Enterobacteriaceae is a large family of small gram negative rods, non- spore
forming and some genera are motile by peritrichous flagella except Tatumella,
Shigella and Klebsiella species which are non motile. They are facultative anaerobic and mostly grow well at 37 °C. Enterobacteriaceae
acquired their nomenclature according to biochemical and antigenic

Recently, the application of new molecular technologies has resulted in many
changes in classification of the Enterobacteriaceae. (5) Members of the
Enterobacteriaceae are the common commensal flora of the gastrointestinal tract
of humans and animals and also can be found in soil, water, and plants (5,6). The family of Enterobacteriaceae has 53 genera (and over
170 species), which include Escherichia, Klebsiella, Proteus,
Enterobacter, Citrobacter, Serratia,
Salmonella, Shigella and others. It is known that only 26 of these genres are associated with various infections in humans including urinary tract infections (UTIs),
septicemia, wound infections, GI tract infections, meningitis, pneumonia and
abscesses. They are one of the
most common causes of
nosocomial infections (5,7). Moreover, members of
this family represent 80% of clinically significant isolates of
gram-negative bacilli and account for 50% of clinically significant bacteria in
clinical microbiology laboratories.(7)  



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