Infectious disease

Question 1

define microbiology

Answer 1

the study of microorganisms: bacteria, fungi, single celled eukaryotes

Question 2

what is the human microbiome

Answer 2

the collection of bacteria, viruses and fungi that live in and on the human body

Question 3

what is the role of the microbiome

Answer 3

• nutrition
• development
• immunity
• behaviour
• protection against harmful bacteria
• digestion
• medicine

Question 4

what is a primary pathogen

Answer 4

cause disease upon infection, not normally associated with host
e.g. plague

Question 5

what is an opportunistic pathogen

Answer 5

cause disease under certain circumstances, can be part of normal flora
e.g. staphylococcus aureus only causes disease under certain circumstances, lots of people are carriers

Question 6

define abiogenesis

Answer 6

spontaneous generation of life from vital forces in non-living matter

Question 7

define biogenesis

Answer 7

organisms arose from seed or germs that had entered the food from the air

Question 8

what are Koch’s postulates

Answer 8

• The microorganism must be easily found in all organisms suffering from the disease, but not in healthy organisms.
• The microorganism must be isolated and grown in pure culture.
• The cultured microorganism should cause disease when introduced into a healthy organism.
• The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent

Question 9

define susceptibility

Answer 9

lack of resistance to a disease

Question 10

define immunity

Answer 10

ability to ward off disease

Question 11

define innate immunity

Answer 11

defences against any pathogen

Question 12

define adaptive immunity

Answer 12

adaptive resistance to a specific pathogen

Question 13

what is innate immunity

Answer 13

• nonspecific defence mechanisms that provide defence immediately or within hours of an infectious agents appearance in the body
• includes physical barriers such as skin, proteins in blood, immune system cells
• does not confer long-lasting or protective immunity to the host

Question 14

what is inflammation

Answer 14

• first response of immune system to infection
• stimulated by chemical factors released by injured cells
• initiated by cells already present in all tissues
  upon activation, cells release inflammatory mediators (histamine, leukotrienes, bradykinin, prostaglandins, serotonin) and attract phagocytes

Question 15

list types of phagocytes

Answer 15

• Macrophages - most efficient phagocytes, respiratory bust
• Neutrophil - circulating phagocytes, granules, respiratory burst
• Dendritic cells - phagocytic cells present in tissues that are in contact with the external environment
• Mast cells - connective tissue and mucous membranes e.g. histamine, heparin, chemokines
• Basophils e.g. histamine, parasitism allergic reaction
• Eosinophils e.g. worm, viral, allergy
• Natural killer cells - destroy compromised host cells that lack MHC expression e.g. virus infection, cancer
• XX T-cells - less common in humans, gastrointestinal site

Question 16

what are antigens

Answer 16

substances that can elicit a response from a B or T cell

Question 17

what is the part of an antigen that binds to an antigen receptor called

Answer 17

an epitope

Question 18

what is adaptive immunity

Answer 18

recognition of traits specific to particular pathogens using a vast array of receptors - slower response

Question 19

what is humoral adaptive immunity

Answer 19

aspects of the immune system conferred by the presence of macromolecules in the liquid part of the blood

Question 20

do antibodies kill pathogens?

Answer 20

no, they mark pathogens for destruction

Question 21

what are the components of immunological memory

Answer 21

memory B-cells and memory T-cells

Question 22

what is active immunity

Answer 22

develops naturally when memory cells form clones in response to an infection
can also develop following immunisation (vaccination)

Question 23

what is immunisation / vaccination

Answer 23

a non-pathogenic form of a microbe or part of a microbe elicits an immune response

Question 24

what is passive immunity

Answer 24

provides immediate short-term protection
e.g. mother to foetus or baby via breastmilk, can be conferred artificially by injecting antibodies into a non-immune person

Question 25

define virulence

Answer 25

the capacity of a microbe to cause disease

Question 26

define pathogenesis

Answer 26

the development of disease

Question 27

what is the difference between virulence and pathogenesis

Answer 27

used interchangeably

Question 28

why do organisms capable of causing disease not cause disease in every exposed individual

Answer 28

- virulence of the microbe - inoculum (number of microbes) - site of infection / port of entry - host susceptibility and capacity to resist

Question 29

portals of entry for pathogens

Answer 29

ingestion - listeria, salmonella inhalation - TB, bordetella penetration - tetanus, Hep B needlestick sexual - chlamydia, gonorrhoea

Question 30

what is an intracellular pathogen

Answer 30

invade host cells for protection from antibiotics and host immune responses and for provision of nutrients

Question 31

what are extracellular enzymes

Answer 31

produced by bacteria which are not directly toxic but which contribute to disease e.g. collegenase causes collagen breakdown (skin, nails, bone) causing spread of pathogen through tissue

Question 32

how can disease be transmitted

Answer 32

- contaminated drinking water - physical contact - coughing / sneezing - blood transfusions - hospital procedures

Question 33

see examples of bacterial diseases in notes

Answer 33

***

Question 34

what is a virus

Answer 34

a very small infectious particle consisting of nucleic acid enclosed in a protein coat and in some cases a membranous envelope

Question 35

properties of viruses

Answer 35

- acellular infectious particle - consists of DNA or RNA core - core is surrounded by a protein coat - coats may be enclosed in a lipid envelope - viruses are replicated only when they are in a living cell -- obligate intracellular parasites

Question 36

give an example of an obligate parasite

Answer 36

viruses

Question 37

what are prions

Answer 37

slow-acting virtually indestructible infectious proteins that cause brain diseases in mammals they propagate by converting normal proteins into the prion version e.g. mad cow disease

Question 38

what do vaccines target

Answer 38

spike proteins already known from previous studies on related/similar viruses

Question 39

define bactericidal

Answer 39

drugs that kill microbes directly

Question 40

define bacteriostatic

Answer 40

drugs that prevent microbes from growing

Question 41

what are the different mechanisms of action of antimicrobial drugs

Answer 41

1. inhibition of cell wall synthesis - penicillins 2. inhibition of protein synthesis 3. inhibition of nucleic acid replication and transcription 4. injury to plasma membrane 5. inhibition of synthesis of essential metabolites

Question 42

what is synergism

Answer 42

occurs when the effect of two drugs together is greater than the effect of either alone

Question 43

what is antagonism

Answer 43

occurs when the effect of two drugs together is less than the effect of either alone

Question 44

give some examples of misuse of antibiotics

Answer 44

- using outdated / weakened antibiotics - using antibiotics for inappropriate conditions - using antibiotics in animal feed - failing to complete a course of antibiotics - using someone else's leftover prescription

Question 45

what are the 4 main methods of antibiotic resistance

Answer 45

1. blocking entry 2. inactivating enzymes 3. alteration of target molecule 4. efflux of antibiotic

Question 46

what are antibiotics

Answer 46

microbial products aimed at other microbes which can be bactericidal or bacteriostatic