Antimicrobials

Question 1

Bactericidal

Answer 1

Kills bacteria

Question 2

Bacteriastatic

Answer 2

Inhibits growth of bacteria

Question 3

Antibacterials that inhibit wall synthesis

Answer 3

Beta-lactams

Glycopeptides

Question 4

Antibacterials that inhibit protein synthesis

Answer 4

Tetracyclines
Aminoglycosides
Macrolides

Question 5

Antibacterials that disrupt cell membrane function

Answer 5

Polymixins - act on gram negative bacteria

Question 6

Antibacterials that disrupt nucleic acid synthesis

Answer 6

Quinolone e.g. trimethoprim, rifampicin

Question 7

Penicillin mechanism

Answer 7

Prevents protein from linking side chains (antimicrobials lecture slide 7)

Question 8

Vancomycin mechanism

Answer 8

Prevents protein from getting to site (antimicrobials lecture slide 7)

Question 9

Types of antibiotic resistance

Answer 9

Intrinsic - no target for drug, permanent
Acquired - acquired new genetic material or mutates, permanent
Adaptive - organism responds to stress, usually reversible

Question 10

Mechanisms of resistance

Answer 10

Drug inactivating enzymes - e.g. b lactamases
Altered target - Target enzyme has lowered affinity for antibacterial e.g. resistance to meticillin, macrolides & trimethoprim
Altered uptake - ↓permeability (e.g. Β-lactams) or ↑efflux (e.g. tetracyclines)

Question 11

Penicillin active against

Answer 11

Streptococci

Question 12

Amoxicillin active against

Answer 12

Streptococci and gram negative

Question 13

Flucloxacillin active against

Answer 13

Staphylococci and streptococci

Question 14

B-lactamase inhibitor combinations

Answer 14

Co-amoxiclav - anaerobes and gram negative

Piperacillin/tazobactam - gram negativ inc pseudomonas

Question 15

Cephalosporins

Answer 15

More gram negative and less gram positive with generations
More broad spectrum but no anaerobe activity
Cetriaxone (good activity in CSF)
Association with C.diff

Question 16

Outline the steps involved in gram staining

Answer 16

• Positively charged crystal violet i added and binds to negatively charged cell components
• Iodine is added and forms a large complex with crystal violet
• Acetone/methanol extract the complexes through gram negative bacteria cell wall
• Red dye added to stain gram negative cells

Question 17

Choice of agent to treat bacterial meningitis

Answer 17

Ceftriaxone, because it can penetrate into the CSF

Question 18

Systemic Inflammatory Response Syndrome (SIRS) criteria

Answer 18

• Temperature > 38.3 or < 36
• Heart rate > 90 BPM
• Respiratory rate > 20 min-1
• White cell count 12 x 10^9 /l
• Acutely altered mental status
• Hyperglycaemia: glucose > 7.7 mmol/l

Question 19

Treatment for sepsis

Answer 19

Give 3:

• High flow oxygen
• Antibiotics
• IV fluids

Take 3:

• Blood culture
• Urine output
• Serum lactate and haemoglobin

Question 20

Gram positive cocci

Answer 20

Staph aureus/ MRSA
Coagulase negative staph
Alpha and beta haemolytic strep
Strep pnemoniae
Strep pyogenes
Staph epidermidis

Question 21

Gram positive bacilli

Answer 21

Clostridium difficile

Question 22

Gram negative cocci

Answer 22

Neisseria meningitidis

Question 23

Gram negative bacilli

Answer 23

Esterichia coli
Haemophilis influenza
Kleibsiella pneumoniae

Question 24

M protein

Answer 24

Resistance to phagocytosis by inhibiting activation of alternative complement pathway on bacterial cell surface

Question 25

Streptokinase function

Answer 25

Dissolution of clots through conversion of plasminogen to plasmin

Question 26

Streptococcal pyrogenic exotoxins

Answer 26

Cleaves Ig G bound to group A strep