Please remember that organisms need time to grow and that the general workflow for microbial culture & sensitivity is:
Specimen receipt > sample inoculated onto plates > overnight incubation > review of culture plates to assess for growth & ID of any organisms > Interim report issued with organism ID > sensitivities set-up for organism(s) + overnight incubation > review of susceptibility results > final report with sensitivities (at least 48h after receipt of specimen).
Adults
GGC Clinical Guidelines: adult infection management.
Paediatrics
NHSGGC. Empiric infection management, primary care, paediatric (227).
Antimicrobial susceptibility testing results from microbiology laboratories are reported in line with European (EUCAST) recommendations. Antibiotic susceptibility is now 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. Susceptibility definitions 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 situations you are more likely to see I reported or a comment indicating high dose should be used.
|
Organism |
Agents affected |
Comment |
|
Pseudomonas aeruginosa |
Piperacillin-tazobactam Ceftazidime Ciprofloxacin |
Please consider whether treatment is required if reported from a non-sterile site |
|
Haemophilus influenzae |
Oral (not IV) amoxicillin Oral (not IV) co-amoxiclav |
|
|
Streptococcus sp |
Levofloxacin |
High dose already in routine use |
|
E.coli |
Temocillin |
Protected antibiotic Please avoid using this agent if another can be safely used. |
Please see table overleaf for full list of antimicrobials and doses recommended in adults if reported as.
For paediatrics please refer to the NHSGGC Guideline. Isolates reported as 'I' (susceptible increased exposure) - dosing schedules for neonates and children (944).
For dosing advice in extremes of weight please discuss with Antimicrobial Pharmacist.
Refer to the https://bnf.nice.org.uk/ and www.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 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 | 1.2g 4 hourly |
| Cefuroxime IV | 1.5g 8 hourly |
| Ceftazidime IV | 2g 8 hourly |
| Ceftriaxone IV | 2g 12 hourly or 4g daily |
| Ciprofloxacin Oral | 750mg 12 hourly |
| Ciprofloxacin IV | 400mg 8 hourly |
| Co-amoxiclav Oral | Co-amoxiclav 625mg 8 hourly + amoxicillin 500mg 8 hourly |
| Cotrimoxazole Oral/IV |
1440mg 12 hourly excluding UTI where 960mg 12 hourly should be used |
| Fluconazole Oral/IV | 800mg daily |
| Levofloxacin Oral/IV | 500mg 12 hourly |
| Meropenem IV | 2g 8 hourly |
| Piperacillin 4g/tazobactam 500mg IV |
4,5g 6 hourly 3 hour infusion with loading dose recommended in critical illness. |
| Temocillin | 2g 8 hourly |
Table updated January 2026.
Dosing of topical agents is largely unaffected by this change. Refer to https://bnf.nice.org.uk/ and https://medicines.org.uk for dosing guidance.
GGC - Microbiology