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Report of the Medical Officer of Health.
117
B. diphtheria in milk.—The presence of B. diphtheriæ in milk has been responsible for many
outbreaks of this disease in every civilised country and in this investigation the possibility of its
occurrence was kept in mind. Many epidemics are reported where epidemiological evidence pointed
strongly to a certain milk supply as the source of infection, but I have found only four instances in
which the B. diphtheriæ has been actually recovered from a suspected milk (n). In a routine examination
of 100 samples of London milk in 1901, Klein (l) states that he isolated B. diphtheriæ from an
enlarged groin gland of a guinea-pig, which had been inoculated subcutaneously with milk sediment.
This is the only instance I have found in which this bacillus had been stated to have been recovered
during routine examination of milk samples which had not been suspected from epidemiological
evidence of being infected. Hewlett (m) found bacilli morphologically resembling B. diphtheriæ in one
of twenty-six milk samples, but was unable to isolate them for confirmatory tests.
In the present investigation smears from the glands of all guinea-pigs presenting an appearance
similar to that described by Klein have been examined microscopically, but in none has any bacillus
other than the B. tuberculosis, or the B. pseudo-tuberculosis rodentium been found. On two occasions
cultures on serum were made from guinea-pigs that presented post-mortem appearances somewhat
similar to those found in animals dying after the experimental inoculation of diphtheria toxin or cultures,
but with negative results. Thus, as with B. typhosus, no evidence of the presence of B. diphtheria)
had been found in the 2,520 samples of milk examined.
Dysentery bacilli in milk.—Bacilli of the dysentery group have not, according to Weber (o), been
found in milk. The bacilli of this group are not of very common occurrence in England, so that one
would not expect to find them in milk here. No evidence of their presence has been found during this
enquiry, either in cultures from the dead guinea-pigs or by direct cultural examination of 111 milk samples.
Bacilli of the food-poisoning group.—(B. enteritidis Gaertner, B. paratyphosus, and B. aertryck).
—Klein (l), in 1901, obtained cultures of the food-poisoning group in 10 of 39 instances from guineapigs
that died after inoculation with London milk samples. Though milk has occasionally (e.g., by
Wernicke) been suspected of causing symptoms associated with the presence of bacilli of this group,
yet Uhlenhuth and Hubener (p) state that these bacilli have not yet been found in milk. Titze and
Weichel (q) have recently (1910) examined twenty different samples of Berlin milk with negative results.
Bacilli belonging to this group, and identified as B. aertryck were very frequently met with in the
early stages of this enquiry, i.e., November and December, 1909, in guinea-pigs inoculated with milk
sediment and they were occasionally found in them up to August, 1910. At first sight, this suggested
that the bacilli were inoculated with the milk, but at this time this same bacillus was very frequently
found in the guinea-pigs amongst the stock (i.e., non-inoculated animals) during an epizootic (discussed
at p. 119). Further animals that survived the epizootic were shown to be excreting the bacillus in their
fæces for some months afterwards, i.e., they were intermittent carriers of the bacillus.
These facts make it clear that the B. aertryck, found in the guinea-pigs post-mortem, was not
necessarily derived from the milk inoculated. However, in order to exclude definitely the possibility
of these bacilli having been derived from the milk an examination of cultures from 111 milk sediments
was made. In not a single instance was the bacillus found, although from artificially inoculated milk
it could be easily recovered by the method (r) adopted.
The non-lactose fermenters met with on plates inoculated from the sediments proved to be mostly
B. fæcalis alkaligenes, B. proteus or cocci.
Identification of organisms isolated from the dead guinea-pigs.—The organisms isolated fall into
the following groups:—Bacilli of the Gaertner group; B. pseudo-tuberculosis rodentium (s); lactosefermenting
organisms of several kinds; bacilli of the Proteus group; and cocci.
The bacilli of the Gaertner group and the B. pseudo-tuberculosis group are considered later (see
p. 120).
The lactose fermenting organisms found here have been compared with the tables of lactose
fermenters isolated by MacConkey (t) from milk and the faeces of man, cows and other animals and
by Orr (u) from milk, and it is found that almost all the lactose fermenters isolated during this investigation
appear in those tables. This similarity strongly suggests that the lactose fermenting bacilli
obtained in this investigation from dead guinea-pigs, and by Orr from milk, are originally derived from
faecal sources.
The bacilli belonging to this group most frequently found were:—
No. 71 (MacConkey's list, obtained mostly from faeces of man, calf and horse) 55 times.
B. coli communis 34 „
B. neapolitanus 15 „
B. grünthal 14 „
(l) Klein; Journ. of Hygiene, 1901, p. 85.
(n) Dean and Todd; Journ. of Hygiene, 1902, Vol. II., p. 194. Eyre; Brit. Med. Journ., 1899, II., p. 586.
Bowhill; Journ. of State Med., 1899, Vol. 7, p.705.
(o) Weber; Milchkunde, Berlin. 1909, p. 453.
(p) Uhlenhuth and Hubener; Central bl. f. Bakt. Abt., I., Ref. Bd. 42, 1908. Beihefl, p. 127.
(q) Titzer and Weichel. Arb. a. d. Kaiserlich, Ges. Bd. 33, p. 516.
(r) The enrichment method of incubating in dulcite-bile-salt broth for 48 hours, before plating, gave the best
results. This enrichment process was generally adopted for the examination of the sediments, but other methods
were also used, e.g., spreading on MacConkey agar plates either directly or after preliminary incubation in broth or
glucose bile-salt-broth. From the plates all bacili of the lactose non-fermenting groups (which include typhosus,
dysentery and paratyphoid bacili) were picked off and examined.
(s) This bacillus presents no resemblance to the tubercle bacillus.
(t) MacConkey; Journ. of Hygiene, 1904, p. 94.
(u) Orr; Report on contamination of milk (Yorkshire), 1908, p. 71.