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The Role of the Microbiology Lab in Antimicrobial Prescription

Discover the role of the microbiology lab in a stewardship programme.
Hello, Dr Jalila. Hi, Dr Faryal. Can you tell me please how the blood culture bottles are processed in the lab and how long does it take? Well, it’s quite simple. So we receive the blood culture bottles from the clinical areas. We incubate them in the convention automated system. And then we wait up to 12, 10 hours maximum. Once the clot is detected by the automated machine, the blood culture bottles are taken off from the machine, and then they are plated on the Petri dishes. And in parallel, a gram stain is also performed. The gram stain is checked by the technical staff, and the culture plates are incubated in the proper incubators for for around 12 to 16 hours of time.
And then once the growth is detected after 16 hours, again, the plates are checked, and the bacteria are identified, either, simply by laboratory– simple laboratory testing over the benches, or if needed then they are sent to the conventional bacterial identification system. The one we have is the Phoenix BD. Jalila, for how long this whole process takes? So around three days, maximum. For fastidious organisms it may reach up to five days. This is quite a long time. Are there any ways we can improve that? Oh yeah, there are new advances in the field. So the art of diagnosis for now is the MALDI-TOF, and MALDI-TOF is a new technique which rapidly identifies the bacteria within a few minutes.
So if you receive the blood culture on one day, if the next day we have a growth, the growth is detected within three to five minutes maximum. This is remarkable. Imagine how many lives one can save. But tell me, Dr. Jalila, is it expensive? Yes, in general it is expensive. The machine itself is expensive. However, the reagents and consumables are very, very cheap. But when you compare that to the cost of a patient’s stay in the hospital for infection control and isolation, the antibiotics, which are used if they are not used in the right way.
So collectively if you compare the cost versus the cost of MALDI-TOF, I think is going to be really cost effective to have MALDI-TOF in such cases. So apart from MALDI-TOF, how about the other newer medical diagnostic tests? Yes, there are a couple of molecular genomic testing, which are done on blood culture broths or on the growth of the bacteria. So these molecular markers can either identify the bacteria or also, can identify the mechanism of resistances of these bacteria. That’s very good. Identifying mechanism of resistance because that can play an important part in stewardship, as well as infection control. So the role of a laboratory in stewardship is very, very important. Yes, you are right.
So for example, if you are detecting a bacteria which is multidrug resistant, and you communicate this to the infection control and to the clinician on a rapid basis, that would definitely help the patient management and also the infection control precautions done on that patient. That’s great. So the role of a microbiology lab and antimicrobial stewardship lies in two things. The first thing is rapid identification and detection of organisms, and in that way, one can select appropriate antibiotics. And the second role is in providing the sensitivities on a rapid basis, as well. So one can do a de-escalation, which is a very important intervention or strategy in any stewardship programme.
Now there is also a role in infection control, as you said, by providing the real time information to infection control in terms of the organisms, multidrug resistant organisms. What do you think about that? Yes, what you mentioned is quite right. So communicating the multidrug resistant organisms through the infection control in the right time, that would put the whole management in its place. Thank you very much. You’re welcome. My pleasure. Thank you. Thank you.

The microbiology lab is essential to the practice of antimicrobial prescribing. The goal of a microbiologist is to promptly and accurately detect nosocomial pathogens and their antimicrobial resistance patterns.

The microbiology lab’s two main roles are as follows:

1) Optimising antimicrobial therapy/treatment of the patient

  • Diagnosis of infection or alternative
  • Antibiotic susceptibility results
  • Therapeutic drug monitoring
  • Biomarkers to guide therapy and facilitate stopping
  • Avoiding unnecessary testing
  • Assisting in correct microbiological sampling techniques and the timing thereof

2) Providing surveillance/data (monitor the impact of any AMS intervention made)

  • Descriptive epidemiology and trend analysis
  • Comparisons between institutions and geographical areas
  • Assessment of the impact of interventions

The microbiologist consultant should attend daily ICU rounds, and their role should consist of the following:

  • Aiding in the interpretation of results
  • Assisting in selecting the optimal targeted antibiotic and the correct duration
  • Providing cumulative surveillance data on resistant organisms for infection control purposes
  • Facilitating infection prevention and control practices

One of the key components of a successful ASP is effective communication with the microbiology team. Not only will this department help the patients get the correct treatment, but they are also vital to the surveillance of antibiotic resistance which will be talked about in step 2.13.

To prescribe the correct treatment for an infection, you need an accurate diagnosis. The video and text below describe how a blood culture is tested in a laboratory.

Flow diagram of blood culture testing process- first Blood culture recieved and incubated in automated system for 10-12hrs- Growth detected, culture removed and placed onto petri dish- gram staining performed- culture plates are incubated 12-16hrs - growth detected- Bacteria identified The process can take up to 3 days, which is quite a long time. This process can be shortened by using new advances and diagnostic techniques.

New Diagnostic Technologies

MALDI-ToF testing is an example of a new technique that rapidly identifies bacteria within a few minutes. It means that a blood culture sample can be tested one day after it is received (the time it takes for growth to occur).

Aside from MALDI-ToF there are other molecular diagnostic tests that can be used, they are able to identify bacteria, and some identify the mechanism of resistance of those bacteria. This can be very useful and can play an important part in AMS and infection control. If a multi-drug resistance organism is detected and reported quickly, infection control specialists and the clinician are able to respond quickly and correctly manage the patient and take the necessary precautions.

Diagnostic Stewardship

Whilst these rapid diagnostic tests are great tools for the diagnosis of infections, some care should be taken. Diagnostic Stewardship is a part of AMS and should be considered in any intervention programme.

It is important to think:

  • Right Test
  • Right Patient
  • Right Time

Cycle Schematic showing how diagnostic stewardship is part of an AMS intervention. Starting with the patient- they receive a clinical evaluation which leads to- Diagnostic stewardship involving right test, right patient, right time- leads to rapid diagnostic tests- rapid diagnostic test performed in the microbiology laboratory- results reported leads to- AMS right interpretation, right antimicrobial, right time leads to - diagnosis and treatment- for the patient

It is important to remember the impact of getting diagnostics wrong, in particular over-using them.

 Flow diagram depicting Overtesting (inappropriate use of diagnostics) =overdiagnosis (increase in false positive results) =overtreatment (increase unnecessary antimicrobial prescriptions)

Please see the additional articles in the see also section for more information on Rapid Diagnostic Technologies.

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Antimicrobial Stewardship for the Gulf, Middle East and North Africa

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