week 1

Question 1

SIRS criteria

Answer 1

• Temperature <36˚C or >38˚C
• Pulse > 90 beats per min
• Respiratory rate > 20 breaths per min
• White cell count < 4 or > 11

Question 2

how is sepsis diagnosed? give examples

Answer 2

one SIRS criteria + documented infection (a host response to the presence of micro-organisms or tissue invasion by microorganisms- eg cellulitis, purulent sputum, x-ray changes in the lung, redness, swelling, heat)

Question 3

exogenous source of infection meaning

Answer 3

via host or from environment- food, water, soil, coughing and sneezing

Question 4

endogenous source of infection meaning

Answer 4

normal flora from another part of the body – skin pathogens, gut pathogens

Question 5

signs of infection

Answer 5

redness, change in skin colour, pain, heat, swelling, loss of function

Question 6

examples of documented infection

Answer 6

Cellulitis
Purulent sputum
X-ray changes in the lung
Redness
Swelling
Heat

Question 7

what is CRB - 65? when is it used

Answer 7

an assessment of community acquired pneumonia. It is mostly used in GP scenarios due to lack of equipment needed for CURB-65.

Question 8

ectoparasites

Answer 8

; large complex multicellular organism, rely on humans to get nutrients to survive + reproduce. E.g., headlice, scabies, tics, fleas.

Question 9

endoparasites

Answer 9

live inside its host e.g., Helminth worms, roundworms, tapeworms… They tend to go under a sexual cycle outside the human host.

Question 10

what are protozoal infections?

Answer 10

single cell parasites that infest inside the body. either extracellular or intracellular. can be ingested or transmitted by blood transfusion, open wounds in aqueous environment or injected by ectoparasites in a blood meal.

Question 11

what are viruses

Answer 11

also, parasites but non-living, obligate and intracellular. no metabolism. possess their own genetic information and can infect all types of cellular organism.

Question 12

what is the core genetic information in viruses?

Answer 12

RNA or DNA, if it is RNA then virus is a retrovirus as it needs to be reverse transcribed to DNA for replication.

Question 13

can viruses reproduce alone?

Answer 13

no require a host

Question 14

state the process of viral replication

Answer 14

1) Attachment 2) Penetration 3) Synthesis of nucleic acid and protein 4) RNA viruses use a reverse transcriptase (retrovirus) 5) Assembly and packaging (maturation) 6) Release

Question 15

why are glycoprotein spikes important?

Answer 15

for docking onto the target on cell surface to invade the cell – good targets for vaccines.

Question 16

briefly explain viral structre

Answer 16

is diverse but in essence; nucleic acid is surrounded by a protein coat (capsid.) Mainly rod shaped with helical nucleic acid or icosahedral with spherical nucleic acids.

Question 17

the viral genome

Answer 17

• DNA or RNA
• Single or double stranded
• Linear or circular
• Genome is very small (some exceptions)
• Encodes functions required for replication once within the host cell
• RNA genome is associated with a higher mutation rate

Question 18

prion disease

Answer 18

a rare, fatal neurodegenerative disease belonging to amyloid group. There is no DNA or RNA involved, there is no classical host immune response and is clinically categorised by dementia and ataxia.

Question 19

what are pili?

Answer 19

short hair-like structure on the cell surface of prokaryotes useful for adhering to tissues.

Question 20

what temperature is required for
a) fungi incubation
b) bacteria incubation

Answer 20

a) room temperature - 25 degrees
b) body temperature - 37 degrees

Question 21

what species give red medium and red colonies in culturing? give example

Answer 21

bacteria that use lactose. lactose turned to lactic acid which lowers pH. gives a surrounding zone of precipitated bile salts. exaplme - e.coli

Question 22

what gives yellow medium and colourless colonies in culturing? give example

Answer 22

Bacteria that do not use lactose, use peptone. Ammonia is formed giving a higher pH and yellow medium agar with colourless colonies. E.g., Salmonella

Question 23

what colour does gram +ve stain? why is this?

