Quiz
DF30, 32, 36, 37 - Microbial Contamination
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Questions in this quiz (21)
1Cell to endospore transformation takes about 8 hours while endospore to cell transformation can take just 15 minutes.
- ATrue
- BFalse
2Endospore formation begins with a vegetative cell dividing by [blank_start]binary fission[blank_end]. Then, DNA becomes more [blank_start]dense[blank_end], and two comparments begin to form by [blank_start]invagination[blank_end]. Next, the larger compartment will [blank_start]engulf and surround[blank_end] the smaller compartment, forming the [blank_start]forespore[blank_end]. [blank_start]Cortex and coat[blank_end] are then formed, and [blank_start]dehydration[blank_end] occurs. There is then [blank_start]lysis[blank_end] of cell and release of the endospore.
- Abinary fission
- Bdense
- Cinvagination
- Dengulf and surround
- Eforespore
- FCortex and coat
- Gdehydration
- Hlysis
3From the endospore core, there is a [blank_start]cortex[blank_end] which includes inner and outer membranes, then a [blank_start]coat[blank_end], and then the [blank_start]exosporium[blank_end].
Physical resistance comes from the coat which has [blank_start]thick layers[blank_end] and the [blank_start]inner[blank_end] membrane which is impenetrable. Chemical resistance comes from the core where there is low [blank_start]water content[blank_end], high concentrations of [blank_start]Ca++ and diplicolinic acid[blank_end], [blank_start]low[blank_end] pH, and small [blank_start]acid-soluble[blank_end] proteins. The cortex also has chemical resistance because of [blank_start]decreased peptidoglycan cross-linking[blank_end] index (2.9% in endospore compared to 33% in vegetative cells), and modified [blank_start]sugar muramic-delta-lactam[blank_end].- Acortex
- Bcoat
- Cexosporium
- Dthick layers
- Einner
- Fwater content
- GCa++ and diplicolinic acid
- Hlow
- Iacid-soluble
- Jdecreased peptidoglycan cross-linking
- Ksugar muramic-delta-lactam
4Sources of contamination:
1. Air
Can contain bacteria including [blank_start]endospore-formers[blank_end] (Bacillus, Clostridium), moulds, and [blank_start]yeast[blank_end].
2. Water
Used as a constituent, for washing, or for cooling. Microbes typically found in water are [blank_start]Pseudomonas[blank_end], Flavobacterium, Chromobacter and Serratia.
3. Operator microflora
[blank_start]Skin and respiratory tract[blank_end] microbes, poor personal [blank_start]hygiene[blank_end] risk, open [blank_start]wound[blank_end] risk, [blank_start]nasal[blank_end] carriage.
4. Raw materials
Natural sources of raw materials (eg from animals or plants) usually [blank_start]extensively contaminated[blank_end]. Physical, chemical or in-process [blank_start]treatment[blank_end] is essential. Storage conditions of raw materials are important. Synthetic raw materials are usually [blank_start]free from[blank_end] contaminating microbes.
5. Equipment
Every machine has characteristic [blank_start]contamination site[blank_end] eg pipelines.
6. Packaging
7. Building and storage
Walls and ceilings – mould flora – hard [blank_start]gloss paint with fungistat[blank_end] is best.- Aendospore-formers
- Byeast
- CPseudomonas
- DSkin and respiratory tract
- Ehygiene
- Fnasal
- Gwound
- Hextensively contaminated
- Itreatment
- Jfree from
- Kcontamination site
- Lgloss paint with fungistat
5Choose the incorrect statment.
- AVegetative cells require temperatures around 55C for death
- BBacterial endospores require temperatures above 100C to kill them
- CDeath from heating is an exponential function and thus occurs more rapidly as the temperature is raised
6Choose the incorrect statement.
