514 The American Journal of Clinical Nutrition 34: APRIL 1981, pp. 514-5 19. Printed in U.S.A. The fate of ingested lactobacilli in the proximal small intestine1’2 Roy M. Robins-Browne,3’4 M.B., B.C/i., F.F.Path. (S.A.) and Myron M. Levine, M.D., D. T.P.H. ABSTRACT A freeze-dried commercial preparation of Lactobacillus acidophilus and Lacto- bacillus bulgaricus (Lactinex) dissolved in skim milk was ingested by four nonfasting and seven fasting informed community volunteers in the Isolation Ward of the Center for Vaccine Develop- ment. Samples of jejunal fluid withdrawn from the volunteers at varying intervals were cultured for lactobacilli on a selective medium. Quantitative counts varied considerably amongst the individuals studied and also in the same person examined on two consecutive occasions. In general, however, it was shown that lactobacilli entered the small intestine and persisted in elevated numbers for about 3 h in fasting subjects and for up to 6 h in nonfasting individuals. By 4 h, counts in fasting volunteers had returned to base-line levels. Although both Lactobacillus species in Lactinex entered the intestine in approximately equal numbers, L. acidophilus was recovered from more samples and in slightly greater numbers than L. bulgaricus. Am. J. Clin. Nutr. 34: 514-519, 1981. KEY WORDS Lactobacillus, intestinal microorganisms Introduction The suggestion that partial or complete replacement of the Gram-negative intestinal flora by a Lactobacillus variety would im- prove health and prolong life dates back to the turn of the twentieth century (1). Since that time numerous attempts have been made, both in healthy subjects and in those with disorders ranging from chronic consti- pation to enterocolitis and septicemia, to sup- plant the usual so-called “putrefactive” flora with a “lactic” variety (2-4). There are many claims for almost panacean effects of Lacto- bacillus therapy, the majority of which stem from uncontrolled observations on small numbers of patients (2-5). Most recently, Lactobacillus therapy has been advocated for the prevention and treat- ment of travelers’ diarrhea, a condition usu- ally associated with enterotoxigenic strains of Escherichia coli (6, 7). These E. coli cause disease by virtue of their ability to colonize the proximal small intestine where they pro- duce enterotoxin (8). It is conceivable that Lactobacilli might interrupt this process by preventing colonization, either by competing for binding sites or by synthesizing substances inhibitory for E. coli or directed against en- terotoxin (9-11). Any of these mechanisms would seemingly operate optimally if lactobacilli were able to colonize the upper small bowel. Yet, despite sundry investigations regarding the capacity of lactobacilli to implant in the human colon, none has dealt with the question of jejunal colonization (12-14). We have recently undertaken a bacterio- logical investigation ofjejunal aspirates from healthy adult volunteers fed a commercial preparation of lyophilized Lactobacillus aci- dophilus and Lactobacillus bulgaricus (Lacti- ‘l-rom the Center for Vaccine Development, Division of Infectious Diseases, University of Maryland School of Medicine, Baltimore, Maryland 21201. 2Supported in part by Public Health Service Research Contract NO 1-A 1-42553 with the National Institute of Allergy and Infectious Diseases, Research Contract DAMD17-78-C-80l 1 with the United States Army Re- search and Development Command and a research grant from Hynson, Wescott and Dunning Inc., Baltimore, Maryland. 3Address reprint requests to: Dr. R. Robins-Browne, Department of Microbiology, University of Natal, P.O. Box 17039, Congella 4013, South Africa. Recipient of an Overseas Travelling Fellowship of the South African Medical Research Council. by guest on May 25, 2015 ajcn.nutrition.org Downloaded from