Diagnosis And Control Of Infection

Question 1

Definition of epidemiology

Answer 1

Study of when and where diseases occurs and how they are transmitted to the population

Question 2

Definition of chain of infection

Answer 2

Concept used to explain how a patient can acquire an infection from another person

Question 3

Definition of reservoirs

Answer 3

Places where pathogens can grow and accumulate

Question 4

Definition of zoonotic diseases

Answer 4

Spread between animals and people

Question 5

Definition of fomite

Answer 5

Objects/materials which are likely to carry infection (clothes, utensils, furniture)

Question 6

Definition of vertical transmission

Answer 6

Transmission from mother to child via placenta

Question 7

Definition of horizontal transmission

Answer 7

Person to person transmission that is not between mother and child

Question 8

Definition of titre

Answer 8

Antibody conc in a sample, associated with the no times someone can dilute a sample and still detect the AB

Question 9

Definition of serconversion

Answer 9

Time period during which a specific AB develops and becomes detectable in the blood

Question 10

Definition of bacteriocidal

Answer 10

Antibacterial agent that kills bacteria

Question 11

Definition of bacteriostatic

Answer 11

Antibacterial agents that inhibit bacterial growth

Question 12

Definition of vaccination

Answer 12

Exposing a person to antigenic material but not pathogenic

Induces adaptive immunity and memory

Question 13

Definition of herd immunity

Answer 13

In contagious diseases that are transmitted from person => person, chains of infection likely to be broken when large nos are immune

Question 14

What 6 factors are considered in epidemiology

Answer 14

Aetiology, identify pathogen causing diseases

Predisposing factors, age, sex, lifestyle, susceptible populations

Incidence, rate of occurrence

Prevalence, all cases in a timeframe

Mode of transmission, how its spread

Public health policy prevention, how to reduce spread

Question 15

How is the chain infection used in epidemiology

Answer 15

Chain of infection, how a patient can acquire an infection from 1 person to another

If chain broken, transmission stops

Question 16

What are reservoirs

What are the 3 main reservoirs

Answer 16

Places where pathogens grow and accumulate

Human, animal, famine

Question 17

What are the 3 main modes of transmission

Answer 17

Contact
Indirect (vehicle/vector)
Vertical

Question 18

What are the 3 methods of transmission via contact

Answer 18

Exposed to pathogen by either touching or being close to an infected person or object

Direct

• Person to person
• No intermediate object involved

Indirect
-Via fomite

Droplet

• Spread in mucus droplets
• Travel short distances
• Sneezing, coughing, talking

Question 19

What are the 3 methods of vehicle (indirect) transmission

Answer 19

Waterborne
-Water contaminated with sewage

Airborne

• Inhalation of small particles, pathogens
• Long distances

Food borne
-Contamination of food w pathogen

Question 20

What are the 2 methods of vector (indirect) transmission

Answer 20

Mechanical

• Passive transport on body
• Contaminated food, water, hands, person to person
• Enteric and eye infections

Biological

• Pathogen spends part of life cycle in vector
• Bite
• Malaria, Zia, rabies

Question 21

What is vertical transmission

Answer 21

From mother to child

Question 22

What are Koch’s 4 postulates

Answer 22

Microbe only found in ill

Microbe must be isolated and cultured

Culture should cause disease in healthy

Microbe reisolated is identical to original

Question 23

What are the 3 exceptions to Koch’s postulates

Answer 23

Asymptomatic infection carriers

Can’t grow in vitro/no susceptible animals

Not all exposed infected

Question 24

What are the 2 main methods of laboratory diagnosis

Answer 24

Direct detection

• culture
• microscopy
• nucleic acid

Indirect detection (serological)

Question 25

How would you culture bacteria and viruses

Answer 25

Bacteria -grow in culture under controlled conditions Viruses -permissive cells => cytopathic effects

Question 26

How would you use microscopy in direct methods

Answer 26

Staining, morphology Electron microscope used for viruses

Question 27

How would you use nucleic acid detection in direct detection methods When would you use this What are the 2 methods

Answer 27

PCR => amplify Hybridisation => complemetary fluorescent probes Detect hard/slow growing organisms

Question 28

How would you use a serological test in indirect methods

Answer 28

Paired samples (acute, convalescent) tested for 4x increase in AB titre (seroconversion) IgM and not IgG = indicative of current infection

Question 29

What are the advantages and disadvantages of culture

Answer 29

Advantages - Confirms organism presence - Can be multiplied for further testing Disadvantages - Time consuming - Must be capable of growing in vitro

Question 30

What are the advantages and disadvanatges in microscopy

Answer 30

Advantages -Quick, day results Disadvanatges -Not v specific

Question 31

What are the advantages and disadvantages of nucleic acid testing

Answer 31

Advantages - Results in hours - Sensitive and specific Disadvantages -Knowledge of DNA sequence needed

Question 32

What are the advantages and disadvantages of serological tests

Answer 32

Advantages - Many body fluids can be used - Cheap, easy - Multiple samples can be analysed Disadvantages - Time consuming to obtain paired serum - Specific AB not always available - Not good for agents that produce disease before AB - AB not detected due to low conc - False positives due to cross reactivity - Tests are retrospective - Cannot distinguish between previous and current infection

Question 33

What are the main properties of antibacterial/antiviral agents

Answer 33

Exploiting differences metabolism and structure of microbe and human cells Can be natural or synthetic

Question 34

What are the 4 targets of bactericidal/bacteriostatic agents

Answer 34

Cell wall synth -peptidoglycan unique to bacteria Plasma membrane -disrupt membrane potential, target LPS Nucleic acid -block enzymes needed for DNA/mRNA synth Protein synth -disrupt prokaryotic ribosomal proteins, RNA, enzymes

Question 35

What are the 3 main targets in antiviral agents

Answer 35

Attachment, entry -inhibit fusion of envelope/receptor attachment Nucleic acid synth -target viral DNA, RNA polymerase Assembly/budding -Inhibit viral proteins needed for maturation/release

Question 36

What are the 4 bacterial strategies for drug resistance

Answer 36

Prevent drug penetrating target Modify/inactivate drug Expulsion from cell by efflux pumps Modify target site

Question 37

What are the 2 viral strategies for drug resistance How do we delay the appearance of drug resistance

Answer 37

Spontaneous mutation Error prone polymerase in RNA virus HAART therapy

Question 38

What are the 4 types of immunity | How can they be acquired?

Answer 38

Natural active -exposed to pathogen Natural passive -Maternal AB Artificial active -vaccine Artificial passive -given AB

Question 39

Requirements of an effective vaccine

Answer 39

Safe, no/few side effects Long lasting protection Formation of memory cells Cheap, easy admin Stable, long shelf life Herd immunity