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AST Flashcards

1
Q

Antibiotic produced by Bacillus subtilis

A

Bacitracin

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2
Q

Antibiotic produced by Bacillus polymyxa

A

Polymyxin

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3
Q

Microorganism that produces Cephalosporin

A

Cephalosporium

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4
Q

Microorganism that produces Penicillin

A

Penicillium notatum

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5
Q

Microorganism that produces Erythromycin

A

Streptomyces erythraeus

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6
Q

Microorganism that produces Neomycin

A

Streptomyces fradiae

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7
Q

Antibiotic produced by Micronospora purpurea

A

Gentamicin

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8
Q

Microorganism that produces Amphotericin B

A

Streptomyces nodusus

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9
Q

Antibiotic produced by Streptomyces noursei

A

Nystatin

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10
Q

Microorganism that produces Chloramphenicol

A

Streptomyces venezuelae

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11
Q

Classification of antibacterial drugs

A

Natural, Semi-synthetic, Synthetic

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12
Q

Drugs produced by bacteria or fungi

A

Natural Drugs

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13
Q

Examples of natural drugs

A

(AKE)
Amphotericin B
Kanamycin
Erythromycin

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14
Q

Define semi-synthetic drugs

A

Modified natural drugs with added chemical groups

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15
Q

Examples of semi-synthetic drugs

A

(CAM)
Carbapenicillin
Ampicillin
Methicillin

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16
Q

Chemically produced drugs

A

Synthetic Drugs

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17
Q

Examples of synthetic drugs

A

(SITC)
Sulfonamides
Isoniazid
Trimethoprim
Ciprofloxacin

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18
Q

1st Gen Drugs

A

(RIPES)
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
Streptomycin

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19
Q

2nd Gen Drugs

A

(CCOKE)
Capreomycin
Ciprofloxacin
Ofloxacin
Kanamycin
Ethionamide

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20
Q

Antimicrobial agents that inhibit bacterial growth; Stops multiplication via binary fission

A

Bacteriostatic Agents

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21
Q

Examples of bacteriostatic agents

A

(DECTS)
Dapsone
Erythromycin
Chloramphenicol
Tetracycline
Sulfonamides

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22
Q

Antimicrobial agents that kill microorganisms; Treatment for life-threatening conditions; Disrupts bacterial structure

A

Bactericidal Agents

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23
Q

Examples of bactericidal agents

A

Aminoglycosides (GAS)
*Gentamicin
*Amikacin
*Streptomycin

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24
Q

Group A Primary Test (Drugs)

