Enterobacterales

Background

Microbiology

• Order of Gram-negative bacilli comprising seven families
  • Enterobacteriaceae
  • Erwiniaceae
  • Pectobacteriaceae
  • Yersiniaceae
  • Hafniaceae
  • Morganellaceae
  • Budviciaceae

Identification

• Main tests include lactose fermentation, mannitol fermentation, triple sugar iron agar (TSI) for H₂S production and gas, indole test, urease test, and growth on citrate

Lactose	PPA	H2S	Mannitol	Indole	Urease	Growth on Citrate	Other Tests	Organism
+	–	–	+	+	+	+	nonmotile, methyl red –	Klebsiella oxytoca
					+/±	+	motile, methyl red +	Citrobacter koseri
					–	–		Escherichia coli
				–	+	+	TSI A/A with gas, nonmotile	Klebsiella pneumonia
					+/±	+	TSI A/A with gas, motile, arginine dihydrolase +	Enterobacter cloacae
					–	+	TSI A/A with gas, motile, arginine dihydrolase –	Klebsiella aerogenes
+/±	–	+	+	–	–/±	+	motile, methyl red +	Citrobacter freundii
±	–	+	+	+	+/±	+	motile, methyl red +	Citrobacter koseri
		–	+	±	+	–		Yersinia enterocolitica
			–	+	–	–	oxidase +	Plesiomonas shigelloides
–	+	+	–	+	+	–/±		Proteus vulgaris
				–	+	+/±		Proteus mirabilis
		±	–	–	+	–	TSI with gas	Proteus penneri
		–/±	–	+	+	–	TSI with gas	Morganella morganii
		–	+	+	+	+	TSI no gas	Providencia rettgeri
			–	+	–	+	TSI no gas	Providencia stuartii
	–	+	–	+	–	–		Edwardsiella tarda
		+/±	+	–	–	±		Salmonella species
		–	+	+	–	–		Escherichia coli (inactive)
				–	–	+	DNAse –	Hafnia species
							DNAse +	Serratia marcescens
					–	–		Shigella species (other than S. dysenteriae)
			–	–	–	–		Shigella dysenteriae