Classification of Micoorganisms

Organism – general definition

living form capable of autonomous functions such as reproduction, metabolism, and growth

Basic unit of living organisms

Cell

Structure of Prokaryotic cells

Free flowing genetic material

What are plasmids

Extra-chromosomal DNA - acquired along with the cell’s own genetic material (acquired from other cells / bacterial species) that code things such as toxic material or antibiotic resistance

Structure of Eukaryotic cells

Put these into groups of pro vs eukaryotes

• Bacteria

• Fungi

• Protozoa

• Archaea

• Animals

• Plants

Eukaryotes

• Animals

• Plants

• Certain micro-organisms (fungi, protozoa)

Prokaryotes

• Bacteria

• Archaea

What levels of the Taxonomic Hierarchy do we use to name species

Give 4 types of microorganisms

• Bacteria

• Viruses

• Fungi

• Protozoa

What transmits Borrelia burgdorferi (& what is this also called)

Certain ticks → transmit Borrelia burgdorferi → Lyme Disease

What transmits Yersinia pestis (& what is this also called)

Rat fleas → transmit Yersinia pestis → Plague (‘Black Death’)

Are fungi pro/eukaryotic & uni/multicellular

Eukaryotic organisms

Can be unicellular or multicellular

Protozoa are eukaryotes that feed on what

bacteria, other protozoa, organic matter and fungi

Name 2 protozoa

Cryptosporidium, Plasmodium

Structure of a virus

• DNA/RNA in a viral coat

• Single- or double-stranded

Are viruses living organisms

No - Generally considered infectious ‘agents’

Not living because they can’t reproduce on their own

Are viruses selective about what cells they infect

Yes

Viruses exist for one primary purpose - what is it?

To reproduce

How do viruses reproduce

Take over reproductive machinery of suitable host cells

Then split by binary fission

6 steps of the Viral replication cycle

What are Prion diseases

Rare group of diseases caused by misfolding of proteins in the central nervous system

True/False: Prion diseases can occur in humans and animals

True - Can occur in humans and animals (eg. cattle)

Give an example of a Prion disease

Familial and sporadic forms of Creutzfeld-Jakob disease (CJD)

How are Prion diseases transmitted

consumption of prion proteins (misfolded proteins) → induce normal proteins to develop into prion proteins

True/False the transmissible agent in prion diseases is genetic material

False: protein (not genetic material)

E.g. of prion disease in cattle (scientific name), what causes it & how it is passed onto humans

bovine spongiform encephalopathy (BSE; ‘Mad Cow Disease’) following consumption of feeds contaminated by prion proteins

Humans develop a variant CJD (vCJD) following consumption of meats contaminated with the above proteins

2 main shapes of bacteria & 1 other

Usually rod- shaped (bacillus) or spherical (coccus) cells

Less commonly: spiral cells known as spirochaetes

4 Laboratory methods to test for bacteria

• Microscopy and staining

• Culture & identification of bacteria

• Antimicrobial susceptibility testing

• Molecular tests

Bacteria can be grown on solid/liquid mediums. Give an example of 1 such medium

Blood agar

Commonly used staining method for bacterial cells

Gram stain

Effect of crystal violet on Gram + and Gram - bacteria

Effect of iodine treatment on Gram + and Gram - bacteria

Effect of decolourisation on Gram + and Gram - bacteria

Effect of counter stain safranin on Gram + and Gram - bacteria

Which is gram + or -

What is the general difference in staining between gram+ and - cells

Can you identify the groups of bacteria present in this image, based on Gram stain?

Gram - bacilli

Gram + cocci

Give 3 e.g. of Gram-positive cocci

• Staphylococcus aureus

• Streptococcus pneumoniae

• Streptococcus pyogenes (‘flesh-eating bug’) (Group A Streptococcus)

Give 2 examples of infections caused by Streptococcus pneumoniae

Pneumonia

Meningitis

Give 3 examples of infections caused by Streptococcus pyogenes (‘flesh-eating bug’) (Group A Streptococcus)

Cellulitis

Pharyngitis

Necrotising fasciitis

Give 2 examples of Gram-negative cocci

Neisseria meningitidis

Neisseria gonorrhoeae

Infections caused by Neisseria meningitidis

Meningitis

Septicaemia

Infection caused by Neisseria gonorrhoeae

gonorrhoea

2 examples of Gram-positive bacilli

Clostridium spp

Bacillus spp

3 examples of subsets of Clostridium spp & their associated infections

• C. difficile → colitis

• C. tetani → tetanus

• C. botulinum → botulism

Give an example of a Bacillus spp bacteria & its unfection

B. anthracis → anthrax

Give 2 examples of Gram-negative bacilli

Escherichia coli

Pseudomonas aeruginosa

2 infections caused by Escherichia coli

Urinary tract infection

Abdominal infections

2 infections caused by Pseudomonas aeruginosa

Pneumonia (cystic fibrosis), bloodstream infections, etc

7 types of infections caused by Staphylococcus aureus

Boils/abscesses

Skin infections eg. Cellulitis

Joint infections (septic arthritis)

Bone infections

Lung infections (pneumonia)

Heart valve infections (endocarditis)

Bloodstream infection; etc.

Give 2 examples of specialist bacteria

Neisseria meningitidis (meningococcus) → meningitis & septicaemia

Neisseria gonorrhoeae (gonococcus) → gonorrhoea

Give an example of an opportunist bacteria

Pseudomonas aeruginosa found in cystic fibrosis & severely immunocompromised patients

Clinical utility of Gram staining of bacteria

Identification

Certain antibiotics may be effective/ineffective against certain bacterial groups

vancomycin is ineffective against Gram-positive/negative bacteria

Vancomycin is ineffective against Gram-negative bacteria

True of False - Presence of microbes = infection

False: Presence of microbes ≠ infection

It could be a potential pathogen or innocent bystander