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Microbiology > Sterilization, Disinfection, Antiseptics, and Antimicrobials > Flashcards

Sterilization, Disinfection, Antiseptics, and Antimicrobials Flashcards

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Biology 101 flashcards
1
Q

What does death / killing refer to when speaking of microbes?

A

Death / killing as the terms refer to microbes detection in culture.

This refers to the loss of the ability to multiply under any conditions.

However, the absence of bacterial growth does not always mean that the bacteria is dead or the culture is sterile.

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2
Q

What does sterilization mean?

A

Sterilization is the complete killing or removal of all living organisms from a particular location.

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3
Q

What does pasteurization mean?

A

This is the use of heat at a temperature sufficient to inactivate pathogenic organisms in liquids.

Note that this takes place at a temperature that is lower than sterilization.

This usually kills vegetative forms of the bacteria but not spores.

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4
Q

What is disinfection?

A

Disinfection is the destruction of pathogenic microorganisms by processes that fail to meet the criteria for sterilization.

This usually occurs via chemical agents and they may be selective.

Bacterial spores, bacteria that have lots of lipids and many viruses are resistant.

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5
Q

What are antiseptics?

A

Antiseptics are disinfecting agents that can be used on skin or vaginal tract.

They reduce the numbers of bacteria on skin and have a lower toxicity than disinfectents but are usually less active at killing microbes.

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6
Q

What does asepsis mean?

A

Asepsis is a term that describes a process where by microbes are prevented from reaching protected environments.

Sterilization and disenfecting techniques make up this process.

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7
Q

What does sterility mean?

A

Sterility is the total absence of viable microorganisms assessed by no growth on any medium.

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8
Q

What does bactericidal mean?

A

This is a compound that kills bacteria.

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9
Q

What does bacteriostatic mean?

A

These are compounds that inhibit microbial growth.

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10
Q

What does sepsis mean?

A

This term means infection.

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11
Q

What does antisepsis mean?

A

This refers to any procedure that inhibits the growth and multiplication of bacteria.

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12
Q

What does aseptic mean?

A

This refers to a state that is without infection.

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13
Q

How are the kinetics of bacterial killing measured and affected?

A

Bacterial killing is affected by the:

  • Medium
  • Concentration of organism
  • Concentration of antimicrobial compound
  • Temperature
  • pH

Presence / absence of endospores

The killing curve can be exponential (logarithmic) and can result in a asymptotic killing curve that requires consideration in killing final numbers, especially if the population is heterogeneous relative to its sensitivity.

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14
Q

What are the methods of controlling bacterial growth?

A

Moist heat

Dry heat

Incineration

UV radiation

Chemicals

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15
Q

How does moist heat work to kill bacteria?

A

Autoclaving at 121o C for 15 minutes in a steam pressureized autoclave at 15 psi kills vegatative microorganisms and endospores.

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16
Q

How does dry heat and incenration kill microorganisms?

A

These two methods oxidize proteins.

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17
Q

How does UV radiation kill bacteria?

A

UV radiation causes thymine dimers and blockes DNA replication.

Bacteria possess repair mechanisms to repair this damage however.

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18
Q

What are some of the common chemicals used to kill microbes?

A

Phenol

Chlorhexidine

Iodine

Chlorine

Quaternary ammonium compounds

Ethylene oxide

Alcohol

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19
Q

How does phenol kill bacteria?

A

This is a disinfectant that is bacterialcidal and denatures proteins.

These also affect the lipid bilayer of the cell membrane.

Example: Hexaclorophene and Lysol

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20
Q

How does chlorhexidine kill bacteria?

A

This is a hand and skin disinfectent. It is bacterialcidal and alters membrane permeability in Gram + and - bacteria.

It is cationic and soaps and anionic compounds will inactivate it.

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21
Q

How does Iodine kill bacteria?

A

Iodine is bacterialcidal in 2% concentrations.

It is an oxidizing agent and denatures proteins.

Example: Tincture (4% iodine and potassium iodide in alcohol) and Idophores

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22
Q

How does chlorine inactivate bacteria and viruses?

A

Chlorine is an oxidizing agent that oxidizes free sulfhydryl groups.

23
Q

How do quaternary ammonium compounds inactivate bacteria?

A

This are hydrophobic and lipophilic compounds that interact with the cell membrane and alter its metabolic properties and activities.

Example: Benzalkonium chloride

24
Q

How does ethylene oxide work on bacteria?

A

This is a gas that is an alkylating agent that replaces labile hydrogens in DNA.

25
Q

How does alcohol deactivate and/or kill bacteria?

A

Alcohol kills bacteria at concentrations of 70 to 95% given sufficient time.

Affects cell wall

Isopropyl alchol is the major type in use.

Endospores may survive.

26
Q

What is a noscomial infection?

A

This is an infection that is acquired in a health care setting (Hospital or clinic).

