Tag Archives: wound swabs

“Enteric flora happens…”

The Art of Microbiology,

Enteric flora (a mixture of bacteria of enteric origin) causes problems for clinicians and microbiologists alike.

The reporting of enteric flora from superficial swabs often triggers a prompt switch to a broad spectrum antibiotic by the clinicians, in order to cover all the possible bacterial species that one might find in enteric flora. I have seen this happen a few times over the past week, to the extent that I sometimes wonder whether this is the best way of reporting such a result…

The bacteria that are found in enteric flora hardly ever cause superficial wound infections (particularly in immunocompetent patients), and even when they do, the laboratory cannot possibly be of any help here because we don’t know which one in the cocktail is the culprit.

In addition one may see a laboratory report with a heavy growth of enteric flora along with a light growth of either Pseudomonas aeruginosa, Bacteroides fragilis, Candida albicans or Streptococcus agalactiae. However, enteric flora naturally contains these micro-organisms anyway, so no surprise there.

Just more unnecessary antibiotics for the patient…

A good proportion of swabs from the peri-anal area will grow enteric flora. This goes without saying, and only demonstrates the relative futility of such swabs…

What about sterile site cultures? When we see ‘enteric flora’ in such areas as peritoneal fluid or pleural fluid, we need to strongly suspect that faecal material has managed to get in there. For example a patient with a perforated appendix will have enteric flora cultured from their peritoneal fluid, the patient with an esophago-pleural fistula will have enteric flora in their pleural fluid.

This does not mean however that we have to start working up every different organism in the mixture (it is faeces after all!). Only if there is clearly a dominant organism, which can certainly happen after a period of time has elapsed under antibiotic pressure, should one consider ID and susceptibilities.

In summary we need to see enteric flora for what it is, and be brave enough to call it as such…

Michael

 

“Nothing lasts forever”

The Art of Microbiology, The Science of Microbiology, , ,

routine_swab_small_500x94

Take a look at the picture above. It is the traditional wound swab. It seems to have been around since the beginning of time.

But not for much longer…. Why?

These swabs are slowly but surely being replaced by swabs that are not only better, but are also adapted/designed to be placed on automated platforms.

The new swabs look something like this:

ecouvillon-milieu-transport-amies-68105-7752837

So what are the differences?

  • The transport medium is liquid. This allows a more standardised concentration of bacteria throughout the transport medium. It also allows the sample to be pipetted out (either manually or on an automated platform) onto the plates, again more standardised than taking the swab out of the gel and directly inoculating onto a plate. In addition, the liquid media allows fastidious organisms such as N. gonorrhoeae to survive for longer.
  • The swab has a screw top cap: This allows automated de-capping in a de-capping instrument.
  • The swab is the same size as a blood collection tube. This is intentional so that such swabs can be placed on automated tracks and automated inoculation platforms.
  • The swab is “flocked”. This means it is made of 1000’s of perpendicular strands of nylon or some other synthetic material. This allows better pick-up and adherence of bacteria compared to traditional cotton swabs.
"Flocked" swab
“Flocked” swab

This change to the “new” swabs may already have happened in your area or region. As automated microbiology processing platforms become increasingly common over the next few years, the trickle towards the new swabs will become a flood.

Adding this to the quality benefits of the new swabs, I would not be surprised if the traditional wound swab becomes extinct in the next 10 years or so.

Rest in peace.

Michael