R. Fuller

The importance of lactobacilli in maintaining normal microbial balance in the crop

1. The effect of lactobacilli on Escherichia coli has been examined in vitro and in chicken crop in vivo. 2. Inhibition of E. coli was dependent on the presence of sufficient numbers of lactobacilli. 3. In a standard test some lactobacilli were bacteriostatic and one was bactericidal. The bacteriostasis was due to the low pH produced by these strains but bactericidal activity could not be accounted for by pH alone. 4. In gnotobiotic animals the bactericidal strain was no more inhibitory for E. coli than was a bacteriostatic strain.

Microbial activity in the alimentary tract of birds.

Nearly all the work on the avian gut microflora has been done using the domestic chicken (Gallus domesticus). There has been some work on the turkey and quail, which have dietary habits similar to the chicken, and there are also a few reports on the pheasant, grouse and goose with respect to fibre digestion. There is virtually nothing known about the gut microflora of carnivorous birds. The greater part of this paper will, therefore, deal with information from the chicken.

Influence of dietary lactose on the gut flora of chicks.

1. The gut microflora of chicks fed on a purified diet containing 300 g lactose plus 300 g starch/kg was compared with that of control birds receiving a diet containing 600 g starch/kg. 2. In 14-d-old conventional chicks, lactose in the diet decreased the incidence of lactobacilli and clostridia in the caecal contents, although when presenting lactose-fed chicks the counts of lactobacilli exceeded those of control chicks. 3. High counts of Proteus sp. were present in the caeca of control birds but they were completely suppressed in conventional birds fed on the lactose diet. In vitro tests showed that this inhibition was partially due to Escherichia coli and Streptococcus faecalis. 4. The growth of Lactobacillus acidophilus was inhibited by lactose when gnotobiotic chicks were monoassociated but not when polyassociated. The protective effect was shown in vitro to be due to L. salivarius. 5. The pH was markedly lowered in the caecum of conventional and polyassociated chicks receiving dietary lactose. Of the strains used in gnotobiotic experiments E. coli, S. faecalis and L. salivarius produced the lowest pH values in the caeca.

The origin of bacteria recovered from the peritoneum and yolk sac of healthy chickens.

Synopsis Subclinical peritoneal and yolk sac infections were demonstrated in about 38 and 23 per cent, respectively, of 121 conventional chicks examined during the first 5 days of life; the incidence varied markedly from hatch to hatch. Organisms were demonstrated in the peritoneum and yolk sac of a proportion of gnotobiotic chicks following per os administration of pure cultures of bacteria isolated either from the peritoneum or yolk sac, or from the intestinal tract of conventional chickens. It is concluded that this subclinical infection arises as a result of the translocation across the gut wall of bacteria present in the lumen of the intestine.