Monthly Archives: January 2015

Nitpicking

"One world" Microbiology, History of Microbiology, The Art of Microbiology, The Science of Microbiology, ,

I’ve been doing some reading lately, mainly on the subject of World War I and it naturally brings to mind topics for this website ….. this time “lice”.

Why are we not able to eradicate parasites such as lice?  Surely if the little blighters do not have a host to live off then they die therefore minus the hosts and we shouldn’t have issues of lice, yes?

I guess it is the age old problem of compliance … there is always a host somewhere who is not willing or able to get rid of them and therefore continues to spread them to those who spend many hours and much money to de-louse their children (mainly) from these wriggly little pests.  I am referring in general to head lice which seem to be a fact of life throughout most kids journey through primary school however with the very popular “selfie” causing a surge in cases in older age groups also.  It is the sort of nuisance that if everyone cared enough to treat and eradicate then we should be able to get rid of ……

The head louse ( Pediculus humanus capitis) is essentially a harmless pest.  It is a wingless insect which spends its entire life on the head of a host feeding off small amounts of blood.  They cannot fly or jump and do not transmit disease although they can be responsible for secondary infections of the skin due to scratching.  They are simply a nuisance and one that should be able to be eliminated from our society.

Body lice (Pediculus humanus corporis and sometimes Pediculus humanus humanus), common during the Great War, are far more dangerous due to their potential to transmit  diseases such as typhus and trench fever.  The two species are physically very similar, almost indistinguishable, but do not interbreed however they have been known to under laboratory conditions.  Again a parasitic pest that should be able to be eliminated with adequate hygiene practises.

If the world can eradicate smallpox (Variola virus – declared obsolete by the WHO in 1979) then why can we not do the same with our Pediculus friends?  Just as we needed the “buy in” of people to get vaccinated against smallpox we should be able to get their “buy in” to de-louse.

“Why do we swab conjunctivae?”

The Art of Microbiology, The Science of Microbiology
Photo courtesy of Tanulai
Photo courtesy of Tanulai

Why do we bother taking conjunctival swabs?

Is it for therapeutic reasons? The patient may expect this investigation. The clinician may be acting out of habit or seeking to reassure the patient that he is doing a professional job.

Is it to discriminate between bacterial and viral conjunctivitis? I think most clinicians can do this fairly well from examination for conjunctivitis. Besides, viral conjunctivitis is self-limiting (as is most bacterial conjunctivitis)

Is it to change management?  The standard therapy for bacterial conjunctivitis in New Zealand and Australia is Chloramphenicol drops/ointment. It is a good broad spectrum antibiotic with excellent coverage against the normal pathogens of bacterial conjunctivitis. (Staph aureus, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis). Failure of this therapy is usually due to poor compliance, not given frequently enough, lack of associated eye cleansing, re-infection etc.. It is almost never due to lack of in-vitro susceptibility of the pathogen to the chloramphenicol. Low resistance rates are probably due to the fact that chloramphenicol is rarely used as  asystemic antibiotic nowadays because of the risk of marrow aplasia.

In summary I think there are a whole heap  of conjunctival swabs taken which frankly do not need to be.

For example if your laboratory receives on average of 12 conjunctival swabs a day costing approx $20 each to process. If 10 swabs are not appropriate then that is $200 a day times 365= $70,000 a year. 

The cost of unnecessary testing is not insignificant….

I think the genuine indications for conjunctival swabbing are as follows:

  • Immunocompromised patient.
  • Clinical/epidemiological suspicion of gonorrheal or chlamydial conjunctivitis.
  • Associated cellulitis of the skin around the eye.
  • Condition not resolving after regular eye cleansing and empirical topical antibiotic therapy given at sufficient frequency and for sufficient duration.

It is time for the lab to stand up and say that these are the patients that we really want conjunctival swabs from, so we can focus our time, money and efforts, and make a genuine difference to the patient….

Michael

 

“The good and bad of lab automation….”

The Science of Microbiology

A little while ago I said I would summarise the potential quality benefits of “Total Lab Automation” (TLA) systems (e.g. Kiestra, Biomeurieux, Copan Wasp). You might be involved in a business case for one for your own laboratory. Even if you are a trainee, this is the sort of stuff I would be asking in an exam question, not the nuances of the CAMP test.…

I have summarised what I think are the main advantages below. Please feel free to add any extra you can think of in the comments section.

  • Plate Tracking: Each plate has a  comprehensive electronic audit trail attached to it, including when it was inoculated, incubated, imaged and read, and by whom.
  • Less menial tasks: Gets rid of finding appropriate plates for each sample, carrying the plates to and from the incubator, “putting up” of specimens, and other repetitive, manual tasks.
  • Better plate spreading. Automated spreading performed by machine will almost always succeed in better use of the whole agar plate and improved isolation of single colonies. It will also be a standardised procedure.
  • Less plate contamination: As the plate has less manual handling and less time spent with its lid off, the risk of plate contamination is much reduced, which is very important for those “sterile site” specimens.
  • Storage of digital images of plates. Plates eventually deteriorate, images do not, and images can be stored to be viewed again at any satge in the future depending on how long you want to store them for.
  • Standardised incubation times. No matter when the plate was inoculated, the system will image the plate after a pre-set incubation time, and thus allow plate reading. This in turn will allow reduction in turnaround times for specimens. The old concept of Day 1, Day 2 etc plate reading should disappear and be replaced by 1st reading, 2nd reading….
  • Less time out of the incubator. the plate goes straight into the incubator when it is inoculated, and essentailly stays in the incubator whilst it is being examined. No hanging around and very little downtime.
  • Remote plate reading: The system should allow you to view the plate images from anywhere, including home.
  • Plate checking: As the person reading the digital image is usually different from the person doing any further work-up, it allows the plate to be checked in case something was missed initially.
  • Plate interpretation: This is still in the developmental stage but software is now available allowing rapid detection of plates with no growth, and plates with colonies of a particular colour. Further development in such software will eventually lead to massive gains in efficiency.

I am sure there are others I have not thought about off the top of my head, but it’s a start that you can add to.

Sounds like a no-brainer. However one must balance all these advantages against two main disadvantages. These disadvantages essentially apply to all forms of automation.

  • Redundancy of staff: Whether staff are made redundant or not due to the implementation of such a system, the fact is that this type of automation will get through more specimens with less staff required. Some (managers) might see this as an advantage, but from a people point of view it is a big downside.
  • What happens if it breaks down? Because of the above, and because it is a complex operation, the consequences can be severe if the system goes down for any length of time….

Michael