Antimicrobial Susceptibility Reporting from Microbiology Laboratory - changes from 14 March 2023
Antimicrobial prescribing: NHS Borders
Changes to antimicrobial susceptibility reporting from microbiology laboratory from 14th March 2023
Reporting of antimicrobial susceptibility testing results is changing in line with new European (EUCAST) recommendations. Higher dosing regimens are required when using particular antibiotics for particular micro-organisms
Antibiotic susceptibility will often be reported as I as well as the more familiar S and R.
Antibiotics reported as I are effective treatment options when given at higher dose and should not be avoided.
The new definitions of these are listed below
|
S |
Susceptible at standard dose |
|
I |
Susceptible, at Increased exposure/increased dose |
|
R |
Resistant even with increased exposure/dose |
Many reports will be unchanged, but below are the micro-organisms you are more likely to see I reported or a comment indicating high dose should be used.
|
Organism |
Agents affected |
|
Pseudomonas aeruginosa |
Piperacillin-tazobactam Ceftazidime Ciprofloxacin |
|
Haemophilus influenzae |
Oral (not IV) amoxicillin Oral (not IV) co-amoxiclav |
|
Streptococcus sp |
Levofloxacin |
- Please see table below for full list of antimicrobials and doses recommended in adults if reported as I.
- For paediatrics please refer to pharmacy or microbiology.
- For dosing advice in extremes of weight please discuss with Clinical Pharmacist/ Antimicrobial Pharmacist.
- Refer to the https://bnf.nice.org.uk/ and medicines.org.uk for advice on dosing in renal or hepatic impairment but taking into account the higher dose required to treat these organisms effectively. If in doubt discuss with Clinical Pharmacist/ Antimicrobial Pharmacist.
- In certain situations (eg endocarditis), increased doses are recommended even if the antimicrobial is reported as “Susceptible at standard dose” (S). These cases should be discussed with a Microbiologist.
- Dosing recommendations below should only be used when reviewing antimicrobial susceptibility results and do not replace referring to the Empirical Antibiotic Therapy Infection Management Guidelines.
|
Drug |
Dose recommended for adults with normal renal/hepatic function where antibiotic reported as I |
|
Amoxicillin Oral |
1g 8 hourly |
|
Amoxicillin IV |
2g 4 hourly |
|
Aztreonam IV |
2g 6 hourly |
|
Benzylpenicillin IV |
Up to 2.4g 4 hourly Minimum doses required according to source and MIC will be specified on reports |
|
Cefuroxime IV |
1.5 g 8 hourly |
|
Ceftazidime IV |
2 g 8 hourly |
|
Ceftriaxone IV |
2g 12 hourly or 4g daily |
|
Ciprofloxacin IV |
400mg 8 hourly |
|
Ciprofloxacin Oral |
750mg 12 hourly |
|
Clarithromycin |
500mg 12 hourly |
|
Clindamycin Oral/IV |
Discuss with microbiologist |
|
Co-amoxiclav Oral |
Co-amoxiclav 625mg 8 hourly + Amoxicillin 500mg 8 hourly |
|
Co-trimoxazole IV/Oral |
1440mg 12 hourly excludes UTI: 960mg 12 hourly |
|
Doxycycline Oral |
200mg daily |
|
Fluconazole IV/oral |
800mg daily |
|
Levofloxacin IV/oral |
500mg 12 hourly |
|
Meropenem IV |
2g 8 hourly |
|
Piperacillin 4g/tazobactam 500mg IV |
4.5g 6 hourly 4 hour infusion with loading dose recommended in critical illness Click here for details |
|
Temocillin IV |
2 g 8 hourly |