Answer 23

displays as a purple colour (they retain crystal violet within their peptidoglycan)

Question 24

what colous does gram -ve bacteria stain?

Answer 24

displays as a pink colour after decolourising from purple.

Question 25

how does gram negative bacteria display pink colonies?

Answer 25

has much thinner cell wall which is why purple strain is able to decolourise

Question 26

MacConkey agar

Answer 26

will never show gram positive colonies as the growth of bacteria is inhibited. selective medium for gram negative.

Question 27

ziehl neelson stain

Answer 27

required for mycobacteria and presents as a pink stain on a blue background. TB and leprosy are both caused by mycobacteria.

Question 28

yeasts

Answer 28

one eukaryotic cell. defined and uni-cellular

Question 29

moulds

Answer 29

mutlicellular

Question 30

what type of disinfectants are most commonly used?

Answer 30

chlorine based

Question 31

what are the most common pathogens associated with HAI's

Answer 31

E.coli (33%) Staphylococcus aureus (20.2%) Clostridium difficile (5.3%)

Question 32

tachypnoea

Answer 32

rapid and shallow breathing

Question 33

erythema

Answer 33

redness or change of colour in the skin

Question 34

normal parameters of blood pressure white cell count temperature urea respiratory rate hemoglobin

Answer 34

less than 120/80 mm/Hg between 4000 and 11000 micro liters 36.5 to 37.2 degrees c 2.5 - 7.8 mmol/L 12-20 breaths per min FEMALES - 115- 165 g/L , MALES - 130 -180 g/L

Question 35

what causes shingles, how does it present and how can it be treated?

Answer 35

display as a unilateral rash and is caused by a viral infection (Varicella-Zoster.) Treat with Eurax to sooth skin discomfort. Aciclovir to remove the bacterial infection and remove the viral burden. Calamine lotion for further skin soothing. Painkillers as required

Question 36

what causes athletes foot, how can it be treated?

Answer 36

caused by dermatophytes that are attracted by the heat and moisture of the feet. Treat with miconazole cream which disrupts cell membrane of fungus therefore destroying cell.

Question 37

societal and behavioral barriers to disease

Answer 37

societal - clean water, waste disposal behavioral - hand washing, condoms, hosptial-serilization

Question 38

physiological barriers to disease

Answer 38

skin, mucous membranes (mouth, nose, eyelids), eyes, mucus, cilia, stomach acid, pancreatic enzymes

Question 39

pyrogens

Answer 39

are peptides secreted by leukocytes (white blood cells) they act on the hypothalamus to increase body temperature and induce fever.

Question 40

interferons

Answer 40

are a type of chemical mediator of inflammation. Interfere with viral replication and also act as antiviral agents.

Question 41

complement proteins

Answer 41

are non-specific and destroy cells

Question 42

phagocytes

Answer 42

are omnivorous scavengers that exist in various forms throughout the body. They detect foreign material and digest it, both destroying pathogens and in some cases provide a link to the specific compounds of immune response. They can change shaped regularly

Question 43

name 5 types of phagocytes

Answer 43

neutrophils - first responders at site of infection monocytes - roaming mononuclear phagocytes in the blood. Differentiate into macrophages in tissues "fixed" phagocytes- organ/tissue specific e.g. osteoclasts microglia- CNS resident Dendritic cells – derived from monocytes - often found in tissues in contact with external environment (& lymph). ‘Early warning’ cells - major role in antigen presentation.

Question 44

define phagocytosis and the way it works.

Answer 44

Phagocytosis is the means by which phagocytes can remove bacteria. The phagocytic cell is attracted to and recognises microbes as being foreign via surface receptors. It extends filopodia, engulfs the microbe, and early phagosomes begin to form. Once contained in a phagosome, fusion with a digestive enzyme containing lysosome occurs.

Question 45

how do phagocytes reach the site of infection?

