Practical

Question 1

single colonies are not always derived from a single cell, true or false ?

Answer 1

true, thats why we use CFU

Question 2

MaConkey agar

Answer 2

contains bile salts, support growth of coliforms and enteric pathogens and colour change based on lactose metabolism

Question 3

selective vs differential media

Answer 3

selective - enhance the growth of organisms and suppress others

differential - allow for a difference appearance so we can differentiate the species

Question 4

fastidious vs non-fastidious

Answer 4

fastidious - specific nutritional requirements

non-fastidious - not specific nutritional requirements

Question 5

colioforms

Answer 5

group of Gram-negative, rod-shaped, facultatively anaerobic bacteria that ferment lactose

indicate enteric pathogens in water

include klebsiella, enterobacter, citrobacter, E. coli

Question 6

counting bacteria

Answer 6

counting chamber - similar to haemocytometer, counts cells in a known volume

flow cytometer - cells pass a light source - includes dead cells

Question 7

what factors can affect the type and number of microbes in the microbiota ?

Answer 7

genetics, mode of birth, diet, antibiotic use, age, environment, infection, immune system, hygiene, lifestyle, medication

Question 8

Bacillus cereus and Bacillus anthracis spores can pose significant threats to human health, but in very different ways

Answer 8

B. cereus - foodborne, survive cooking and pasteurization

B. anthracis - germination leads to toxin production, long dormancy period

Question 9

blood agar

Answer 9

Base: Tryptic soy agar or nutrient agar

Additive: ~5% sheep blood (sometimes horse or human blood)

It’s mainly used to detect hemolytic activity — the ability of bacteria to break down red blood cells

Question 10

blood agar nutrients

Answer 10

C N P S K Mg Ca Fe B-vitamins

Question 11

TVC

Answer 11

total viable count, the quantification of viable microorganisms capable of growing on a nonselective solid media incubated aerobically at mesophilic temperatures

can be used to detect contamination

Question 12

sterilisation

Answer 12

inactivation of all viable microorganisms

Question 13

pasteurisation

Answer 13

heat treatment to reduce total number

Question 14

disinfection

Answer 14

reduce number of organisms present

Question 15

antisepsis

Answer 15

used on living tissue to reduce the growth of microorganisms.

Question 16

asepsis

Answer 16

prevent introduction of microorganisms to the site.

Question 17

2 types of heat sterilisation

Answer 17

moist and dry

Question 18

types of sterilisation

Answer 18

heat, radiation, chemical

Question 19

Nutrient agar

Answer 19

general purpose medium that allows the growth of a wide range of organisms

Question 20

mannitol salt agar

Answer 20

differential and selective and indicator medium to isolate S. aureus particularly pathogenic strains.

mannitol –> acid = colour change to yellow (if not remains pink)

contains high salt concentration which means only staphylococcus can grow

Question 21

CFC agar

Answer 21

isolation of Pseudomonas, green colonies whilst others are colourless

Question 22

ChromID agar

Answer 22

contains chromogenic substrates like esculin which is digested by C. difficile

Question 23

improving lettuce micrbiota

Answer 23

irradiation, ultrasound, chlorine washing

Question 24

B. subtilis spores are resistant to …

Answer 24

heat, desiccation, pressure, radiation, chemicals

Question 25

lateral flow assay

Answer 25

The technique is based on capillary action to detect toxins and antigens

Question 26

agglutination assay

Answer 26

An agglutination assay is a laboratory technique used to detect the presence of specific antigens or antibodies in a sample, based on their ability to cause agglutination, or clumping, of particles (such as red blood cells or latex beads)

Question 27

C-reactive protein (CRP) in serum

Answer 27

shows inflammation, use anti-CRP antibodies conjugated to beads leads to positive agglutination result

Question 28

Anti-streptolysin O (ASO) antibody in serum

Answer 28

produced by immune system when streptococcus is present streptolysin O is the toxin produced by the strain latex beads are surrounded by streptolysin O for anti-ASO to bind

Question 29

What other parameters could we vary that would influence how effective UV radiation is in inhibiting bacterial growth?

Answer 29

wavelength of UV, exposure time, distance, species, cell density, growth phase, moisture, intensity