Infection S1 (Done)

Question 1

For my first ever flashcard of ESA 3

What is an infection and how is it caused?

Answer 1

Invasion of a host’s tissues by micro-organisms

AND

Subsequent disease caused by:
- Microbial multiplication

• Toxins
• Host response

Question 2

What is meant by ‘commensal’

How are they relevant to humans and infection?

Answer 2

Commensalism is a relation between two organism where one derives benifit and the other is unharmed

Microbiota living on the skin and mucosal surfaces engage in a commensal relationship with humans

Normally harmless or even beneficial however transfer to other sites can be harmful (cause infection)

Question 3

List the ways in which we might get an infection from our environment.

For each give an example of an infection we might acquire via this route.

Answer 3

Food

• Gastroenteritis

Air

• Influenza

Water

• Cholera

Animals

• Malaria

Surfaces

• Tetanus

Human Contact

• Syphilis

Question 4

What is meant by the terms ‘vertical transmission’ and ‘horizontal transmission’?

Give an example of infection that could be transmitted vertically

Answer 4

Horizontal Transmission

• Transmission between organisms

Vertical Transmission

• Transmission of infection from mother to child at or before birth
• E.g. HIV

Question 5

What is an ‘vector’ in regards to infection?

Give an example

Answer 5

An organism that can transfer pathogens and parasites from one organism to another, usually remaining uninfected itself

E.g. Mosquitoes are a vector for malaria

Question 6

What are the modes of horizontal infection?

Hint: 3 basic categories

Answer 6

Contact:

• Direct
• Indirect
• Vectors

Inhalation

• Droplets (small clusters of liquid particles in air)
• Aerosols (colloid of fine solid/liquid particles in gas/air)

Ingestion

• E.g. Faecal-oral transmission

Question 7

What are the 5 stages of an infection?

Answer 7

Exposure

Adherence

Invasion

Multiplication

Dissemination

Question 8

What factors determine the course/severity of an infection?

Answer 8

Pathogen

• Virulence factors
• Inoculum size
• Antimicrobial resistance

Patient

• Site of infection
• Co-morbidities
• Immune response

Question 9

Give some examples of virulence factors

How do they cause disease?

Answer 9

Virulence factors

• Exotoxins (Enzymes, AB toxins, Superantigens, Cytolytic)
• Endotoxins

These can cause damage either directly, or damage can be consequent to host immune response

Question 10

What are the 3 basic steps to determining if a patient has an infection?

Answer 10

History

Examination

Investigations

Question 11

You are taking a patient history and suspect infection, what things are particularly important to ask about?

Answer 11

Symptoms

• Focal/systemic
• Severity
• Duration

Potential exposures

• What have you been doing?
• Who with?
• Where?
• Were there animals?

Question 12

Give some examples of supportive investigations you might carry out with a patient with suspected infection

Answer 12

Full blood count

• Neutrophils + Lymphocytes

C reactive protein

• Inflammation

Liver and kidney function tests

Imaging

• Xray
• Ultrasound
• MRI

Histopathology

Question 13

How might you test a patient for bacterial infection and determine the specific species responsible?

Answer 13

Take a specimen

• E.g. Swab, fluid, tissue

M, C&S

• Microscopy (Bacterial and host cells)
• Culture bacteria
• Test antibiotic Susceptibility

**Antigen detection **

• ELISA

Nucleic acid detection

• PCR
• Sequencing/Hybridisation

Question 14

What methods are available to test specifically for viral infection?

Answer 14

Antigen/antibody Detection

• ELISA

Viral nucleic acid detection

• PCR
• Sequencing/Hybridisation

Question 15

Who might be involves in treatment of patients with infections?

Answer 15

All Clinicians

Specialties with specific interest

• Infectious disease
• Medical microbiology and virology
• Genitourinary
• Health protection

Question 16

What is pictured here?

Label the lines

Answer 16

A Virus

Top Left Clockwise

• Envelope
• Spikes (for attaching to specific cell surfaces)
• Nucleic acid (DNA or RNA)
• Protein Coat

Question 17

What are some common symptoms of infection?

What micro-organisms are typically associated with the two major categories of symptom?

Answer 17

Systemic (generally viral):

Fever

Fatigue

Weight loss/loss of appetite

Aches, pains, burning, itching (Can be localised)

Localised (generally bacterial):

Redness

Heat

Swelling

Pain

Question 18

How are viruses classified by nucleic acid?

Answer 18

Baltimore classification (I to VII)

Classifies virus by nucleic acid type:

I - dsDNA

II - ssDNA

III - dsRNA

IV - (+)ssRNA

V - (-)ssRNA

VI - ssRNA-RT

VII - dsDNA-RT

Question 19

How are class VI and VII of viruses different to classes the other classes of viruses?

