CarbaLux Test Clox

 

 

To identify the nature of participating carbapenem hydrolyzing enzymes the supplemental CarbaLux AmpC test (Test Clox) is suitable. This assay is always carried out in connection with the Test CF and usually carried out, when the Test CF was positive, with a dark tube. As AmpC enzymes are often active in Enterobacter cloacae or Ent. aerogenes spp., both assays may be performed in parallel with these species.

The tubes contain cloxacillin, in addition to the fluorescent CF-substrate. The method consists of a selective inhibition of AmpC enzymes by cloxacillin. The protocol is that of the Test CF.

Condition of the test tubes after 120 min at 37 °C

 

Condition of the test tubes after 120 min at 37 °C
 enzyme  Test  Test Clox on AmpC
 carbapenemase opt. with participation of blaAmpC  dark  dark
 carbapenemase negative and blaAmpC hyperproduction. neg  fluorescent  fluorescent
 Carbapenemase negative and blaAmpC hyperproduction  dark  fluorescent

 

 

Metallo beta-lactamases, widespread resistance enzymes, can be recognized according to the same principle of enzyme inhibition. Bacteria containing such enzymes cannot be treated with beta-lactam antibiotics such as penicillins, cephalosporins or carbapenems. The new CarbaLux extraction agent PIC is used for this purpose. Fill each 0.1 ml into two prefabricated tubes, one with the conventional extraction buffer, the other with the PIC buffer. Transfer and suspend one full loop of bacteria into each tube. Both tests are completed in a few minutes. The result is read under the UV lamp and evaluated using the table.

 

combined result of the assays on metallo-beta-lactamases
 Tube 1 with normal CarbaLux buffer  Tube 2 with PIC buffer  Result  Application of carbapenems in therapy possible
 dark  fluorescent  metallo-beta-lactamase  no
 dark  dark  other carbapenemase(s) with or without metallo-beta-lactamase  no
 fluorescent  fluorescent  no carbapenemases  yes

 

 

 

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