Answer 45

chemotaxis and diapedesis

Question 46

chemotaxis

Answer 46

chemical attractants from invading bacteria and tissue leukocyte attract local neutrophils, and monocytes from the blood stream.

Question 47

diapedesis

Answer 47

mast cells and basophils release histamine making the endothelium permeable and allowing cells through.

Question 48

briefly describe the role of dendritic cells

Answer 48

found in tissue that is in close contact to the external environment and are mainly derived from circulating monocytes in the blood. They digest the trapped antigens and present them to other cells in the immune system- this is a specific immune response

Question 49

specific immunity is a _ line responce that comes into play when _ has not worked

Answer 49

3rd non-specific

Question 50

antigens

Answer 50

defined as “substances recognised by the immune system as being ‘non-self’ and which provoke an immune response”

Question 51

what are the stages of specific immunity

Answer 51

challenge > recognition > activation > elimination

Question 52

what is an epitope

Answer 52

One molecule may have several antigenic determinant sites, each individual one is called an epitope

Question 53

humoral immunity antibody structure

Answer 53

4 polypeptide chains cross linked by disulphide bridges

Question 54

methods of specific antigen elimination

Answer 54

humoral; antibody mediated, antibodies belong to the gammaglobulin class of proteins called immunoglobulins, act indirectly cell-mediated; cells are ultimately responsible for antigen elimination. requires cell-cell contact. three main types of lymphocytes involved.

Question 55

3 key lymphocytes in cell-mediated specific immunity

Answer 55

B- cells T-cells natural killer cells

Question 56

b cells

Answer 56

mature in bone marrow when stimulated produce antibodies and can differentiate into plasma cells. are activated when free antigens bind to immunoglobulin receptors on the b surface.

Question 57

t cells

Answer 57

mature in the thymus. two subtypes cytotoxic t-cells and helper t-cells. o Helper = release interleukins and activate macrophages o Cytotoxic T-cells (Th1) activate B-cells (Th2), and help recruit neutrophils and macrophages (Th17) o Regulatory T-cells act to dampen immune response and memory T-cells increase longevity of immunity

Question 58

natural killer cells

Answer 58

kill virus infected/ cancerous cells

Question 59

activation of t cells

Answer 59

require peptide antigens to be presented to the t cells receptors. this is done by an antigen presenting cell in the context of MHC proteins

Question 60

what activates cytotoxic cells?

Answer 60

class 1 MHC proteins. (Activate CD8+ cytotoxic cells)

Question 61

what activates helper cells

Answer 61

class 2 MHC proteins (activate CD4+ helper cells)

Question 62

what are the ways that antibodies are able to eliminate antigens

Answer 62

opsonisation neutralisation complement activation

Question 63

opsonisation

Answer 63

promotion of phagocytosis. The coating of bacteria, viruses or infected body cells by antibodies causes them to be targeted for destruction by macrophages and other cytotoxic cells. The variable region of the antibody binds to the pathogen, leaving the constant region free. The constant region will bind to receptors on macrophages and indicate that the attached particle is to be phagocytosed.

Question 64

neutralisation

Answer 64

bacterial toxins may be specifically neutralised by antibodies. Serum from patients who have survived a rare snakebite can be used as an antidote. Transfer of the antibodies in the serum allows for the binding and neutralization of the venom molecules (usually short peptides).

Question 65

complement activation

Answer 65

can be activated via several pathways – in response to antigen-antibody complexes or the presence of bacterial surface molecules. each complement protein in the cascade cleaves its successor. The products of each cleavage either embed in the membrane or go off to activate other systems. Eventually the late components assemble together to form a pore. This pore allows high concentrations of Ca2+ to accumulate in the cells and destroy them.

Question 66

clonal proliferation trigger

Answer 66

bind of antigens to B or T cells during infection

Question 67

clonal proliferation process

Answer 67

1) specific antigen binds to a naive B-cells, via Ig-R activating it, T-cell moves to the B-cell and activates it. ACtivated B-cell proliferates. most differentiate into antibody producing plasma cells, some into memory cells.