“When the patient and the microbiology lab don’t agree”

I am signing out blood culture results. A patient has an E. coli resistant to amoxycillin clavulanate (augmentin) in both their blood culture and urine specimen. I ring up the patient’s doctor to see how the patient is doing. The patient is currently on augmentin but is nevertheless feeling much better, has been switched to oral augmentin and is ready to be discharged home. Hmm… What should I do? Should I change the antibiotic or am I just treating myself rather than the patient…?

Or the patient who develops a post-operative wound infection and they get treated empirically with flucloxacillin, to which they “respond” well, becoming afebrile and the wound discharge dries up. A swab of the wound then grows an MRSA. Should they complete their course of flucloxacillin or should they switch to an antibiotic to which the MRSA is susceptible to?

The joys of being a clinical microbiologist!

These scenarios have a few possible explanations:

  • Some patients will get better from infections, even bacteraemias and septicaemias, whatever you have used to treat them. Not all patients who contracted infections in the pre-antibiotic era succumbed to them.
  • Just because an antibiotic has tested resistant in the lab does not mean there will be no clinical response. Lots of other factors come into play here, e.g. dosage and pharmacokinetics, penetration into site of infection, host immunity, etc.
  • The isolated pathogen is not actually the cause of infection.

Clinical microbiologists are often left in a difficult situation here. Do they listen to the laboratory telling them that the isolate is resistant to an antibiotic, or do they listen to the clinician telling them that the patient is better. And what happens if they listen to the clinician and then the patient takes a turn for the worse…

It is almost a no-win situation. Is it any wonder that older, more experienced clinical microbiologists like myself end up becoming slightly insane!

These scenarios, or something similar happens to me every few weeks. It is not often discussed how to approach this situation, and it is probably glossed over somewhat in clinical microbiologist training. I was certainly never trained how to deal with it. In fact it could even be regarded as something of a taboo subject…

I think the answer lies in a case by case approach, taking into account the type of infection, the pathogenicity of the organism, the degree of resistance to the antibiotic, the reserves of the patient and how unwell they were on presentation, and a multitude of other factors that cannot possibly be learned from a textbook.

There is a lot of science in microbiology, but sometimes experience, intuition and common sense count even more than knowledge. Antimicrobial susceptibility results are important, but they are not the whole story by any stretch of the imagination.

Michael

Apologies for the paucity of posts recently, a combination of busyness and laziness!

 

One thought on ““When the patient and the microbiology lab don’t agree”

  1. Couldn’t agree more on your thoughts: “It is not often discussed how to approach this situation” & “… never trained how to deal with it”.

    I think in the future such confusing results will be resolved by the interconnection of the lab LIMS and the hospital electronic charts by some sort of AI.

    A similar issue arises with PCR tests that are common now. A weak result may signal an emerging infection, remnant NA from a resolved infection or just noise. Had a case of Flu B in a child. Two weeks later swabs were taken for another respiratory episode. Trace Flu B RNA was still present (along with another virus) and reported (no quantity assessments are made due to institution policy). The lab report infuriated the clinician claiming a lab error was made.

    Kind regards,
    Matjaz

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