Tag Archives: choosing wisely

“Choosing wisely bacteriology II: Swabs from the peri-anal area”

The Art of Microbiology, ,

There is so much scope for “choosing wisely” in general bacteriology, it is difficult to know where to start…

Peri-anal swabs are rarely of value in changing patient management. That is primarily because you are swabbing an incredibly “dirty” area in the first place. You can be sure that your peri-anal area will almost inevitably grow mixed enteric flora on culture. That is completely normal. It is no reflection on your personal hygiene!

So as a result the following swabs have very dubious microbiology value:

  • Swabs from peri-anal abscesses:- The very fact that you can swab a peri-anal abscess means that it is either self-discharging or has been intentionally incised. Either way the patient should be well on the way to recovery. And you will probably grow mixed enteric flora. On occasion, antibiotics may be indicated if there are systemic symptoms such as a fever, or there is extensive erythema surrounding the abscess. If an antibiotic is used, then it should be necessarily relatively broad spectrum, covering staphylococci, streptococci, anaerobes, and enterobacteraciae. The swab result rarely impacts on the choice of antibiotic.
  • Swabs from sacral ulcers:- This condition has the double whammy of not only being chronic, but is also in the peri-anal region. Rarely, if ever, does a superficial swab from a sacral ulcer change management. A well taken punch biopsy might…

We still accept such swabs at my laboratory, although sometimes I wonder if we are just encouraging poor practice.

Maybe we are just too nice…

We do however put a comment on all such swabs stating the following: “Superficial swabs from the peri-anal area are generally contraindicated. These swabs often grow a mixture of enteric flora, and are unhelpful in making clinical management decisions.”

I like report comments. Unlike one off educational material,  report comments offer continuous feedback to the lab user and can hopefully induce a change in culture over the long term.

Michael

“Choosing Wisely Bacteriology: Ear swabs for otitis externa”

The Science of Microbiology, ,

There is plenty of scope for choosing wisely in the microbiology laboratory. The most obvious targets are actually within infectious serology, a department now essentially in the process of being superseded by molecular methods. However there are lots of opportunities within culture based bacteriology also, with an impressive proportion of superficial swabs being of low clinical value… I will try and review some of these sample types over the next few weeks.

Otitis externa is a common condition, especially in the summer when people go and bathe in rivers and lakes and get their ear canals repeatedly wet with non-sterile water…

The microbiology laboratory receives lots of ear swabs from patients with otitis externa. But in the vast majority of cases, the swab result is absolutely meaningless in terms of managing the infection.

But it is very tempting to take an ear swab nevertheless. Who wouldn’t want to take a swab to a discharging ear!

Bacteria and fungi are usually bit part players only in otitis externa. The actual condition is a vicious circle of infection of ear debris- inflammation- swelling, blockage, leading to more infection and so the cycle goes on.

Releasing the blockage by clearing the debris, along with drying the ear canal are just as effective as antimicrobial drops, if not more so.

Most otitis externa swabs grow Pseudomonas aeruginosa or Staphylococcus aureus. A few grow Candida or Aspergillus species. Others simply grow a bacterial soup! (Our lab doesn’t report more than two organisms from an ear swab)

It actually doesn’t matter that much…

And antimicrobial susceptibilities are essentially useless as well. The treatment of otitis externa is with topical agents and it is well documented that the clinical response to topical antimicrobials is poorly correlated with their in-vitro susceptibility patterns.

Mild cases of otitis externa can often be managed with acetic acid drops alone (a drying agent with some anti-bacterial activity).

More severe cases usually get drops which often contain a bit of everything; a broad spectrum anti-bacterial, an anti-fungal, and a bit of steroid to reduce the inflammation.

So ear swabs should be reserved for recalcitrant cases of otitis externa, where the clinician is at the stage of discussing the case with an ENT specialist.

For the remainder, who cares that much what the swab grows…

From a choosing wisely perspective, how do we approach this? One option is to reject all ear swabs from otitis externa patients unless the clinical details suggested recalcitrant infection. Alternatively a comment could be added to every ear swab result saying that ear swabs are not indicated for otitis externa, except in special circumstances.

Time to act…

Michael