Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Microbiology Prelim > Microbial Control > Flashcards

Microbial Control Flashcards

(103 cards)

Start Studying
1
Q

Sepsis

A

microbial contamination.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Asepsis:

A

absence of significant contamination. o Aseptic surgery techniques prevent microbial contamination of wounds. o Antimicrobial chemicals, expected to destroy pathogens but not to achieve sterilization § Disinfectant: the destruction of vegetative pathogens, used on objects § Antiseptic: used on living tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Nosocomial

A

hospital infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Sterilization:

A

Removal of all microbial life (heat, filtration) o For food: Commercial sterilization to kill C. botulinum endospores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Sanitization

A

reduce microbe numbers to safe levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Bacteriostatic:

A

Inhibits bacterial reproduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

bactericidal

A

kills bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

RATE OF MICROBIAL DEATH

A

Bacterial populations subjected to heat or antimicrobial chemicals die at a constant rate. • Microbial Death Curve, plotted logarithmically, shows this constant death rate as a straight line.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

EFFECTIVENESS OF ANTIMICROBIAL TREATMENT

A

t depends on: • Time it takes to kill a microbial population is proportional to number of microbes. • Microbial species and life cycle phases (e.g.: endospores) have different susceptibilities to physical and chemical controls. • Organic matter may interfere with heat treatments and chemical control agents. • Exposure time: Longer exposure to lower heat produces same effect as shorter time at higher heat. • Environmental influences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

ACTIONS OF MICROBIAL CONTROL AGENTS

A

• Alternation of membrane permeability • Damage to proteins • Damage to nucleic acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

PHYSICAL METHODS OF MICROBIAL CONTROL

A

Not for use on living organisms Somehow, alter membrane permeability and/or structure of proteins and nucleic acids Heat is very effective (fast and cheap).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Thermal death point (TDP):

A

The lowest temperature at which all cells in the culture are killed in 10 min.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Thermal death time (TDT):

A

Time to kill all cells in a culture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Decimal Reduction Time (DRT):

A

Minutes to kill 90% of a population at a given temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

MOIST HEAT STERILIZATION

A

Denatures proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Autoclave

A

Steam under pressure Most dependable sterilization method • Steam must directly contact material to be sterilized. • Pressurized steam reaches higher temperatures. • Normal autoclave conditions: 121.5 OC for 15 min. • Prion destruction: 132 OC for 4.5 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

PASTEURIZATION

A

Significant number reduction (esp. spoilage and pathogenic organisms) it does not sterilize!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

The historical goal of pasteurization

A

the destruction of M. tuberculosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Classic holding method: (pasteurization)

A

63 OC for 30 min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Flash pasteurization (HTST):

A

72 OC for 15 sec. o Most common in the US o Thermoduric organisms survive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Ultra-High Temperature (UHT):

A

140 OC for < 1 sec o Technically not pasteurization because it sterilizes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

DRY HEAT STERILIZATION

A

• Kills by sterilization • Flaming of loop • Incineration of carcasses o Anthrax o Foot and mouth disease o Bird flu

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

FILTRATION

A

Air filtration using high efficiency particulate air (HEPA) filters. Effective to 0.3 µm Membrane filters for fluids. • Pore size for bacteria: 0.2 – 0.4 µm • Pore size for viruses: 0.01 µm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

