Lakhasly

using sequences of single-copy housekeeping gene regions, which are used in multilocus sequence analysis in the ab- sence of sufficient available whole genome sequences.In ad- dition, a deoxyribonucleic acid (DNA)-DNA hybridization cut-off of 70% or greater for species identification and an average nucleotide identity of 95% or greater has also been used for speciation within the Enterobacteriaceae.Furthermore, except for Shigella dysenteriae type 1, all commonly isolated Enterobacteriaceae are catalase positive.Epidemiology Enterobacteriaceae inhabit a wide variety of niches

using sequences of single-copy housekeeping gene regions,
which are used in multilocus sequence analysis in the ab-
sence of sufficient available whole genome sequences. In ad-
dition, a deoxyribonucleic acid (DNA)–DNA hybridization
cut-off of 70% or greater for species identification and an
average nucleotide identity of 95% or greater has also been
used for speciation within the Enterobacteriaceae. These new
methods in combination with phenotypic characteristics
represent the reason for changes in the classification and
nomenclature used in this chapter. In general, the Entero-
bacteriaceae consist of a diverse group of gram-negative
bacilli or coccobacilli; they are non–spore forming, facul-
tative anaerobes capable of fermenting glucose; they are
oxidase negative (except for Plesiomonas sp.); and, with
rare exception (Photorhabdus and Xenorhabdus spp.), they
reduce nitrates to nitrites. Furthermore, except for Shigella
dysenteriae type 1, all commonly isolated Enterobacteriaceae
are catalase positive.
Epidemiology
Enterobacteriaceae inhabit a wide variety of niches