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HHD 2 > Antimicrobials 2 > Flashcards

Antimicrobials 2 Flashcards

1
Q

What are bacteriocidal antibiotics?

A

they kill bacteria dead

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2
Q

Give examples of bacteriocidal antibiotics

A

penicillin
cephalosporins
metronidazole

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3
Q

What are bacteriostatic antibiotics?

A

they make bacteria stop working
bacteria are then cleared by the immune system

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4
Q

Give examples of bacteriostatic antibiotics

A

macrolides
lincosamides
tetracyclines
fusidic acid

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5
Q

How is the in-vitro antimicrobial activity of drugs assessed?

A

determining minimum inhibitory concentration (MIC) and minumum bactericidal concentration (MBC)

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6
Q

What is the minimum inhibitory concentration?

A

the lowest concentration of a chemical that prevents visible growth (bacteriostatic)

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7
Q

What is the minimum bactericidal concentration?

A

lowest concentration of a chemical that results in death (bactericidal)

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8
Q

Practically, how is the antimicrobial activity of a chemical assessed?

A

overnight aerobic incubation of a standard size inoculum of bacteria in a low protein liquid medium at pH 7.2

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9
Q

Why may the antimicrobial activity of a chemical differ in vivo?

A

conditions in vivo will be different from incubation conditions thus antimicrobial activity will change

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10
Q

If a drugs has a MBC 4x greater than the MIC then the drug is classed as …

A

bactericidal

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11
Q

What are broad spectrum antibiotics?

A

they act against both gram positive and gram negative bacteria

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12
Q

When are broad spectrum antibiotics used?

A

prior to formal identification of the (specific) disease causing bacteria

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13
Q

Give examples of broad spectrum antibiotics

A

amoxicillin
co-amoxiclav
tetracyclines

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14
Q

What are narrow spectrum antibiotics?

A

they act against a specific family of bacteria

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15
Q

When are narrow spectrum antibiotics used?

A

best when used with culture sensitivity and testing

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16
Q

Give examples of narrow spectrum antibiotics

A

Macrolides
Clindamycin

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17
Q

What is pharmacokinetics?

A

This is what the body does to the drug
ADME

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18
Q

What does absorption refer to ?

A

bioavailability of the drug

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19
Q

What does distribution refer to ?

A

the process by which a drug diffuses from intravascular fluid space to extravascular fluid spaces

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20
Q

Elimination of the drug after administration usually occurs from …

A

liver or kidney

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21
Q

What is pharmacodynamics?

A

this is what the drug does to the body

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22
Q

Regarding pharmacodynamics, the antimicrobial effects of the drug at the site of infection is…

A

concentration dependent
time dependent

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23
Q

What are the clinical functions of pharmacodynamics?

A

-used to predict drug efficacy in patients
-provide a rational basis for determining the optimal dosing regimens

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24
Q

The pharmacodynamics of an antimicrobial drug relates its pharmacokinetics to the _________ of the antimicrobial effects at the site of action.

A

time course

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25
Q

What is the most common side effect of antibiotics ?

A

allergic reactions

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26
Q

How are allergic reactions to antibiotics typically avoided?

A

by avoiding the drug

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27
Q

What is an option for patients with an allergy to a specific antibiotic who have no other antibiotic options?

A

desensitisation
(may be possible)

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28
Q

What serious allergic reactions can arise from antibiotic use?

A

Stevens Johnson Syndrome (SJS)
Toxic Epidermal Necrolysis (TEN)

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29
Q

SJS and TEN can present as

A

serious skin and mucous membrane disorders
rashes, skin peeling and sores on mucous membranes

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30
Q

What antibiotics can be implicated in SJS and TEN?

