Disk diffusion test is still a valid technique. It is described in details in both Guidelines used in Europe - BSAC and EUCAST. In general,   it would not be recommended for  anaerobic bacteria and fungi.

I recently hear that from a professor, but I was not sure about that. Have seen significant publication of researchs of epidemiology of antimicrobial resistance in which authors used disk diffusion? 

Thanks.

Good day

You can use the disk diffusion test especially for screening because it is much cheaper than the MIC test. The disc diffusion test is used in many pathological labs to determine the antimicrobial sensitivity of clinical isolates. In research we have used it to test a variety of solutions used in dentistry as well as for initial screening of plant extracts for antimicrobial activity.

P D Brandt, FS Botha & F A de Wet Antibacterial Properties of Five Bonding Agents SADJ September 2008, Vol 63 no 8 p448 - p451

PJ van der Vyver, FS Botha, D Herbst & M. Ismail Antimicrobial Efficacy and Irrigating Potential of Irrigation Solutions using Different Activation Methods: SADJ, March 2009, Vol 64 no 2 p56 - p62

I just retired as a director of a Reference Clinical Microbiology lab which served many of the area hospitals for over 30 years. We exclusively used disc diffusion or the etest which determines MIC on solid media. You must keep up with the NCCLS guidelines which they issue every year but it is often preferable for fastidious organisms which may not grow well in broth media.

Thanks Donald and Francien.

I completely agree abobe comments. Disk diffusion is widely and universally ised in the UK and is cheap, cost effective and reasonably reliable.

Disc diffusion is an old standard technique of antimicrobial assay.  The method is still been used and well recognized. It is very cheap and well used in the UK, USA, and many African countries. The method exclusively used on solid media when  determining the MIC of  antimicrobial agent, especially those that may not grow in broth medium.

Yes disk diffusion test is especially designed for screening of antimicrobial susceptible agents from plant and animal origin. The radius around the disc diffusibility and antimcirobial action, if it is lesser, then compound will be more active and has very high susceptibility to the microbes. The test is used to  determine the antimicrobial sensitivity of clinical isolates round the world.  It is highly applicable method and till the date no second alternative of Kirby Bauer test has been developed so far. 

Any of you know about a recent review article which could state the utility and still validity of disk diffusion technique?

Depends on the case, because if you want to measure the inhibition of a new drug is better to use the MIC assay. However if you are working with antibiotics of clinical use you could detect the susceptibility or the resistant of one strains against diferente antibiotics with a simple method.

But the technique is still valid.

Yes, technique is still valid. Clinical laboratory are still using it. However, CLSI proposed broth micro dilution methods are advantageous.  

Yes, however my question is oriented not to clinical application, rather to epidemiological researh of antimicrobial resistance patterns.

Thanks Lucinda. We are in a city in Colombia where no published studies have being made about antimicrobial resistance, however two hospitals collect data using DD. The discussion if would be possible to analyze the patterns during the last five years and report them in a decent international journal. I worked very long time ago in antimicrobial resistance doing that in Venezuela, and we published that kind of studies in JAC, IJAA, JC, Chemotherapy, among other good journals.

Thanks!

In clinical rutinary studies disk diffusion is still a good option or automatized dilution. For epidemiological studies I think that are better manual dilution test

Well this method still work and is valid more so to clinical application.

Well Mr. Alfonso, Disc diffusion study is a valid test in initial stage of identifying antimicrobial activity and susceptibility of microbes towards the particular antimicrobial agent. However, if the activity has to be done with accurate concentration of the antimicrobial agent, cup plate is more useful as suggested by Dr. Lucinda.

I am medical doctor, MSc, and PhD student. Thanks for the information.

well still disk diffusion method is used to check antimicrobial susceptibility but still it has some disadvantages like irregular zone of inhibition during placing your disc at required place..other method like turbidimetric and cup-plate method has found to be much better as compared to  disk diffusion...

There are serious limitations to the use of disk diffusion method.  Results may be unexpected or borderline.  In such cases another method of testing may be required or the test may need to be repeated for confirmation.

Although widely used for antimicrobial susceptibility testing, the disk diffusion method is not applicable to some organisms.  The following are examples of organisms to which disk diffusion method cannot be applied

1. Microorganisms that are fastidious, slow growing or have special growth requirements cannot be tested by disk diffusion method

2. Mycobacterial and fungal susceptibility testing requires specialised technique that are usually available only in reference laboratories

3.  Special techniques may be required to detect penicillin resistant Streptococcus pneumoniae, methicillin resistant Staphylococcus aureus, and aminoglycoside resistant Enterococcus faecalis,

In addition, disc diffusion methods may indicate in vitro susceptibility of certain agents for some organisms, despite lack of therapeutic efficacy in actual practice, e.g. Salmonella typhi susceptibility to aminoglycosides and enterococcus susceptibility to cephalosporins.

So the answer to your question is yes, except that certain antibiotics can be problematic to test with the disk diffusion method because of the specific physiochemical properties of the molecules. Vancomycin, colistin, and macrolides such as clarithromycin have higher molecular weights and therefore diffuse very slowly in agar.  The limited diffusion and poorly resolved concentration gradient around these disks result in only a few millimetres of difference in zone sizes between susceptible and resistant strains, which could result in a potentially ambiguous reading.  Results can also be influenced by the positioning of the light source on the plate. Plates are often read with use of reflected light, with the exception of linezolid, oxacillin, and vancomycin for both S. aureus and Enterococcus species. In these cases, the zones of inhibition should be measured by using transmitted light in order to ensure an accurate measurement of zone diameter. If results are unexpected or borderline, another method of testing may be required or the test repeated for confirmation.

Professor Sayed S Bukhari MD FRCPath

Disc diffusion is still acceptable, however replication of experiment is important for accuracy

Good Luck

The bioautographic and diffusion  methods (disc or well diffusion) are known as qualitative techniques since these methods will only give an idea of the presence or absence of substances with antimicrobial activity. On the other hand, dilution methods are considered as quantitative assays as they determine MIC. That means that you must perform the disc or well diffusion assay followed by determination of MIC using different methods as broth dilution method, agar dilution method or broth dilution method and disc-diffusion assay.

In my opinion, disc diffusion technique stil lthe main method wich we have to use to determine the phenotypic profil on antimicrobial susceptibility. It was able to detec some resistance and interactions between antibiotics.

I use disc  diffusion to test isolates susceptibility as well as MIC in tubes or plates. Disc  diffusion works well for epidemiological studies. If you want to know an specific amtibiotic concentration to use in any experiment as a selective marker, I recomend you to use any technique that help you to konw MIC because this way you have more precise data

We many in India Dependent of Disc diffusion methods, it serves many primary purposes in choosing the optimal antibiotic but needs few quality control as we have few facilities  and minimally trained technicians However MIC is becoming a order of the day needs more investments, and funding, and above all automation, however many upcoming Institutes are following CLSI guidelines incorporating automation,Dr.T.V,Rao MD Professor of Microbiology   

Disc diffusion methods is widely used in African countries including Tanzania. The results or acceptable and cheap method for developing contries