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MICRO ADYA > Microbiology 3 - Antimicrobial Agents 2 > Flashcards

Microbiology 3 - Antimicrobial Agents 2 Flashcards

1
Q

What mnemonic can be used to help decide which antibiotic to use?

Other factors:

A

CHAOS
Choice depends on the:
Host charcteristics
Antimicrobial susceptibilities of the
Organism itself, as well as the
Site of infection

Other:

  • cost of drug
  • pharamcokinetics - absorption, distribution, elimination
  • spectrum- use narrow spectrum where possible
  • bactericidal>bacteriostatic
  • route of administration
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2
Q

What is the Minimum Inhibitory Concentration and Breakpoint of an antibiotic useful for?

A

Working out sensitivity
MIC > breakpoint = resistant
MIC < breakpoint = sensitive

MIC: minimum inhibitory concentration

Breakpoint: pre-determined concentration required to inhibit the growth of an organism

so if MIC < breakpoint –> organism is susceptible

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3
Q

What antibiotic should be given for gram pos cocci in clusters?

A

Flucloxacillin

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4
Q

What antibiotic should be given empirically for gram neg cocci?

A

Ceftriaxone (could be meningococcus)

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5
Q

What is the “eagle effect”?

A

Increasing the penicillin dose –> decreasing antibacterial activitity after a point

This is because:

  • penicillins are only effective when cells are dividing as they inhibit cell wall synthesis
  • when you have high bacterial load, bacteria might be in stationary phase of growth - so not susceptible to penicillins
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6
Q

How does the choice of antibiotic to treat UTI differ between community and hospital?

A

Community: nitrofurantoin/ trimethoprim
Hospital: cephalexin/ augmentin

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7
Q

What are the reasons for misusing antibiotics?

A
  1. no infection present
  2. inappropriate duration
  3. wrong drug
  4. wrong dosage
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8
Q

Common side effects of antibiotics

A

GI upset (i.e. diarrhoea)- MOST COMMON

Fever and rash (SJS)

Renal dysfunction

Acute anaphylaxis

Liver dysfunction (abnormal LFTs seen), Hepatitis

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9
Q

Which antibiotcis should not be given to children?

Which antibiotics should not be given to pregnant women?

A

Tetracyclines - because they stain teeth yellow

Trimethoprim- as it is a folate antagonist–>NTD

*tetracycline is also contraindicated in pregnancy

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10
Q

How does the infection site influence the choice of antibiotics used?

A

Factors to consider:

  • pH
  • lipid solubility
  • ability to penetrate blood brain barrier
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11
Q

Which areas of the body are hard to treat with antibiotics?

A
  1. bone- osteomyelitis
  2. brain - meningitis
  3. heart- endocarditis
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12
Q
A
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13
Q

Indications for IV antibiotics?

A
  1. Sepsis
  2. Site inaccessible - brian, heart, bone
  3. some antibiotcis not absorbed well orally - eg aminoglycosides
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14
Q

When do you switch from IV to PO antibiotics?

A

Usually when patient is stable on IV antibioitics for 48 hours

(except for deep sited infections such as meningitis)

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15
Q

Specific infection for which you use IM administration?

Is IM adinsitration advisable long term?

A

Gonorrhoea- IM ceftriaxone

Not for long term use

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16
Q

What is Type 1 pattern of activity and which antibiotics use this effect?

A

Type 1: concentration dependent

*try to maximise cMax

Drugs: aminoglycosides eg gentamicin

Administration: generally as single dose PO to maximise concentration

Risks: ototoxicity and nephrotoxicity

17
Q

What is Type II patern of activity and which drugs use it?

A

Type II: time dependent - maximise time above MIC.

MOA: given frequently (3-4 times per day). Looking into giving IV as well

Drugs:

  • penicillins
  • linezolid
  • erythromycin
  • cephalosporin
  • carbapenem
18
Q

What is Type III activity? Which drugs?

A

Both concentration dependent and time dependent : i.e. depends on AUC under MIC

**given as INFUSIONS to maximise AUC

Drugs:

  • vancomycin
  • tetracycline
  • macrolides
  • oxalozidinediones
19
Q

Which bacteria commonly cause skin infections?

Examples of skin infections

Treatment of skin infections

A

Staph

Group B strep

Examples: impetigo, cellulitis, wound infections

Treatment: flucloxacillin

*unless penicillin allergy or MRSA –> VANCOMYCIN

20
Q

INvasive skin infections caused by Group A streptococcus

Treatment?

A

GAS- strep pyogenes

Causes cellulitis and necrotizing fasciitis

Treatment:

Adjunctive use of protein synthesis inhibitors - eg clindamycin

21
Q

Most common organisms causing CAP

A
  1. Typical

Strep pneumoniae

Haemophilius influenzae

Moxarella Catharlis (only in COPD patients)

  1. Atypical - usually more severe

Mycoplasma

Chlamydia

Legionella

22
Q

Empicial antibiotic regime for CAP

A

Mild: Amoxicillin + clarithromycin

Severe: co-amoxiclav + clarithryomycin

(Clavulinic acid- cover against organisms resistant to amoxicillin)

23
Q

Organisms causing HAP

A

Most common: enterobacteracia (gram negatives) - e coli, klebsiella

Second most common: Staph Aureus

Pseudomonas

Fungi

Actinobacter Baumanii

24
Q

Empirical antibiotic regime for HAP

1) First line
2) Second line- used in ITU??

A

1) First line:

Ciprofloxacilin + vancomycin

Cipro: cover against gram negatives i.e. enterobacteraciae (most common cause of HAP)

Vancomycin: cover against gram positives i.e. MRSA

2) Second line (used in ITU)

Piptazobactam + vancomycin

Piptazobactam: provides cover against pseudomonas - 3rd most common cause of HAP

Vancomycin: cover against gram positive MRSA

25
Q

Specific antibiotic therapy for MRSA

A

Vancomycin

26
Q

Specific antibiotic therapy for pseudomonas

A

Piptazobactam/ciprofloxacin +/- gentamicin

Piptazobactam: combination of piperacillin (broad spectrum pencillin) + tazobactam (beta lactamase inhibitor)

27
Q

Common organisms causing bacterial meningitis

Treatment:

A

N. meningitidis

H. influenzae

Listeria monocytogenes

Treatment: ceftriaxone +/- amoxicillin

Indications for adding amoxicillin: >65 or pregnant women

28
Q

Treatment of bacterial meningitis in babies

A

Cefotaxime + amoxicilli

*not ceftriaxone because of risk of jaundice

29
Q

Empirical therapy for cystitis

A

Uncomplicated cystitis

first line nitrofurantoin

*not trimethoprim because of increasing resistance

30
Q

In whcih patients is nitrofurantoin not recommedned?

A

Pregnant women, especially in third trimester

31
Q

When should you take nitrofurantoin?

A

After emptying bladder because it concentrates in the bladder

32
Q

How do you treat catheter associated UTIs?

A
  • *• Remove catheter** (but give stat doses before removal of infected catheter)
  • *• Gentamicin or Amikacin** (stat 30-60 mins before the procedure)
33
Q

Treatment of pyelonephritis

A

Broad spectrum antibiotics

Co-amoxiclav + gentamicin

(or can use amikacin instead of gentamicin)

34
Q

Treatment of C difficile colitis

A

STOP the offending antibiotic (usually a cephalosporin)

If SEVERE, treat with:

PO metronidazole

If the above fails, use PO vancomycin

MICRO ADYA (22 decks)

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