A

penicillin
cephalosporins

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31
Q

Antibiotic associated colitis a side effect of antibiotic use due to …

A

disruption of the normal balance of the gut flora
eradication of the normal gut flora by antibiotic which results in an overgrowth of other microbes which include clostridium difficile

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32
Q

____% of patients may develop anti-biotic associated diarrhoea

A

5-25%

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33
Q

What kind of antibiotics are often implicated in antibiotic-associated colitis ?

A

broad spectrum antibiotics
Clindamycin (this is a narrow spectrum antibiotic)
cephalosporin
coamoxiclav
amoxicillin (to a lesser extent?)

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34
Q

What is pseudomembranous colitis ?

A

medical condition in which the colon gets inflamed in association with excessive intake of antibiotics

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35
Q

What are the symptoms of pseudomembranous colitis?

A

watery diarrhoea
abdominal pain along with cramping
fever
mucousy stools
nausea
dehydration

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36
Q

Another side effects of antibiotic induce/mediated flora change is _________.

A

opportunistic candidal infections which may occur in mouth or vagina

overgrowth of fungal species
Candida albicans may take over where there is limited competition from bacteria due to antibiotic treatment

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37
Q

What is the effect of antibacterial on typhoid vaccine?

A

antibacterials inactivate typhoid vaccine

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38
Q

Miconazole (antifungal) interacts with what drugs?

A

Alfacalcidol- miconazole reduces effects of alfacalcidol

Calcitriol- miconazole possibly reduces effects of calcitriol

ciclosporin- miconazole possibly inhibits metabolism of ciclosporin which increases its plasma concentration

Coumarins- miconazole enhances the anticoagulant effect of coumarins; avoid concomitant use if possible

(coumarins include warfarin)

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39
Q

Miconazole (antifungal) interacts with what drugs?

A

Alfacalcidol- miconazole reduces effects of alfacalcidol

Calcitriol- miconazole possibly reduces effects of calcitriol

ciclosporin- miconazole possibly inhibits metabolism of ciclosporin which increases its plasma concentration

Coumarins- miconazole enhances the anticoagulant effect of coumarins; avoid concomitant use if possible

(coumarins include warfarin)

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40
Q

MHRA (Medicines and healthcare products regulatory agency) employs the use of _________ and __________ to monitor adverse effects observed due to drugs/medication

A

Yellow card schemes
Medical alerts

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41
Q

In 2012, a medical alert for the potential reminder of hypersensitivity for which drug was announced by the MHRA?

A

chlorhexidine

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42
Q

In 2016, a medical alert for the potential reminder of serious interaction with warfarin for which drug was issued by the MHRA?

A

topical miconazole, including oral gel

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43
Q

What is the Yellow Card scheme used for ?

A

used to report suspected side effects or adverse drug reactions to any medicines, vaccines and even medical devices

medical devices e.g. implants

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44
Q

What are components of a typical bacterial cell?

A

cell wall
plasma membrane
chromosome
cytoplasm
ribosome

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45
Q

Whats is the MOA of penicillin?

A

beta-lactams present in penicilln interfere with the crosslinking of peptidoglycan protein in the bacterial cell wall

(bacterial cell wall- peptidoglycan crosslinks present)

Penicillin (beta lactam) binds to the transpeptidase enzyme which is responsible for peptidoglycan cross-links

this weakens the strength of the cell wall

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46
Q

Penicillin have a ______ dependent bactericidal action

A

time dependent

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47
Q

What adverse drug reaction is associated with penicillin?

A

allergy

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48
Q

What is a contraindication of penicillin use ?

A

methotrexate (immunomodulatory) - dihydrofolate reductase enzyme inhibitor
probencid (kidney disease)

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49
Q

What is the purpose of a beta-lactam ring

A

disrupt peptidoglycan cell wall- prevent cross-links from forming

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50
Q

What enzyme is responsible for the formation of the peptidoglycan crosslinks?

A

bacterial DD-transpeptidase enzyme

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51
Q

What is a requirement for penicillin to work?

