Monthly Archives: April 2013

“Lumbar Puncture: Creating headaches not only for the patient…”


25 years ago, examination of cerebro-spinal fluid (CSF) was a fairly straightforward process. You got a cell count, Gram stain, protein and glucose levels. For the really complex patient you might have added a couple more tests like an Indian Ink or a TB culture.

Not any more….

There are now dozens of tests that can potentially be performed on CSF, most of them molecular, and a particular increase in viral PCR, e.g HSV, EBV, CMV, VZV, HHV6, etc. etc. The acronymical list goes on…

If you work in a clinical microbiology lab, then the chances are you will have come across one of the following scenarios:

  • A CSF sample arrives into the lab with a long list of molecular tests requested. The cell counts, protein and glucose are then completely normal on initial testing.
  • A CSF sample arrives into the lab with a long list of molecular tests requested by a doctor who is in the process of studying for post-graduate exams and wants to show off his/her expertise.
  • A CSF sample arrives into the lab with a long list of molecular tests requested. By the time some of these tests are performed, the patient has long recovered and is sitting at home watching ER with a glass of wine in hand.

CSF testing can now be fairly problematic. Cost issues, poor positive predictive value of individual tests, available CSF volume, distributing bits of CSF to different reference labs, lack of clinical details can all contribute to this headache. Not to mention that the results of these tests often have little or no direct effect on the management of the patient. 

I am convinced that there are huge numbers of molecular tests performed on CSF samples which turn out to be completely unnecessary.

Good communication between the laboratory and clinicians is obviously key, but I also believe that more and more the laboratory needs to become the gatekeeper for complex CSF testing, as opposed to being the submissive, and passive recipient of such requests.


I have added a short powerpoint on toxoplasmosis to the website

“Microbiological Efficiency is over-rated…”

We all know of colleagues who seem to be able to do twice as much work as the rest of us, in about half the time…..

However efficiency is only a very minor quality in the world of microbiology. There are other qualities that are much more important;

  • The ability to spot the unusual.
  • The ability to know when to ask for help.
  • The ability to recognise and focus on what is important and to ignore what is unimportant.
  • To be able to stop and look up more information on an interesting micro-organism.
  • To be passionate about microbiology and have the ability to inspire this passion in your colleagues.

I have come across many excellent microbiologists over the years. Some are fast workers, some slow.

In summary, everybody works at their own pace.

It is not a race, nor do we work in a factory….


Efficiency is overrated in life as well as work. Click on the article here for an interesting insight into this…

Old Wives Tales: Antibiotic Duration and its Effect on Antibiotic Resistance

As a child you may remember being told by your doctor to finish your course of antibiotics so that the bug does not become resistant…. I think such a myth still exists today, possibly to a somewhat lesser extent. In reality, a longer than necessary course of antibiotics just prolongs the selection pressure for resistant organisms to thrive and thus leads to antibiotic resistance. 

In fit healthy people, antibiotic courses for straightforward UTIs, URTIs, simple soft tissue infections etc., can often be remarkably short (if antibiotics are needed at all), and people may notice a significant improvement in their symptoms after just one or two doses.

It is also important to note that the patient’s immune system usually works in tandem with antibiotic therapy so when the pathogenic bacterial load has been reduced by the first few doses of antibiotics it makes it easier for a patient’s immune system to complete the job of controlling the infection.

The real message to get across here is that antibiotic courses should be of sufficient duration to deal with the infection but not so prolonged that it unnecessarily promotes selection of resistant bacterial strains.

For most antibiotic courses, the maximal effect usually occurs after the first couple of doses and then any further effect tails off very quickly after this. I occasionally come across patients both in the hospital and community setting where the patient has been on the same antibiotic for weeks if not months to treat a particular infection. Only very rarely is this indicated, and in my opinion should never be done without consultation with a specialist.