15: Enterobacteria

Chapter 15 Enterobacteria

Most of the commensal Gram-negative rods that inhabit the normal gastrointestinal tract, and sometimes cause disease, belong to the family Enterobacteriaceae. All species belonging to this family are Gram-negative, facultative anaerobes that ferment glucose. The major medically important species are listed in Table 15.1.

Table 15.1 Enterobacteria commonly causing human disease

Genus Representative species (no. of species) Disease
Escherichia E. coli (5) Gastroenteritis, wound and urinary tract infection
Shigella S. dysenteriae Dysentery
S. flexneri
S. boydii
S. sonnei
Salmonella S. typhi Enteric fever (typhoid)
  S. typhimurium (7 subgroups) Food poisoning
Klebsiella K. pneumoniae (7)  
Morganella M. morganii (2) Urinary tract infection and other types of sepsis
Proteus P. mirabilis (4)
Providencia P. stuartii (5)
Yersinia Y. pestis (11) Plague, septicaemia, enteritis, etc.
Citrobacter C. freundii (4) Low pathogenicity, opportunistic infections
Enterobacter E. cloacae (13)
Serratia S. marcescens (10)

General characteristics of enterobacteria

Culture and identification

Grow well on ordinary media (e.g. blood agar, MacConkey’s agar), producing characteristic circular, convex and glistening/mucoid colonies. Some motile species form swarming patterns on agar cultures. Most species are non-pigmented; a few produce red, pink, yellow or blue pigments.

Enterobacteriaceae ferment a large number of carbohydrates. This property, together with other biochemical tests, is used to identify and differentiate species.

Jan 4, 2015 | Posted by in General Dentistry | Comments Off on 15: Enterobacteria
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