A

the bacteria must be growing for it to work

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52
Q

Briefly compare the bioavailability of oral dose amoxicillin and penicillin V

A

amoxicillin has a greater oral bioavailability (74-92%) compared to penicillin v

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53
Q

How is penicillin G administered and why is this?

A

Penicillin G is administered intravenously
it is not acid stable thus cannot be delivered orally

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54
Q

Amoxicillin is equally well absorbed with food or in the fasting state. True or false

A

True

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55
Q

When is co-amoxiclav better taken (for better absorption)?

A

it is better taken at the start of a meal

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56
Q

When is penicillin V better taken (for better absorption)?

A

it is better absorbed in the fasting state

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57
Q

Is penicillin able to cross the BBB?

A

no it is not because it is poorly lipid soluble

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58
Q

How is penicillin eliminated after drug administration?

A

excreted unchanged by tubular secretion in the kidneys

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59
Q

Penicillin excretion/elimination can be blocked by…

A

probencid (used in kidney disease)

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60
Q

Penicillin excretion/elimination can be blocked by…

A

probencid (used in kidney disease)

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61
Q

Why is a dose reduction of penicillin necessary for patient with kidney disease on probencid?

A

this is because probencid can block tubular excretion of penicillin

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62
Q

Amoxicilling is a __________ spectrum antibiotic which can be used to treat … (name the conditions)

A

broad

Dental abscesses
otitis media
bronchitis
pneumonia
urinary tract infections
gonorrheoa

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63
Q

Phenomethylpenicillin (Pen V) is a _______ spectrum antibiotic for use as amoxicillin. How is it dosed?

A

narrow spectrum
dosed QDS (4x daily) on an empty stomach

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64
Q

What is the benefit of co-amoxiclav?

A

(as amoxicillin)

reduced resistance due to clavulanic acid which inhibits beta-lactamase enzyme
((beta-lactamase enzyme developed to increase resistance to beta-lactam which interferes with cell wall synthesis)

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65
Q

Co amoxiclav side effects can include …

A

pseudomembranous colitis?
risk of c. difficle

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66
Q

When should co-amoxiclav be used?

A

after consultation with secondary care

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67
Q

When antibiotics are under the antibiotic class “penicillins”

A

penicillin
amoxicillin
coamoxiclav

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68
Q

What are the most common side effects of penicillins?

A

rash
diarrhoea
abdominal pain
nausea/vomiting
drug fever
hypersensitivity
allergic reactions

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69
Q

When should you contact a health care provider immediately when using penicillins?

A

bloody stool
anaphylaxis
severe skin reaction
fever

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70
Q

What is the MOA of metronidazole (broad spectrum antibiotic)?

A

inhibits DNA synthesis once converted into an active form by anaerobic bacteria

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71
Q

Metronidazole is active against… (name the microorganisms)

A

anaerbobic bacteria
Protozoa

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72
Q

Metronidazole has _________ dependent bactericidal action

A

dose/concentration dependent

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73
Q

What adverse reactions are associated with metronidazole?

A

Di-sulfiram reaction where there is an acute sensitivity to alcohol
- immediate feeling of a hangover
should NOT be taken with alcohol.

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74
Q

What are the contraindications for metronidazole?

A

interacts with coumarin anticoagulants like warfarin

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75
Q

What is the clinical use of metronidazole?

A

dental abscess and NUG (necrotising ulcerative gingivitis)
also used to treat pseudomembranous colitis (C.difficile)

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76
Q

Briefly describe bioavailability of metronidazole?

A

excellent bioavailability after oral administration
food has no effect on bioavailability of metronidazole

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77
Q

Briefly describe distribution of metronidazole

A

lipid soluble drug thus has wide distribution throughout the body

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78
Q

When is the peak serum concentration of metronidazole reached?

A

after one hour of administration

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79
Q

How is metronidazole eliminated from the body?

A

eliminated unchanged in the urine

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80
Q

Disulfiram reaction associated with metronidazole is more unpleasant than serious. What must you warn you patients of?

