Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Clinical Bacteriology > (P) Lec 3.2: Bacterial Pathogenesis and Epidemiology, Antimicrobials and Mechanism of Bacterial Resistance, and Indigenous Microbial Flora > Flashcards

(P) Lec 3.2: Bacterial Pathogenesis and Epidemiology, Antimicrobials and Mechanism of Bacterial Resistance, and Indigenous Microbial Flora Flashcards

Chapter 13 of Mahon's

1
Q

Performed on bacteria and fungi isolated from clinical specimens to determine which antimicrobial agents might be effective in treating infections caused by these organisms

A

Antimicrobial Susceptibility Testing

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

Only organisms that are likely to be contributing to an infection should be tested

A

Antimicrobial Susceptibility Testing

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

Often performed by a disk diffusion or dilution (minimal inhibitory concentration [MIC]) method

A

Antimicrobial Susceptibility Testing

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

Inoculum concentration of bacteria to be tested must be ______

A

Standardized

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

____ results may occur if too few bacteria are tested

A

False-susceptible

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

____ results may be the outcome of testing too many bacteria

A

False-resistant

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

Name the standard

Standard Suspension

A

McFarland 0.5 standard: contains 99.5 mL of 1% sulfuric acid and 0.5 mL of 1.175% barium chloride.

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

Name the standard

Bacterial Inoculum Size

A

1.5 × 10^8 CFU/mL

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

Name the standard

Standard Medium

A

Mueller-Hinton Heated Agar

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

Name that standard

Standard Depth

A

4-6 mm

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

Name that standard

Standard pH

A

7.2-7.4

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

Name that standard

Atmosphere requirement

A

Aerobic, no CO2

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

Name that standard

Temperature

A

35 - 37°C

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

Disk Diffusion

A

1.5 x 10^8 CFU/mL

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

Broth Dilution

A

5 x 10^5 CFU/mL

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

Agar Dilution

A

1 x 10^4 CFU/mL

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

Composition of Mueller Hinton Agar

A
  • Beef infusion solids
  • Starch
  • Casein hydrolysate agar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the storage guidelines of Mueller Hinton Agar?

A
  • Store prepared media below 8°C
  • Protect from direct light
  • Store the dehydrated powder in a dry place and tightly sealed containers at 2 - 25°C
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Main Purpose of 0.5 McFarland Standard

A

To adjust the turbidity of bacterial suspensions to a standardized level

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

Most common composition of 0.5 McFarland Standard

A
  • 99.5 mL of 1% sulfuric acid
  • 0.5 mL of 1.175% barium chloride

Can be prepared by adding specific volume of 1% sulfuric acid and 1.175% barium chloride to obtain a barium sulfate solution with a specific optical density

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

Storage of 0.5 McFarland Standard

A

Stored in an upright position at 4°C to 25°C and protected from light

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

Under the proper storage conditions, how long does the 0.5 McFarland Standard last?

A

12 weeks from date of manufacture

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

Used to determine the minimum inhibitory concentration (MIC) or the lowest concentration of antimicrobial agent required to inhibit the growth of the bacterium

A

Dilution Susceptibility Testing

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

Those that are attainable in vivo following standard dosing of the respective antimicrobial agent

A

Serial Two Fold-Dilution Concentrations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Once the MIC has been determined, the organism is interpreted as ____, ____, ____ or ____ to each agent

A

Nonsusceptible, susceptible, intermediate, or resistant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

They described a test that measured the effectiveness with which penicillin in serum killed bacteria associated with endocarditis

A

Schlichter and MacLean

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What year did Schlichter and MacLean describe the Serum Bactericidal Test?

A

1940s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Analogous to the MIC-MBC test except that the medium used is patient’s serum

A

Serum Bactericidal Test

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Results relate to the amount of antimicrobial agent and any other antibacterial factors (e.g., antibody, opsonins, complement) present in the patient’s serum)

A

Serum Bactericidal Test

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Also known as oxacillin resistance screening agar

A

Oxacillin Agar Screen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

A specialized medium used for the screening of oxacillin-resistant microorganisms, primarily focusing on detecting MRSA

A

Oxacillin Agar Screen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are the steps involving oxacillin agar screen?

A
  1. Allow medium to reach room temperature.
  2. Take the specimen swab and roll it near the edge of the plate.
  3. Then, use a sterile loop to perform a four-quadrant streak starting from that area to get isolated colonies.
  4. Incubate aerobically at 35°C.
  5. Examine after 24 hours for typical MRSA colonies. Re-incubate plates an additional 24 hours before discarding.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Used to detect VRSA and Enterococci resistant to VAN

A

Vancomycin Agar Screen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What are the steps involving vancomycin agar screen?

