W3 - Antimicrobial agents 2 Flashcards
Name some (5) mis-uses of antimicrobial agents
- No infection present
- Selection of incorrect drug
- Inadequate or excessive dose
- Inappropriate duration of therapy
- Expensive agent used when cheaper is available
approx. ________ of hospitalised patients given an antimicrobial experience an adverse event. Name 5 adverse events
5%
- GI upset
- Fever & rash
- Renal dysfunction
- Acute anaphylaxis
- Hepatitis
Describe CHAOS in terms of prescribing abx
CHOICE of the correct antimicrobial depends upon the:
- HOST characteristics
- ANTIMICROBIAL susceptibilities of the
- ORGANISM itself and also the
- SITE of the infection
Name a few factors that should influence choice of abx
- Use NARROW SPECTRUM if possible
- Use BACTERICIDAL drugs if possible
- Ideally choice should be based upon a bacteriological diagnosis
- Consider local sensitivity patterns
- Patient characteristics: allergy, genetics
- Cost
- Pharmacokinetics: absorption, distribution, elimination
- Route of administration: IV for serious infection or if patient not absorbing P.O., or if needing to access deep sites/CNS
- Dosage: age, weight, renal function, hepatic function, drug monitoring
What is the minimum inhibitory concentration (MIC)?
s the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation
Name 4 ways for measuring MIC/susceptibility
- Serial dilution
- Gradient MIC strips
- Agar disc diffusion method
In terms of breakpoint tables for interpretation of MICs and zone diameters, interpret the result of the 2 values.
- MIC > breakpoint – resistant
- MIC < breakpoint – sensitive
Describe how to treat infection in patient on an empirical basis
Collect specimens prior to abx –> use broad-spectrum agent that will likely cover causative agent –> switch to more specific/narrow spectrum abx based on culture results
What evidence can be used to determine if a patient actually requires an antimicrobial?
evidence of a systemic response:
Fever?
Raised CRP?
raised wbc (neutrophils +++) or reduced wbc?
Also consider:
- Duration of symptoms
- Underlying risk factors
- Likely source of infection
- Exclude other pro-inflammatory medical disease
If decided to use an antimicrobial agent, which route of administration should be used?
i.v. - Serious (or deep-seated) infection
p. o. - Usually easy, but avoid if poor GI function or vomiting
- Different classes of antimicrobial have different oral bioavailabilities
- i.v. to p.o. switch is recommended in hospital for most infections if patient has stabilised after 48hr of IV therapy
i. m. - Not an option for long-term use
- Avoid if bleeding tendency or drug is locally irritant
Topical - Limited application and may cause local sensitisation
Skin infections (impetigo, cellulitis, wound infection) - which abx to use?
Flucloxacillin (unless penicillin allergy or MRSA)
Skin infections (impetigo, cellulitis, wound infection) - which organisms are common causative agents?
S. aureus and B-haemolytic Streptococci
What is iGAS?
invasive group A Streptococcal infections
Describe iGAS treatment
- Aggressive and early debridement
- Antibiotics – adjunctive use of protein synthesis inhibitors esp. clindamycin (also has good skin & soft tissue penetration)
- Use of IVIg
What is the Eagle Effect?
The Eagle effect describes a phenomenon in which bacteria or fungi exposed to concentrations of antibiotic higher than an optimal bactericidal concentration (OBC) have paradoxically improved levels of survival than at the OBC due to a decreased net rate of cell death
