16. Infectious diseases

Question 1

Symbiosis

Answer 1

close and often long-term interaction between different biological species (micro-organism and host)

Question 2

Commensalism

Answer 2

beneficial for the micro-organism and neutral for the host

Question 3

Mutualism

Answer 3

beneficial for both the micro-organism and the host

Question 4

Parasitism

Answer 4

the micro-organism benefits at the expense of the host → the host is damaged

Question 5

Exotoxins

Answer 5

Gram + and – Secreted Highly toxic

Question 6

Endotoxins

Answer 6

Gram – Not Secreted Low toxicity

Question 7

Gram Staining

Answer 7

Gram positive bacteria = deep violet

Gram negative bacteria = faint pink (red)

Question 8

OBLIGATE ANAEROBES

Answer 8

do not require O2, even small quantities can be toxic

Question 9

FACULTATIVE ANAEROBES

Answer 9

utilise O2 if present, can grow in its absence

Question 10

MICROAEROPHILES

Answer 10

prefer low concentrations of O2, growth inhibited at normal O2 levels

Question 11

KAPNOPHYLIC

Answer 11

bacteria requires increased concentration (5–10–20%) of CO2 for growth

Question 12

Phase 1 of bacterial growth

Answer 12

Cells are adapting to new conditions Cell size increases Cell numbers increase slowly

Question 13

Phase 2 of bacterial growth

Answer 13

Phase of exponential growth Cell numbers increase rapidly Log phase growth summarised by the equation N = NO x 2n NO = original number of cells N = number of cells after n divisions n= number of divisions

Question 14

Phase 3 of bacterial growth

Answer 14

Growth ceases because of… Nutrient limitation Bacterial waste products inhibiting growth O2 depletion Changes in pH

Question 15

Phase 4 of bacterial growth

Answer 15

Caused by the depletion of cellular energy reserves

Question 16

Answer 16

Non-blanching rash

If a glass tumbler is pressed firmly against the rash, the marks will not fade

Question 17

Gram +ve bacteria

Answer 17

Thick peptidoglycan layer

Question 18

Gram -ve bac

Answer 18

Thin peptidoglycan layer

Question 19

b-lactam antibiotics

Answer 19

Bind to and inhibit the transpeptidase enzymes (PBPs)

PBPs catalise the formation of peptide bridges between glycan chains

Defective cell wall

Question 20

Endemic

Answer 20

normal occurrence of a particular disease

within a given population

Question 21

Epidemic

Answer 21

An outbreak of a new or unexpected increase of disease in a given population within a short period of time

Question 22

Pandemic

Answer 22

an epidemic of infectious disease that has spread through human populations across a large region or even worldwide

Question 23

Zoonotic

Answer 23

A reservoir of virus normally found in animals but periodically infect humans e.g. Rabies

Question 24

Answer 24

Non-enveloped virus

Question 25

Answer 25

Enveloped virus

Question 26

Tissue Tropism

Answer 26

Refers to the specific cells and tissues of a host that supports the growth of a particular virus

Question 27

Species (or Host) Tropism

Answer 27

Preference for a particular host species (animal)

Question 28

6 steps of the infective cycle

Answer 28

Attachment Penetration into the cell Release of the genome into the cell Replication of the genome and production of protein Assembly of progeny viruses Released from the infected cell

Question 29

Virulence

Answer 29

the degree of damage caused by a microbe

Question 30

pathogenicity of a virus

Answer 30

ability to cause disease - determined by virulence factors