- AMoist heat is the most widely used method to control microbial growth
- BMoist heat is more effective than dry heat for killing microorganisms
- CMoist heat causes denaturation and coagulation of vital proteins such as enzymes
- DMoist heat cannot eliminate endospores
7Autoclaving is done at [blank_start]15psi/103.kPa[blank_end], steam press and at [blank_start]121[blank_end] degrees (pure steam) for [blank_start]15[blank_end] minutes.
You can autoclave most culture media, glassware, [blank_start]some[blank_end] pharmaceutical preparations, surgical dressings; cotton wool, gauze etc, metal instruments (for example, [blank_start]scalpels[blank_end]), small articles of [blank_start]heat-resistant[blank_end] equipment, waste material from lab for [blank_start]safe[blank_end] disposal.
You cannot autoclave [blank_start]toxic[blank_end] chemicals (phenol), heat-labile compounds ([blank_start]antibiotics[blank_end]), heat-sensitive equipment, and [blank_start]some[blank_end] types of plastics.- A15psi/103.kPa
- B10psi/69kPa
- C20psi/138kPa
- D121
- E112
- F126
- G15
- H30
- I10
- Jsome
- Kall
- Lscalpels
- Mcatheters
- Nheat-resistant
- Osterile
- Psafe
- Qquick
- Rtoxic
- Ssafe
- Tantibiotics
- UNSAIDs
- Vsome
- Wall
83 Types of pasteurisation:
1. Old Method - Batch
[blank_start]63[blank_end]C for [blank_start]30[blank_end] minutes
2. New Method - Flash
[blank_start]71[blank_end]C for [blank_start]15[blank_end] minutes
3. Ultra-high-temperature (UHT) milk for complete sterilisation
[blank_start]140[blank_end]C for at least [blank_start]1 second[blank_end]- A63
- B30
- C71
- D15
- E140
- F1 second
9Which of these sterilisation methods kill endospores? Select all.
- ABoiling water
- BAutoclaving
- CDry heat oven
- DBatch and flash pasteurisation
- EUHT pasteurisation
- FFlamaing/incineration
- GFreezing
10Dry Heat sterilisation methods: flaming & incineration, hot air oven, and freezing. At what temperature and for how long must things be in the hot air oven to become sterile?
- A2 hours at 160C
- B1 hour at 150C
- C1.5hours at 260C
11Choose the incorrect statement.
- APore sizes can be as small as 0.45micrometres for normal bacteria.
- BPore sizes can be as small as 0.1micrometres for Mycoplasma bacteria.
- CPore sizes can be as small as 0.2micrometres for normal bacteria.
12Choose the incorrect statement about radiation.
- ASensitivity of microorganisms to radiation varies: G- sensitive; G+ more resistant; endospores highly resistant.
- BRadiation can be ionising (eg gamma rays, x-rays) or non-ionising (eg UV)
- CA wavelength of 260 nm damages the DNA in the cell by forming pyrimidine dimers, or by direct protein damage.
- DApplications of UV radiation the sterilisation of benches and air, water treatment
- EUV radiation can be used to sterilise large volumes of liquids as it can penetrate these to a significant depth
13UV light can kill bacteria by causing covalent bonds to form in the DNA making thymine dimers.
- ATrue
- BFalse
14Ionising radiation (x-rays, gamma rays) kills [blank_start]indirectly[blank_end] by inducing reactive chemical radicals ([blank_start]free radicals[blank_end]) by breaking individual molecules into ions, hence 'ionising' radiation.
With gamma radiation for non-thermal sterilisation of reagent preparations or small equipment, [blank_start]3.14 Gy/min using caesium-137[blank_end] is standard.
