Tag Archives: diagnostic stewardship

“A Smorgasbord of Microbiology”

Future of Microbiology, The Art of Microbiology, The Wandering Microbiologist,

I was fortunate enough to have attended the ECCMID conference in Barcelona a couple of weeks ago, the so-called “Glastonbury” of microbiology conferences. (it is just the drugs that are different…). In general, the conference venue wasn’t great, but the industry exhibition was very impressive, a massive well-lit hall with a true smorgasbord of microbiology tests & platforms available. There were literally hundreds of stands offering a vast array of products. Some of the stands were very flashy affairs, demonstrating fully functioning microbiology platforms. Most importantly, some were even offering free coffee!, although we all know there is no such thing as a “free lunch”. Microbiology is big business now. It can’t have been cheap to hire the floor space at ECCMID, so it must be worth their while.

Healthcare in general is becoming ever more expensive to fund. There are good reasons for this. There is so much more that we can do now than even a generation ago. Stem cell transplants, CAR-T therapy, new anti-cancer drugs, minimally invasive cardiac procedures (e.g. TAVI) to name but a few. In addition, we have a lot more elderly people. Good healthcare and its associated cost will keep a patient alive, who will then inevitably present later in life with further health issues to manage. Spending on healthcare undoubtedly improves life expectancy, but there is a ceiling on life expectancy and there is a law of diminishing returns which eventually kicks in…

With regards to microbiology, there is no difference really. There are so many more things we can offer in a microbiology lab which we could not offer even 20 years ago. Multi-plex & rapid turnaround PCRs, 16s RNA sequencing, metagenomics are a few examples. There are more antibiotics to perform susceptibilities on, and we can now perform both phenotypic and genotypic susceptibility testing. There are a lot more infectious conditions we can now effectively diagnose, usually with PCR based methods. We are also required to spend a lot more money on good quality assurance frameworks, and rightly so, it’s critically important! The landscape has changed out of all recognition in the microbiology lab. A generation ago, it was mainly culture-based bacteriology. Times have changed…

All of this means that diagnostic stewardship plays an increasingly important role in the microbiology laboratory, if we are to have any hope of limiting costs whilst providing good value to the clinicians and patients. What tests and platforms should we have in the laboratory, and which patients should we perform these tests on? Personally, I think diagnostic stewardship should be a key component and focus of the jobs of both clinical microbiologists and laboratory managers alike.

“Diagnostic Stewardship is a never-ending process…”

When wandering around the industry exhibition hall, it is easy to get caught up in the euphoria and hype; “I’ll have one of those, and I’ll take that as well”, but there is now an almost infinite array of things that a microbiology lab can have… The key is to listen to what the industry reps have to offer, and then work out what is going to give most value to your particular patient cohort. Will that 24-plex respiratory PCR improve patient management over and above the incumbent 16-plex? Will this assay which gives me susceptibility results from positive blood cultures in 2 hours instead of 6 hours decrease patient mortality? 

Diagnostic stewardship is a fascinating area. Industry presents us with all these options. It takes an effective team working together in the lab to make the right decisions.

Michael

“Do we perform too much antimicrobial susceptibility testing?”

Antimicrobial Resistance, Confessions of a Microbiologist, The Science of Microbiology, , ,

As lab workers, we like to be helpful. In general, we want to provide as good a service as possible. But sometimes I think we try a little too hard…

One of our key areas of work is antimicrobial susceptibility testing. This is our bread and butter of course. This is one thing that we can do but no one else can, and we like to show off our skills! But there are many circumstances where performing antimicrobial susceptibility testing adds little value for the patient and thus unnecessarily uses up valuable laboratory resources.

Polymicrobial cultures The clinical value of antimicrobial susceptibility testing is inversely proportional to the number of different organism types present in the sample. This includes sterile site samples. Many times in my career I have been asked to do susceptibilities on samples which have grown several different organisms. I almost always push back on this. It should very much be the exception as opposed to the norm.

Eye and Ear Swabs Conjunctivitis and otitis externa are primarily managed by topical preparations, which can even be antiseptics as opposed to antibiotics. In-vitro susceptibility testing correlates poorly with response to topical antibiotics. Antimicrobial susceptibility testing on ear and eye swabs should only happen in a small minority of cases.

Enterobacteriaceae, enterococci & pseudomonas in superficial wound swabs These organisms cause infection in only a very small proportion of samples that they are actually found in. Susceptibilities should only be performed when there is compelling evidence from the clinical details that they are causing problems. 

