Fastidious Gram-Negatives: Identification by the Vitek 2 Neisseria-Haemophilus Card and by Partial 16S rRNA Gene Sequencing Analysis

Brita Bruun,Lisbeth Nielsen,Jens Jørgen Christensen,Annemarie Hesselbjerg,Dennis Schrøder Hansen,Ute Wolff Sönksen

doi:10.2174/1874285801004010123

Abstract

Taxonomy and identification of fastidious Gram negatives are evolving and challenging. We compared identifications achieved with the Vitek 2 Neisseria-Haemophilus (NH) card and partial 16S rRNA gene sequence (526 bp stretch) analysis with identifications obtained with extensive phenotypic characterization using 100 fastidious Gram negative bacteria. Seventy-five strains represented 21 of the 26 taxa included in the Vitek 2 NH database and 25 strains represented related species not included in the database. Of the 100 strains, 31 were the type strains of the species. Vitek 2 NH identification results: 48 of 75 database strains were correctly identified, 11 strains gave `low discrimination´, seven strains were unidentified, and nine strains were misidentified. Identification of 25 non-database strains resulted in 14 strains incorrectly identified as belonging to species in the database. Partial 16S rRNA gene sequence analysis results: For 76 strains phenotypic and sequencing identifications were identical, for 23 strains the sequencing identifications were either probable or possible, and for one strain only the genus was confirmed. Thus, the Vitek 2 NH system identifies most of the commonly occurring species included in the database. Some strains of rarely occurring species and strains of non-database species closely related to database species cause problems. Partial 16S rRNA gene sequence analysis performs well, but does not always suffice, additional phenotypical characterization being useful for final identification.

Highlights

Fastidious Gram-negative bacteria comprise a number of different genera and species that may cause serious systemic infections
For the Neisseria pharyngis strain was the result of 16S rRNA gene sequence analysis in conflict with the conventional phenotypic identification, where the “gold standard” species was not among the listed taxon matches
Remarkable variations in score bit differences between strains belonging to the same species were seen for all the strains of A. segnis, C. hominis, H. parainfluenzae and K. kingae

Summary

Introduction

Fastidious Gram-negative bacteria comprise a number of different genera and species that may cause serious systemic infections. Their fastidious nature often makes identification a challenge in the routine microbiology laboratory, and their ability to cause invasive disease makes correct identification important. Their ability to cause endocarditis (HACEK group of bacteria: Haemophilus spp., Aggregatibacter spp, Cardiobacterium species, Eikenella corrodens, and Kingella kingae), animal-bite infections (e.g. Capnocytophaga spp., Neisseria weaveri, and Pasteurella spp.) and their role in abscess formation (E. corrodens, Aggregatibacter actinomycetemcomitans) illustrates their importance [1]. As far as we know, there are only two fully automated identification systems for identification of fastidious Gram negative bacteria on the market, Vitek 2 Neisseria-Haemophilus (NH)

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