Use of the RAPID ID 32 A system for rapid identification of Clostridium species important in food hygiene

The identification of Clostridium species using conventional biochemical reactions or commercially available miniaturized ready-to-use test kits often yields uncertain results. One of these test kits, the RAPID ID 32 A identification system for anaerobes (bioMérieux, Marcy-l'Etoile, France), is based on the evaluation of the action of preformed bacterial enzymes and allows classification to the species level within 4 h. This study intended to assess the suitability and reliability of this system for the rapid identification of Clostridium species relevant to food hygiene. For this purpose, 122 test strains of 18 different Clostridium species were examined via RAPID ID 32 A. Of these, 110 (90.2%) were correctly identified to the species level within 4 h. In addition, six strains were successfully classified after examination with supplementary biochemical reactions suggested by the manufacturer, which required an overall examination time of 72 h. The identity of five Clostridium strains could not be determined and in one case the test kit yielded a wrong species classification. Altogether, a correct identification was possible for 116 (95.1%) of the isolates, the total error rate was 4.9%. Using the RAPID ID 32 A system a great number of Clostridium species which are relevant to food hygiene and are often difficult to identify can be correctly and reliably classified within 4 h. Nevertheless, the test system has to be regarded as not yet completely satisfactory, e.g., because C. tyrobutyricum isolates were only insufficiently identified. Further improvements of the system are desirable in order to make it universally applicable in food microbiology.