Monthly Archives: February 2015

“Impetigo: Where can the lab be of value?”

Impetigo is a common skin condition and we certainly still see plenty of it here in NZ. The word Impetigo comes from the Latin “Impetere” meaning “to attack”. It can be classified clinically into the more common non-bullous (vesicles then crusts) and the less common bullous types.

Non-bullous impetigo
Non-bullous impetigo





There are quite a few reasons why swabbing impetiginous lesions is of rather limited clinical value.

  • Most impetigo infections run their natural course. Treatment may shorten the duration of symptoms and reduce transmissability, but the fact remains that most infections will get better no matter what you do.
  • For mild to moderate impetigo the standard treatment should be with topical antiseptics or topical antibiotics (only the more severe end of the clinical spectrum requires oral antibiotics). Swabbing these lesions will not change this management in the vast majority of cases. In addition in-vitro susceptibility testing correlates very poorly with in-vivo response to topical antibiotics.
  • Impetigo is almost always caused by either Staphylocccus aureus or Streptococcus pyogenes (or both). Swabbing in order to confirm this fact is a little academic.
  • Clinical failure of treatment of impetigo often occurs in patients where the isolated bacteria have in-vitro susceptibility to the antibiotic used. I.e. there are other reasons for the treatment failure such as non-compliance, re-infection…
  • In a lot of cases impetigo is caused by the synergistic action of Staphylococcus aureus and Streptococcus pyogenes. Breaking this synergy often goes a long way to treating the condition. Therefore if both Staph aureus and Strep pyogenes are isolated from such a swab the treating antibiotic does not necessarily need to cover both bacteria to have an effect. (conceptually tricky to explain!)

So what impetigo lesions do you really need to swab? I would say if there is extensive impetigo which has not responded empirically to a reasonable course of a penicillinase resistant beta-lactam e.g. flucloxacillin (where compliance has been good), then swabbing is appropriate.

However I suspect this cohort must represent a tiny minority of clinical cases. Regardless of how big your laboratory is, if you are getting more than two or three skin swabs per week with clinical details saying “impetigo”, then you are probably getting too many….


Remember also the role of nasal swabbing (to look for Staph aureus colonisation) in patients with recurrent episodes of impetigo. This is totally appropriate!, but another story.

“Getting exams in perspective”

If you got an A in your most recent exam, well done, give yourself a clap on the back…

Then forget about it.

Getting top marks in academic exams means little in the real world. It does not mean you are going to be a good leader or a good manager. It doesn’t mean you are going to be innovative, nor does it mean you are going to get on with your work colleagues. It doesn’t tell your employer how you will deal with stressful situations or how much effort you will put into the job. It doesn’t even say whether you will turn up on time or take lots of sick days. Simply put it does not mean you are going to be a great microbiologist. Far from it.

Along the same lines, if you barely scraped through your last examination, don’t worry about it. It does not prevent you doing well all these things above. It does not mean you are going to be a mediocre microbiologist…

The point is that exams are a transient hurdle to be crossed, the passing of which will give you choices in your career/life. You need to play the game (give the examiners what they are looking for) to pass exams. After the hurdle is crossed, you can put yourself to the test, and that is always much more revealing……


“It’s Not Rocket Science but it Saves Lives”

We have a poster that says this above our handwashing basin in our laboratory and it’s true!

The United Nations states that “washing hands is the most cost-effective intervention for the worldwide control of disease” and yet studies have shown that up to 50% of people do NOT wash their hands after using the toilet.  Here are some interesting facts and figures based on basic hygiene:

* Between 2 and 10 million bacteria colonise our bodies between the fingertip and the elbow.  The fingertip bacterial load doubles after using the toilet.

* Touchscreen devices such as mobile phones, keyboards and tablets harbour 18 times more bacteria than toilet flush handles.  Not to mention the number of people that actually use their mobile phones while on the loo – YUCK!

* The bottoms of handbags are known for being covered in bacteria including faecal coliforms especially if they are placed on toilet floors whilst using public facilities –  a lot of these handbags are then placed or stored on kitchen worktops – hang your bag where possible.

* 80% of communicable diseases are transmitted by touch.  Touch referring to the touching of food as well as ones own mouth, eyes, ears etc. – not simply person to person contact.

* Critical hand washing times are before food preparation and before and after using the toilet.  Only 20% of people wash their hands before preparing food.

* Flushing the toilet with the lid up spreads a fine bacterial mist over an area of 6 square metres – see guys, it pays to always leave the seat down then it is easier to close the lid.

So it is very much “back to basics” with this topic but important to remember on a daily basis especially as the cold and flu season is just around the corner and washing hands has been shown to reduce the rate of sick days by more than 20% not to mention we are still in the thick of BBQ season and I am sure hand washing reduces the rates of those gastro organisms also.