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Microbiology > Bacteriology Exam 2 (Antibiotic Resistance and ID) > Flashcards

Bacteriology Exam 2 (Antibiotic Resistance and ID) Flashcards

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1
Q

Responsibilities of the lab director

A
  1. direct observation of test performance
  2. monitoring reporting of test results
  3. review of QC results/preventative maintenance records
  4. observation of instrument maintenance
  5. assessment of test performance through PT
  6. competency assessment reviews
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2
Q

Gram negative color in gram stain

A

pink/red

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3
Q

Gram positive color in gram stain

A

purple

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4
Q

What color will salmonella be on HE/XLD plates?

A

Black from production of H2S

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5
Q

What color will Shigella be on HE/XLD plates?

A

clear - color will remain original color of the plate (blue/green on HE and red/orange on XLD) because they do not ferment the carbohydrates

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6
Q

What color will normal flora be on HE/XLD plates?

A

bright yellow color

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7
Q

CNA agar

A

allows gram-positive bacteria to grow and inhibits gram-negative bacteria

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8
Q

What is Chocolate agar used to grow? What type of agar is this?

A

Neisseria gonorrhoeae and Haemophilus influenzae.
It is an enriched agar

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9
Q

HE agar

A

Selective - inhibit the growth of nonpathogenic GNR and selects for Salmonella and Shigella spp.
Differential - non-enteric pathogens that do grow will appear as orange to salmon-color colonies (e. coli)

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10
Q

EMB agar

A

Selective - inhibits the growth of gram positive and allows GN bacilli to grow
Differential - fermentation of lactose appears as dark purple to black, or with a green metallic sheen and non-lactose fermenters remain colorless and translucent

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11
Q

Blood agar plate

A

Nutritious - supports growth for all organisms except most fastidious
Differential - shows different hemolysis abilities

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12
Q

Beta hemolysis on blood agar plate

A

Complete clearing around colonies due to complete lysis of RBC

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13
Q

Alpha-hemolysis

A

partial lysis - greenish discoloration around colony

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14
Q

Gamma-hemolysis

A

no hemolysis of RBC - no halo or change produced around colonies

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15
Q

MAC agar

A

Selective - only allows for gram negatives to grow, inhibits gram positive
Differential - lactose fermenters will be pink and non-lactose fermenters will be clear/yellow (color of the plate)

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16
Q

PEA agar

A

sheep BA supplemented with PEA to inhibit the growth of GN bacteria

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17
Q

MTM agar

A

enriched and selective media to allow N. gonorrhoeae and Neisseria meningitidis to grow

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18
Q

Thioglycollate broth

A

Allows for the growth of anaerobes

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19
Q

XLD agar

A

like HE agar; inhibits non-enteric GN bacilli and gram positive organisms to allow for the detection of Shigella and Salmonella spp.
Differential by exhibiting colors for the fermentation of carbohydrates

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20
Q

Bile Esculin Agar (BEA) - primary purpose

A

differential for group D streptococci vs enterococci
differential for enterobacteriaceae
differentiation of listeria monocytogenes

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21
Q

Blood Agar (BA) - primary purpose

A

cultivation of non-fastidious microorganisms, determination of hemolytic reactions (nutritious and differential)

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22
Q

Bordet-Gengou agar - primary purpose

A

Bordetella pertussis - pearl-like colonies with narrow zone of hemolysis
Bordetella parapertussis - brown colonies with green/black color on reverse side
Bordetella bronchiseptica - brown colonies with a rough pitted surface

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23
Q

Brain-heart infusion agar or broth (BHI) - primary purpose

A

Cultivation of fastidious and nonfastidious organisms (not selective or differential)

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24
Q

Buffered charcoal-yeast extract agar (BCYE) - primary purpose

A

Enrichment for Legionella spp.
Supports the growth of Francisella and Nocardia spp.

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25
Q

Campy-blood agar - primary purpose

A

Selective for Campylobacter spp.

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26
Q

CDC anaerobe 5% sheep blood agar - primary purpose

A

improved growth of fastidious, obligate, slow-growing anaerobes

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27
Q

Cefsulodin-irgasan novobiocin (CIN) agar - primary purpose

A

Selective for Yersinia spp; may be useful for isolation of Aeromonas spp.

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28
Q

Chocolate agar - primary purpose

A

cultivation of fastidious microorganisms
ex. Haemophilus spp, Brucella sp, and pathogenic Neisseria spp.

