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LF255 - Clinical Microbiology > Lecture 3: Use of Antibiotics > Flashcards

Lecture 3: Use of Antibiotics Flashcards

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1
Q

What is the normal oral temperature?

A

37 degrees

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2
Q

What is the normal axillary (armpit) temperature?

A

36.3 degrees

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3
Q

What is the normal rectal temperature?

A

37.7 degrees

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4
Q

What is the normal (ear) temperature?

A

37.7 degrees

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5
Q

What is temperature regulated by?

A

The hypothalamus

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6
Q

What does a fever trigger?

A

Release of prostaglandin E2 (PGE2)

This acts on the hypothalamus

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7
Q

What are internal pyrogens?

A

Cytokines
IL-1
IL-6
TNF

Can cross the blood brain barrier

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8
Q

What are external pyrogens?

A

Gram negative bacterial lipopolysaccharides

Superantigens, some bacterial toxins are super pyrogens

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9
Q

What is the normal respiration rate for an adult at rest?

A

Range from 15-20 breaths per minute

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10
Q

When is a respiration rate considered abnormal?

A

Over 25 breaths or under 12 breaths per minute

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11
Q

What areas within the brain are control points to respiration rate?

A

Medulla
Pons
Cerebral cortex

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12
Q

What are the chemical influences on respiration rate?

A

Chemoreceptors in blood and CSF, O2, CO2, pH

Drugs, medication, hormones

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13
Q

What is the normal heart rate?

A

Normal pulse is 60 to 100 beats per minute

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14
Q

What numbers are recorded when measuring blood pressure?

A

Systolic pressure - arterial contraction

Diastolic pressure - arterial relaxation

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15
Q

What unit is blood pressure measured in?

A

mm Hg

Millimetres of mercury

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16
Q

What is considered a normal blood pressure?

A

<120/<80

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17
Q

What values are considered pre-hypertension?

A

120-139/80-89

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18
Q

What values are considered high blood pressure (hypertension)?

A

140/90

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19
Q

What are the common features of a gram-positive bacteria?

A

Cell wall mostly peptidoglycan

Peptide cross links for stability of the cell wall

Cross links formed by penicillin binding proteins

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20
Q

What does Beta-lactams inhibit?

A

Inhibits formation of cross-links by penicillin binding proteins

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21
Q

What are common gram-positive bacteria in the bowel?

A

Enterococci
Alpha-haemolytic streptococci
Beta-haemolytic streptococci

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22
Q

What are common gram-negative rods?

A

Escherichia coli

Klebsiella pneumoniae

Pseudomonas aeruginosa

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23
Q

What are the common features of gram-negative cell wall?

A

External layer cross-linked peptidoglycan with a lipid bilayer

Porin channels allow small hydrated molecules to pass across

Outer membrane

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24
Q

What are the anaerobes of the bowel?

