Antimicrobial Agents 2

Question 1

What are broad spectrum antibiotics good for?

Answer 1

An optimal initial choice for nosocomial pneumonia and severe sepsis.

Question 2

What methods are used to help identify the pathogen?

Answer 2

Gram stain: CSF, Joint aspirate, Pus

Rapid antigen detection: Immunofluorescence, PCR

Question 3

When is each route of antibiotic administration appropriate?

Answer 3

IV: Serious (or deep/ CNS) infection.

PO: Avoid if poor GI function or vomiting. Different classes of antimicrobial have different oral bio-availabilities

IM: Not an option for long-term use. Avoid if bleeding tendency or drug is locally irritant.

Topical: Limited application + may cause local sensitisation.

Question 4

When is it recommended to switch from IV to PO?

Answer 4

Recommended in hospital for most infections if the patient has stabilised after 48 hours IV therapy

Question 5

What are the three patterns of activity for antibiotics?

Answer 5

Type I: Conc. dependent killing + prolonged persistent effects

Type II: Time-dependent killing + minimal persistent effects

Type III: Time-dependent killing + moderate to prolonged persistent effects.

Question 6

What are the Type I antibiotics?

Answer 6

Aminoglycosides

Daptomycin

Fluoroquinolones

Ketolides

Question 7

What is the goal of Type I antibiotic therapy?

Answer 7

Maximize concentrations

The higher the peak above MIC the better the response

Question 8

What are the Type II antibiotics?

Answer 8

Carbapenems

Cephalosporins

Erythromycin

Linezolid

Penicillins

Question 9

What is the goal of Type II antibiotic therapy?

Answer 9

Maximize duration of exposure

The longer the time above the MIC the better

Question 10

What are the Type III antibiotics?

Answer 10

Azithromycin

Clindamycin

Oxazolidinones

Tetracyclines

Vancomycin

Question 11

What is the goal of Type III antibiotic therapy?

Answer 11

Maximize amount of drug for maximal time

Often given as infusion

Constant big area under curve

Question 12

What is the recommended length for a course of antibiotics for N. meningitidis meningitis?

Answer 12

7 days

Question 13

What is the recommended length for a course of antibiotics for Acute osteomyelitis (adult)?

Answer 13

6 weeks

Question 14

What is the recommended length for a course of antibiotics for bacterial endocarditis?

Answer 14

4-6 weeks

Question 15

What is the recommended length for a course of antibiotics for Gp A Streptococcal pharyngitis?

Answer 15

10 days

Question 16

What is the recommended length for a course of antibiotics for Simple cystitis (in women)?

Answer 16

3 days

Question 17

What are common skin infections and what pathogens cause them?

Answer 17

Impetigo, Cellulitis + Wound Infections

Common organisms include S. aureus + beta-haemolytic Streptococci

Question 18

What antibiotics are used to treat skin infections?

Answer 18

Flucloxacillin (unless penicillin allergy or MRSA)

Question 19

What is the treatment for Invasive Group A Streptococcal (iGAS)?

Answer 19

Aggressive + early debridement

Abx: adjunctive use of protein synthesis inhibitors esp. clindamycin (also has good skin + soft tissue penetration)

Use of IVIg

Question 20

What is the Eagle effect?

Answer 20

Penicillin doesn’t have a good effect at a higher conc., also pencillin isn’t good against high conc. of bacteria.

Question 21

Why does the Eagle effect happen?

Answer 21

In cases of high bacterial burden, the bacteria isn’t actually replicating so penicillin doesn’t really work.

Question 22

What is the treatment for pharyngitis?

Answer 22

Benzyl penicillin x 10 days

Question 23

What is the treatment for mild community acquired pneumonia?

Answer 23

Amoxicillin

Question 24

What is the treatment for severe community acquired pneumonia?

Answer 24

Co-amoxiclav + clarithromycin

Question 25

What are hospital-acquired respiratory tract infections?

Answer 25

2nd most common cause of HAI Associated with highest mortality (23%) Greatest risk associated with tracheal intubation + mechanical ventilation

Question 26

What is the treatment for hospital-acquired respiratory tract infections?

Answer 26

Cephalosporin; ciprofloxacin; piperacillin/ tazobactam If MRSA colonised/ risk, consider addition of Vancomycin

Question 27

What are the main bacteria for meningitis?

Answer 27

N. Meningitidis S. pneumoniae Listeria in the very young/ elderly/ immuno-compromised

Question 28

What is the treatment for meningitis?

Answer 28

Ceftriaxone (+/- amoxycillin if Listeria likely)

Question 29

What is the treatment for meningitis in a baby less than 3 months old?

Answer 29

Cefotaxime PLUS Amoxicillin (to cover for listeriosis) Ceftriaxone not used in neonates as displaces BR from albumin + because it can cause biliary sludging

Question 30

What is the treatment of Neisseria meningitidis?

Answer 30

Benzylpenicillin (high dose) or Ceftriaxone/Cefotaxime

Question 31

What is the treatment for community acquired simple cystitis?

Answer 31

Trimethoprim x 3d (7 for men + pregnant women) Nitrofurantoin x 3d (7 for men + pregnant women) Nitro preferred in first 2 trimesters

Question 32

What is the treatment for hospital-acquired UTI (commonest type of HAI)?

Answer 32

Cephalexin or co-amox

Question 33

What is the treatment for an infected urinary catheter?

Answer 33

Change under gentamicin cover

Question 34

What is the treatment for C. diff?

Answer 34

STOP the offending abx (usually a cephalosporin); If severe, Rx with PO vancomycin. If above fails, use PO fidaxomicin. Final step IV metronidazole + oral vanc.

Question 35

What are things to recover if there is no improvement within 48 hours?

Answer 35

Does the patient really have a bacterial infection? (Have I collected the relevant cultures?) Is there a persistent focus present (e.g. an infected vascular or urinary catheter)? Is there a deep-seated collection (e.g. intra-abdominal) that requires drainage? Could the patient have bacterial endocarditis? Am I using the correct dose of the antimicrobial? Is another infection present (esp consider Candida)?

Question 36

Give 6 common side effects of antibiotics

Answer 36

GI upset Hepatitis Fever Rash Renal dysfunction Acute anaphylaxis

Question 37

When are IV antibiotics used?

Answer 37

When patient not absorbing PO When deep sites/ CNS involvement

Question 38

What is the MIC? How is this measured?

Answer 38

the least amount of antibiotic required to inhibit growth in vitro Gradient strips or disc diffusion

Question 39

What does MIC relation to the breakpoint line indicate?

Answer 39

Above= unlikely to be successful at normal doses used. Reported as resistant Below= likely to be successful: either reported as “susceptible” or “susceptible with optimized dosing” (not at normal BNF dosing)