Monthly Archives: February 2016

“The Need for Speed”


Direct antibiotic susceptibility testing for urine samples (i.e. using the initial urine sample as the inoculum) is now fairly well established, and performed, I think, by a majority of clinical microbiology laboratories. In this way, a susceptibility report can be sent back to the requestor less than 24 hours after the sample hits the laboratory.

Direct susceptibility testing is not perfect, and you don’t need a research paper to tell you that. Common sense will tell you that if you don’t use a standardised inoculum, then occasionally you will get it wrong…

But then antibiotic susceptibility testing in general was never an exact science in the first place… (Check out this article for a bit more detail on this.)

My opinion on this is that the advantages of getting an expedited result back to the requestor far outweigh the occasional error that might occur.

With this in mind, and the advent of E-swabs, I think we should now be seriously looking at direct susceptibility testing of Staphylococcus aureus in superficial skin swabs.

I am looking at carrying out a trial setting up a Staphylococcus susceptibility plate on an inoculum taken directly from the e-swab. In this way, a Staphylococcus aureus (and MRSA) isolate could potentially be reported along with antibiotic susceptibilities in well under 24 hours.

Real time, albeit slightly imperfect microbiology….


Would be interested to know if anyone else has looked at this already.

“Pressure Control”

Controlling the volume of Multi-Drug Resistant Organisms (MDROs) within an institution is just as much about controlling the selection pressure as it is about controlling the transmission. (Don’t tell the Infection Control nurses that, but it is absolutely true!)

In my opinion the selection pressure control is actually the more important of the two. There will always be transmission despite our best efforts…

For those who are involved with antimicrobial stewardship and Infection Control, you will be aware that we are very good at monitoring our MRSA/ESBL/VRE/CRE rates etc., etc. We look at pretty graphs illustrating this every month at our committee meetings.

However we are not so good at monitoring our selection pressure. By this I mean that we should be taking 5 or 6 key broad spectrum antibiotics (e.g. meropenem, piperacillin tazobactam, tigecycline, ciprofloxacin, etc.) and monitoring objectively their usage on a month by month or quarter by quarter basis.

Most of us have guidelines on the clinical indications for the appropriate use of these key broad spectrum antibiotics. Some institutions go further and require endorsement by an Infection Specialist before their use. However very few of us actually monitor this usage in an objective fashion and then present these surveillance findings at monthly infection control/stewardship meetings.

I have come across institutions with sophisticated antimicrobial stewardship guidelines and well established anti-microbial stewardship committees. Yet the same institutions can have ITUs where more than half the patients passing through the door will get a carbapenem. An MDRO arriving in such a unit simply thinks all his birthdays have come at once, and will make himself at home in no time at all…

That is selection pressure!

If I was a CEO of a hospital that had a problem with endemic Carbapenem Resistant Enterobacteraciae (CRE), I would want to know exactly how much of each of the key broad spectrum antibiotics were being used in the hospital, and then whereabouts they were being used, by whom, and why.

For me, the antimicrobial pharmacist is one of the key members of any infection control team. You can write as many guidelines as you want, but unless you have a firm handle on exactly how much selection pressure you have in your hospital, and how that pressure is trending over time, you may find yourself sitting on an MDRO time bomb.


Do bacteria have birthdays? Not sure about that!

“The Digital Microbiologist”


We have now had the Kiestra TLA up and running for a week in our laboratory. As you can expect, the learning curve is steep and the sorting out of “teething problems” is a daily process at present.

Nevertheless one can undoubtedly see the potential, both in the short and long term.

One aspect of the system amongst many that I particularly like is the digital images of the agar plates.

These are advantageous for the following reasons:

  • Enhanced signout process: Whilst authorising a result one can not only check the request form, but also digital images of the agar plates, with all the attached audit trails.
  • Long term storage of plate images: Real agar plates dry up and need to be thrown away after a week or so. Digital images can be stored for as long as you need them.
  • Remote work-up: Theoretically both plate reading and review could occur outwith the laboratory. We have not attempted this yet but the potential is certainly there and I am sure will be utilised eventually. Plates on the “smart incubators” that become ready for reading in the middle of the night could be read immediately by dayshift people in a partner laboratory on the other side of the world!

It would be nice to have digital imaging of the Gram stains also and I am sure this will come in the near future.

Once you have become a digital microbiologist, I suspect it would be very difficult to go back to the way things were done before…