Lecture 9: Antibiotics

Question 1

define an antibiotic

Answer 1

a chemical compound made by another microorganism which inhibits or kills bacteria

Question 2

the majority of antibiotics are derived from which bacterial species?

Answer 2

streptomyces

Question 3

what does a bacteriostatic agent do?

Answer 3

restricts the growth and reproduction of bacteria but it is the patient’s own immune system which kills off the bacteria and leads to recovery from the infection

Question 4

what does a bactericidal agent do?

Answer 4

causes bacterial cell death

Question 5

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Answer 5

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Question 6

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Answer 6

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Question 7

examples of bactericidal antibiotics

Answer 7

• penicillin
• gentamicin
• vancomycin
• ciprofloxacin
• metronidazole

Question 8

examples of bacteriostatic antibiotics

Answer 8

• doxycyline
• calrithromycin
• azithromycin
• linezolid

Question 9

which antibiotics inhibit cell wall synthesis?

Answer 9

Beta-lactams:
- penicillins
- cephalosporins
- carbapenems

Glycopeptides:
- vancomycin

Question 10

which antibiotics inhibit protein synthesis?

Answer 10

• gentamicin
• doxycycline
• clarithromycin
• erythromycin
• clindamycin
• chloramphenicol
• linezolid

Question 11

which antibiotics inhibit DNA synthesis?

Answer 11

• metronidazole
• fluoroquinolones

Question 12

which antibiotics inhibit folic acid synthesis?

Answer 12

trimethoprim
co-trimoxazole

Question 13

how do beta-lactams work?

Answer 13

bind to penicillin binding proteins (PBP) in the cell wall or cell cytoplasm, thereby inhibiting cell wall formation
- inhibited by beta lactamases

Question 14

cephalosporins all cover

Answer 14

Group A, B, C streptococci
Viridans group Streptococci
E.coli
Klebsiella
Proteus mirabilis

Question 15

cephalosporins are LAME because they dont cover

Answer 15

Listeria
Atypicals
MRSA (except 5G)
Enterococcus

Question 16

when is meropenem (a carbapenem) indicated?

Answer 16

• active against gram positive, gram negative and pseudomonas
• severe infections: unresponsive to other abx and haematology patients
• lung infections in cystic fibrosis patients.

Question 17

beta lactam adverse reactions

Answer 17

• mild (5%): rash, fever
• severe (0.05%): anaphylaxis

Question 18

beta-lactams drug interactions

Answer 18

• carbapenems: valproate and probenecid
• all beta-lactams: typhoid vaccine

Question 19

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Answer 19

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Question 20

which antibiotic is exclusively used to treat lower urinary tract infections?

Answer 20

nitrofurantoin

Question 21

gram-positive cocci include

Answer 21

staphylococcus
streptococcus
enterococcus

Question 22

gram-positive rods include

corny mike’s list of basic cars

Answer 22

corneybacteria
mycobacteria
listeria
bacillus
nocardia

Question 23

gram-positive anaerobes can be remembered with the CLAP mnemonic:

Answer 23

clostridium
lactobacillus
actinomyces
propionibacterium

Question 24

list some common gram-negative bacteria

Answer 24

• Neisseria meningitidis
• Neisseria gonorrhoea
• Haemophilia influenza
• E.coli
• Klebsiella
• Pseudomonas aeruginosa
• Moraxella catarrhalis

Question 25

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Question 26

the five atypical bacteria causing atypical pneumonia can be remembered with the ‘legions of psitacci MCQs’ mnemonic

Answer 26

legionella pneumophilia
chlamydia psittaci
Mycoplasma pneumoniae
Chlamydophilia pneumoniae
Q fever (coxiella burnetti)

Question 27

antibiotics used to treat MRSA include:

Answer 27

doxycycline
clindamycin
vancomycin
teicoplanin
linezolid

Question 28

when is vancomycin used?

Answer 28

• MRSA
• 1st line for gram-positive infections in individuals with penicillin allergy: skin and soft tissue infections, streptococcus meningitis, infective endocarditis
• C.diff when given orally

Question 29

vancomycin side-effects

Answer 29

red man syndrome:
- flushing
- erythema
- pruritus
- affecting upper body, neck and face > lower body
- myalgia, dyspnea, hypotension

Question 30

aminoglycosides toxicity e.g. gentamycin, streptomycin

Answer 30

• nephrotoxicity
• ototoxicity/vestibulotoxicity
• neuromuscular blockade

Question 31

tetracycline class side effects

e.g. doxycycline

Answer 31

• photosensitivity
• gastritis, oesophageal ulceration
• contraindicated in pregnancy
• can cause permanent tooth staining in children < 8

Question 32

when is erythromycin indicated?

Answer 32

• skin & soft tissue infections
• community acquired pneumonia

Question 33

when is clarithromycin indicated?

Answer 33

• skin & soft tissue infections
• community acquired pneumonia
• atypical pneumonia: listeria, mycoplasma, psitcossis
• helicobacter pylori
• toxoplasma gondii

Question 34

when is azithromycin indicated?

Answer 34

• typhoid fever: salmonella typhi and paratyphi
• STI: gonorhoea, chlamydia

Question 35

macrolides side effects

the mycins except gentamicin

Answer 35

• jaundice
• ototoxicity
• prolonged QT syndrome
• GI disturbance
• avoid clarithromycin and azithromycin in pregnancy unless benefit outweighs risk

Question 36

when is metronidazole indicated?

Answer 36

bacteria- Clostridium, helicobacter
parasitic- giardia, entameoba

Question 37

when is trimethoprim used?

Answer 37

UTIs

Question 38

when is co-trimoxazole used?

Answer 38

• pneumocystis jiroveci pneumonia
• toxoplasmosis
• multi drug resistant organisms e.g. mycobacterium, stenotrophomonas

Question 39

what is the minimum inhibitory concentration (MIC)?

Answer 39

lowest concentration which prevents visible growth of a bacterium or bacteria

Question 40

doxycycline spectrum and usage

Answer 40

broad-spectrum
- soft tissue and skin infections
- CAP + atypicals
- genito-urinary infection
- rickettsia
- malaria prophylaxis and treatment
- bone and joint: septic arthritis and osteomyelitis