Tag Archives: focused antibiotic reporting

“Choices”

Antimicrobial Resistance, The Art of Microbiology,

2011-July-HI-2VitekCardsNEW

How many antibiotic susceptibilities do you release to the clinicians for any particular isolate?

At the extreme end of the scale, some microbiology laboratories think nothing of releasing 15-20 antibiotic susceptibilities for the one isolate. This sometimes happens in labs rich enough to have a Vitek or Phoenix where the system panels contain many different antibiotics, often customised for a particular institution.

However more is not always necessarily better…

The main reasons for not routinely releasing an antibiotic susceptibility on an isolate are as follows:

  • Unnecessarily broad spectrum for the clinical indication.
  • Low threshold to developing antibiotic resistance.
  • Relatively poor efficacy compared to other antibiotics for the clinical indication.
  • Logistically difficult to use.

The majority of mainstream diagnostic labs probably give a choice of 5-10 antibiotics per isolate. Even then that is still a lot of antibiotics for the clinicians to mull over. It also gives a lot of scope for non-standardised practice…

More laboratories, including my own, are looking more and more towards focused antibiotic reporting, in order to “guide” clinicians towards the optimal treatment regime.

For example we routinely release 2 antibiotics for a Staphylococcus aureus isolate from a general wound swab. (If MALDI-ToF succeeds in reliably differentiating between MSSA and MRSA, then one could potentially release flucloxacillin/cloxacillin alone, without doing formal susceptibility testing, and with a comment “Further susceptibilities available on request”)

We routinely release 4 antibiotics on urinary E.coli isolates. I am thinking of reducing this to 3.

For MSSA (Methicillin Susceptible Staphylococcus aureus) isolates from blood cultures and invasive sites we routinely release just the one antibiotic, flucloxacillin. The same principle applies with Streptococcus pneumoniae and penicillin from blood cultures. By doing this we make it crystal clear what the expected standard treatment is. Of course we have a few others ‘up our sleeve’ should they be required in the case of allergy, treatment failure etc.

And then of course it is always important to remember that we have the choice of releasing (or testing) zero antibiotics, where the clinical details are absent or they are not indicative of acute infection. We should probably use the zero option more, along with a comment saying “Antibiotic susceptibilities available on request”.

Occasionally we get calls from clinicians, a little bit upset or grumpy that we have not released more antibiotics. Being thick skinned, I don’t mind this at all. It gives me the opportunity to build relationships with the clinicians, and also to explain our thinking…

Michael

 

“Keeping a Low Profile”

Antimicrobial Resistance, The Science of Microbiology, , ,

What do tigecycline, daptomycin, ceftaroline, have in common?

They are all relatively new broad spectrum antibiotics, to which various MDROs are often susceptible. They are also manufactured and marketed by pharmaceutical companies in whose basic interest it is that we use as much of these antibiotics as possible.

However to maintain the life expectancy of these antibiotics for use against MDROs, we actually have to do the opposite, i.e. use them as little as possible. These antibiotics really should only be used when we have no other reasonable or viable choices. They should essentially be protected antibiotics, and this is often the case in anti-microbial guidelines issued by Antimicrobial Stewardship committees.

How can the laboratory assist in this objective? Can they help?

It is my belief that the laboratory is of paramount importance in protecting antibiotics like these…..

The most important thing the laboratory can do is not to test or routinely report susceptibilities to these types of antibiotics, except when they are really needed. In this way usage can be targeted and antibiotic selection pressure can be minimised.

If every Gram negative isolate in blood cultures from the laboratory was released with tigecycline susceptibilities, not only would all the general clinicians be aware of this choice, but some would find a way to prescribe it, despite good stewardship guidelines being in place. Such a practice essentially normalises the antibiotic.

Much like some of the newer chemotherapeutic drugs should remain in the domain and expertise of oncologists, the same can be said for some of the newer antimicrobials staying in the domain of Infectious Diseases physicians and Clinical Microbiologists.

Sometimes it is better not to know…… Ignorance is bliss.

Michael

“Damage Limitation…”

Confessions of a Microbiologist, The Science of Microbiology,

Bacteriology laboratories vary hugely in the number of antibiotics they release to the clinicians…

Some laboratories release up to 20 antibiotics on every reported isolate (particularly those ones with Vitek/Phoenix systems)

In contrast, some laboratories release as few antibiotics as possible to the requestors.

Personally I am very much in the latter camp. I strongly believe that it is the laboratory’s responsibility to guide the clinicians as much as possible in their antibiotic choices in order that the patient gets the most appropriate therapy and the unnecessary use of broad spectrum antibiotics is minimised.

For example:

i) A coagulase negative staphylococcus isolated from one bottle of a blood culture set: In the absence of prosthetic material or severe immunocompromise this is almost certainly going to be a contaminant. It should thus be reported as such and no antibiotics released.

ii) A Staphylococcus aureus isolated from a blood culture: Unless there is a history of allergy this should be reported with flucloxacillin alone (if it is susceptible to this). Flucloxacillin (or whatever your equivalent is (cloxacillin, dicloxacillin) is well established as the optimal treatment for Staphylococcus aureus bacteraemia. If you start releasing antibiotics such as erythromycin, ciprofloxacin etc on all such isolates you can be sure that somewhere along the line a clinician will elect to use one of these drugs. (possibly due to lack of knowledge or interest in microbiology).

iii) A Pseudomonas aeruginosa isolated from a chronic leg ulcer. In the vast majority of cases this will be colonising only. If the laboratory starts releasing ciprofloxacin (and other antibiotics) for all such isolates, then there will inevitably be a lot of inappropriate quinolone use.

iv) An amoxycillin susceptible E.coli isolate in a blood culture. Why report meropenem when it is amoxycillin susceptible?

These are only a few examples amongst many…

I strongly believe that the laboratory has a role in “focusing” the anti-microbial prescribing of clinicians. It is also important to note there will be the odd occasion where a coagulase negative staphylococcus bacteraemia does need treated, where a Staph. aureus bacteraemia does need something apart from flucloxacillin, where a pseudomonas is causing problem in a leg ulcer. In these cases the laboratory should ensure it is easily accessible to the clinician so that further antibiotics can be tested/reported.

To those laboratories that insist on reporting all antibiotics on everything, I would encourage that you review this practice. You may find that by careful and appropriate restriction of antimicrobial reporting, the clinicians (and patients) will eventually thank you for it….

Michael