Antibiotic Resistance

Question 1

What is resitance?

Answer 1

When a previously suspetible organsims can no longer be killed by an antibiotic at levels which can be sfely achieved clinically

Question 2

What is intermediate resitance?

Answer 2

Can be treated with an increase from the standard dose

Question 3

What is the therapeutic index?

Answer 3

The difference between the dose necessary for treatment and that causing harm (usually large)

Question 4

What is intrinsic resistance?

Answer 4

When all strains of a species are resistant (naturally)

Question 5

What is the Minimum inhibitory concentration (MIC)?

Answer 5

The lowest concentration of an antibiotic that COMPLETELY inhibits the groeth of a bacterium

Question 6

What is the Minimum Bactericidal Concentration (MBC)?

Answer 6

The lowest dose that completely kills a bacterium

Question 7

What is higher the MIC or MBC?

Answer 7

MBC

Question 8

What is the “antibiotic breakpoint”?

Answer 8

• A concentration chosen for labratory testing that will differentiate sensitive from resistant populations of bacteria
• Allows labratories to test only one concentration rather than having to determine the MIC

Question 9

What defines the breakpoint?

Answer 9

• Distribution of MICs of target bacteria
• Achievable theraapeutic concentration in tissue
• Maximum achievable concentration

Question 10

What are streptococci naturally resistant to?

Answer 10

Aminoglycosides

Question 11

What are Pseudomonas spp. naturally resistant to?

Answer 11

Beta lactams

Question 12

What are Mycoplasma spp naturally resitant to?

Answer 12

Beta lactam antibiotics

Question 13

What are enterobacteriaciae resitant to?

Answer 13

Metronidazole

Question 14

Through which mechanisms can bacteria become resitant?

Answer 14

• Enzymatic inactivation
• Enzymatic addition
• Impermeability
• Efflux
• Alternative pathway
• Altered target

Question 15

How are enzymes inactivated through destruction?

Answer 15

Beta lactam ring can be hydrolysesd and breaked open

Question 16

How can enxymes be inactivated through addition?

Answer 16

Aminoglycosides for example can come along and drop acetlyase enzume on tp reducing the drug down to a non-useful form

Question 17

How do efflux pumps work?

Answer 17

Piece of cellular machinary that actively with ATP can pump antibiotics such as Tetracyclines, Quinolones and Macrolides out of the cell.

• May have an important role in organsims gaining higher levels of resitance
• Tetracyclines, Quinolones, Macrolides

Question 18

What organism can cause resitance through an aleternative pathway through mec A?

Answer 18

MRSA

Question 19

What antibiotics can be affected by an altered binding site?

Answer 19

• Rifampicin
• Fluoroquinolones
• Sulphonamides

Question 20

What can happen as a result of fluoroquinolones being used below their therapeutic index?

Answer 20

Hypermutability

Question 21

What are the 2 main genes involved in quinolone resitance?

Answer 21

• GyrA and parC
• Mutation of 1 gene encodes low level resistance
• Mutations in both genes encodes a high level of resistance

Question 22

What antibiotic is the most active fluoroquinolone against 2nd strep s pneumoniae mutants?

Answer 22

Gemifloxacin

Question 23

How can resitance be transmitted between organisms?

Answer 23

- Transformation 
(Penicillin in S.pneumoniae) 
- Conjugation 
(Beta-lactamases, enterobacteria)
- Transposons 
(Eryhtromycin in S pyogenes)

Question 24

What is conjugation?

Answer 24

One bacteria shares genetic material to another via a plasmid

Question 25

What are transpons and integrons?

Answer 25

• Small segments of DNA that encode their own transmission
• Many bacteria have these mobile gentic elements
• Allow genome plasticity
• May collect resistance determinants

Question 26

What is a MinION?

Answer 26

Handheld device that reads individual bases on DNA which can then help identify bacteria’s genome (type and/or resistance)

Question 27

What is a superbug?

Answer 27

• An organism that has gained resistnace to a critical drug

- Or an organism that has gained resitance to multiple antibiotics

Question 28

What are some examples of superbugs?

Answer 28

• MRSA - Methicillin Resistant Staph Aureus
• GISA - Glycopeptide Resistant Staph Aureus
• VRE - Vancomycin Resistant Enterococcus
• ESBLs - Expanded spectrum beta-lactamases

Question 29

What enzyme can break down carbapenem?

Answer 29

Carbapenamase

Question 30

What are the 3 major classes of carbapenemases?

Answer 30

• Klebsiella pneumoniae carbapenemase (KPC) requires serine
• New Delhi metallo-betalactamase (NDM) requires zinc
• Oxa-48 group requires serine

Question 31

What is colistin?

Answer 31

Last resort antibiotic for multi-drug resistant g -ve infections including pneumonia

Question 32

What infections do we worry about most?

Answer 32

• When the consequences of infection are severe and the organsim is common
• When the organism is naturally resistant to many antibiotics
• When the infection is in a site where it is difficult to get high concentrations of antibiotic

Question 33

How do we plan on tackiling the problem of antibiotic resistance?

Answer 33

• Optimise the treatment of bacterial disease
• Better diagnosis/diagnostics
• Focussed treatment
• Appropriate length of courses

Question 34

How are resistant bugs treated?

Answer 34

• Culture essential
• Susceptibility testing
• Use the most bactericidal drug available
• Consider the use of combinations