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29
Q

Chromogenic media - primary purpose

A

Used for the identification of Acinetobacter, MRSA, beta lactamase and carbapenemase producing organisms, and a variety of other organisms

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30
Q

Columbia colistin-nalidixic acid agar (CNA) - primary purpose

A

Selective for the isolation of gram-positive cocci

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31
Q

Cystine-tellurite blood agar - primary purpose

A

Isolation of Corynebacterium diphtheriae

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32
Q

Eosin methylene blue agar (EMB) - primary purpose

A

Isolation and differentiation of lactose-fermenting and non-lactose fermenting enteric bacilli

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33
Q

Hektoen enteric (HE) agar - primary purpose

A

Differential, selective medium for the isolation and differentiation of Salmonella and Shigella spp. from other GN enteric bacilli

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34
Q

LIM broth - primary purpose

A

Enriched and selective media for the isolation of Streptococcus agalactiae

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35
Q

Loeffler medium - primary purpose

A

Isolation and growth of Corynebacterium spp.

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36
Q

MAC agar - primary purpose

A

Isolation and differentiation of lactose fermenting and non-lactose fermenting GN enteric bacteria

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37
Q

MacConkey sorbitol agar - primary purpose

A

For the selection and differentiation of E. coli O157:H7 in stool specimens

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38
Q

Mannitol salt agar - primary purpose

A

Selective differentiation of staphylococci

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39
Q

Phenylethyl alcohol (PEA) agar with or without blood - primary purpose

A

Selective isolation of aerobic gram positive cocci/bacilli and anaerobic gram positive cocci

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40
Q

Regan Lowe agar - primary purpose

A

Enrichment and selective medium for isolation of Bordetella pertussis and Bordetella parapertussis

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41
Q

Selenite broth - primary purpose

A

Enrichment and isolation of Salmonella spp.

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42
Q

Skirrow agar - primary purpose

A

Selective for Campylobacter spp.

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43
Q

Streptococcal Selective agar (SSA) - primary purpose

A

Selective for streptococcus pyogenes and Streptococcus agalactiae

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44
Q

TM and MTM agar - primary purpose

A

Selective for N. gonorrhoeae and N. meningitidis
Supports the growth of Francisella and Brucella spp.

45
Q

Thioglycollate broth - primary purpose

A

Supports growth of anaerobes, aerobes, microaerophilic, and fastidious microorganisms

46
Q

Thiosulfate citrate-bile salts (TCBS) agar - primary purpose

A

Selective and differential for Vibrio cholerae and Vibrio parahaemolyticus

47
Q

Todd-Hewitt broth supplemented with antibiotics (LIM) - primary purpose

A

Selection and enrichment for Streptococcus agalactiae in female genital specimens

48
Q

What is the incubation temperature for most medically relevant bacteria?

A

35-37 degrees C

49
Q

What temperature does Listeria monocytogenes and Yersinia enterocolitica grow at optimally?

A

20-40 degrees C

50
Q

What temperature can Campylobacter jejuni grow at?

A

42 degrees C

51
Q

Positive and negative reaction for Catalase testing
Which MOs are catalase positive and which are catalase negative?

A

Positive reaction: production of bubbles (most staphylococci)
Negative reaction: no production of bubbles (streptococci and enterococci)

52
Q

Oxidase testing - what does a positive and negative reaction look like? What is the test used for? What organisms are typically oxidase pos/neg?

A

Used for the differentiation of enterobacteriaciae and non-enterobacteriaciae.
Positive oxidase reaction - production of a purple color (pseudomonas and aeromonas non enterobacteriaceae)
Negative - no purple color present (enterobacteriaeceae)

53
Q

Slide Coagulase testing - what does a positive reaction look like? What is the test used to distinguish?

A

Positive reaction - clumping shown on slide
Negative reaction - no clumping
Slide coagulase indicates bound coagulase present (found on cell wall).
Used to distinguish Staph aureus from Coagulase negative Staph

54
Q

Free coagulase test - what is a positive/negative reaction? What is it used for?

A

Free coagulase is a test done in a tube to distinguish staph aureus from coagulase negative staph.
Positive - turbid tube
Negative - clear tube
*done after slide coagulase to confirm

55
Q

Indole testing - positive result and what is the test used for

A

Positive indole - blue/green color
This test detects the degradation of tryptophan into indole.
Used to confirm E. coli (indole positive)

56
Q

PYR testing - what is it used for and what is a positive result

A

Positive result is a bright pink/red color
PYR test is useful in the identification of Strep pyogenes and enterococcus spp. which test positive.

