“The Need for Speed”


Direct antibiotic susceptibility testing for urine samples (i.e. using the initial urine sample as the inoculum) is now fairly well established, and performed, I think, by a majority of clinical microbiology laboratories. In this way, a susceptibility report can be sent back to the requestor less than 24 hours after the sample hits the laboratory.

Direct susceptibility testing is not perfect, and you don’t need a research paper to tell you that. Common sense will tell you that if you don’t use a standardised inoculum, then occasionally you will get it wrong…

But then antibiotic susceptibility testing in general was never an exact science in the first place… (Check out this article for a bit more detail on this.)

My opinion on this is that the advantages of getting an expedited result back to the requestor far outweigh the occasional error that might occur.

With this in mind, and the advent of E-swabs, I think we should now be seriously looking at direct susceptibility testing of Staphylococcus aureus in superficial skin swabs.

I am looking at carrying out a trial setting up a Staphylococcus susceptibility plate on an inoculum taken directly from the e-swab. In this way, a Staphylococcus aureus (and MRSA) isolate could potentially be reported along with antibiotic susceptibilities in well under 24 hours.

Real time, albeit slightly imperfect microbiology….


Would be interested to know if anyone else has looked at this already.

2 thoughts on ““The Need for Speed”

  1. Michael – There are so many pitfalls with direct specimen method, especially with urine. More than 1 uropathogen, some lesser amounts of contaminants (Staph. epi., diphtheroids, etc) clouding the results. Also, unknowns contained in the urine itself that may react with the antibiotic discs, agar media. Most uropathogens grow rapidly so that standardized susceptibility tests (especially automated) as well as Id tests can be processed with results ready the same day as the direct method results. You maybe sacrifice a few hours at most, but have a more accurate, reliable, reproducible result.
    Thanks — “Old School” RON

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