Tag Archives: antibiotic prescribing

Challenging the Dogma of Empirical Antibiotics

Future of Microbiology, , ,

A lot of antibiotic treatment of infectious diseases is still “empirical” in nature. “Empirical” generally means “based on experience”, so to administer an empirical antibiotic means to give the antibiotic that is most likely to work based on previous experience with that infection.

Antibiotic treatment has traditionally been empirical because waiting for culture and susceptibility results was simply far too slow. Only a generation ago the average turnaround time for a microbiology culture test was 3 days and counting….

A lot of antibiotic treatment is still empirical in nature. If you go to your GP with a sore throat or a urinary tract infection, chances are high you will receive an empirical antibiotic. If you attend your local Sexual Health clinic with symptoms of gonorrhoea, you will likely be getting some empirical ceftriaxone long before the diagnosis is established. If you go to your local hospital with pneumonia, you will likely get a macrolide antibiotic (to cover atypical pathogens) as well as a beta-lactam.

However microbiology labs are improving all the time. We now have the potential in many areas to make empirical treatment redundant for certain infections. Check out the following examples:

  • Rapid antigen and PCR tests are now available for the laboratory diagnosis of sore throat, with a turnaround time of minutes to a few hours.
  • Bacteriology automation, such as Kiestra TLA, can reduce turnaround times for urine cultures to less than a day, and a day and a half for wound swabs. I suspect a lot of patients with straightforward UTIs and wound infections can wait that long for a result without outcomes being adversely affected.
  • Rapid PCR tests for atypical respiratory pathogens (Legionella spp., Mycoplasma pneumoniae, Chlamydia pneumoniae) can mean that macrolide coverage for community acquired pneumonia can be stopped early, or not even started.
  • Ultra-fast PCR tests for influenza can prevent any antibiotics being prescribed in patients who present with Upper Respiratory Tract Infection (URTI).
  • PCR tests with genotypic antimicrobial susceptibility information (e.g. Neisseria gonorrhoeae, Mycoplasma genitalium) can avoid the use of empirical antibiotics and selection pressure for antibiotic resistance.

Costing silos, resistance to change, and a lack of vision are amongst the main reasons that it takes so long for treatment protocols to move to “directed therapy” wherever possible.

There are still areas where empirical antibiotics will continue to be necessary. The acutely septic patient presenting to hospital is one such example. However large swathes of infections, particularly in the community setting are still managed by empirical antibiotic therapy. This is the way it always has been. However that doesn’t mean it is the way it always should be…

The next big revolution in clinical microbiology labs should be to challenge the dogma of empirical antibiotic treatment. This would be a huge step forward towards counteracting the development of antibiotic resistance.

Michael

“There is always a flipside….”

The Science of Microbiology, ,

It is fascinating to compare differences in antibiotic prescribing practices between New Zealand and the UK.

In the UK, due to high MRSA and C. difficile rates there has been a national drive to reduce/eradicate routine prescribing of cephalosporins and beta-lactam/beta lactamase inhibitor combinations. This (along with increased infection control measures) has had dramatic effects on MRSA and C. difficile rates. When I left for New Zealand in 2006, MRSA rates in the UK were up at 35% of all Staph aureus isolates. Now on my return it is down closer to 10%, much the same as in New Zealand.

However there are potential downsides to such a change. As a consequence there is much more prescribing of gentamicin for Gram negative cover. It is generally given to more patients and in longer duration. This potentially increases the risk of both ototoxicity and nephrotoxity. There is also increased prescribing of vancomycin and possibly as a consequence, Vancomycin Resistant Enterococci are more of an issue in the UK than in NZ, where they are very rare.

In terms of efficacy, beta-lactams are often thought of as the most efficacious antibiotics, so there is also a potential concern that avoidance of these antibiotics (with the exception of amoxycillin) may lead to increased numbers of clinical failures. To prove this objectively however would be incredibly difficult, if not impossible.

It is interesting that some of my antibiotic recommendations/advice given in New Zealand would be seen as ridiculous here in the UK, and vice versa…. Not wishing to look like the fool that I am,  I have learnt to adapt very quickly to the prescribing culture here!

Nevertheless it is difficult to argue with the very impressive reductions in MRSA and C.diff rates here in the UK . However there is always a flipside….

Michael