A

NO alcohol
When it occurs- tachycardia and flushing can occur

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81
Q

Disulfiram reaction can occur up to _______ after stopping metronidazole

A

up to 72 hours after stopping metronidazole

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82
Q

What is the effect of metronidazole on warfarin (coumarin)?

A

the anticoagulant effects of warfarin increases
this has cause bleeding in some cases

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83
Q

What should you do if metronidazole is prescribed to a patient on warfarin?

A

monitor INR (international normalised ratio)

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84
Q

What are the most common side effects of metronidazole?

A

nausea/vomiting
dizziness
headache
vaginal candidiasis
metallic taste

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85
Q

Combined use of alcohol and metronidazoe may lead to…

A

cramps
nausea/vomiting
flushing
headache
red-brown urine discoloration

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86
Q

What is the MOA of macrolides (bacteriostatic)?

A

they inhibit protein synthesis by acting on bacterial ribosomes

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87
Q

Macrolides have the same site of action as ___________ antibiotics. Considering this, how should they be administered?

A

clindamycin
they should not be administered concurrently as they will compete for the same site of action

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88
Q

What are adverse reactions associated with macrolides?

A

GI disturbances are common and unpleasant

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89
Q

Macrolides have a __________ post anti-biotic effect

A

prolonged

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90
Q

What are the clinical uses of macrolides?

A

used if a patient is allergic to penicillin and metronidazole

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91
Q

What are the members of the macrolide class of antibiotics ?

A

erythromycin
clarithromycin
azithromycin

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92
Q

What macrolide commonly has resistance against it?

A

erythromycin

93
Q

Describe the bioavailability of macrolide antibiotics

A

Erythromycin and azithromycin have low bioavailability (40%); this is even lower in the presence of food

clarithromycin has good bioavailability, can be administered with or without food

94
Q

Oral administration of erythromycin and azithromycin antibiotics must be done in a ________ state. Why is this ?

A

fasting state
this is because their bioavailability is even lower in the presence of food

95
Q

What macrolides have a wide distribution?

A

erythromycin
clarithromycin

96
Q

Briefly describe the distribution of azithromycin

A

sequestered within tissues by macrophages
not as widely distributed as the others

97
Q

How are macrolides eliminated after administration?

A

erythromycin and azithromycin are excreted by the liver

98
Q

Macrolides are contraindicated for use with what drug ?

A

domperidone (anti-sickness molecule)

99
Q

Avoid using macrolide antibiotics with the following drugs…

A

salmeterol
simvastatin

100
Q

What are the most common side effects of macrolide antibiotics?

A

abdominal pain
diarrhoea
anorexia
nausea/vomiting

101
Q

Taste alteration is a common side effect of what macrolide antibiotic?

A

clarithromycin =

102
Q

Macrolides have a high rate of GI side effects. What instructions are given to minimise these side effects?

A

do not crush, chew, break or open enteric coat or delayed release pill

103
Q

What is the MOA of lincosamides?

A

they inhibit protein synthesis by acting on bacterial ribosomes

(same site of action on bacterial ribosomes as macrolides thus they will compete if give concurrently)

104
Q

Lincosamides has a ___________ post antibiotic effect

A

prolonged

105
Q

What adverse reactions are associated with lincosamides?

A

mild diarrhoea (common)
pseudomembranous colitis (rare but fatal)

106
Q

What are the clinical uses of lincosamides?

A

effective at penetrating poorly vascularised bone and connective tissue; diabetics ? bone infections?

107
Q

What are the members of the lincosamide class of antibiotics?

A

clindamycin

108
Q

What is the clinical use of clindamycin?

A

currently being questioned whether it is appropriate as a pre-surgery dose before implants

109
Q

Clindamycin is ________ absorbed

A

rapidly

110
Q

Briefly describe the distribution of clindamycin

A

widely distributed throughout the body
may be actively transported into and out of host cells

111
Q

How is clindamycin eliminated after administration?

