misfolded infectious proteins

🔗 Chain of Infection

Remember:

Reservoir → Portal of Exit → Transmission → Portal of Entry → Susceptible Host

If you can break one link, you can help prevent infection.

🧼 Infection control

Know why nurses use:

Hand hygiene
PPE
Aseptic technique
Cleaning/disinfection
Isolation
Safe handling of equipment
Safe management of wounds and invasive devices

🏥 HAIs

Know:

What they are.
Examples.
Why hospital patients are vulnerable.
How healthcare workers can transmit them.
How nurses help prevent them.

💊 Antimicrobial resistance

Remember:

Overuse/misuse → susceptible microbes die → resistant microbes survive → resistant microbes reproduce → resistance increases.

And:

Antibiotics do NOT treat viral infections.

👤 High-risk/susceptible patients

Remember:

Older adults
Premature/neonatal patients
Immunocompromised patients
Cancer patients
Transplant patients
Diabetes
Burns
Surgical patients
ICU patients
Long-stay hospital patients

🧠 A few definitions you absolutely need

Microbe = small organism.

Pathogen = disease-causing microbe.

Colonisation = microorganism is present without necessarily causing disease.

Infection = organism enters tissue and produces an immune response.

Communicable = can be transmitted between people.

Reservoir = place where pathogen survives.

Source = where the person acquired the pathogen.

Portal of exit = how the pathogen leaves.

Transmission = how it travels.

Portal of entry = how it enters.

Susceptible host = person vulnerable to infection.

HAI = healthcare-associated infection.

Aseptic = free from contamination.

Antisepsis = killing/reducing microbes on living tissue.

MRO = microorganism resistant to multiple antimicrobial drugs.

Zoonosis = infection transmitted between species.

📝 One-page memory map

MICROBIOLOGY

⬇

Microbes
→ Bacteria
→ Fungi
→ Protozoa
→ Viruses
→ Prions

⬇

Infection

Reservoir
↓
Portal of exit
↓
Transmission
↓
Portal of entry
↓
Susceptible host

⬇

Prevent infection

🧼 Hand hygiene
🥼 PPE
🧴 Cleaning/disinfection
🩺 Aseptic technique
🚪 Appropriate isolation
💉 Safe invasive-device care
💊 Responsible antimicrobial use