Role of antibody and enterobactin in controlling growth of Escherichia coli in human milk and acquisition of lactoferrin- and transferrin-bound iron by Escherichia coli.

Growth of Escherichia coli NCTC 8623 in human milk was slow during the first 10 h of incubation, but this bacteriostatic effect had disappeared by 24 h. The bacteriostatic phase could be abolished by adding sufficient iron to saturate the lactoferrin in human milk, and also by adding supernatant from a 24-h milk culture or by adding enterobactin, an enterobacterial iron chelator. Growth in the presence of enterobactin was even more rapid than in the presence of excess iron. Partial loss of bacteriostatic activity could be achieved by absorbing the milk with bacterial antigens, but no clear correlation with removal of antibodies to O, K, or H antigens was apparent. When E. coli was grown in human serum trace-labeled with 59Fe, the organisms acquired iron from transferrin during growth. Cultivation of E. coli in a minimal medium supplemented with transferrin or lactoferrin doubly labeled with 125I and 59Fe showed that iron acquisition occurred without either assimilation or degradation of the iron-binding proteins.

Gas-lipuid chromatographic analysis of metabolic products in the identification of bacteroidaceae of clinical interest.

The acid end-products of 185 isolates from the family Bacteroidaceae were separated and analysed by gas-liquid chromatography on broth cultures. Different media were evaluated and definitive studies were performed in a fully supplemented complex medium. The limitations of this approach to the identification of a wide range of strains from various clinical sources were determined and the results were compared with those of a series of morphological, biochemical, tolerance and antibiotic-resistance tests. All test strains were identified to generic level by simple microscopic and colonial observations and GLC analysis; additional tests were required to allow species or subspecies identification of most strains. Population differences were detected between some species or subspecies isolated from different clinical sites by quantitative analyses of fatty acids, but individual strains could not always be separated because of overlapping ranges of distribution of acids that were common products of more than one species or subspecies. Small differences in minor products between different species or subspecies were variable and are not considered adequate for discrimination at these taxonomic levels without support from other observations. The potential application of the GLC technique to the rapid and accurate identification of these organisms in hospital laboratories is considered.