A

excreted mainly by the liver

112
Q

What are the most common side effects of clindamycin?

A

pseudomembranous colitis (may be severe)
diarrhoea
nausea/vomiting
rash
hypersensitivity
jaundice

113
Q

When should a healthcare provider be consulted immediately with use of clindamycin?

A

if severe diarrhoea during treatment or for up to 8 weeks after treatment
may be pseudomembranous colitis

114
Q

What is the mechanism of action of tetracycline antibiotics?

A

inhibits protein synthesis by binding to bacterial ribosomes

immunomodulatory, they can penetrate macrophages as well

has a different site of action to macrolides and lincosamides

115
Q

Tetracyclines have bacteriostatic action and have _________ post antibiotic effect

A

prolonged

116
Q

What are the adverse reactions associated with tetracycline use?

A

chelate calcium ions so are deposited in bones and teeth

117
Q

Tetracyclines should not be prescribed to …

A

pregnant/nursing mothers
children under 9 years old

118
Q

What are the clinical uses of doxycyline (tetracycline member)

A

oro-antral communication
some advocate long courses for periodontitis
acne and rosacaea

119
Q

Tetracyclines and oxytetracyclines are in the DPF but not included in various guidelines. True or false

A

true

120
Q

Briefly describe absorption of tetracyclines

A

oral dose is rapidly absorbed
absorption of tetracyclines is reduced by the chelation with aluminium, magnesium and calcium ion

121
Q

Briefly describe the distribution of tetracyclines

A

wide distribution throughout the body

122
Q

Briefly state how tetracycline is eliminated after administration

A

excreted from the kidneys primarily by glomerular filtration

123
Q

List the members of the antibiotic class “tetracyclines”

A

tetracycline
doxcycycline

124
Q

What are the most common side effects of tetracycline?

A

nausea/vomiting
diarrhoea
anorexia
abdominal pain
tooth discoloration in children <8 years old
liver toxicity

125
Q

What additional warnings come with tetracyclines and why?

A

avoid prolonged sunlight exposure, use sunscreen, wear protective clothing

Tetracyclines may cause the skin to be more sensitive to sunlight

This is because tetracycline chelates calcium which affects vitamin D absorption ????

126
Q

What is the MOA of cepalosporins ?

A

Similar to penicillin
betalactam ?
prevents crosslinks of peptidoglycan from forming

127
Q

What antibiotic has the highest levels of resistance in the UK?

A

cephalosporins

128
Q

Cephalexin and cephradine are both in the DPF but there are no dental indications in the current UK guidelines. True or false

A

True

129
Q

Briefly describe the absorption of cephalosporins

A

The are acid stable so they can be absorbed orally
they have high bioavailability (80-95%)
food can lower the bioavailability of cephaosporins but not those in the DPF

130
Q

How are cephalosporins eliminated after administration?

A

they are excreted from the kidneys primarily by glomerular filtration

131
Q

List the members of the antibiotic class of cephalosporins

A

cephhalexin
cephradine

132
Q

What are the common side effects of cephalosporins ?

A

rash
diarrhoea
nausea/vomiting (rare)
hypersensitivity (allergic) reactions
serum sickness vaginal candidiasis

133
Q

What is a concern for patients with a penicillin allergy for prescription of cephalosporins?

A

cross-sensitivity may occur in patients with documented penicillin allergy
keep in mind when prescribing cephalosporins

134
Q

What is the MOA of fusidic acid?

A

inhibits protein synthesis

135
Q

Fusidic acid is a ___________ spectrum antibiotic

A

narrow

136
Q

What are the clinical uses of fusidic acid?

A

good against staphylococcus aureus
topical sodium fusidate cream can be used for angular chelitis (if antifungal has not worked)

137
Q

Chlorhexidine is a ___________ which means that there are 2 positive charges at its polar ends

A

bisguanide

138
Q

Chlorhexidine is highly active against _______ and ________ but not _______________.

