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YEAR 5: Microbiology and Infection > MI: Antimicrobials 2 > Flashcards

MI: Antimicrobials 2 Flashcards

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1
Q

List some ways in which antibiotics can be misused.

A
  • No infection present
  • Selection of incorrect drug
  • Inadequate or excessive dose
  • Inappropriate use of empirical antibiotics

NOTE: about 50% of people with bacteraemia will get better by themselves

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2
Q

List some common adverse events associated with antibiotics.

A
  • GI upset
  • Rash and fever
  • Renal dysfunction
  • Acute anaphylaxis
  • Hepatitis
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3
Q

What does the ‘CHOICE’ of correct antimicrobial depend on?

A

CHAOS

  • Choice of drug - narrow spectrum where possible, considering local sensitivity patterns and cost
  • Host characteristics (e.g. age, pregnancy)
  • Antimicrobial susceptibility
  • Organism
  • Site of infection (e.g. bone, CSF)
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4
Q

How is the type of drug decided upon?

A
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5
Q

Which types of infection typically require IV antibiotics?

A
  • Serious infection
  • Deep/CNS infections
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6
Q

What is MIC?

A
  • Minimum inhibitory concentration - minimum concentration of drug required to inhibit bacterial growth
  • There is a regulatory body that sets the MIC cut-off
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7
Q

What is the agar diffusion method?

A
  • A disc is impregnated with antibiotic
  • As distance from the disc increases, the concentration of antibiotic decreases logarithmically
  • The border of the clear zone is the MIC
  • This is time-consuming
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8
Q

What type of antibiotics should be used in nosocomial infections and severe sepsis?

A

Broad-spectrum

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9
Q

Why should as large a sample as possible be sent when identifying organisms?

A

More sample means higher sensitivity

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10
Q

For what samples would you do gram staining as a preliminary investigation?

A
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11
Q

Name two methods of rapid antigen detection.

A
  • PCR
  • Immunofluorescence
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12
Q

What factors about the site of infection can affect antibiotic choice?

A
  • pH at the infection site
  • Lipid-solubility of the drug
  • Ability to penetrate the blood-brain barrier
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13
Q

Which two types of infection require special consideration because they are difficult to penetrate with antibiotics?

A
  • Osteomyelitis
  • Endocarditis
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14
Q

In which circumstances would you avoid IM administration of antibiotics?

A
  • Bleeding tendency
  • Drug is locally irritant
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15
Q

What is an important predictor of efficacy?

A
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16
Q

Describe the type I pattern of antibiotic activity. Give an example of an antibiotic of this type.

A
  • Concentration-dependent killing
  • Peak above the MIC (Cmax) is the most important parameter
  • Example: aminoglycosides
  • These drugs tend to be given as one big dose
  • The benefits of achieving a higher Cmax must be balanced with the increased toxicity
  • Trough concentration should also be measured to ensure that the drug is being eliminated (this determines the frequency of drug administration)
17
Q

Describe the type II pattern of antibiotic activity. Give an example of an antibiotic of this type.

A
  • Time-dependent killing
  • Time spent above the MIC is the most important factor
  • Example: penicillins
  • Therefore, penicillins need to be given frequently
18
Q

Describe the type III pattern of antibiotic activity. Give an example of an antibiotic of this type.

A
  • Concentration and time-dependent
  • AUC above the MIC is the most important factor
  • Example: vancomycin

NOTE: infusions may be used to maintain an AUC above the MIC

19
Q

What are the main side-effects of aminoglycosides?

A

Ototoxicity and nephrotoxicity

20
Q

Name two common organisms that cause skin infections.

A
  • Streptococcus pyogenes*
  • Staphylococcus aureus*
21
Q

How are simple skin infections treated?

A

Flucloxacillin

NOTE: unless penicillin allergic or MRSA

22
Q

How should invasive group A streptococcal infection be treated?

A
  • Aggressive and early debridement
  • Early use of antibiotics (e.g. clindamycin)
  • Use of IVIG
23
Q

What is the eagle effect?

A
  • There is a relative lack of efficacy of beta-lactams in infections with a high bacterial burden
  • This is because beta-lactams only work on dividing bacteria
  • In cases of high bacterial burden, a lot of bacteria may be in the stationary phase of the cell cycle
24
Q

List some common organisms that cause bacterial respiratory tract infections.

A
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Moraxella catarrhalis
  • Atypical: Legionella, Mycoplasma, Chlamydia
25
Q

What is used to treat:

  1. Pharyngitis
  2. CAP (mild)
  3. CAP (severe)
A
  1. Pharyngitis = Benzylpenicillin (10 days)

2. CAP (mild) = Amoxicillin

3. CAP (severe) = Co-amoxiclav and clarithromycin

26
Q

List some treatment options for hospital-acquired pneumonia.

A
  • Cephalosporins
  • Ciprofloxacin
  • Tazocin
  • If MRSA, consider adding vancomycin
27
Q

List the main pathogens that cause meningitis.

A
  • Neisseria meningitidis
  • Streptococcus pneumoniae
  • Listeria monocytogenes (in the very young, elderly and immunocompromised)
28
Q

What is the mainstay of treatment for bacterial meningitis?

A

Ceftriaxone

NOTE: consider adding amoxicillin if Listeria is likely

29
Q

How is menigitis in babies < 3 months treated?

A

Cefotaxime + amoxicillin

NOTE: ceftriaxone is NOT used in neonates because it displaces bilirubin from albumin and causes biliary sludging

30
Q

What are the treatment options for N. meningitidis meningitis?

A
  • Benzylpenicillin
  • Ceftriaxone or cefotaxime
31
Q

Outline the treatment of:

  1. Simple cystitis
  2. Hospital-acquired UTI
  3. Infected urinary catheter
A
  1. Simple cystitis - trimethoprim (3 days)
  2. Hospital-acquired UTI - cephalexin or co-amoxiclav
  3. Infected urinary catheter - change catheter under gentamicin cover
32
Q

How is C. difficile colitis treated?

A
  • Stop the offending antibiotic (usually a cephalosporin)
  • If severe, treat with metronidazole or vancomycin
33
Q

What are some important things to consider if there is no response to antibiotics within 48 hours?

A
  • Does the patient have a bacterial infection?
  • Is there a persitent focus of infection?
  • Is there a deep-seated collection that requires drainage?
  • Could the patient have bacterial endocarditis?
  • Is the dose appropriate?
  • Is there another infection present (consider Candida)?
34
Q

How should you approach lack of response after 48 hours of ABx administration?

A
  • Does the patient have a bacterial infection - collected 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)?
35
Q

What is the recommended length of course for the following infections?

  1. N. meningitidis meningitis
  2. Adult osteomyelitis
  3. Bacterial endocarditis
  4. Grp A streptococcus pharyngitis
  5. Simple cystitis
A
  1. 7 days
  2. 6 weeks
  3. 4-6 weeks
  4. 10 days
  5. 3 days
    6.

YEAR 5: Microbiology and Infection (24 decks)

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