This test assesses the antibiotic susceptibility of a bacterial strain believed to be responsible for infection.


The antibiotic tested, if effective, to inhibit microbial growth on ke levy cultured.


They can be obtained in a few hours up to 24 hours after isolation of the strain (total duration of the examination on average 48 hours).

For each test antibiotic sensitivity is expressed in a letter of play:

– S: Sensitive;

– R: resistant;

– I: intermediate.

also sometimes used a quote in “plus” (+) and “minus” (-) 4-5 “more” then being a sign of greater sensitivity, and 4-5 “less” of resistance.

The choice is then made based on the clinical picture, infectious outbreak site and the result given by the antibiogram.


The bacterial strain is cultured in the presence of the antibiotics tested.

Is measured on agar medium diameter of the inhibition of bacterial growth around the disk containing the antibiotque.

When using a liquid medium, the reading is visual or automatic. Is carried out in   this case a geometric sequence antibiotic dilution which bacterium culture is added: thus determined the minimum inhibitory concentration; this technique long to realize, is now supplanted by the one on agar medium.

Many laboratories use it for robots that perform automatically review.

Processing If the clinical course is not satisfactory, the examination can then be completed by the study of the minimum bactericidal concentration.


B40 to B60.

Practical advice:

Even before a germ known susceptibility testing can be useful if you suspect a strength development, which is increasingly common.

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