Selective enrichment medium for carbapenem-resistant bacteria

Abstract

The present invention relates to a method for direct detection and differentiation of carbapenem-resistant bacteria in a sample comprising (i) inoculation with said sample of a culture medium comprising at least meropenem and/or ertapenem and at least one chromogenic agent, (ii) incubation of said culture medium under conditions allowing the growth of carbapenem-resistant bacteria, and (iii) detection of colonies formed on said culture medium corresponding to a carbapenem-resistant bacteria, as well as a culture medium suitable for use in such a method.

1 . Method for direct detection of carbapenem-resistant bacteria in a sample comprising the following successive steps:
 a) Inoculation with said sample of a culture medium comprising at least meropenem and/or ertapenem and at least one chromogenic agent,   b) Incubation of said culture medium under conditions allowing the growth of carbapenem-resistant bacteria, and   c) Detection of colonies formed on said culture medium corresponding to carbapenem-resistant bacteria.   
     
     
         2 . Method according to  claim 1 , characterised in that the carbapenem-resistant bacteria are selected from the group consisting of the following genera:  Pseudomonas, Burkholderia, Acinetobacter, Proteus, Serratia, Enterobacter , et  Klebsiella  et  Escherischia.    
     
     
         3 . Method according to  claim 1 , characterised in that said bacteria are bacteria containing a gene coding for a beta-lactamase which hydrolyses carbapenems of the KPC Family ( Klebsiella pneumoniae  carbapenase). 
     
     
         4 . Method according to  claim 1 , characterised in that said method does not include a preliminary isolation step of the different bacterial strains present in a sample. 
     
     
         5 . Method according to  claim 1 , characterised in that said chromogenic agent is sensitive to the activity of at least one enzyme selected in the group consisting of β-D-glucuronidase, β-galactosidase, β-D-glucosidase and a deaminase. 
     
     
         6 . Method according to  claim 1 , characterised in that the chromophore released by enzymatic hydrolysis of the chromogenic agent is chosen from among O-nitrophenyl, P-nitrophenyl, ChloroNitrophenyl, Hydroxyphenyl, Nitroanilide, Phenolphthalein, Thymophthalein, Hydroxyquinoline, Cyclohexenoesculetine, Dihydroxyflavone, Catechol, Resazurin, Resofurin, VBzTM, VLM, VLPr, VQM, Indoxyl, 5-bromo-4-chloro-3-indoxyl, 5-bromo-6-chloro-3-indoxyl, 6-chloro-3-indoxyl, 6-fluoro-3-indoxyl, 5-lodo-3-indoxyl and N-Methylindoxyl. 
     
     
         7 . Method according to  claim 1 , characterised in that said culture medium is an agar culture medium. 
     
     
         8 . Method according to  claim 1 , characterised in that said culture medium contains meropenem at a concentration between 0.25 and 2 mg/L, preferably between 0.3 and 1 mg/L. 
     
     
         9 . Method according to  claim 1 , characterised in that said culture medium contains ertapenem at a concentration between 0.5 and 2 mg/L, preferably between 0.9 and 1.2 mg/L. 
     
     
         10 . Culture medium suitable for use in a detection method as defined in  claim 1 . 
     
     
         11 . Culture medium according to  claim 10 , characterised in that the culture medium is an agar culture medium.