27
Q

What is a community acquired infection?

A

A community acquired infection is one that is acquired before admission to a hospital.

28
Q

What does cross infection mean?

A

This is when an infection is transmitted from one patient to another via unwashed hands or some other vehicle.

29
Q

How does chlorine kill bacteria?

A

Chlorine denatures proteins.

Example: Clorox

30
Q

How does hydrogen peroxide kill bacteria?

A

Hydrogen peroxide kills bacteria by denaturing its proteins.

Can be inactivated by catalase.

31
Q

How do the disinfectents, formaldehyde and glutaraldehyde act on bacteria?

A

Both of these denature and modify proteins.

32
Q

How do gentian violet and malachite green work?

A

These compounds work by modifying bacterial DNA.

33
Q

True or false: Moist heat is better than dry heat for killing bacteria.

A

True

34
Q

True or false: Filtration is a method used to filter endotoxins.

A

True; pore size is 0.2 um

35
Q

What is an antibiotic?

A

These are antimicrobials of microbial origin, most of which are produced by fungi or by bacteria of the genus Streptomyces.

36
Q

What is an antimicrobial?

A

This is any compound with sufficient antimicrobial activity that it can be used in teh treatment of infectious disease.

37
Q

What is a chemotherapeutic?

A

This is a broad term that encompasses antibiotcs, antimicrobials, and drugs used in the treatment of cancer.

In the context of infectious diseases, it implies that teh agent is not an antibiotic.

38
Q

What does ‘Minimal Inhibitory concentration’ refer to?

A

This is a laboratory term that defines the lowest concentration (ug / ml) that is able to inhibit the growth of a microorganism.

39
Q

What does the term resistant mean?

A

This refers to organisms that are not inhibited by clinically achievable concentrations of an antimicrobial agent.

40
Q

What does spectrum mean?

A

This is an expression of the categories of microorganisms against which an antimicrobial is typically active.

A narrow spectrum agent has activity against only a few organisms.

A broad spectrum agent has activity against organisms of a diverse type.

41
Q

What does susceptible or sensitive refer to?

A

These terms are applied to microorganisms indicating that they will be inhibited by concentrations of the antimicrobial agent that can be achieved clinically using the generally recommended dosage schedules.

42
Q

Antimicrobials that act on cell wall synthesis.

A

B-lactam antimicrobials (Penicillins, cephalosporins, carbapenems, and monobactams) - Have a beta lactam ring. Interfere with peptidioglycan crosslinking.

43
Q

True or false; Carbapenems have the broadest spectrum of activity of all beta lactams.

A

True; easy to get into Gram + and Gram - cells

44
Q

Antimicrobials that inhibit protein synthesis.

A

Aminoglycosides - Bind to bacterial ribosomes and prevent initiation

Tetracyclines / Doxycycline - Bind the 30S ribosomal subunit and blocks aminoacyl-tRNA. Broad spectrum.

Chloramphenicol - Binds the 50S ribosomal subunit.Blocks peptidyl transferase.

Macrolides - Block translocation step in ribosome.

Clindamycin - Blocks translocation step in ribosome.

Oxazolidinones - Blocks 50S subunit.

Quinupristin-dalfopristin - Blocks 50S ribosome

45
Q

Inhibitors of nucleic acid synthesis.

A

Quinolones - Blocks action of DNA topoisomerase

46
Q

Inhibitors of folate.

A

Sulfonamides - Compete with PABA for binding to dihydropteroate synthase

Trimethoprim-Sulfamethoxazole - Inhibits dihydrofolate reductase

47
Q

Other antibiotics.

A

Metronidazole - Induction of breaks in DNA

Rifampin - Inhibits DNA-dependent RNA polymerase

Polymyxin B - Alter membrane permeability

Colistin - Alter membrane permeability

48
Q

What is dilution testing used for?

A

Dilution testing is done to determine the minimum inhibitory concentration by using serial dilutions of the antimicrobial agent in broth that span a clinically significant range of concentrations.

49
Q

What is difussion testing used for?

A

A defined amount of antimicrobial agent is seeded onto a plate and the agent diffuses into the medium to produce a circular gradient around the disk. The size of the zone of growth inhibition is a measure of the minimum inhibitory concentration.

50
Q

What are modes of bacterial antibiotic resistance?

A

Enzymatic deactivation

Efflux pumps

Altered targets

Chromosomal resistance

Mutational resistance

Plasmid and conjugation-based resistance factors

51
Q

What is specific therapy?

A

This is antimicrobial therapy that is targeted at a specific organism.

52
Q

What is empiric therapy?

A

This is therapy that is based soley on clinical findings.

53
Q

What is prophylaxis?

A

This is the use of antibiotics to prevent infection.

Can be dangerous as it may lead to resistant organisms.

Microbiology (16 decks)

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