1
Q
What are the properties of an ideal disinfectant?
A
An ideal disinfectant should be:
- Fast-acting
- Act against many microbes without harming tissues
- Have penetrating power (improves if dirt and debris are first removed)
- Inexpensive/Cost-effective
- Easy to prepare and use
- Chemically stable
- Have an inoffensive odor
- Not harmful or safe to the environment
- Non-corrosive and non-staining
- Non-flammable
- Have a residual effect
2
Q
What is the mechanism of action of phenols and phenolics?
A
They destroy plasma membranes and denature proteins.
3
Q
Who first used phenol (carbolic acid) as a disinfectant?
A
Joseph Lister
4
Q
Why is phenol rarely used today?
A
Because it is a skin irritant and has a strong odor.
5
Q
In what products is phenol still used today?
A
Some throat sprays and lozenges.
6
Q
What additional property does phenol have aside from being a disinfectant?
A
It acts as a local anesthetic.
7
Q
What are phenolics?
A
Chemical derivatives of phenol
8
Q
Give examples of phenolics and their uses
A
Cresols:
Derived from coal tar (example: Lysol).
Biphenols (pHisoHex):
Effective against gram-positive staphylococci and streptococci; used in nurseries but excessive use in infants may cause neurological damage.
Xylenols and Orthophenylphenol:
Used in laboratories and hospitals.
9
Q
What are the advantages of phenolics?
A
They are stable, persist for long times after application , and remain active in the presence of organic compounds.
10
Q
Halogens are capable of what?
A
Effective alone or in compounds.
11
Q
What was one of the first antiseptics used?
A
Tincture of iodine (alcohol solution)
12
Q
What is the mechanism of action of iodine?
A
It combines with the amino acid tyrosine in proteins and denatures proteins.
13
Q
What are some disadvantages of iodine use?
A
It stains skin and clothes and is somewhat irritating.
14
Q
What are iodophors?
A
Compounds with iodine that are slow releasing and take several minutes to act.
15
Q
Where are iodophors used and what is their limitation?
A
They are used as skin antiseptics in surgery but are not effective against bacterial endospores.
16
Q
They are used as skin antiseptics in surgery but are not effective against bacterial endospores.
A
Iodophors
17
Q
Give examples of iodophors.
A
Betadine and Isodine
18
Q
What happens when chlorine is mixed in water?
A
It forms hypochlorous acid (HOCl)
19
Q
Equation of HOCL
A
Cl₂ + H₂O → H⁺ + Cl⁻ + HOCl
20
Q
What is hypochlorous acid of Chlorine used for?
A
To disinfect drinking water, pools, and sewage.
21
Q
What is one limitation of chlorine use?
A
easily inactivated by organic materials
22
Q
What is the active ingredient of bleach?
A
Sodium hypochlorite (NaOCl)
23
Q
What are chloramines?
A
Compounds consisting of chlorine and ammonia; they are less effective as germicides.
24
Q
Against which organisms are alcohols effective?
A
They kill bacteria and fungi, but not endospores or naked viruses.
25
What is the mechanism of action of alcohols?
They denature proteins and disrupt cell membrane
26
Do alcohols leave residue after use?
No, they evaporate leaving no residue
27
How are alcohols commonly used in medical settings?
To mechanically wipe microbes off skin before injections or blood drawing.
28
How long is sufficient for alcohol soaking to disinfect small instruments?
10–15 minutes
29
Why are alcohols not good for open wounds?
Because they cause proteins to coagulate
30
What is the optimum concentration of ethanol for disinfection?
70%
31
Which alcohol is known as rubbing alcohol, and how does it compare to ethanol?
Isopropanol; it is a better disinfectant, cheaper, and less volatile.
32
What is the general mechanism of action of heavy metals?
Metal ions combine with proteins then cause denaturation, proteins lose function = microbes die
33
How do heavy metal ions bind to microbial proteins?
By **attaching to sulfhydryl (–SH) groups**,
leading to **enzyme inactivation** and **disruption of essential metabolic processes**.
34
How do metals like silver and copper affect cell membranes?
They attach to membranes, increase permeability, and cause leakage of cell contents.
