Commonly Isolated
Enterobacteriaceae continued
Clinical Microbiology Review 184
KEY REACTIONS
ORGANISM PATHOGENICITY POSITIVE NEGATIVE OTHER
Serratia marcescens
Proteus vulgaris&
mirabilis
Morganella morganii
Providencia
Yersinia enterocolitica
UTI = urinary tract infection; RTI = respiratory tract infection; IMViC = indole, methyl red, Voges-Proskauer, citrate.
Some produce red pigment when
incubated at RT.
Swarming. Burned chocolate odor.
P. mirabilisis most common & indole
neg. P. vulgarisindole pos, A/A on
TSI because of sucrose fermentation.
P. rettgeriis urease pos.
GN coccobacilli. Bipolar staining. Op-
timal temperature 25°–30°C. Motile
at 25°C but not 35°C. CIN agar is
selective. Incubate 48 hr. Red “bull’s-
eye” colonies surrounded by colorless
halo. Y. pestiscauses plague.
Opportunistic pathogen.
Pneumonia & septicemia
in immunosuppressed
UTI, wound infections,
septicemia
Mainly nosocomial infec-
tions. UTI, wound infections.
UTI, diarrhea
Diarrhea
VP, citrate, motility
H 2 S, MR, PD, urease,
motility
Indole, MR, PD, urease
(weak), motility, ODC
Indole, MR, citrate,
PD, motility
MR, urease
Lactose, H 2 S, in-
dole, PD, urease
Lactose
Lactose, H 2 S, VP,
citrate
Lactose, H 2 S, VP
Lactose, H 2 S, VP,
citrate, PD