A

bacteria and candida
but not M.tuberculosis

139
Q

0.4% solution of chlorhexidine can be used for…

A

hibiscrub- surgical scrub

140
Q

0.2% aqueous solution of chlorhexidine can be used for…

A

anti-plaque mouthwash

141
Q

2% chlorhexidine can be used for…

A

denture disinfectant

142
Q

What is the effect of fluoride on bacterial metabolism?

A

fluoride inhibits enolase enzyme of glycolysis
thus it inhibits bacterial metabolism

Enolase

143
Q

What is the problem with under-dosage of antibiotics?

A

if the concentrations are not sufficient to kill them, the bacteria may develop resistance

144
Q

Who discovered penicillin and where? (Briefly state how)

A

Alexander Fleming
1928

Mould juice inhibited staphlycoccus

145
Q

In 2017, WHO released a list of antibiotic resistant “priority bacteria”; this lists includes bacteria that pose the greatest threat to human health. What is the purpose of this list ?

A

It is intended to guide and promote research and development of new antibiotics in an effort to address global resistance to antimicrobial medicines

146
Q

Give examples of “critical” WHO superbugs

A

-acinetobacter baumannii (chest and blood infections)
-pseudomonas geruginosa (chest and blood infections)
-enterobacteriaceae inlcuding klebsiella, E.coli, proteus, Serratia

147
Q

Give examples of “high priority” WHO superbugs

A

-Enterococcus faecium
-Staphylococcus aureus
-Helicobacter pylori
-Campylobacter spp
-Salmonellae
-Neisseria gonorrhoeae

148
Q

Enterobacter faecium is ___________ resistant

A

vancomycin

149
Q

Staphlococcus aureus is ____________ resistant

A

methicillin (hence MRSA)
Vancomycin intermediate and resistant

150
Q

Helicobacter pylori is _____________ resistant

A

clarithromycin

151
Q

Campylobacter spp is _____________ resistant

A

fluroquinolone resistant

152
Q

Neisseria gonorrhoeae is ___________ and ___________ resistant

A

cephalosporin
fluoroquinolone

153
Q

Acinetobacter baumanni is ___________ resistant

A

carbapenem

154
Q

Pseudomonas geruginosa is _____________ resistant

A

carbapenem

155
Q

Enterobacteriaceae are ____________ resistant

A

carbapene, ESBL producing strains

156
Q

List “medium priority” WHO superbugs

A

-streptococcus pneumoniae
-Haemphilus influenzae
-Shigella spp.

157
Q

Streptociccus pneumoniae _____________ non-susceptible

A

penicillin

158
Q

Haemophilus influenzae is ___________ resistant

A

ampicillin

159
Q

Shigella spp are _________________ resistant

A

fluoroquinolone

160
Q

The most vulnerable immuno-compromised patients include those undergoing treatment for… (name the treatments)

A

cancer
transplants

161
Q

Antibiotics select for …

A

resistant bacteria
only bacteria that are resistant to that particular antibiotic will survive

162
Q

Antibiotic resistance facilitates ____________. (Name the process)

A

natural selection

163
Q

How is bacteria able to resist antibiotics?

A

Degradation- enzymes break them down
Alteration- enzymes deactivate the antibiotic
Efflux- protein pumps them out

164
Q

New proteins in bacteria can confer resistance. How are new proteins developed in bacteria?

A

Mutations in genes give rise to new, structurally different proteins

Proteins can be acquired from another bacteria

165
Q

What are the mechanisms by which bacteria can become resistant to antibiotics?

A

Mutation

Conjugation
Transformation
Transduction

166
Q

Resistant genes are often expressed on __________ of DNA

A

plasmid

167
Q

What is a plasmid ?

