Tomato paprika was chosen for examination, because
it is a characteristic Hungarian product, and exhibits a
diverse microflora.
The selectivities ofthe BBL and X broths were
compared by inoculating the two media with the same
series oftest bacteria. Sixteen ofthe 94 E. coli strains
originating from food-poisoning cases in Hungary
(17%) caused only turbidity in both media, but no gas
production.
Among the Gram-positive and -negative bacteria only
the coliforms were able to grow and produce gas in these
broth, whereas most ofthe test bacteria produced
turbidity in BBL medium (Table 1).
Table 2 lists the logarithmic average ‘‘x’’ values for
the two media, the repeatability and comparability.
Within the framework of the nationwide round test,
the applicability ofBBL and X broths was compared,
using deep-frozen tomato paprika samples. The logarithmic values ofthe coliform counts detected by the
MPN in BBL and X broths are illustrated in Fig. 1 for
the 15 laboratories that took part in the testing. The
data generally demonstrate no significant difference in
counts between BBL and X broths.
Besides the selective isolation ofcoliforms, X broth
has another possible application: it is better than
traditional protein-containing media for investigations
ofthe protein composition ofcoliform bacteria, as the
sample preparation for the sodium dodecylsulfate–
polyacrylamide gel electrophoresis is simpler (Bernath!
and Morovjan, 1998 ! ). The low-cost medium can be
easily prepared and stored for a longer time without the
risk ofdecomposition. It is patented in Hungary: C12 N
1/20 (Hungarian Patent C12 N 1/20, 1987).
The basis ofthe selectivity ofthe medium is that
Gram-negative bacteria are able to utilize simple
inorganic nitrogen-containing substances as nitrogen