A

(CATG-CATriona Gray)
Cefazolin
Ampicillin
Tobramycin
Gentamicin

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25
Group B Primary Test Selectivity (Drugs)
(PICCA) Piperacillin Imipenem Cefuroxime Ciprofloxacin Amikacin
26
Group C Supplemental Report Collectively
(CAT) Chloramphenicol Aztreonam Tetracycline
27
Define MIC
(Minimal Inhibitory Concentraton) Lowest concentration of drug that inhibits bacterial growth Increasing dilution --> smaller activity of drugs against organisms
28
Define MBC
(Minimal Bactericidal Concentration) Lowest concentration of drug that kills bacteria
29
Ratio of the toxic dose to the therapeutic dose; Ratio of how much dosage is safe and lethal
Therapeutic Index Higher TI --> more effective chemotherapeutic agent
30
What are the mechanisms of action of antibacterial agents?
Cell Wall Inhibitors Protein Synthesis Inhibitors Nucleic Acid Inhibitors Cell Membrane Inhibitors Essential Metabolite Inhibitors
31
Most selective antibiotics with a higher therapeutic index
Cell Wall Inhibitors
32
Inhibit the activity of transpeptidase enzymes in which cell growth stops and death of cells often follows
Cell Wall Inhibitors
33
These drugs are effective against Gram (+) bacteria
Cell Wall Inhibitors
34
Give the examples of cell wall inhibitors and their action
*Bacitracin (inhibits synthesis of peptidoglycan precursors) *B-lactams (inhibits transpeptidase) *Isoniazid (can be bactericidal or bacteriostatic) *Vancomycin (inhibits translocation and elongation of peptidoglycan)
35
These antibiotics bind to 30S subunit (smaller) that results in the misreading of mRNA.
Protein Synthesis Inhibitors
36
These drugs target aerobic and anaerobic, gram (+) and gram (-) bacteria
Protein Synthesis Inhibitors
37
Protein synthesis inhibitors are effective against what examples of microorganisms?
(FIMPT) Bacteroides fragilis Haemophilus influenzae Neisseria meningitidis Streptococcus pneumoniae Mycobacterium tuberculosis
38
Examples of protein synthesis inhibitors
Aminoglycosides, Tetracycline
39
Examples of nucleic acid inhibitors and their action
*Rifampicin (inhibits RNA polymerase and synthesis) *Quinolones (effective against enteric bacteria like E. coli) *Metronidazole (treatment for amoeba, disrupts DNA, effective for anaerobic bacteria)
40
What drugs are effective against Gram (-) bacteria
Cell Membrane Inhibitors
41
Examples of cell membrane inhibitors
Polymyxin B and E
42
First mutant bacteria
Pseudomonas aeruginosa
43
This targets the permeability of cell walls
Cell Membrane Inhibitors
44
Examples of essential metabolite inhibitors
Folic Acid (Sulfamethoxazole) Cord Factor (Isoniazid) *For TB; Virulence Factor
45
Principle of AST
Measures the ability of an antibiotic or other microbial agent to inhibit bacterial growth
46
What is an antibiogram
Profile of the susceptibilities of specific pathogenic bacteria against antimicrobial agents
47
Primary goal of AST
To determine whether the bacterial isolate is capable of expressing resistance to the antimicrobial agents selected for treatment
48
Purpose of AST
*To guide the clinician in selecting appropriate antimicrobial agent *To gather epidemiologic data on microbial resistance
49
Purpose of standardization
*To optimize bacterial growth conditions *To optimize conditions for antimicrobial integrity and activity *To maintain reproducibility and consistency of the resistance profile
50
Most common method in Antimicrobial Susceptibility Testing
Disk Diffusion Method (Kirby-Bauer Test)
51
Medium used in Kirby-Bauer Test
Mueller-Hinton Agar
52
Standard used in DDM and its components
0.5 Mcfarland/Barium Sulfate Suspension *99.5 mL of 1% Sulfuric Acid *0.5 mL or 1.175% Barium Chloride
53
Standard inoculum in DDM
1.5 x 10^8 organisms/mL
54
pH of DDM
7.2-7.4 (slightly alkaline)
55
Depth of plate in DDM
4 mm
56
Condition of DDM
Aerobic (NO CO2)
57
Temperature of DDM
35-37*C
58
Incubation time in DDM
16-18 hours
59
Diameter of antibiotic disk
6 mm
60
Bacterial count in DDM
Petroff-Hausser
61
If sample is too turbid then Mcfarland, what do you do?
Dilute and add NSS
62
If sample is too diluted than Mcfarland, what do you do?
Add colony
63
The standard susceptibility medium for non-fastidious bacteria
Mueller-Hinton Agar
64
Composition of MHA
(BANCV) Beef infusion Agar Nucleic Acid Casein Vitamins
65
Used to improve the detection of oxacillin resistant staphylococc
MH broth with 2% NaCl
66
Utilized for testing susceptibility for streptococci, N. meningitidis, and other fastidious organisms
MH broth with 5% lysed horse or sheep blood
67
Where is sheep's blood collected?
Jugular vein
68
Preferable when preparing culture media for BAB due to the large RBC compared to humans
Sheep's blood
69
Alternative method of testing for MRSA aside from adding 2% NaCl
Plate containing 6 ug/ml of oxacilin in Mueller-Hingon Agar supplemented with 4% NaCl
70
Factors affecting disk diffusion
(ATGpNC) *Amount of inoculum *Thickness of susceptibility plate *Growth rate of microbe *pH of medium *Number of disks per plate *Concentration of divalent bonds
71
If the agar is too thick -->
Smaller ZOI
72
If the agar is too thin -->
Larger ZOI
73
If the temperature is higher than 35*C -->
False detection of MRSA (due to mutated mecA gene)
74
If the temperature is lower than 35*C -->
Larger ZOI
75
Incubation of plates in CO2 leads to -->
Decreased pH
76
Increased pH -->
Decreased activity of tetracycline drugs
77
Decreased pH -->
Decreased activity of aminoglycosides and erythromycin
78
Placement of more than 12 may result in -->
Overlapping of zones
79
Can affect the testing of aminoglycosides and tetracycline against PAE.
Concentration of divalent bonds (Ca ang Mg)
80
Procedure for AST
1. Pure inoculum are obtained by selecting 4-5 colonies of the same morphology. 2. Colonies are being suspended into 0.05% NSS to achieve a turbid suspension. 3. Bacterial suspension & Mcfarland solution are compared by matching the turbidity of the tubes against a dark background. 4. Perform Lawn Streaking. Turn the plate 60 degrees between each streaking 5. Within 15 minutes of inoculation antimicrobial agents are applied into your MHA. 6. Within 15 minutes. of disk placement, plates are inverted & incubated at 35C for 16-18hrs. 7. Diameter of each inhibition zone is measured using a caliper or ruler.
81
If there is no ZOI -->
Measure the size of the antibiotic disk in mm. Do NOT report as zero
82
Distance between each disk
15 mm
83
How many discs fit in 150 mm?
12
84
How many discs fit in 100 mm?
5-6
85
Causes of false resistant AST
*15 mins delay (disc application) *increased moisture *too thick medium *increased organisms --> decrease ZOI
86
Causes of false sensitive
*15 mins delay (incubation) *increased drying *too thin *decreased organisms --> larger ZOI
87
Define susceptible
Microorganisms should respond to therapy with that antimicrobial agent; Effective against the microorganism
88
Define intermediate
*MIC approaches or exceeds the level of antimicrobial agent that can be achieved *Clinical response is likely to be less than with a susceptible strain *Can be both effective or resistant against the organism
89
Define resistant
No or small ZOI. Antibiotic is not the appropriate choice for treatment
90
In case the organism is susceptible to 2 antibiotics, what should you do?
Determine the drug that works best for the px
91
It uses manual gravity based inoculation technique; Has mechanism to read ESBL; Results after 8-12 Hours
Phoenix System
92
Inocula are manually introduced to the broth microdilution tray
Microscan Walkaway System
93
Fully automated equipment that is designed for the identification of bacteria and AST; Optical readings every 15 minutes; Final reading is 6-8 hours
Vitek System
94
2 types of MRSA and define
*Healthcare Associated MRSA (due to invasive procedures or devices such as surgeries, artificial joints, intravenous tubing) *Community Associated MRSA (begins as a painful skin boil, spread by skin-to-skin contact, at risk populations are crowded areas)
95
The only difference between CA and HA MRSA
location where it is acquired
96
Tests for MRSA that are recommended by CLSI
(BCLPCN) *Broth microdilution testing *Cefoxitin disk screen test *Latex agglutination for PBP2a (Penicillin‐binding protein 2a) *Plate containing 6 ug/ml of oxacilin in Mueller-Hingon Agar supplemented with 4% NaCl *Chromogenic agars *Nucleic acid amplification test (PCR) --> detects mecA gene

BACTE LAB (FINALS) (2 decks)

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