Inhibition of heat-labile toxin from Bordetella parapertussis by fatty acids

Antimicrobial factors and microbial contaminants in human milk: recent studies

An overview of recent studies of antimicrobial factors and microbial contaminants found in human milk is presented. The incidence of gastrointestinal and respiratory infections in infants receiving human milk continues to be lower than in those not breast-fed due to the presence of specific antibody and possibly anti-adhesion factors in the milk. Whether the many other antimicrobial factors, which have been shown to be active in vitro or in animal model systems, have any influence on infant infections is still not clear. Microbial contaminants in human milk are rare, as are associated infant infections from the milk. However, some contaminants such as cytomegalovirus are commonly transferred to infants from the milk of seropositive mothers, fortunately without any adverse effects in the infants. Human T-lymphotropic virus type 1 is transferred via human milk in endemic areas, human milk being the main source of mother-to-infant transmission. While some reports suggest human immunodeficiency virus type 1 transfer may occur through human milk, this is not the predominant mode of transmission to infants.

Heat-labile toxin from Bordetella parapertussis induces contraction of smooth muscle cells in culture

The ability of Bordetella heat-labile toxin (HLT) to contract various types of cells in culture was examined. HLT from B. parapertussis induced contraction of cultured smooth muscle cells from trachea, intestine, uterus and vas deferens as well as from aorta. The time required for contraction decreased as the dose of B. parapertussis HLT increased from 3 to 100 MID/ml. Upon exposure of cells to concentrations of toxin greater than 100 MID/ml, at least 2 hr was required for contraction. HLT from B. parapertussis did not affect cultured cardiac or skeletal muscle cells within 8 hr after the exposure to HLT (100 MID/ml). No effect on other types of primary culture cells or established cells such as Chinese hamster ovary (CHO) cells has been described. These data indicate that the primary target cells for HLT might be smooth muscle cells.