The factor which initiated the present investigation was the routine use of the blood agar
medium developed by Professor W.M. Levinthal and
used in this Unit for many years. The details of
its production are given in the Appendix, but the
important features in so far as HILB are concerned
are:(1) the use of human blood, which is much superior
to horse, ox, sheep or rabbit blood, (2) the addition of horse pancreatic digest made with the minimum possible amount of heating, (3) the use of 2%
Evans peptone (with no Lab Lemco) which has also
received the minimum amount of heating (4) the use of
{the minimum amount of agar for adequate solidity
(0.8-0.9% New Zealand, according to batch), (5) the
use of thick plates (25 ml. in a 4" Petri dish) with
the minimum amount of drying and (6) the addition of
it small amount of penicillinase to destroy traces of
penicillin which the donor may have been given
before the blood was collected.Our finding concerning the superiority of
Transfusion Service citrated blood over the blood
of other species, contrasts with the use of sheep
271
blood by Lutz et al, (1956) and by Gardner and
Dukes (1955) in their studies on similar organisms
in France and the U.S.A. respectively. Gardner
and Dukes went so far as to state that citrated
human blood was unsuitable for solid medium. It
may be that their organism, which they call Haemophilus va inalis is different from HILB, or the
medium may differ in other respects, e.g., pH,
ordinary laboratory media being near the upper
limit for growth of HILB of around pH 7.5, and
relatively small increases therefore jeopardising
the growth- promoting quality of the medium. It
seems likely at this stage of our experience of the
organism, that some unexplained failures of growth
may have been due to undetected variations in pH,
although some cases were adequately explained by
the demonstration of traces of penicillin in the
medium.Clinically, the outstanding feature of this
organism is, in our experience, its apparent ability
to cause puerperal pyrexia. Attempts to arrange
for inoculation of volunteers failed, owing to the
natural reluctance of clinicians in charge to put
at risk patients in the puerperium, so that the
evidence for its human pathogenicity is limited to
the marked association with pyrexia revealed by
comparison with control cases, 71% being the
incidence in cases of puerperal pyrexia of 99° F.
272
or over, as compared with 31 ¡, in a control group
collected at the same time. The high incidence of
positive cultures throughout the series, even in
control groups, naturally throws some doubt on the
pathogenicity of the organism and it is clear that
it does not rank with,for example, Strep. pyogenes
as a pathogen of the female genital tract. However,
one may draw a comparison here with H. influenzae,
which is a commonly occurring organism capable of
both commensal and pathogenic properties.The effects of puerperal HILB infection are
not confined entirely to mild degrees of pyrexia,
as is seen in Table 3, where, out of 12 cases with
a temperature of 100 °F. or more, 11 (92%) yielded
HILB, of which 9 were in almost pure + ++ growth.
None of these cases showed evidence of any other
possible cause of pyrexia apart from HILB. This
power to produce quite severe reactions in a
minority of cases has been confirmed by experience
since gained, and the unwillingness of the clinicians in charge of the patients to subject them to
inoculation with HILB, indicates that they have a considerable respect for its pathogenic powers.
In one case, a temperature of 103°F. has been
recorded, without any other cause found than the
isolation of HILB in +++ growth