35
How do some heavy metals interfere with microbial nucleic acids?
By interacting with DNA and RNA, interfering with replication and transcription.
36
What additional damaging effect do metals such as copper and iron cause?
They generate reactive oxygen species (ROS), which damage proteins, lipids, and nucleic acids.
37
What heavy metals are included in disinfectants?
Copper, selenium, mercury, silver, and zinc
38
What is oligodynamic action?
The property where very tiny amounts of heavy metals are effective
39
What concentration of silver nitrate was used to protect infants against gonorrheal eye infections (ophthalmia neonatorum) until recently?
1% silver nitrate
40
What organic mercury compounds are used to disinfect skin wounds?
Merthiolate and mercurochrome
41
What is copper sulfate used for?
To kill algae in pools and fish tanks.
42
What organisms does selenium kill, and where is it used?
It kills fungi and their spores. It is used for fungal infections and in dandruff shampoos (selenium sulfide)
43
Where is zinc chloride used?
In mouthwashes
44
Where is zinc oxide used?
As an antifungal agent in paints.
45
What is the origin of the term “oligodynamic”?
From Greek: oligos = small,
dynamis = power,
Oligodynamic = means “small quantity, strong effect.”
46
What is oligodynamic action in relation to heavy metals?
It is the action of certain heavy metals to kill bacteria.
47
Which metals can prevent bacterial growth through oligodynamic action?
Silver, copper, zinc, and mercury.
48
How do metal ions kill bacteria?
They combine with proteins, causing denaturation (loss of protein function).
49
What is the mechanism of action (MOA) of quats?
They disrupt microbial membranes and may also denature proteins.
50
What is the mechanism of action (MOA) of quats?
They disrupt microbial membranes and may also denature proteins.
51
What type of agents are quats classified as?
Surface active agents; **specifically cationic (positively charged) detergents.**
52
Against which organisms are quats most effective, and against which are they less effective?
They are effective against gram-positive bacteria but less effective against gram-negative bacteria.
53
What other organisms can quats destroy?
Fungi, amoebas, and enveloped viruses
54
Give examples of quats
Benzalkonium chloride and cetylpyridinium chloride.
55
What are commercial examples of quats used in labs?
Zephiran and Cepacol (also found in lab spray bottles)
56
What resistant strains are a concern with quats in hospitals?
Pseudomonas strains, which can grow in the presence of quats
57
What are the advantages of quats?
Strong antimicrobial action, colorless, odorless, tasteless, stable, and nontoxic.
58
What are the disadvantages of quats?
They **form foam**, organic matter interferes with effectiveness, and **they are neutralized by soaps and anionic detergents.**
59
Why are aldehydes considered effective antimicrobials?
They are **highly reactive** molecules that **combine with nucleic acids and proteins**, **inactivating them by cross-linking and alkylating molecules.**
60
How do aldehydes inactivate proteins?
By forming covalent crosslinks with several functional groups.
61
What is formaldehyde gas commonly used as?
Formalin, a 37% aqueous solution
62
What are the uses of formalin?
Preserving biological specimens,
inactivating viruses and bacteria in vaccines,
and embalming in mortuaries.
63
What are the drawbacks of formaldehyde use?
It irritates mucous membranes and has a strong odor.
64
How does glutaraldehyde compare to formaldehyde?
It is less irritating and more effective
65
What is special about glutaraldehyde as a disinfectant?
It is one of the few chemical disinfectants that is a sterilizing agent.
66
How is glutaraldehyde commonly used
As a chemical sterilant, especially in hospitals and mortuaries.
67
What concentration of glutaraldehyde is used, and what is its commercial name?
A 2% solution, known as Cidex
68
What is the activity of 2% glutaraldehyde (Cidex)?
Bactericidal, tuberculocidal, and viricidal in 10 minutes.
Sporicidal in 3 to 10 hours
69
Where is glutaraldehyde commonly used?
To disinfect hospital instruments and in mortuaries for embalming
70
What are sterilizing gases, and how do they work?
They are **chemicals that sterilize in a chamber** similar to an autoclave;
they denature proteins by **replacing functional groups with alkyl groups.**
71
What is the activity of ethylene oxide?
