Selective culture medium and method for detecting carbapenem-resistant bacteria in a test sample
The present invention relates to a culture medium comprising a carbapenem, a carbapenemase activator and a M-type penicillin. It also relates to a method for detecting carbapenem-resistant bacteria in a test sample using said culture medium.
1. A method for detecting carbapenem-resistant bacteria in a test sample comprising the following successive steps:
a) inoculating a culture medium with said test sample, wherein said culture medium comprises a carbapenem, a M-type penicillin and a carbapenemase activator selected from the group consisting of divalent cations and mixtures thereof, and is suitable for growth of class A, B and D carbapenemase-producing bacteria; and
b) incubating said culture medium under conditions suitable for growth of carbapenem-resistant bacteria; and
c) detecting colonies formed on said culture medium, wherein detection of colonies is an indication of the presence in said test sample of at least one species of carbapenem-resistant bacteria producing a carbapenemase belonging to class A, B or D.
2. The method according to claim 1 , wherein the carbapenem is selected from the group consisting of ertapenem, biapenem, doripenem, imipenem, meropenem, tebipenem, panipenem and mixtures thereof.
3. The method according to claim 1 , wherein the carbapenem is ertapenem and the concentration of ertapenem in the culture medium is from 0.1 to 1 μg/ml.
4. The method according to claim 1 , wherein the carbapenem is doripenem and the concentration of doripenem in the culture medium is from 0.01 to 0.1 μg/ml.
5. The method according to claim 1 , wherein the carbapenemase activator is a divalent cation selected from the group consisting of zinc, magnesium, manganese and mixtures thereof.
6. The method according to claim 1 , wherein the divalent cation is zinc.
7. The method according to claim 1 , wherein the M-type penicillin is selected from the group consisting of cloxacillin, dicloxacillin, flucloxacillin, oxacillin, methicillin, nafcillin and mixtures thereof.
8. The method according to claim 1 , wherein the M-type penicillin is cloxacillin.
9. The method according claim 1 , wherein the carbapenem is ertapenem, the divalent cation is zinc, and the M-type penicillin is cloxacillin.