APPLIED MICROBIOLOGY, Aug. 1969, p. 207-213
Copyright © 1969American Society for Microbiology
Vol. 18, No. 2
Printed in U.S.A.
Effi.iency of a Multitest System (Enterotube) for
RapidIdentification of Enterobacteriaceae
E. GRUNBERG, E. TITSWORTH, G. BESKID, R. CLEELAND, JR., AND W. F. DELORENZO
Department ofChemotherapy, Hoffmann-La Roche, Inc., Nutley, New Jersey 07110
Received for publication 6 June 1969
Enterotube, a multiple-test system which combines nine biochemical tests useful in
the identification ofmembers of the family Enterobacteriaceae, was tested and com-
pared with the PathoTec test system in the identification of gram-negative bacilli
isc ated from clinical specimens. It was found that both the Enterotube and the
PathoTec systems rapidly and accurately defined the position of the organisms in the
mnujor groups of thefamily Enterobacteriaceae. Discrepancies were noted between the
results of citrate tests on Simmons' citrate-agar and in the Enterotube, as well as
between Simmons' citrate-agar and the PathoTec citrate test. It was concluded that
theEnterotube system provides a simple, reliable, and rapid method for the pre-
sumptive identification of Enterobacteriaceae. The major advantage of the Entero-
tube is that all tests are done simultaneously by inoculation from a single isolated
Rapid idsntification of gram-negative bacilli of
the family j nterobacteriaceae isolated from clini-
cal specim ns has long posed a problem for the
clinical laboratory. "The group to which an
organism belongs must be determined by a com-
bination of biochemical tests, not by a single
property" [e.g., lactose fermentation (4)]. Various
schema based on selected biochemical tests have
been advocated to simplify the identification of
Ewing (4) list eight biochemical reactions which
serve to separate members of the family into
Salmonella -Arizona - Citrobacter
Proteus-Providencia (Proteus inconstans). Seven-
teen additional tests for further categorizing the
organisms are listed by these authors. Isenberg
and Berkman (7) recommend a battery of 12
biochemical reactions which characterize
broad subdivisions within the Enterobacteriaceae.
It is evident that the preparation of 12 to 25
individual cultures is costly not only in terms of
time but also in terms of media preparation and
(11) devised an enrichment
broth which permits rapid detection of lactose
and sucrose fermentation, indole production, and
medium which, when used with carbohydrate-
system for the detection of carbohydrate fermen-
tationand hydrogen sulfide formation.
The use of the PathoTec test reagent-impreg-
nated paper strips (General Diagnostics Div.,
N.J.) for the determination ofcertain biochemical
tests-cytochrome oxidase, phenylalanine deami-
nase, urease, and lysine decarboxylase activity,
production (Voges-Proskauer test)-has been
reported (1, 6, 10). The test-paper strips eliminate
the need for special media and can be stored
indefinitely. However, since a heavy growth of
the organism is needed for the performance of
the tests, a 24-hr pure culture, preferably on
solidmedium free ofindicators, is required.
A method which would reduce the number of
inoculations and the equipment needed to per-
form a series of biochemical tests for the identifi-
cation of Enterobacteriaceae would be of great
benefit to the diagnostic bacteriologist. Recently
a multiple-test system, Enterotube, which com-
bines in a single unit nine of the biochemical
tests most useful for the identification ofmembers
developed. This paper describes a study carried
out to test the efficiency and accuracy of the
routinely used in this laboratory.
5, 7, 8). Edwards and
in comparison with
VOL. 18, 1969
IDENTIFICATION OF El
identifying certain species of clinically important bacteria.
Curr. Therap. Res. 7:130-138.
7. Isenberg, H. D. and J. I. Berkman. 1962. Microbial diag-
nosis in a general hospital. Ann. N.Y. Acad.
8. Kauffmann, F. 1956. A simplified biochemical table of En-
9. Kovacs, N. 1928. Eine vereinfachte Methode zum Nachweis
der Indolbildung durch Bakterien. Z. Immunitatetsforsch
10. Mann, P. H., and A. L. Gandelman. 1965. An evaluation of
reagent-impregnated paper strips for use in the process of
identifying certain species of clinically important bac-
teria. H. Testing for the production of indole. Curr. Therav.
11. Sanders, A. C., J. E. Faber, Jr., and T. M. Cook. 1957. A
rapid method for the characterization of enteric pathogen
using paper discs. Appl. Microbiol. 5:36-40.
12. Yow, E. M.. and E. S. Townsend. 1953. A comparison of the
sensitivity of Pseudomonas aeruginosa to various antibi-
otics. Antibiot. Chemother. 3:709-717.