It kills all microbes and endospores, but requires **4 to 18 hours of exposure.**
72
What are the drawbacks of ethylene oxide?
It is toxic and explosive in pure form.
73
What is an advantage of ethylene oxide?
is highly penetrating
74
Where is ethylene oxide used in hospitals?
special chambers to sterilize mattresses and large equipment
75
Why is ethylene oxide commonly used for chemical sterilization?
Because of its low boiling point
(**10.4°C at atmospheric pressure**)
it behaves as a gas at room temperature.
76
What is the mechanism of action of EtO?
It chemically **reacts with amino acids, proteins, and DNA** to prevent microbial reproduction.
77
How is ethylene oxide sterilization carried out
In a **specialized gas chamber**, **followed by aeration** to **disperse the gas** before the product is safe to handle.
78
What materials can be sterilized with EtO?
Plastics (e.g., petri dishes, pipettes, syringes, medical devices),
cellulose, and sealed packages, without affecting integrity.
79
What is the mechanism of action of peroxygens
They **oxidize cellular components of microbes**, disrupting membranes and proteins.
80
How is ozone used in disinfection?
Along with chlorine to disinfect water
81
What additional benefit does ozone provide?
It helps neutralize unpleasant tastes and odors.
82
How does ozone compare to chlorine as a killing agent?
It is more effective but less stable and more expensive.
83
What is ozone chemically?
highly reactive form of oxygen
84
How is ozone produced?
By exposing oxygen to electricity or UV light.
85
How is hydrogen peroxide used?
As an antiseptic and disinfectant for inanimate objects.
86
Why is hydrogen peroxide not good for open wounds?
Because it is quickly broken down by catalase present in human cells.
87
Where is hydrogen peroxide effective in disinfection?
Surfaces, equipment, and medical instruments.
88
When is hydrogen peroxide sporicidal?
At higher temperatures
89
What industries use hydrogen peroxide?
The food industry and contact lens disinfection
90
Where is benzoyl peroxide commonly used?
In acne medications
91
Why is peracetic acid considered highly effective?
It is one of the most effective liquid sporicides available
92
What is the spectrum of peracetic acid?
Kills bacteria and fungi in less than 5 minutes.
Kills endospores and viruses within 30 minutes.
93
Why is peracetic acid widely used in disinfection of food and medical instruments?
Because it does not leave toxic residues
94
Which of the following is NOT a type of surfactant?
a) Cationic
b) Anionic
c) Non-ionic
d) Phenolic
a) Cationic
b) Anionic
c) Non-ionic
**d) Phenolic** - not a surfactant
95
Identify the type of detergent and its primary function:
Soap (anionic): __________
Acid-anionic detergents: __________
Quaternary ammonium compounds (cationic): __________
Soap (anionic): **Degerming** (mechanical removal of microbes through scrubbing).
Acid-anionic detergents: **Sanitizing** (commonly used in food and dairy industry).
Quaternary ammonium compounds:
**Bactericidal, denature proteins, disrupt plasma membranes** (used as antiseptics for skin, instruments, utensils).
96
T/F:
Soaps have high value as antiseptics
False — soaps have little value as antiseptics, mainly act through mechanical removal of microbes.
97
What is emulsification in the context of soaps and detergents?
Emulsification is the **breaking down of oily film on skin into smaller droplets,** allowing microbes and dirt to be mechanically removed during scrubbing.
98
Enumerate the four types of surfactants and state which is the most active disinfectant type.
Cationic
Anionic
Non-ionic
Amphoteric
👉 **Amphoteric compounds are the most active disinfectants** and less affected by organic matter.
99
Which viruses are susceptible and not susceptible to surfactants?
Surfactants are =
**Active against:** Bacteria and enveloped viruses (e.g., feline herpesvirus).
**Not active against:** Non-enveloped viruses (e.g., feline calicivirus).
100
Give two main uses of surfactants in medicine/pharmacy.
Wound disinfection.
Preservatives in pharmaceutical preparations (e.g., eye drops).
