“The Narrow Minded Microbiologist”

Let’s take the following scenario…

You isolate an E. coli from a blood culture, and it turns out to be susceptible to all the antibiotics that you have tested it against (everything from amoxycillin to meropenem).

So how many antibiotics do you (the lab) report to the clinicians for the above case?

i) One, amoxycillin (with a comment saying other susceptibilities available on request)

ii) Two or three relatively narrow spectrum agents.

iii) Several choices, including broad spectrum ones like ceftriaxone, piperacillin/tazobactam or meropenem.

iv) “The works”! i.e. everything you test against.

I suspect a good proportion of laboratories would fall into category iii !

But really I think we should all be in category i or ii…

Meropenem & co. should never get near a microbiology result report unless it is clear it is really needed.

Out of sight, out of mind…

Traditionally clinical microbiology laboratories would give as much information as possible to the clinicians (we are far too nice…), but with little regard to the potential collateral damage such a policy could cause.

Remember that clinicians may have different agendas when treating an individual patient. (Check this article out)

Things are changing. People are beginning to realise just how important a role the laboratory can play in good anti-microbial stewardship. As the discipline grows, this will become a core focus for microbiologists.

It is not just antibiotic reporting of course. The laboratory has many other important roles in the field of anti-microbial stewardship such as :

  • Creating an “antibiogram” to guide empiric antibiotic choices for guidelines.
  • Use of rapid diagnostics to expedite identification of causative organisms.
  • Use of rapid diagnostics to expedite identification of MDROs.
  • Use of suitable report comments to discourage antibiotic use when the result suggests it may not be necessary.

The microbiology result report is key in communicating the laboratory information to clinicians in such a manner that the result is interpreted the way we want it to be.

Stay narrow, stay focused…





“The Charlatan Microbiologist”

I still get a little nervous every time my work phone rings…

Will it be a question that I am unable to answer? (I get a few of these)

Will it be a complaint about a result or some aspect of laboratory policy. (I get quite a few of these as well..)

Or will it just be a standard “bread and butter” clinical enquiry where the answer is engrained in my cerebellum?

Fear of the unknown…

I am not very good at remembering the 3rd line treatment for recalcitrant giardiasis.

I am not very good at thinking on my feet, especially in a stressful situation.

and I am not very good at documenting all the clinical advice I give out.

Sometimes I feel like a bit of a fraud…

But then I remember the things I am good at.

I am good at building relationships with clinicians and gaining their trust.

I am good at turning the conversation from “result interpretation” into “patient interpretation”

I am good at diffusing complaints with a healthy dose of empathy and a bit of Irish charm.

I am good at knowing when and who to ask if I have a difficult microbiological problem.

On reflection, I am not completely useless.

Maybe we are all charlatans in some respect. We all have limits to our microbiological knowledge, our patience, our energy reserves.

And it is good to remind ourselves that it is often the non-microbiological aspects of our job that are the most important…


“The Antibiotic Free Period”

The patients who get the most courses of antibiotics are as expected, the ones who get the most infections, and these infections are often recurrent at the one site. A few examples are the elderly person who gets recurrent urinary tract infections, the toddler who gets recurrent otitis media, or the patient with chronic obstructive pulmonary disease (COPD), who gets recurrent bouts of bronchitis.

The antibiotic selection pressure on such patients is often intense, and one can often see by observing their microbiology results over time, that the infecting organisms become increasingly resistant, until multi-drug resistant organisms (MDROs) appear, and the clinician is forced to resort to less routine and more exotic antibiotics to treat the infection.

Whilst some of these “infections” will absolutely require antibiotics, many don’t, and many more were probably not bacterial infections in the first place.

What these patients really need is “An Antibiotic Free Period” . A period where the playing field is level. When MDROs have to compete against their susceptible counterparts in the absence of selection pressure, the increased fitness of the susceptible bacteria will win in the end. (This may take a while, and varies from patient to patient, and from organism to organism, but it will happen eventually.)

MDROs really don’t like level playing fields, they much prefer the odds slanted in their favour…

How can the microbiology laboratory assist in creating antibiotic free periods for patients?

Well we can add a comment to the result, for example “Uncomplicated otitis media does not routinely require antibiotic therapy” or “The isolation of pseudomonas from a patient with COPD does not imply acute infection.”, etc., etc.

or we can simply withold susceptibilities. For example an E. coli in a urine from an elderly Rest Home patient could have a comment along the lines of: “No clinical details have been provided with this sample. Asymptomatic bacteruria occurs in a significant proportion of elderly patients. If this patient has urinary symptoms, and they are continuing, please contact the laboratory for antimicrobial susceptibilities.”

It is my experience that the presence of an MDRO on a microbiology result report causes a reflex reaction from the requestor and increases the chance that the patient will be treated with antibiotics.

However the exact opposite should really apply. The threshold for treating an infection caused by an MDRO, as opposed to a susceptible one, should go up, not down.

One of the roles of microbiology laboratories, and clinical microbiologists, should be to facilitate antibiotic free periods where the opportunity arises…


There were seven new subscribers last week during the “Purple Cow Giveaway”. Rather than draw 5 from 7, I will ensure all seven new subscribers get a copy of my book. 🙂