Antibiotics (organised by organism/disease)

Question 1

Mycobacterium tuberculosis

Answer 1

Not classified according to Gram staining, because of mycolic acid wall. Acid-fast.

1st 2 months: rifampicin, ethambutol, isoniazid, pyrazinamide (plus pyridoxine aka Vit B6 to prevent isoniazid-related neuropathy)

Following 4 months: rifampicin and isoniazid (plus pyridoxine)

Question 2

Meningitis

Answer 2

Can be N. meningitidis, Strep Pneumoniae, E coli, or viruses

If you suspect bacterial meningitis, give adults 1.2g IV/IM benzylpenicillin, or ceftriaxone plus vancomycin, before CT then LP for culture.

Question 3

UTI

Answer 3

Usually E. Coli (G- anaerobic bacilli) or Staph saprophyticus (G+ coagulase-negative). Also Proteus mirabilis (G- fac anaerobic bacilli, swarming, maltose fermenting).

nitrofurantoin, or trimethoprim

Question 4

H. pylori

Answer 4

Gram negative spirilli

PPI plus amoxicillin plus clarithromycin or metronidazole

Question 5

Community-acquired pneumonia

Answer 5

Usually strep pneumoniae (G+ fac anaerobe)

amoxicillin, plus clarithromycin or doxycycline if severe.

Question 6

Hospital-acquired pneumonia without risk factors for MDR

Answer 6

Usually Strep Pneumoniae (G+ fac anaerobe), H influenzae (G- fac anaerobic coccobacilli), Staph aureus (G+ aerobes)

Empirical treatment = monotherapy with coverage for P aeruginosa, so:

piperacillin/tazobactam, or meropenem

Question 7

Hospital-acquired pneumonia with risk factors for MDR (e.g. ventilation or septic shock)

Answer 7

Likely P aeruginosa, K pneumoniae, MRSA, Legionella.

Give combination therapy:
meropenem OR piperacillin/tazobactam
PLUS
ciprofloxacin OR gentamicin
PLUS
vancomycin

Question 8

C difficile

Answer 8

G+ anaerobic bacilli

If mild, metronidazole (and ideally hold any other Abx, anti-peristaltic agents, PPIs).

If severe (>4 stools per day), oral vancomycin and consider hospital admission.

Question 9

Chlamydia trachomatis

Answer 9

G-, aerobic, intracellular coccoid/bacilli.

Doxycycline, and no sex ‘til a week after treatment. Retest after 3 months.
If pregnant/breastfeeding, azithromycin, and retest after 3 weeks