A

small ring of bacterial DNA

168
Q

Name a single, important characteristic of plasmid DNA

A

they can move easily between bacteria

169
Q

Briefly describe conjugation

A

this is where the plasmid passes directly from one bacterium to another
(direct contact between bacterial cells)

170
Q

What are the three mechanisms of horizontal gene transfer ?

A

conjugation
transformation
transduction

171
Q

Briefly describe transformation

A

DNA from dead bacteria can be taken up from the environment
the DNA taken up may include the resistant gene

172
Q

Briefly describe transduction

A

certain viruses can pick up DNA from one bacteria and pass it to another

173
Q

The process of transduction has been exploited by scientists as a laboratory technique referred to as … (name the technique)

A

targeted gene insertion

174
Q

Resistant strains of bacteria do no usually cause problems for healthy people. True or false

A

True
cause problems for the immunocompromised

175
Q

MRSA stands for …

A

methicillin resistant staphlococcus aureus

176
Q

MRSA can be found on …

A

the skin and nose

177
Q

MRSA can cause …

A

poor wound healing
septicaemia
endocarditis

178
Q

What are some reasons why MRSA is associated with hospital care?

A

point of entry through skin
High density of at risk population (immunocompromised)
elderly and immunocompromised

179
Q

Where is clostridium difficile found?

A

GI tract

180
Q

What does Clostridium difficle cause?

A

colitis (inflammation of colon)

181
Q

Clostridium difficile over-growth is associated with the use of which antibiotics?

A

4 C’s

Co-amoxiclav
clindamycin
cephalosporin
ciprofloxacin

182
Q

What is CPE?

A

Carbapenamase producing enterobacteriaceae

(gives resistance to carbapenem antibiotic)

183
Q

What is an obligate anaerobe?

A

unable to grow in contact with oxygen

184
Q

Many pathogenic bacteria will not grow in culture at all. True or false

A

True

185
Q

When should microbial culture be undertaken?

A

when resistance is suspected

186
Q

Why is a microbial culture from the mouth problematic?

A

rich in microbial diversity
some bacteria grow more readily in culture than others - many pathogenic bacteria will not grow in culture

187
Q

Many hospitals require microbial cultures before prescribing following antibiotics? (State the antibiotics)

A

co-amoxiclav
clindamycin (lincosamide)
cephalosporins

188
Q

Give examples of specimens that can be collected for microbial cultures

A

pus sample aspirate
Nasal swab for MRSA testing before surgery

189
Q

A clinical required form for microbial culture should contain :

A

clinical condition
recent/current treatment details
patient details
reason for test being requested

190
Q

What must you consider when transporting specimens for microbial testing ?

A

timescale
transport medium- should be compatible with organism e.g. anaerobes
safe robust containers
appropriate labelling of specimen and clinical request form

191
Q

What is the purpose of clinical MIC breakpoints ?

A

Identify whether a bacterium is
-susceptible
-intermediate
-resistant

192
Q

What agar is used for the disc diffusion method for staphylococci?

A

Mueller-Hinton agar

193
Q

What agar is used for the disc diffusion method for streptococci?

A

mueller-hinton agar + 5% defibrinated horse blood

194
Q

The MIC and zone diameter of inhibition (for disc diffusion method) are inversely related. What does this mean?

A

This means that the more susceptible the microorganism is, the lower the MIC and the larger the zone of inhibition

(less of antimicrobial concentration required to cause inhibition of growth)

195
Q

Broth dilution tests involve…

A

broth dilutions with different concentrations of the antibiotic (hence dilutions)

196
Q

What is the MBC ?

A

this is the lowest concentration of antibacterial agent that reduces the viability of the bacterial inoculum by >99.9%

197
Q

There are genotypic methods that can be used to detect resistance genes. Give an example of this

A

DNA based assay
MRSA has MecA gener which confers resistance to methicillin and flucloxacillin

198
Q

Give an advantage of genotypic methods of antimicrobial susceptibility testing

A

quicker

199
Q

Give disadvantages of genotypic methods of antimicrobial susceptibility testing

A

expensive
thus not routinely used

200
Q

Why are there only a few efficacious antivirals?

