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Flashcards in Infection Session 2 Deck (59):
1

Why is physiological state relevant in gestational diabetes?

During pregnancy bacteria in the large bowel can cause gestational diabetes

2

What is the difference in calendar and relative time when considering a patient with a suspected infection?

Calendar time considers seasonal diseases e.g. Flu or chickenpox
Relative considers time since a potential exposure

3

By what 7 mechanisms can infection occur?

Contiguous spread
Inoculation
Haematogenous
Ingestion
Inhalation
Vector
Vertical transmission

4

How do aerosols form?

Around a 'seed' e.g. a dust particle

5

Why is chickenpox so contagious?

Virus rapidly multiplies in lungs and is transmitted via inhalation

6

What sequence does management of infection usually take?

History --> examination --> diagnosis --> specific+/- supportive Tx --> infection prevention in hospital and community

7

How are the vast majority of infection diagnoses made?

History alone

8

Why is debridement of tissue sometimes used to treat infection?

Dead tissue has a low redox potential and bloodflow so is a perfect environment for anaerobic bacteria

9

Why does the dead space left following debridement often need packing?

Blood/serosa can accumulate here and promote microbial growth

10

What outcomes are possible following an infection?

Resolution
Chronic infection --> potential disability
Death

11

What is an antibiotic?

Antimicrobial produced by a living organism

12

What are the four main types of antimicrobials?

Antibacterial
Antiviral
Antiprotozoal
Antifungal

13

What is the difference between a bactericidal and bacteriostatic antibacterial agent?

Bactericidals kill, bacteriostatics inhibit

14

What are the ideal features of antimicrobial agents?

Selectively toxic
Few adverse effects
Reach site of infection
Oral/IV formulation
Long half-life for infrequent dosing
No interference w/other drugs

15

How do beta-lactams act as antibacterials?

Inhibit cell wall regeneration by binding to penicillin binding protein so new X-links cannot be formed

16

How do glycopeptides act as antibacterials?

Bind to peptidoglycan thus blocking cell wall X-linking enzyme

17

What mechanisms can bacteria use to be resistant to beta-lactams?

Decrease their permeability to them
Express beta-lactamases to inactivate drug
Alter target enzyme so it has a lower affinity

18

Which classes of antibacterials inhibit protein synthesis by blocking a variety of enzymes?

Tetracyclines
Aminoglycosides
Macrolides

19

How can bacteria be resistant to tetracyclines?

Increase efflux to actively pump out before it takes effect
Alter target enzyme

20

Which class of antibacterials do trimethoprim and rifampicin belong to and how do they act?

Quinolones (floroquinolones clinically)
Bind to DNA gyrase to interfere with DNA supercoiling

21

What are polymixins?

Antibacterials that inhibit cell membrane function

22

Will a bacterium only ever have one mechanism of resistance to one particular drug?

No, might have different mechanisms for same class as well as multiple mechanisms for different classes

23

Does there need to be a high level of antibiotic exposure for a chromosomal gene mutation resulting in antibiotic resistance to occur?

No

24

What two methods form the basis of antibiotic resistance?

Chromosomal gene mutation
Horizontal gene transfer

25

What is the qualitative method of measuring antibiotic activity?

Disc sensitivity to examine zone of inhibition around disc

26

What is the quantitative measure of antibiotic sensitivity?

Minimum inhibitory concentration

27

How is minimum inhibitory concentration measured?

Bacterial broth is cultured in a serial dilution of antibiotic

28

Are carbapenems broad or narrow spectrum?

Broad - including anaerobes and most G-ve

29

What are penicillins mainly active against?

Streptococci

30

What is flucoxacillin active against?

Staph and streptococci

31

Give an example of a commonly used beta-lactamase inhibitor combination therapy.

Co-amoxiclav

32

How do new generation of cephalosporins compare to old generations?

Increased G-ve spectrum and decreased G+ve activity

33

Are cephalosporins active against anaerobes?

No

34

What is the relevance of cephalosporins to C.diff infection?

Broad spectrum so widespread use --> resistant C.diff strains

35

How does the activity of vancomycin against G+ve bacteria compare to its activity against G-ve?

Active against most G+ve but not G-ve

36

Why is vancomycin given orally for intestinal infections?

Not normally absorbed into the blood

37

Why must care be taken with vancomycin use?

It has a narrow therapeutic window

38

What class of antimicrobials does vancomycin belong to?

Glycopeptides

39

Why are tetracyclines not widely used in hospitals?

Broad spectrum

40

In what common situation might carbapenems, tetracyclines or macrolides be used?

Penicillin allergy

41

What are tetracyclines active against?

Chlamydia
Some protozoa
Atypical pneumonia pathogens

42

Why are tetracyclines not given to children under 12 y.o.?

Stain bones and teeth yellow

43

Which antimicrobial is reserved for severe G-ve sepsis?

Gentamicin

44

Why is gentamicin reserved as a last resort for severe G-ve sepsis?

Profound activity against G-ve but is potentially nephrotoxic

45

What is used in primary care as an alternative to penicillin for mild G+ve infections?

Macrolides

46

Why are macrolides used in combination with drugs for typical respiratory pathogens?

They are active against atypical respiratory pathogens

47

Name two macrolides.

Erythromycin
Clarithromycin

48

What activity do quinolones have?

Very active against G-ve and atypical pathogens

49

Why is there a concern with quinolones and C.diff infection?

Rapidly increasing resistance

50

What action do trimethoprim and sulphonamides have?

Inhibit folic acid synthesis

51

What is trimethoprim most commonly used for in the UK?

UTI

52

When might you use a combination of trimethoprim and sulphonamides?

In a specific and unusual infection

53

What class of antifungals acts by inhibiting cell-membrane synthesis?

Azoles

54

What is an over-the-counter antifungal used to treat Candida?

Fluconazole

55

How does the activity of Azoles and Polyenes differ even though their mechanism of action is the same?

Azoles active against yeasts +/- moulds
Polyenes active against more complicated moulds

56

Why can aciclovir be used against Herpes simplex and Varicella Zoster viruses?

Upon phosphorylation it inhibits viral DNA polymerase

57

How does Tamiflu work?

Inhibits viral neuraminidase

58

What is metronidazole active against?

Anaerobic bacteria and several protozoa

59

What are the 7 patient factors which can affect disease?

Age
Gender
Physiological state
Pathological state
Social factors
Time
Place