LOW TEMPERATURE

A

• Slows enzymatic reactions à inhibits microbial growth • Freezing forms ice crystals that damage microbial cells • Refrigeration (deep freezing, lyophilization)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
High pressure in liquids
denatures bacterial proteins and preserves flavor
26
Desiccation
prevents metabolism
27
Osmotic pressure
causes plasmolysis
28
IONIZING RADIATION
• X-rays, gamma rays, electron beams
29
What element is most commonly used in Ionizing radiation
Commonly used Cobalt-60 radioisotope
30
bacteria that are sensitive to ionizing radiation
Salmonella and pseudomonas
31
UV Light
Most effective wavelength ~ 260 nm • Effect: thymine dimers • Actively dividing organisms are more sensitive because thymine dimers cause \_\_\_\_? • Used to limit air and surface contamination. Use at close range to directly exposed microorganisms E.g.: germicidal lamps in OR, cafeteria, and our lab
32
MICROWAVE
Wavelength: 1 mm - 1m • H2O quickly absorbs energy released as heat to environment • Indirect killing of bacteria through heat
33
CHEMICAL METHODS OF MICROBIAL CONTROL
• Few chemical agents achieve sterility. • Consider the presence of organic matter, degree of contact with microorganisms, and temperature • Disinfectants regulated by EPA • Antiseptics regulated by FDA
34
USE-DILUTION TEST
1. Metal rings dipped in test bacteria are dried. 2. Dried cultures of S. choleraesuis, S. aureus, and P. aeruginosa are placed in disinfectant for 10 min at 20°C 3. Rings are transferred to culture media to determine whether bacteria survived treatment.
35
DISK-DIFFUSION METHOD
The disk of filter paper is soaked with a chemical and placed on an inoculated agar plate; a zone of inhibition indicates effectiveness.
36
PHENOL =
carbolic acid (historic importance) • Phenolics: Cresols (Lysol); disinfectant
37
BISPHENOLS
• Hexachlorophene (pHisoHex, prescription), hospitals, surgeries, nurseries • Triclosan (toothpaste, antibacterial soaps, etc).
38
CHLORINE
• Oxidizing agent • Widely used as a disinfectant • Forms bleach (hypochlorous acid) when added to water. • Broad spectrum, not sporicidal (pools, drinking water)
39
IODINE
• More reactive, more germicidal • Alters protein synthesis and membranes. • Tincture of iodine (solution with alcohol) à wound antiseptic • Iodophors combined with an organic molecule o iodine detergent complex (e.g. Betadine®). Occasional skin sensitivity, partially inactivated by organic debris, poor sporicidal activity
40
Ethyl (60 - 80% solutions) and isopropyl alcohol
• Denature proteins, dissolve lipids • No activity against spores and poorly effective against viruses and fungi
41
MERCURIC CHLORIDE
(HgCl2, Greeks & Romans for skin lesions); Thimerosa
42
COPPER
against chlorophyll-containing organisms à Algicides
43
SILVER NITRATE (AGNO3):
Antiseptic for eyes of newborns
44
ZINC (ZNCL2)
in mouthwashes, ZnO in antifungal In paint
45
SURFACE ACTING INGREDIENTS/SURFACTANTS
soaps and detergents
46
The major purpose of soap:
Mechanical removal and use as wetting agent
47
Acidic-
Anionic detergents: Anion reacts with the plasma membrane. Nontoxic, non-corrosive, and fast-acting. Laundry soap, dairy industry.
48
Cationic detergents
Quaternary ammonium compounds (Quats). Strongly bactericidal against a wide range, but especially Gram (+) bacteria
49
SULFUR DIOXIDE:
wine
50
ORGANIC ACIDS:
Sorbic acid, benzoic acid, and calcium propionate; Inhibit metabolism; Control molds and bacteria in foods and cosmetics
51
SODIUM NITRATE AND NITRITE:
prevents endospore germination; In meats; Conversion to nitrosamine (carcinogenic)
52
ALDEHYDES (alkylating agents)
• Inactivate proteins by cross-linking with functional groups (-NH2, -OH, -COOH, -SH)
53
Glutaraldehyde:
sterilant for delicate surgical instruments (Kills S. aureus in 5, M. tuberculosis in 10 min)
54
Formaldehyde:
Virus inactivation for vaccines
55
CHEMICAL STERILANTS
for heat sensitive material • Denature proteins • Ethylene oxide
56
PLASMA
• Luminous gas with free radicals that destroy microbes • Use: Tubular instruments, hands, etc
57
HYDROGEN PEROXIDE:
OXIDIZING AGENT • Inactivated by catalase à Not good for open wounds Esp. effective against anaerobic bacteria • Effervescent action may be useful for wound cleansing through the removal of tissue debris
58
Resistance order
Prions bacterial endospores Mycobacteria protozoa cyst g -ve bacterium Fungal spores virus without envelope gram +ve Virus with lipid
59
STERILIZATION
- The killing or removal of all viable organisms within a growth medium
60
INHIBITION
- Effectively limiting microbial growth.
61
DECONTAMINATION
- The treatment of an object to make it safe to handle.
62
DISINFECTION
- Directly targets the removal of all p
63
HEAT STERILIZATION
- Is the most widely used method of controlling microbial growth - Simplest means of sterilizing materials provided the material is itself resistant to heat.
64
Decimal reduction time
Amount of time required to reduce the viability tenfold
65
Antimicrobial agents can be classified as
bacteriostatic, bacteriocidal and bacteriolytic
66
MINIMUM INHIBITORY CONCENTRATION (MIC)
Is the smallest amount of an agent needed to inhibit the growth of a microorganism - Varies with the organism used, inoculum size, temp, pH, etc.
67
DISC DIFFUSION ASSAY
The antimicrobial agent added to the filter paper disc The antimicrobial agent added to the filter paper disc - MIC is reached at some distance § Zone of Inhibition – an area of no growth around the disc.