A
  1. Dip the swab into the inoculum (comparable to 0.5 McFarland std) to the plate medium (BHI w 6 mg/L of vancomycin) by streaking over the entire agar surface.
  2. Inc. 24 hrs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Resistant to VAN if:

A

They had developed mutations in their cell walls

36
Q

Susceptible to VAN if:

A

They acquired a plasmid containing vanA vancomycin resistance gene from vancomycin-resistant enterococci

37
Q

Used to detect inducible clindamycin resistance in bacteria, particularly in coagulasenegative staphylococci (CoNS) and Staphylococcus aureus

38
Q

The two antibiotics being observed in D-Test are ____ and ____

A

Erythromycin and clindamycin

39
Q

Synergy Testing

Its antibacterial activity is significantly greater than that of a single agent

40
Q

Synergy Testing

The activity of the combination less than (and MICs are greater than) that of the single agents

A

Antagonism

41
Q

Synergy Testing

The activity of the combination is equal to that of the single agents

A

Indifference

42
Q

A method used to study the antimicrobial activity of a compound over time. This assay helps determine the bactericidal or bacteriostatic properties of an antimicrobial agent against a particular microorganism

A

Time-Kill Assay

43
Q

What are the steps involving Time-Kill Assay?

A
  1. Prepare bacterial inoculum
  2. Add antimicrobial agent
  3. Incubate (on time intervals)
  4. Serially diluted, and then plated onto suitable agar
  5. Read the number of colonies
44
Q

What are the steps involving E-Test?

A
  1. Prepare bacterial inoculum
  2. Uniformly spread bacteria on MHA
  3. Impregnate E-test strip
  4. Incubate
  5. Read
45
Q

A quantitative method used to determine the MIC of antimicrobial agents against specific microorganisms

46
Q

It is produced by microorganisms i.e. bacteria and fungi, that it sends outside its cell to harm or kill another microorganism

A

Antibiotics

47
Q

A drug used to treat infections caused by bacteria and other microorganism

A

Antibiotics

48
Q

Name the antibiotic

Bacillus subtilis

A

Bacitracin

49
Q

Name the antibiotic

Bacillus polymyxa

50
Q

Name the antibiotic

Streptomyces nodosus

A

Amphotercin B

51
Q

Name the antibiotic

Streptomyces venezuelae

A

Chloramphenicol

52
Q

Name the antibiotic

Streptomyces erythraeus

A

Erythromycin

53
Q

Name the antibiotic

Streptomyces griseus

A

Streptomycin

54
Q

Name the antibiotic

Micromonospora purpurea

A

Gentamicin

55
Q

Name the antibiotic

Cephalosporium spp. (fungi)

A

Cephalothin

56
Q

Name the antibiotic

Penicillium notatum (fungi)

A

Penicillin

57
Q

Inhibitors of Cell Wall Synthesis

Antibiotic: B-lactams

Give the examples, principles, and any additional notes.

A

Examples: Penincillins, Cephalosporins, Carbapenams (Imipenem), Monobactams (Azotreonam)
Principle: Targets the enzyme mediating the transpeptidation
Additional Notes: Methicillin for penincillin-resistant Staph.

58
Q

Inhibitors of Cell Wall Synthesis

Antibiotic: Glycopeptides

Give the examples, principles, and any additional notes.

A

Example: Vancomycin
Principle: Binds into the substrate of the transpeptidation enzyme
Additional Notes: DOC for Clostridium difficile and for MRSA

59
Q

Inhibitors of Protein Synthesis

Antibiotic: Aminoglycosides

Give examples and principles.

A

Examples: Gentamicin, Tobramycin, Kanamycin
Principle: Acts on 30S subunit; not active against anaerobes, used with a penicillin for Enterococcus

60
Q

Inhibitors of Protein Synthesis

Antibiotic: Tetracyclines

Give examples and principles.

A

Examples: Tetracycline, Doxycycline
Principle: Reversible binding to 30S subunit
Contraindication: tetracyclin affects bone and teeth in infants

61
Q

Inhibitors of Protein Syntheis

Antibiotic: Phenicols

Give examples and principles.

A

Examples: Chloramphenicol
Principle: Acts on 50S subunit

62
Q

Inhibitors of Protein Synthesis

Antibiotic: Macrolides

Give examples and principles.

