Approaches to the Identification of Aerobic Gram‐Negative Bacteria

Abstract

The description of aerobic Gram‐negative bacteria is long established, based on culture conditions and the failure to retain crystal violet‐iodine complex by Gram's staining method. This chapter shows dichotomous phenotypic and biochemical identification algorithms for Gram‐negative bacteria that are fastidious and grow poorly or not at all on sheep blood agar. The use of KIA/TSI slants as part of the workup of Gram‐negative organisms has largely been discontinued due to the introduction of matrix‐assisted laser desorption ionization‐time of flight mass spectrometry, which provides more rapid and specific identification. The major limitation of analyzing the 16S‐23S ribosomal RNA (rRNA) region for bacterial identification and community profiling is the current lack of a reference database containing combined 16S rRNA and 23S rRNA gene sequences.