An Address on THE BACTERIAL FLORA OF THE INTESTINE IN HEALTH AND IN CHRONIC DISEASE
Authors: J. Cruickshank
Journal: BMJ (1928)

x openinii this (lisclissioni it is my intention to give a. brief review of our knowledge of intestinal bacte'ria, to: liscuss the subjoet in genceral; 'and to omit as far 'as is possible teclhnical-matter-of -laboratory nature.--Thebacterial flora of the -intestine of tlhe adult is-extremelv complicated, and I' thliik -it mayr be approached most easily by a studv of the development of these organisms iin the inifanit.In the newly born infant the meco6ihium is sterile, b)ut organisms appear in small niulmbers within the first twenity-four liours.Durinig the first few days the organisms mnost frequently founid aile StapljIeloceccus'albus, iStreptococclis faccalis, and meembers of the Bacillus coli' group.With the first sample of meconium-free faieces short, slender, Gram-positive bacilli appear, to which Tissier gave the niame Bacillus bifiduls.In the neext few days there is a rapid increase in these organisms and a dimiiinution in the coliform and other organisms until a film of tlhe stool shows practically nio otlher bacteria, -althouigh by cultural methods coliform organisms, strepto- 'cocci, staphvlocotci, 'and spore-bearing organismsca'n be'shown to be present in small numbers.So -long as -breast-feeding is the only means ofinourislhment the" -bacterial flora of the infanit's faeces is predominantly of' the B. bifidg.stype, 95 per cent. of the organisms in a' 'film being of this type.The flora of infants w-ho are artificially fed slioivs greater complexity, and -the pre- dominanlt orgaisnism are of coliform type.Streptococci are found in greater numbers than in the suckling's stool, and spore-bearing organisms are present in most cases.The facces of breast-fed infants are always distinctlv acid in reactioni, wlhereas the stools of the artificially fed chiildreni are alkaline or neutral.This difference iln reaction of the stools of the breast-fed inifant anid tlhose of tlhe artificiallv fed is of conisiderable importance in relation to the types of bacterial flora.The alkalinity of the faeces of infanits fed on cow's milk has been attributed by Miller to the actioni of putrefactive bacteria on the large amount of proteini whliclh is present ill couw's milk as compared with hluman milk, w-hile Schlossmanin believes that the impor- tant factor is tlhe protein fat ratio.The acidity of the suckling's stool lhas been attributed to the hiiglh content of -lactose in the breast milk, an-d it has been showni experi- mentally that the addition of lactose to the dietary of rats results in hiiglily acid contents of the caecum wlhereas a hiiglh protein diot does not plroduce this.Cltu:k and 'Marriott have suggested that the poverty of huma'n milk in buffer salts allows of a rapid .change in the reaction, and the acids produced -are free to act upon the intestinal miucosa, cansing a rapid evacuatioln of the contents and aan acid stool.In support of this is the observationi that in diarrlhoeal conditionis the stools are usually acid as compared with normal.It lhas been establislhed that B. bifidus anid related organisms of the B. acidophilus type can survive exposure to highl-acid.fluids' which destroy coliform organisms, anid the predominance of these organisms in the stool of the breast-fed infanit and the poverty in coliform organlisms has been attributed to the acid reaction of the intestinal contents.The absenice of spore-bearing oiganisms in the suckling's stool is attributed to the same factor, anid it has been shown that the growth of these organisms is markedly inhibited in highly acid media in which B. bifiduis anid B. acidophlut.), survive.Some workers, however, are of opiniioni that the acidresistanit organisms are directly anitagoniistic to the growth of B. coli and the spore-bearing anaerobes.* Given in op2ning a discussion in the Section of Patlhology and Bacteriolocz at the Annual MIeeting of the British Medical Association, Cardiff, 1928.After the period of breast-feeding the chiid is quicklv introduced-to a variety of foodstuffs, and during adolescence and adult life manyv kin-ds o'f proteins and carbohydrates are ingested; Opportunity is-offered for the invasion 'of tlhe alimentary tract by many organisms, and the bacterial