101
Why are non-ionic surfactants (alcohol ethoxylates) a concern despite their usefulness?
They are more efficient at penetrating skin than many other surfactants, **but they can enhance the toxicity of other toxic chemicals,** raising concerns about low-level exposure.
102
Which dye is commonly used to treat fungal skin infections like ringworm?
a) Acriflavine
b) Crystal violet
c) Malachite green
d) Both b and c
a) Acriflavine
b) Crystal violet
c) Malachite green
**d) Both b and c**
103
What are the uses of **yellow acridine dyes** (e.g., acriflavine, proflavine)?
Used for antisepsis and wound treatment in medical and veterinary clinics.
104
Give two examples of **antimicrobial dyes** and the microbes they are active against.
**Crystal violet & Malachite green** → Active against gram-positive bacteria and fungi (used in ointments/solutions for skin infections like ringworm).
**Acriflavine & Proflavine** → Used for wound treatment and antisepsis.
105
What is the antimicrobial application of the following:
Acetic acid
Propionic acid
Ammonium hydroxide solution
Acetic acid → Food preservation, inhibits bacteria/fungi.
Propionic acid → Food preservation, especially against molds.
Ammonium hydroxide → Aqueous disinfectant solution.
106
Which organic acid is widely used in cheese, baked goods, and soft drinks to control mold growth?
a) Sorbic acid
b) Boric acid
c) Benzoic acid
d) Calcium propionate
a) Sorbic acid
107
T/F: Boric acid is commonly used in eye washes.
True
108
Enumerate the organic acids and their uses:
**Sorbic acid** (Ca, Na, K salts): Prevent mold growth in cheeses, baked goods, soft drinks, fruit juices, jams, jellies.
**Benzoates** (sodium benzoate, methylparaben): Preservative in fruit juices, jams, jellies, soft drinks, salad dressings, margarine, pharmaceuticals.
**Boric acid**: Used in eye washes.
**Calcium propionate**: Prevents mold growth in bread.
109
Why are organic acids widely used in food preservation?
They are effective in controlling mold growth, extend shelf life, and are safe at low concentrations without altering food quality significantly.
110
Define preservatives and explain their role in microbial control
Preservatives are **static agents used to inhibit the growth of microorganisms**, most often in foods. They must be nontoxic if consumed.
111
Enumerate examples of preservatives
Calcium propionate
Sodium benzoate
Formaldehyde
Nitrate
Sulfur dioxide
112
What is the role of salt in food preservation?
a) Adds flavor only
b) Prevents food browning
c) Retards bacterial growth
d) Acts as antifungal
a) Adds flavor only
b) Prevents food browning
**c) Retards bacterial growth**
d) Acts as antifungal
113
Why are salts specifically effective against meat spoilage organisms?
Salts prevent the growth of some types of bacteria **responsible for meat spoilage.**
114
What is the function of =
Nitrates/ Nitrites
Nitrosamines
Nitrates
Maintains pink color in cured meats = **Nitrates/Nitrites**
Prevents botulism in canned foods = **Nitrosamines / Nitrates/Nitrites**
Adds flavor in cheese = **Nitrates**
115
T/F: Sodium nitrate (NaNO₃) is more commonly used in curing meats than sodium nitrite (NaNO₂).
False, sodium nitrite (NaNO₂) is more commonly used
Microbiology
flashcards
Decks in class (22)
# Cards
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Module 6106
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Module 7181
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Module 8. 1132
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Module 8.2115
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Module 8.3283
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Module 9188
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9191
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11.1191
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11.2170
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Module 11.2160
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Module 12 (Slide 1 To 39)94
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Module 12 (Slide 40 To 65)76
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Module 12 (66-101)156
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Module 12 (-110 Last)25
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LAB EXAM 1 EXERCISES31
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LAB EXAM 1 PPT CULTURE MEDIA107
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Module 13 (VIRUSES)64
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Module Virology Pt.1 (RNA VIRUSES)85
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Module Virology Part 2 (DNA)57
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Module VIROLOGY Part 3 (Introduction)98
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RNA (Picorna-Coronaviridae)83
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RNA VIRUS (REO - RHABDOVIRIDAE)49
