“Note this post is really only useful for people who are working/preparing to work/might work in a clinical microbiology laboratory.”

The antimicrobials that are “released”  to clinicians vary enormously from lab to lab. When I say released I mean the antibiotic susceptibilities which are available for the clinicians to view. To some extent it is dependent on what is tested in the first place.

 

Why is it important?

I think it is important to only release a limited range of antimicrobial to the clinicians for three main reasons.

i)   To ensure the patient receives the most efficacious antimicrobial.

ii)  To ensure the patient does not receive an inappropriately broad spectrum antimicrobial.

iii) To ensure the patient receives a safe antimicrobial.

 

i)To ensure the patient receives the most efficacious antimicrobial.

 

For example it is well recognized that flucloxacillin is superior to most other antimicrobials for the treatment of Staphylococcus aureus bacteraemia. Thus when a Staphylococcus aureus in a blood culture is diagnosed by the lab, I think the laboratory has a duty to only report/release flucloxacillin (if susceptible), not vancomycin, erythromycin, cotrimoxazole, ciprofloxacin etc. etc., which in my opinion are all poorer alternatives. You can be sure that when such antibiotics are reported , then occasionally they will be used…

 

For the patient who may be allergic or unable to take flucloxacillin for any reason, it is reasonable to add a comment stating “Other antimicrobial susceptibilities are available on request.”, necessitating a quick phone call to the laboratory by the clinician.

 

Such restriction channels/focuses the clinician into making the correct antimicrobial choice.

 

Reporting of penicillin for Streptococcus pneumonie and Streptococcus pyogenes are other such examples where restrictive antimicrobial reporting can be useful.

 

 

ii)To ensure the patient does not receive an inappropriately broad spectrum antibiotic.

This is particularly a problem when reporting on Gram negative enterobacteraciae. Often the organism will be susceptible to all “Gram negative”  antimicrobials including amoxicillin, but a whole list of antimicrobials including broad spectrum ones such as piperacillin/tazobactam and meropenem will be released to the clinicians. Again when these type of antimicrobials are “released”, they will occasionally be used, and thus unnecessarily increase the risk of selection of multi-drug resistant organisms (MDROs).

 

Such restriction of antimicrobial reporting I believe is very important and is a key responsibility of the microbiology laboratory. Reporting restriction rules (much like the rules for restricted prescribing of antimicrobials) can be discussed (and approved if necessary) with the antimicrobial stewardship committee.

 

 

iii)To ensure the patient receives a safe antimicrobial.

In some cases the laboratory will have clinical information available that allows it to restrict antimicrobials on the basis of safety. For example: If the patient is known to be pregnant then it may be prudent not to release antimicrobials such as trimethoprim, quinolones, nitrofurantoin etc, because these antimicrobials can be potentially detrimental during some or all of pregnancy.

 

Summary

To summarise, the lab can, and should have an influence on antimicrobial prescribing behaviours by the antimicrobials that we test and report.  Reporting 20 antimicrobials on the one isolate is neither helpful to the clinician nor the patient and should be a thing of the past…

Michael