68
Antimicrobial drugs are classified on the basis of
- Molecular structure - Mechanism of action - Spectrum of antimicrobial activity
69
Characteristics of the ideal antimicrobial drug:
Selectively toxic to the microbe but nontoxic to host cells - Microbicidal rather than microbiostatic - Relatively soluble and function even when it is highly diluted in body fluids - Remains potent long enough to act and is not broken down or excreted prematurely - Not subject to the development of antimicrobial resistance - Complements or assists the activities of the host’s defences - Remains active in tissues and body fluids - Readily delivered to site of infection - Not excessive in cost - Does not disrupt the host’s health bu causing allergies of predisposing the host to other infections.
70
Inhibition of cell wall synthesis
Pencillin, Cephalosporins
71
Beta-Lactam drugs
selective inhibitors of bacterial cell wall synthesis
72
Inhibition/alteration of cell membrane function
Detergents disrupt cytoplasmic membrane o Ex. Valinomycin, Daptomycin, Telavancin
73
Inhibition of protein synthesis:
Bacteria have 70S ribosomes while mammalian cells have 80 S ribosomes, which explains why antimicrobials can inhibit protein synthesis in bacterial ribosomes without having a major effect on mammalian ribosomes Ex. aminoglycosides, Macrolides, Azalides and Ketolids, Lincosamides, tetracyclines, Glycylcyclines, Chloramphenicol, Streptogramins, Oxazolidinones
74
Inhibition of Nucleic acid synthesis:
on of Nucleic acid synthesis: o Inhibiting growth by binding strongly to DNA-Dependent RNA polymerase of bacteria and inhibits RNA synthesis. (Rifampicin) o Inhibit microbial DNA synthesis by clocking DNA gyrases (Quinilones and fluoroquinolones) o Sulfonamides enter into reaction and compete for active center of enzyme. o More examples: Trimethoprim and Timetrexate
75
SULFA DRUGS:
discovered by Gerhard Domagk in the 1930’s\Inhibit growth of bacteria (sulfanilamide is the simplest) - Isoniazid is a growth analog effective only against Mycobacterium.
76
NUCLEIC ACID-BASE ANALOGS:
formed by adding bromine or fluorine
77
QUINOLONES:
antibacterial compounds that interfere with DNA gyrase (e.g., ciprofloxacin)
78
Gram Negatives and positives
vary in their sensitivities to antibiotics but Broad spectrum antibiotics are effective against both groups.
79
B-lactam antibiotics are
one of the most important groups of antibiotics of all time and over half of all antibiotics used worldwide. Composed of Penicillins, Cephalosporins & Cephamycins.
80
Penicillin
Discovered by Alexander Fleming - Effective against Gram-positive, but some synthetic forms can act against gram-negative bacteria - Targets the cell wall synthesis - Natural: Benzylpenicillin (Penicillin G)
81
Methicillin
(acid-stable)
82
Oxacillin
(acid-stable)
83
Ampicillin
(broad spectrum & acid stable)
84
Carbenicillin
(broad spectrum & acid stable)
85
CEPHALOSPORINS
- Produced by fungus Cephalosporium - Targets cell wall synthesis - Treats Gonorrhoea
86
Daptomycin
produced by streptomyces- g+ve infection
87
Platensimycin
New antibiotic, BS, MRSA and vancomycin-resistant Enterococci
88
Aminoglycoside
Kanamycin, neomycin, amikacin
89
Macrolides
Erythromycin- lactone rings bonded to sugars
90
Tetracyclines
30S inhibition, BS, Used in Humans and animals, aureomycin, Terramycin
91
AZT-
block Reverse Transcriptase DNA
92
NNTRI
Bind directly to RT and inhibit reverse transcription
93
FUSION INHIBITORS
prevent viruses from successfully fusing with the host cell
94
Two categories of drugs successfully limit influenza infection:
- ADAMANTANES - NEURAMINIDASE INHIBITORS
95
Interferons
are small proteins that prevent viral multiplication by stimulating antiviral proteins in uninfected cells
96
Mechanism of drug resistance:
- Drug inactivated by Penicillinases - Decreased permeability to drug or increased elimination of drug from cell. - Change in metabolic patterns - Change in drug receptors
97
Methicillin-resistant S. aureus
(MRSA)
98
Origin of drug resistance:
Nongenetic origin of drug resistance o Microorganisms that are metabolically inactive may be phenotypically resistant to drugs, but their offspring are fully susceptible. Ex. Mycobacteria o Lose specific target structure for drug for several generations and may become resistant. Ex. Penicillin-susceptible organisms may change to cell wall deficient L forms o Microorganisms may infect host at sites where antimicrobials are excluded or not active. Ex. gentamycin not effective against Salmonella enteric fevers because they are found intracellularly and Gentamycin do not enter the cells.
99
The genetic origin of drug resistance
Result of change and subsequent selection process
100
Chromosomal Resistance
Result of spontaneous mutation
101
Cross-resistance
o Microorganisms resistant to a certain drugs may also be resistant to other drugs that share a mechanism of action.
102
Limitation of drug resistance:
- By maintaining high levels of drugs in tissues to inhibit both the original population and first-step mutants - Spontaneously administering two drugs that do not give cross-resistance - Avoiding exposure of microorganisms to a particularly valuable drug by limiting its use.
103
Bacteriophage therapy
- Use of bacteriophages to treat infections - A form of the virus that attacks bacteria

Microbiology Prelim (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions