Correlation study between the identification carried out with API galleries and MALDI-TOF technique of bacteria isolated from the digestive content of fish from the RASPA project

Abstract

Introduction: Correct bacterial identification is crucial in various fields such as medicine, microbiology and food industry, and there are different techniques that can be employed for this purpose. In this study we compare the identification results using two different techniques: the traditional API (Analytical Profile Index) technique and matrix-assisted laser desorption ionisation/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), highlighting the advantages and disadvantages of each and assessing the health significance of the isolates. Material and methods: The 47 strains used in this work were obtained from the digestive contents of fish from the Macaronesian Atlantic Network for the Sanitary Surveillance of Fishery and Aquaculture Products (RASPA) project. These were previously identified using the API technique and stored in the laboratory of the Infectious Diseases Unit of the Faculty of Veterinary Medicine of the ULPGC. After thawing, the reactivation process was carried out and complementary tests were performed with specific culture media and biochemical tests to confirm their correct recovery and, finally, the strains were identified using MALDITOF MS. The correlation between both identification methods was classified as species, genus or non-correlation (failed identification). Results: The MALDI-TOF technique showed a high correlation with the API technique, with 72.34% agreement in genus and species, highlighting the high accuracy in the identification of Enterobacter cloacae. The correlation values obtained were 14.89% in genus and 12.76% of failed identifications. The high reliability of the API technique and the speed and accuracy of MALDI-TOF MS are highlighted. Finally, the isolated bacteria could represent a health risk.