57
Q

What does IMViC stand for? (what are the 4 tests involved in this tube)

A

Indole, Methyl Red, Voges-Proskauer, and Citrate

58
Q

Describe all of the positive results found in IMViC tests. Interpret what they mean.

A

Indole + = red ring color (production of tryptophanase)
Methyl Red + = red color (production of acid from glucose fermentation)
Voges-Proskauer + = red color (production of acetoin from glucose metabolism)
Citrate + = blue color (utilization of citrate as carbon source pH turns alkaline)

59
Q

T/F: An organism can be positive for methyl red and voges-proskauer

A

False. These have inverse relationships. If an organism is positive for one, it cannot be positive for the other.

60
Q

What is E. coli IMViC result?

A

Positive Indole (red)
Positive Methyl Red (red)
Negative Voges-Proskauer (yellow)
Negative citrate (green)

61
Q

What is Enterobacter spp. and Klebsiella pneumoniae IMViC result?

A

Negative indole
Negative Methyl Red
Positive Voges-Proskauer
Positive citrate

62
Q

What is found in the slant of TSI slants? What is found in the butt?

A

Slant = lactose and sucrose
Butt = glucose

63
Q

What are the four things to look for in TSI slant? Describe the colors which will be seen if each are found.

A

The slant and the butt (alkaline will be red, acid will be yellow)
H2S production - black color
Gas production - cracks in the butt

64
Q

What would a K/A tube look like? Interpret what this means.

A

Alkaline, red slant = no sucrose or lactose fermented
Acidic, yellow butt = glucose fermented

65
Q

What would a K/K tube look like? Interpret the results.

A

Red tube throughout, no sugars fermented

66
Q

What would an A/A tube look like? Interpret the results.

A

Yellow tube throughout indicating acid production, all sugars fermented

67
Q

Mechanisms of antibiotic resistance (5 of them)

A

Lack of drug affinity
Inaccessibility
Efflux pumps/ABC transporters (removal of drug)
Innate enzymes to break down the drug
Biofilms (capsule)

68
Q

Fluoroquinolones: what do they target in bacteria and what drug names are included in this group of antibiotics?

A

Inhibit DNA synthesis -> target topoisomerases and dna gyrase
Any drug ending in “floxacin” (ciprofloxacin and naladixic acid)

69
Q

Trimethoprim sulfamethoxazole: what does it target in bacteria

A

Targets DNA synthesis by inhibiting folic acid/B12 synthesis

70
Q

Rifamycins: what do they target in bacteria and what antibiotics are included in this group?

A

Inhibits RNA synthesis by targeting DNA-dependent RNA polymerase
Any drugs starting in “Rif” are included in this group (Rifampin)

71
Q

Beta lactams - what they do they target in bacteria and what classes of drugs are included in this group?

A

Inhibits cell wall synthesis by targeting penicillin binding proteins (alter peptidoglycan structure)
Drugs included are:
Pencillins (anything ending in cillin)
Cephalosporins (anything starting with cef)
Carbapenems (anything ending in penem)

72
Q

Glycopeptides and glycolipopeptides: what do they target in bacteria and what antibiotics are included in this group?

A

Target cell wall synthesis by inhibiting transglycosylation and transpeptidation
Examples: Vancomycin

73
Q

Aminoglycosides: What do they target in bacteria and what drugs are included in this group?

A

Inhibit protein synthesis by targeting the 30S ribosome function
Drugs included are anything ending in “mycin/micin”

74
Q

Tetracyclines: what do they target in bacteria and what drugs are included in this group?

A

Inhibit protein synthesis by targeting the 30S ribosome.
Examples are anything ending in cycline.

75
Q

Macrolides: what do they target in bacteria and what drugs are included in this group?

A

Inhibit protein synthesis by targeting the 50S ribosome.
Examples are anything ending in “ythromycin” (erythromycin)

76
Q

Phenicols: what do they target in bacteria and what drugs are included in this group?