Answer 19

VI:

Retroviruses (ssRNA-RT) that replicate with reverse transcriptase (creating a DNA intermediate) as opposed to host machinery

VII:

Similar to retroviruses, dsDNA-RT viruses replicate through the use of reverse transcriptase (creating an RNA intermediate) as opposed to host machinery

Question 20

Give examples of Non-enveloped DNA viruses

Answer 20

Single stranded:

Parovirus 19

Double stranded:

Adenovirus

BK virus

HPV

JC virus

Question 21

Give examples of Enveloped DNA viruses

Answer 21

Double stranded:

Herpes

Hep B

Molluscum

Contagiosum

Question 22

How might we classify viruses by capsid shape?

Answer 22

Icosahedral or helical

Question 23

Apart from nucleic acid type and capsid shape, how else might we classify viruses?

Answer 23

Enveloped or Non-enveloped

Question 24

Give examples of ss(+), icosahedral, non-enveloped viruses

Answer 24

Coxsachievirus

Echovirus

Enterovirus

Hep A, E

Norovirus

Question 25

Give examples of ss(+), Enveloped viruses

Answer 25

HIV Hep C Rubella Encephalitis viruses Yellow fever virus West nile virus

Question 26

Give examples of ss(-), Helical, Enveloped viruses

Answer 26

Ebola, Lassa, Marburg Measles, Mumps Influenza, parainfluenza viruses Respiratory syncytial virus (RSV)

Question 27

Give an example of a ds, Icosahedral, Non-enveloped virus

Answer 27

Rotavirus

Question 28

What are bacteriophages?

Answer 28

Viruses that infect bacteria and replicate within the bacteria May be DNA or RNA based

Question 29

What is shown in this diagram? Label the black boxes

Answer 29

Bacteriophage **From top anticlockwise:** Head Collar Tail Long tail fibres Base plate

Question 30

What are the 3 bacterial shapes?

Answer 30

Coccus Spirillus Bacillus (plural bacilli)

Question 31

What are the common arrangements of bacterial cocci?

Answer 31

Clusters Chains (honorable mention to diplococci, which could be both, depending on how you look at things)

Question 32

What is the structural difference between gram negative and gram positive bacteria? Why do they stain differently and what colours are they?

Answer 32

**Gram positive:** Plasma membrane is surrounded by thick peptidoglycan cell wall Stains purple Thick peptidoglycan cell wall retains crystal violet **Gram negative:** Plasma membrane is surrounded by thin peptidoglycan cell wall and then a lipopolysaccharide outer membrane Stains red Thin peptidoglycan cell wall doesn't retain crystal violet and instad retains red counter stain

Question 33

How does oxygen tolerance of bacteria differ?

Answer 33

**Aerobes:** Can survive in the presence of oxygen Obligate anaerobes require oxygen **Anaerobes:** Can survive in absence of oxygen Obligate anaerobes require an oxygen free environment to survive (unless able to form spores)

Question 34

What are bacterial spores? What is their relevance to disease?

Answer 34

Resistant form of bacteria that can survive extreme conditions (high temperature, dessication, lack of nutrients) Generally, spores cannot cause disease directly, must first germinate in favourable conditions (however some can secrete toxins)

Question 35

Give examples of gram positive bacteria classified by bacterial shape

Answer 35

**Cocci:** Staph aureus Coagulase neg staph Alpha and beta haemolytic streptococci (strep pyogenes = beta) Streptococcus pneumoniae Enterococcus faecalis **Bacilli:** Listeria monocytogenes Bacillus anthracis Bacillus cereus

Question 36

Give examples of gram negative bacteria classified by shape

Answer 36

**Cocci:** Nesseria meningitidis/gonorrhoeae Moraxella catarrhalis Acinetobacter baumannii **Bacillus:** E. coli Klebsiella pneumoniae Proteus spp Salmonella typhi Pseudomonas aeruginosa Haemophilis influenzae

Question 37

What are the mechanisms of bacterial pathogenesis? Give an example of a cell feature involved in each mechanism

Answer 37

**Virulence factors:** Host entry (Polysaccharide capsule) Adherence (Pili) Invasiveness (Enzymes such as collagenases) Iron sequestration (siderophores) **Toxins:** Endotoxins (lipopolysaccharide toxins) Exotoxins (E.g. Diptheria toxin)

Question 38

What are the broad categories of fungus? Give examples of each category

Answer 38

**Yeasts (Single-celled):** Candida albicans Cryptococcus neoformans Pneumoystis jiroveci **Molds (multicellular):** Aspergillus spp Dermatophytes (ringworm, athlete's foot)

Question 39

What are the broad categories of parasites? Give examples for each category

Answer 39

**Protozoa (single celled):** Giaria lamblia Cryptosporidium parvum Plasmodium falciparum Trypsnodoma cruzi **Heminths (Worms, Multicellular)** Roundworms Tapeworms Flukes