Serological Relationships Existing between Bacterial Parasites and Their Hosts

Abstract

Summary One hundred strains of aerobic and facultative bacteria were isolated from fecal specimens from one healthy human being (HBI); 99 similar strains were isolated from a second healthy human being (HBII). Eighty-six of the 100 strains from HBI and all of the strains from HBII belonged in the coliform group. Of the 86 coliform strains isolated from HBI, 61 typical Escherichia strains and 1 strain that resembled Bacterium coli-mutabile were agglutinated when combined with HBI serum in dilutions ranging from 1:640 to 1:1,280, and 10 strains (3 typical Escherichia cultures and 7 slow-lactose-fermenters) were agglutinated to titres of 1:160 or 1:320. Fourteen of the coliform organisms (1 typical Escherichia and 13 Escherichia-like forms that produced orange-brown pigment) and 11 of the non-coliform types failed to react with serum dilutions higher than 1:40. Three gram-negative, non-lactose-fermenting rods were agglutinated to a titre of 1:80. Positive precipitin tests were obtained with HBI serum and a coliform strain that was agglutinated by HBI serum diluted 1:1,280. Ninety-two of the 99 coliform strains from HBII were agglutinated when combined with HBII serum in dilutions ranging from 1:80 to 1:160; 2 strains were agglutinated by serum dilutions of 1:320; 5 failed to be agglutinated by serum dilutions higher than 1:40. At the beginning of this investigation the agglutinin concentrations in serum from HBI, HBII, and HBIV for Salmonella typhosa H and O, S. paratyphi, and S. schottmülleri antigens were, in general, too low to be considered significant. Following the ingestion of typhoid-paratyphoid vaccine, the agglutinin titres for certain typhoid-paratyphoid antigens increased slightly in the serum of each of the 3 human beings. HBI, whose serum contained unusually high anticoliform antibody concentrations, did not respond to ingested typhoid-paratyphoid antigens as actively as did HBII and HBIV. The ingestion of killed suspensions of 2 native coliform strains for which HBI had not naturally produced high concentrations of antibodies failed to elicit a demonstrable antibody response in HBI. Although living Lactobacillus acidophilus cells were maintained in large numbers in the intestinal tract of HBI for a period of 14 months by feeding acidophilus milk, no antibodies for them could be demonstrated in serum from their host. The high antibody concentrations for particular coliform strains in serum from HBI remained practically constant over a period of 4 years.