I used Enterotube II several years ago and I had never problems.
Certainly, since then there are new methods that include more biochemical
tests, making your analysis tol become more reliable.
Nevertheless, if at least at the begining you are asked to work with your
referred methods, you should consider that with biochemical kits (whatever
they are, authomated or not) is impossible to get accurate results all the
time, in part due to the fact that the genes coding for such biochemical
activities may change so frequently that your isolate can give positive or
negative reaction even if literature reports the contrary for the given
species. These probabilites are considered in the final identification even
in methods such as RNA prints and Gas Cromatography Microbial identification
(by fatty acid profiles).
In most of cases, the first consideration will be to screen your target
bacteria from the rest of the bacterial community. For the Enterobacteriacea
family, the first step once you have your isolates is to confirm that they
are Glucose+ Oxidase-. If that is not the case, the bacteria may belong to
other different families but not to Enterobacteriaceae and maybe this
Negative confirmation will be enough for your purposes (such as reporting a
food or clinical specimen as Salmonella Negative).
If the isolate belongs to Enterobacteriaceae, then you inoculate an
Enterotube II (Otherwise you use the Oxiferm tube), incubate and read after
24 hrs. of incubation. For some tests you will need additional reagents such
as Kovac's .
Each test has an assigned value. By following the instructions for the
Enterotube, you will get a final5 digits number. These number is listed in
the list provided by the manufacturer. Note that most of the numbers will
gives you the probability for the genus (e.g. Salmonella enteritidis 0.8
Shigella dysenteriae 0.2)
As always, pay special attention to the isolation steps (suitable media,
careful prime isolation, etc.) which are criticals in order to recover your
bacteria, specially those injured at sublethal levels.
I hope this information will be helpful to you. If you do need anything
else, send me a mail.
Gustavo Limón
Food Microbiologist
asik at total.net
