Infection Model

Question 1

What is the infection model?

Answer 1

Pathogen + Patient (Mechanism of infection) ->
Infection ->
Management ->
Outcome

Question 2

Separate the microbial kingdoms into eukaryotes and prokaryotes

Answer 2

Prokaryotes - bacteria
Eukaryotes - Fungi (yeast and Moulds), parasites (protozoa and helminths)

Virus not contained in either

Question 3

Describe how age affects the likelihood of infection with meningitis as an example

Answer 3

Neonates/infants - group B strep meningitis or E. coli meningitis

Children - neisseria meningitidis or strep pneumoniae

Adults - neisseria meningitidis or strep pneumoniae

Elderly - listeria monocytogenes

Question 4

At what ages are people most vulnerable to infection and why?

Answer 4

Post 6 months - immature adaptive immune system and no longer breast fed so no maternal Abs from placenta or breast feeding

Elderly - increased risk of comorbidity and gradual immunosuppression

Question 5

Give an example of how sex can influence a risk of infection

Answer 5

Females more likely to contract urinary tract infections due to proximity or urethral opening to anus

Question 6

What is the link between infection and pregnancy?

Answer 6

Pregnant women are more susceptible to infection from usually non-pathogenic microbes and infections are usually more severe.

Result from changes in hormone levels and immune suppression

Question 7

What is the link between infection and the menstrual cycle?

Answer 7

The menstrual cycle affects the likelihood of infection because the environment of the uterus and vagina change, with fluctuations in pH

Question 8

How does the time of year influence the likelihood of infection?

Answer 8

Many microbial diseases have annular peaks in occurrence eg. flu and norovirus (winter vomiting virus) due to temperature and humidity allowing better survival as particulates and replication in extremities eg nasal cavity

Question 9

Describe the contiguous spread mechanism of infection

Answer 9

Contiguous spread is when microbiota spread in the same plane. Eg entering open wound from skin, entering peritoneum from ulcer

Question 10

Describe the inoculation mechanism of infection

Answer 10

The introduction of a microbe to a tissue via contact or transmission of fluid eg. Medical interventions

Question 11

Describe the haematogenous mechanism of infection

Answer 11

Introduction of microbe to secondary infection sites via the circulation. Eg endocarditis in people with poor dental hygiene (tend to affect heart due to turbulent flow around valves helping transmission)

Question 12

Describe the ingestion mechanism of infection

Answer 12

Swallowing microbe infected material. Most commonly faeco-oral transmission

Question 13

Describe the inhalation mechanism of infection

Answer 13

Breathing in microbes that can be expelled from other sources via coughing/sneezing etc. with microbes remaining in the air in aerosols/nuclei droplets

Question 14

Describe the vector mechanism of infection

Answer 14

The transmission of an infection via a secondary carrier eg. Malaria, zika virus, Lyme disease

Question 15

Describe the vertical transmission mechanism of infection

Answer 15

Transfer of microbes from maternal source eg. Intrauterine, vaginal during birth (HIV), via placenta, via breast feeding

Question 16

Why would non-bacteriocidal medications be preferable in some infections?

Answer 16

Prevents release of endotoxins (only released when organism degenerates e.g. Lipoproteins in cell wall) that can be potentially damaging

Question 17

What are the 3 main parts of diagnosing an infection?

What are the 2 main things we need to identify?

Answer 17

History
Examination
Investigations

Causative agent
Location

Question 18

Treatment can be separated into 2 main types, what are they?

Describe the 2 subcategories for each

Answer 18

Specific - antimocrobials and surgery

Supportive - symptom relief and physiological restoration

Question 19

Give an example of a symptom relief treatment and what it does

Answer 19

Antipyretics (eg NSAIDs) - reduce fever/calor

Question 20

Give an example of a physiological restoration treatment and when it would be used

Answer 20

Fluid replacement eg. Diarrhoea, sepsis

Question 21

Surgical treatments for infection can be categorised as 3 main types, what are these?

Answer 21

Drainage
Debridement
Dead space removal