Antibiotics

Question 1

Define the cephalosporin generations and their sensitivities

Answer 1

1st: cefalexin, cefazolin
- active against staph, strep, proteus, some E. coli and klebsiella

2nd: cefaclor, cefuroxime, cefoxitin
- less gram +ve cover, greater gram -ve –> H. influenzae, enterobacter, neisseria

3rd: cefotaxime, ceftriaxone, ceftazidime
- broad spectrum gram -ve cover, can penetrate CNS, covers pseudomonas

4th: cefepime
- extended spectrum with similar gram +ve cover to 1st gen, greater beta lactamase resistance, crosses BBB, active against pseudomonas

Question 2

Empiric treatment of septicaemia

Answer 2

CNS/meningococcal: cefotaxime
CAP: augmentin + roxithromycin
GI: ceftazidime + metronidazole
GU: augmentin + gentamicin
Skin/bone: flucloxacillin
Unknown: augmentin + gentamicin + metronidazole
Neutropenia: tazocin (piperacillin/tazobactam) + gentamicin

Question 3

Treatment of gram positive cocci infections

Answer 3

1. Penicillins
2. Cephalosporins, particularly 1st and 4th generations
3. Macrolides (erythromycin, roxithromycin, clarithromycin)
4. Lincosamides (clindamycin)

Question 4

Microbes covered by lincosamides (clindamycin)

Answer 4

1. GPC - skin and soft tissue infections
2. Protozoal infections
3. Anaerobes

Question 5

Microbes covered by macrolides (erythromycin, roxithromycin, clarithromycin)

Answer 5

1. GPC

2. Mycoplasma (a common cause of CAP and atypical pneumonia)

Question 6

Treatment of Staphylococcus

Answer 6

• Flucloxacillin

- Clindamycin

Question 7

Treatment of Enterococci

Answer 7

Amoxycillin + Gentamicin (synergistic)

Question 8

Treatment of Neisseria

Answer 8

• Cefuroxime

- Ceftriaxone

Question 9

Treatment of Moraxella

Answer 9

Quinolones (ciprofloxacin)

Question 10

Treatment of infections caused by GNB

Answer 10

• Aminoglycosides (gentamicin)

- Cephalosporins, particularly 2nd and 3rd generations

Question 11

Treatment of Chlamydia

Answer 11

Macrolides:

• Azithromycin for genital
• Roxithromycin for chest

Question 12

Treatment of Syphilis

Answer 12

Benzylpenicillin

Question 13

Treatment of mycobacteria

Answer 13

Rifamycins (rifampicin) - very low barrier for development of resistance so must be co-prescribed with something else

Question 14

Treatment of anaerobes (including anaerobic GPB)

Answer 14

Nitroimidazoles (metronidazole)

Question 15

Microbes covered by nitroimidazoles (metronidazole)

Answer 15

• Anaerobes
• Anaerobic GPB
• Protozoal infections e.g. Giardia, trichomonas

Question 16

Name antibiotics that cover pseudomonas

Answer 16

1. “Tazocin” (piperacillin + tazobactam)
   - extended spectrum penicillin + beta lactamase inhibitor
   - may be used with aminoglycoside (gent)
2. Ciprofloxacin (quinolone)
3. Ceftazidime (3rd gen)
4. Meropenem (carbapenem)
5. Cefepime (4th gen)

Question 17

Name broad spectrum antibiotics

Answer 17

1. Augmentin
2. Carbapenems (meropenem)
   - anaerobes + aerobes, beta lactamase stable
3. Tetracyclines (doxycycline)
   - mainly skin + STI infections
4. Quinolones (ciprofloxacin)
   - pseudomonas, beta lactamase resistant, cystic fibrosis
5. Co-trimoxazole
   - MRSA, pneumocystis jirovecii, stenotroph maltophilia, toxoplasmosis, s. aureus
6. Aminoglycosides (gentamicin)
   - poor against streps + anaerobes so use with penicillin +/- metronidazole