A

Inhibits protein synthesis by targeting the 50S ribosome
Examples: Chloramphenicol

77
Q

Additive effect

A

2 drugs cause twice the effect

78
Q

Indifferent drug combination therapy

A

combination of drug causes no effect

79
Q

Synergistic drug combination therapy

A

2 drugs effect is greater together than it is individually

80
Q

Antagonistic drug combination therapy

A

one drug counteracts the other (better apart)
example: birth control and antibiotics

81
Q

Beta-lactamase
What organisms typically possess these?

A

enzyme produced by bacteria that breaks down beta lactams
Ex. H. influenzae, M. catarrhalis, N. gonorrhoeae, and staph species

82
Q

Clavulanic acid + amoxicillin

A

Good for use on organisms that are resistant to beta lactams.
Includes a beta lactamase inhibitor + beta lactam

83
Q

2nd generation cephalosporins

A

very effective against gram negatives

84
Q

3rd generation cephalosporins

A

first generation that can cross the blood brain barrier

85
Q

Antibiotics used for the treatment of infections suspected to be caused by MDR bacteria

A

Carbapenems

86
Q

Vancomycin - group it belongs to, what is it effective against, and role of inhibition

A

Great for gram positive, cannot cross the cell wall of gram negative bacteria (great for Clostridium difficile)
Inhibits cell wall synthesis
A part of Glycopeptides

87
Q

Inhibitors of cell wall synthesis

A

beta lactams (carbapenems, penicillins, cephalosporins)
glycopeptides (vancomycin)

88
Q

inhibitors of protein synthesis

A

aminoglycosides, tetracyclines, macrolides, chloramphenicol

89
Q

Chloramphenicol

A

protein synthesis inhibitor that is not used often because it is very toxic and can cause aplastic anemia by suppressing bone marrow

90
Q

inhibitors of DNA and RNA synthesis

A

quinolones (DNA), fluoroquinolones(DNA), metronidazole(DNA), rifampin (RNA)

91
Q

Rifampin

A

great for M. tuberculosis

92
Q

Sulfonamides/Trimethoprim

A

Combined to make SXT (aka Bactrim) - inhibitor of folic acid pathway

93
Q

Nitrofurantoin

A

synthetic antibiotic used to treat recurrent cystitis; inhibitor of DNA/RNA/protein synthesis

94
Q

empiric vs definitive therapy

A

empiric therapy is drugs given before test results are given (“educated guess”)
definitive therapy is drugs given after test results received

95
Q

Intrinsic resistance

A

resistance resulting from the normal genetic, structural, or physiologic state of a MO

96
Q

Acquired resistance

A

resistance to antibiotics gained by transfer of genetic material through horizontal transmission

97
Q

MIC

A

minimum amount of drug to stop bacterial growth

98
Q

Larger zone of inhibition = more _______ to drug

A

susceptible

99
Q

Smaller zone of inhibition = more _______ to drug

A

resistant

100
Q

MacFarland standard and what is the density of bacterial suspension

A

0.5, 1.5 x 10^8 CFU/mL

101
Q

Broth dilution method for measuring MIC of antibiotics

A

The MIC is the lowest concentration of antibiotics that prevents visible growth

102
Q

Microdilution vs macrodilution total broth volumes

A

Microdilution = 0.05-1 mL
Macrodilution = 1 mL or greater

103
Q

Relationship between MIC and zone of inhibition

A

As MIC increases, zone of inhibition decreases (inverse relationship)

104
Q

How to interpret the E-test

A

MIC determined where the growth ellipse intersects the E test strip at the highest and clearest point (always round up!)

105
Q

MecA gene

A

Gene found in MRSA; causes resistance to penicillinases
If organism has this gene, penicillin or oxacillin will not work

106
Q

erm gene

A

Found in inducible clindamycin resistant staphylococci - having this gene means that the organism has resistance to erythromycin and induces clindamycin resistance so you cannot use clindamycin to treat

107
Q

msrA gene

A

having this gene means bacteria has resistance to erythromycin but it does not have genes to induce resistance to clindamycin –> can still use clindamycin to treat

108
Q

D zone test

A

Used to determine if clindamycin is truly susceptible or resistant
Flattened clindamycin indicates that erythromycin induced resistance -> erm gene
No flattening indicates that there is erythromycin resistance only -> msrA gene

109
Q

Modified Hodge Test (MHT) purpose and interpretations

A

Detects carbapenemase enzyme production
Positive control, negative control, and sample
Positive results show a clover leaf-like indentation meaning bacteria are resistant to all carbapenems

Microbiology (24 decks)

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