When gamma rays bombard water, a [blank_start]positive water free radical[blank_end] is formed
and an electron (e -) is liberated. This electron reacts with another water molecule and thus produces a [blank_start]negative water free radical[blank_end] (H2O-). These positive and negative water free radicals then [blank_start]dissociate[blank_end] into free hydrogen and hydroxyl radicals. The [blank_start]hydrogen[blank_end] free radicals are strong reducing agents; the [blank_start]hydroxyl[blank_end] free radicals are strong oxidizing agents.- Aindirectly
- Bfree radicals
- C3.14 Gy/min using caesium-137
- D20Gy/min using C-13
- Epositive water free radical
- Fnegative water free radical
- Gdissociate
- Hhydrogen (H+)
- Ihydroxyl (OH-)
15Ionising radiation is [blank_start]penetrating[blank_end] and therefore can be used to sterilise products even after they have been [blank_start]packaged[blank_end]. However the equipment is [blank_start]expensive[blank_end] to operate, and requires [blank_start]elaborate safety precautions[blank_end] (lead shielding of operators). Used to sterilise lab products ([blank_start]petri dishes[blank_end]), treatment of [blank_start]sewage[blank_end] and industrial sludges, and in food [blank_start]preservation[blank_end].
- Apenetrating
- Bpackaged
- Cexpensive
- Delaborate safety precautions
- Epetri dishes
- Fsewage
- Gpreservation
16The death curve of microbes is logarithmic.
- ATrue
- BFalse
17 The time it takes to achieve sterility, or to reduce microbial numbers to an acceptable level, depends in part on the number of organisms present at the beginning of sterilisation.
- ATrue
- BFalse
18Which of these does not effect time taken to sterilise?
- AInitial population size
- BpH
- CDilution of agent
- DPopulation composition
- EHumidity
- FTemperature
- GOrganic matter presence
19Microbe populations are most susceptible to chemical bactericidal agents when they are:
- AIn their exponential growth phase
- BIn their stable population phase
20Chemical agents:
1. Alcohol - [blank_start]Non[blank_end] toxic to people, does [blank_start]not[blank_end] kill endospores, good for [blank_start]skin swabs.[blank_end]
2. Aldehydes - [blank_start]Toxic[blank_end] to people, [blank_start]kills[blank_end] endospores, used for [blank_start]preserving tissue[blank_end]
3. Quarternary ammonium compounds - Not [blank_start]irritating[blank_end], [blank_start]detergent[blank_end] action, [blank_start]inactivated[blank_end] by organic matter, endospores [blank_start]not killed[blank_end], used as detergents or skin antiseptics
4. Halogens and H2O2 - Wide [blank_start]activity[blank_end], inactivated by [blank_start]organic matter[blank_end], [blank_start]chlorine[blank_end] for water and [blank_start]iodine[blank_end] for skin antiseptic
5. Heavy metals - [blank_start]silver[blank_end] dressings or oldschool [blank_start]eyedrops[blank_end] for babies of mothers with gonorrhea, [blank_start]toxic[blank_end].
6. Phenols - wide [blank_start]spectrum[blank_end] of activity, [blank_start]endospores[blank_end] not killed, [blank_start]toxic, irritant, good for cleaning[blank_end].- ANon
- Bnot
- Cskin swabs.
- DToxic
- Ekills
- Fpreserving tissue
- Girritating
- Hdetergent
- Iinactivated
- Jnot killed
- Kactivity
- Lorganic matter
- Mchlorine
- Niodine
- Osilver
- Peyedrops
- Qtoxic
- Rspectrum
- Sendospores
- Ttoxic, irritant, good for cleaning
21Sterilising gases kill endospores but are toxic and explosive.
Conditions:
- [blank_start]Ethylene oxide[blank_end] 700ppm
- [blank_start]40-50%[blank_end] relative humidity
- Temperature [blank_start]38C for 5-8hours[blank_end] (or 54C for 3-4 hours)- AEthylene oxide
- B40-50%
- C20-30%
- D38C for 5-8hours
- E74C for 2-3hours
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- PHCY211 (Formulation) Quiz on DF30, 32, 36, 37 - Microbial Contamination, created by Mer Scott on 06/05/2018.
- Author
- Mer Scott
- Language
- English
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