- The molecular relationship of 39 biochemically identified
strains of Klebsiella pneumoniae was determined by DNA-DNA
hybridization experiments. Cultures examined were isolated
from vegetables, pulp mills, drinking water and clinical
(human and animal) habitats. These organisms produced reassociation
values of 7% to 100% with ATCC 13882 K. pneumoniae
as the labeled reference indicating a high degree of heterogeneity
within the species. After dividing cultures into
three groups on the basis of hybridization values, it was
observed that isolates exhibiting low values to ATCC 13882
were most often from 'environmental' habitats in contrast to
those highly related to ATCC 13882 which were predominantly
from clinical origins. No discernable pattern was observed
for those cultures producing intermediate values to ATCC
13882, i.e., cultures were isolated from environmental and
Additional hybridization experiments were carried out
using a vegetable isolate (V-236) and K. pneumoniae biotype oxytoca (ATTC 13182) as labeled references. Values obtained
for these two organisms correlated to a high degree with the
two low hybridization groups, relative to ATCC 13882, established
above. Cultures which were highly related to V-236
exhibited low molecular relatedness (less than 40%) to ATCC
13882 while cultures highly related to ATCC 13182 exhibited
intermediate relatedness (40% to 75%). Furthermore, the
internal homogeneity of each group, ATCC 13882, ATCC 13182
and V-236, is sufficient to recommend the establishment of
three independent species within the genus Klebsiella corresponding
to each group.
Although biochemically similar, each group was found to
have phenotypically distinct reaction patterns to four tests.
These tests include indole production (I), pectin liquefaction
(Pc), fecal coliform response (FC) and growth at 10°C (10°).
The most frequent reaction pattern associated with each group
is I-, Pc-, FC+, 10°- for ATCC 13882, I+, Pc+, FC-, 100+ for
ATCC 13182 and I-, Pc-, FC-, 10°+ for V-236.
The molecular, phenotypic and environmental relationships
of these three groups is of public health significance.
This is due to the frequency with which Klebsiella exhibiting
a FC+ reaction are isolated from a clinical environment and,
in general, the molecular relationship between organisms of
the group which are FC+ and FC-. In other words, by following
the above recommendations, essentially all FC- Klebsiella would be removed from the species K. pneumoniae thereby leaving
only those organisms which are FC+ and clearly associated
with clinical environments.