A

Examples: Erythromycin, Azithromycin, Clindamycin
Principles: Acts on 50S subunit; clindamycin for gram (+) and gram (-) anaerobes

63
Q

Inhibitors of DNA

Antibiotic: Quinolones

Give the examples.

A
  • Ciprofloxacin
  • Norfloxacin

For P. aeruginosa and other anaerobes

64
Q

Give the resistance and disease.

Agent: S. pneumoniae

A

Resistance: Penicillin
Disease: Pneumonia

65
Q

Give the resistance and disease.

Agent: Shigella

A

Resistance: Multiple Resistance
Disease: Dysentery

65
Q

Give the resistance and disease.

Agent: Salmonella typhi

A

Resistance: Multiple Resistance
Disease: Typhoid

66
Q

Give the resistance and disease.

Agent: Neisseria gonorrhoeae

A

Resistance: Penicillin and Tetracycline
Disease: Gonorrhea

66
Q

Give the resistance and disease.

Agent: Mycobacterium tuberculosis

A

Resistance: Multiple Resistance
Disease: Tuberculosis

67
Q

Give the resistance and disease.

Agent: S. aureus

A

Resistance: Methicillin and Cancomycin
Disease: Skin and soft tissue infections

68
Q

Give the resistance and disease.

Agent: Klebsiella, Pseudomonas

A

Resistance: Multiple Resistance
Disease: Pneumonia, UTI

69
Q
  • Presence of genes responsible for resistance to its own antibiotic
  • Lack transport system or target for that antibiotic
  • Due to increase efflux activity
A

Natural Antimicrobial Resistance

70
Q
  • Gene changes or exchanges that result from acquired resistance are usually caused by genetic mutation(s)
  • Acquisition of genes from other organisms via gene transfer mechanisms, or a combination of mutational and gene transfer events
A

Acquired Antimicrobial Resistance

71
Q

Acquired Antimicrobial Resistance

Process by which bacteria take up free, extracellular DNA from their environment and incorporate it into their own genome

A

Transformation

72
Q

Acquired Antimicrobial Resistance

A process of horizontal gene transfer where genetic material is transferred directly from one bacterial cell to another through a physical connection known as a pilus or conjugation bridge

A

Conjugation

73
Q

Acquired Antimicrobial Resistance

Process by which bacterial DNA is transferred from one bacterium to another by a bacteriophage (a virus that infects bacteria)

A

Transduction

74
Q

Specific Antimicrobial Resistance

Aminoglycosides

Inactivation of Drugs by Enzymes

A
  • Acetyltransferases
  • Phosphotransferases
  • Adenylyltransferase
75
Q

Specific Antimicrobial Resistance

Chloramphenicol

Inactivation of Drugs by Enzymes

A
  • Chloramphenicol
  • Acetyltransferases
76
Q

Specific Antimicrobial Resistance

Macrolide

Inactivation of Drugs by Enzymes

A
  • Esterases
  • Methyltransferases
  • Hydrolytic enzymes
77
Q

Specific Antimicrobial Resistance

Tetracycline, B-lactams, aminoglycosides, quinolone

Alteration of Membrane Permeability

A

Changes in porins, efflux pumps, altered membrane composition, biofilm formation, membrane lipid modifications

78
Q

Specific Antimicrobial Resistance

Macrolide

Alteration of Intracellular Target Site

A
  • Methylation of 23S rRNA
  • Blocking erythromycin binding site
79
Q

Specific Antimicrobial Resistance

Aminoglycosides

Alteration of Intracellular Target Site

A
  • Altered protein in 30S ribosome
80
Q

Specific Antimicrobial Resistance

B-lactams

Alteration of Intracellular Target Site

A
  • Alteration in penicillin binding proteins
81
Q

Specific Antimicrobial Resistance

Rifampin

Alteration of Intracellular Target Site

A
  • Altered DNA-dependent RNA polymerase
82
Q

Specific Antimicrobial Resistance

Quinolones

Alteration of Intracellular Target Site

A
  • Modified DNA gyrase
  • Topoisomerase IV
83
Q

Specific Antimicrobial Resistance

Sulfonamides

Overproduction of Target Enzyme

A
  • Increased levels of Dihydropteroate synthase
84
Q

Specific Antimicrobial Resistance

Trimethoprim

Overproduction of Target Enzymes

A
  • Increased levels of Dihydrofolate reductase (DHFR)

Clinical Bacteriology (33 decks)

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