Enterococci in urines In contrast to wounds, enterococci commonly cause urinary tract infections (they can also represent contamination). However, because amoxycillin achieves concentrations in urine which exceed the MICs of most Enterococcus faecalis and Enterococcus faecium isolates (check out this reference), susceptibility testing is essentially futile, unless the clinical details suggest the patient has a penicillin allergy. A simple comment to this effect will suffice.

Beta-haemolytic streptococci Because beta-haemolytic streptococci are inherently susceptible to beta-lactams, susceptibility testing for these antibiotics is somewhat academic in the majority of simple wound/soft tissue infections.  I would do if the clinical details suggested penicillin allergy.

Anaerobes Anaerobes rarely require formal susceptibility testing. Bacteroides fragilis has predictable response to beta-lactam/beta-lactamase inhibitor combinations. and is often part of a polymicrobial infection anyway (see polymicrobial cultures). In our lab anaerobic susceptibility testing is most often performed for C. acnes causing joint infections, where we test penicillin (almost always susceptible, maybe we don’t need to test…) and clindamycin (very occasionally resistant).

Coagulase negative staphylococci from blood cultures Again these should only be performed when it is clear that the coagulase negative staph is the suspected pathogen (prosthetic material, premature neonates, etc.) which will only be the small majority of the total number of isolates.

Pseudomonas in sputa Once a patient with COPD becomes colonised with Pseudomonas aeruginosa in their sputum, it is generally there to stay. Pseudomonas susceptibility testing should only be done when it is clear from the clinical details that it is causing a problem, i.e. the patient is failing standard management. We also need to review susceptibility testing protocols on pseudomonas isolates from patients with bronchiectasis and cystic fibrosis. There is now increasing evidence that annual susceptibility testing on Pseudomonas isolates from Cystic Fibrosis patients is more than sufficient.

Candida from vaginal swabs It’s not just bacteria! Recurrent vaginal candidiasis is a common problem, and we are often asked to perform antifungal susceptibilities on such isolates. In my opinion it is hardly ever justified. Nystatin based topical therapy often works in these patients. Candida albicans isolates are usually susceptible to generous dosing of azoles. It is only Nakaseomyces glabrata (formerly known as Candida glabrata), where I occasionally acquiesce and perform susceptibility testing…

Of course, we can perform antimicrobial susceptibility testing but not report the results, having them stored just in case. But my view is that we should minimise this approach as it is generally wasteful. We should perform antimicrobial susceptibility testing when we are confident that we are going to report the results of at least some of the antibiotics from a testing panel.

At my lab we have progressed a lot in this area over the past decade and now perform minimal amounts of antimicrobial susceptibility testing in all of the areas above. What about your own lab? Is there room for improvement, and can you think of other areas where too much antimicrobial susceptibility testing is performed, that I have not thought of?

Michael

“A simple approach to uncomplicated UTI”

Confessions of a Microbiologist, The Art of Microbiology, , ,

We have a “no clinical details-no test” policy at my lab, so in general, we get accompanying clinical details with the vast majority of samples received for microbiology testing. After all, at the end of the day, clinicians just want their requests processed…

This is great, but it always irritates me slightly when we get a urine sample into the laboratory from a young adult female with symptoms of a straightforward cystitis with no supporting clinical information to suggest that a “complicated UTI” is being queried.

My first reaction when seeing this is “Why are you sending this urine sample to the lab? Do you think this is going to help your patient?”

In New Zealand, and I suspect most of the rest of the world, uncomplicated UTIs are treated empirically according to local antibiograms, usually with a short course of nitrofurantoin or trimethoprim. In most cases, this settles things down, and no further medical input is required.

We receive approximately 400 urine samples for microbiology processing into our lab each day. My rough estimate is that 5-10% of these urines have clinical details that suggest an uncomplicated UTI. It doesn’t sound much, but it certainly adds up over the course of a year, and the total cost of processing all these would likely cover a scientist’s salary.

...And if we received urine cultures into the lab on every uncomplicated UTI diagnosis, then we would be completely overwhelmed!

During the early stages of the COVID pandemic, when we were getting hammered by SARS-CoV-2 PCR requests, we urged clinicians to send us critical samples only. This certainly reduced the number of requests where the clinical details suggested uncomplicated UTI. But old habits die hard, and now we are more or less back to baseline.

I have often wondered whether we should only accept urines where the clinical details are suggestive of a complicated UTI, but we have not gone there yet. Some might wonder if such an approach is too “hardline”, but it remains an option and I think a very reasonable one at that.

People sometimes think diagnostic stewardship is all about optimising the use of very expensive laboratory tests, e.g multiplex PCR assays, but in actual fact, looking after less costly but higher volume tests such as urine culture is every bit as important…

Michael