Study These Flashcards
A

Clostridium spp

Anaerobic streptococci

Bacteroides spp

25
What is metronidazole active against?
Only active against obligate anaerobes
26
What is the mode of action of Metronidazole?
Activated by reducing environment Damage and destroy DNA and chromosome Negative oxidation-reduction potential of obligate anaerobic bacteria acts as an electron sink, capturing electrons that would be transferred to hydrogen ions
27
What does reduction of metronidazole create?
A concentration gradients that drives uptake of more drug Promotes formation of intermediate compounds and free radicals that are toxic to the cell - shearing DNA
28
Why are coliforms grown under anaerobic conditions physiologically resistant?
The oxidation-reduction potential is not sufficiently negative to convert the antibiotic to its active form in facultative bacteria
29
What new compound have promising activity against mycobacterium tuberculosis?
PA 824
30
What is the mode of action of Gentamicin?
Enters the gram-negative cell by an active transport system based on oxidative metabolism Needs active uptake and proton motive force Inhibits protein synthesis
31
What is Gentamicin active against?
No activity against anaerobes, streptococci and enterococci
32
What are teichoic acids? And where are they found?
Polymers of glycerol or ribitol linked via phosphodiester bonds Found in the cell wall of gram-positive bacteria Extend to the surface of peptidoglycan layer
33
What type of bacteria are teichoic acids found in?
Gram-negative bacteria
34
What are teichoic acids linked to?
Either covalently bonded to N-acetylmuramic acid of the peptidoglycan layer or linked to the plasma membrane lipids found in the cytoplasmic membrane
35
What contribution do teichoic acids make?
Structural support for the cell wall Negatively charged so contribute to the negative charge of the gram-positive cell wall Scaffold against turgor pressure Anchoring point Immunogenic inflammatory compounds
35
What is the rough process of cell wall biosynthesis?
Synthesis starts in the cytoplasm Amino acids are added Appended to lipid carrier 1 Lipid II is a precursor for peptidoglycan biosynthesis Polymerizes via enzymes to stich sugars
36
What does Beta lactam antibiotic interfere with?
Synthesis of peptidoglycan of bacterial cell wall Bind covalently to the active site of penicillin binding proteins Preventing peptide cross lining by penicillin binding protein enzymes
37
What does bacterial cell wall biosynthesis UDP pentapeptide bind with?
Lipid II precursor
38
How are penicillin binding proteins inhibited?
Shared spatial structure of the terminal D-Ala-D-Ala terminus of the peptidoglycan pentapeptide and beta-lactams
39
What bacteria is Benzylpenicillin active against? Why?
Only activity against gram positives (not MSSA & MRSA) Cannot cross the protein channels Bacteria produce Beta-lactamase that cuts the bond of the 4-membered beta-lactam ring
40
How does ampicillin differ from benzylpenicillin?
Ampicillin differs only by the addition of an amino residue
41
Why does benzylpenicillin have no activity against b-lactamase negative coliforms?
Not sufficiently polar to cross the outer lipid bilayer
42
What are ampicillin able to do?
They are polar enough to go through the porin channel in the outer lipid bilayer of the gram-negative cell wall
43
What kinds of bacteria are amoxicillin active against?
Active against coliforms (those that are Beta-lactamase negative)
44
What is an example of a Beta-lactamase inhibitor?
Co-amoxiclav (combination of amoxicillin and clavulanic acid)
45
What is clavulanic acid?
Beta-lactam like agent Has no useful antibacterial activity Binds avidly to the active site of Beta-lactamase enzymes
46
What is the mechanism of action of clavulanic acid?
3 amoxicillin molecules are inactivated by the Beta-lactamase enzyme, inactivating it Leaves amoxicillin unaltered to perform its function
47
What has the activity of co-amoxiclav been enhanced by?
Addition of clavulanic acid
48
What is the general activity of piperacillin-tazobactam similar to?
Similar to co-amoxiclav but has anti-pseudomonal activity
49
What are cephalosporins?
Large class of antibiotics Not inactivated by standard Beta-lactamase 1st generation: better gram-positive activity 2nd-3rd generation: better gram-negative activity
50
What are some common carbapenems?
Imipenem Meropenem Ertapenem
51
What activity do imipenem and meropenem have?
Anti-pseudomonal activity
52
What agents are imipenem and meropenem resistant to?
Resistant to the activity of standard Beta-lactamase of MSSA, E.Coli, Klebsiella pneumoniae and Bacteroides spp
53
How can resistance to carbapenems be acquired with pesudomonas?
Mutation in gene coding for the protein prevents antibiotic using this channel Permeability changes are another mechanism
54
What are 2 examples of glycopeptides?
Vancomycin and teicoplanin
55
What is the activity of glycopeptides restricted to?
Gram-positive bacteria Due to large size preventing them crossing the outer lipid membrane of gram-negative bacteria
56
What is glycopeptides mode of action?
Acts on peptidoglycan synthesis Sits across 2 terminal alanine residues of peptidoglycan building block - preventing its incorporation
57
What do vancomycin and teicoplanin have activity against?
Specific activity against gram-positive bacteria
58

LF255 - Clinical Microbiology (10 decks)

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