A

this is because it is difficult to interfere with viral activity without damaging the host cell

201
Q

What is the only antiviral drug in the DPF?

A

aciclovir

202
Q

When is the only time aciclovir is effective?

A

on an actively replicating virus

203
Q

When is aciclovir ineffective?

A

in latent viruses in cells e.g. herpes labialis

204
Q

What kind of patients benefit from active antiviral therapy?

A

immunocompromised patients

205
Q

What is the mechanism of action of aciclovir ?

A

aciclovir triphosphate blocks herpes viral DNA polymerase

aciclovir is initially converted by viral thymidine kinase to aciclovir monophosphate
Aciclovir monophosphate is converted by host kinases to aciclovir monophosphate

206
Q

What is the active form of aciclovir ?

A

aciclovir triphosphate

207
Q

State the clinical use of aciclovir

A

primary and secondary herpes infections e.g. herpetic stomatitis and labialis

208
Q

Ideally, aciclovir be started in the __________ phase of herpes infection.

A

prodromal phase

209
Q

?What is the consequence of a later start of aciclovir in herpes infection?

A

will reduce discomfort, length and viral shedding period

210
Q

What form of aciclovir is used to treat recurrent herpetic ulcers?

A

topical 5% cream

211
Q

What form of aciclovir is used to treat severe herpetic stomatitis an herpes zoster ?

A

oral tablet/suspension

212
Q

What forms of aciclovir can be used to treat primary gingivostomatitis ?

A

Topical 5% cream
oral tablet/suspension

213
Q

Selective toxicity is difficult to achieve in antifungals. Why is this?

A

this is because both fungal and host cells are eukaryotic

214
Q

What are the types of antifungals?

A

Azoles- miconazole, fluconazole
Polyenes- Nystatin

215
Q

What is the MOA of azole antifungals ?

A

affect cell membrane synthesis
inhibit ergosterol synthesis

216
Q

Aside from its anti-fungal function, miconazole is also bacteriostatic against what bacterial species?

A

Staphylococcus aureus

217
Q

What is the clinical use of miconazole oromucosal gel?

A

angular cheilitis

218
Q

What is the clinical use of fluconazole tablets?

A

prevention of candidal infections in HIV patienst

219
Q

What is the dose of fluconazole tablets and why?

A

1x daily
this is because they have a long half-life

220
Q

What is the MOA of polyene antifungals?

A

binds to the sterols in fungal cytoplasmic membrane
alters cell wall permeability- causes leakage of cell contents and death

221
Q

What is the clinical use of nystatin?

A

used to prevent mucosal candidiasis

222
Q

Nystatin is too toxic for systemic use. True or false

A

True

223
Q

Nystatin is absorbed by the alimentary canal. True or false

A

False

224
Q

What are drug interactions of fluconazole?

A

avoid use with clopidogrel
Possible interactions with - carbamazepine (anticonvulsant), citalopram (SSRI), diazepam (BZD), ibuprofen(NSAID), midazolam (BZD), simvastatin, warfarin

225
Q

What are the drug interactions of miconazole?

A

avoid use with warfarin {[warfarin binds to albumin, miconazole competition for albumin binding increases free warfarin and increases risk of bleeding???}}

possible interactions with atorvastatin, carbamazepine, vitamin D substances

226
Q

What are the interactions of Nystatin ?

A

no major interactions with commonly used drugs

227
Q

What are the interactions with aciclovir?

A

no major interactions with commonly known drugs

228
Q

Briefly describe absorption of fluconazole

A

rapidly absorbed
>90% bioavailability

229
Q

How is fluconazole eliminated after administration?

A

excreted from kidneys primarily through glomerular filtration
80% excreted unchanged

HHD 2 (37 decks)

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