Bacterial Growth in Amniotic Fluid Is Dependent on the Iron-Availability and the Activity of Bacterial Iron-Uptake System

In the present study, the relationship among iron-availability, antibacterial activity, role of meconium as an iron source and the activity of bacterial iron-uptake system (IUS) for bacterial growth in amniotic fluid (AF) were investigated. Staphylococcus aureus ATCC 6538 and its streptonigrin-resistant (SR) mutant with defective IUS were used as the test strains. The growth of S. aureus in AF was stimulated dosedependently by addition of meconium. Bacterial growth stimulated by meconium was re-inhibited dose-dependently by addition of iron-chelator, dipyridyl and apotransferrin. Iron concentration was correlated with the meconium content in AF (r(2)= 0.989, p=0.001). High-affinity IUS of S. aureus was expressed only in AF but not in AF with meconium. The growth of SR strain was more retarded than that of the parental strain in the iron-deficient brain heart infusion (ID-BHI), clear AF and AF containing apotransferrin. The retarded growth of both strains in the ID-BHI and AF was recovered by addition of holotransferrin, hemoglobin and FeCl3. Taken together, the antibacterial activity of AF is closely related with low iron-availability. Bacterial growth in AF considerably depends on the activity of bacterial IUS. Meconium acts as one of the exogenous iron-sources and thus can stimulate bacterial growth in AF.

Newly Developed Mecometer Method for Objective Assessment of Meconium Content

We developed a new method for an objective assessment of the meconium content in amniotic fluid. By establishing a standard scale through a serial dilution of a known amount of meconium into the amniotic fluid, we developed a new method 'mecometer 'that can objectively measure the meconium content in meconium-stained amniotic fluid samples. The objectivity and reliability of this mecometer were verified by 300 student volunteers. At least 70% of the volunteers could objectively measure and digitally describe the meconium content in meconium-stained amniotic fluid samples. We believe our newly developed mecometer is a very simple, reliable, and portable method, not requiring any instruments.

In vitro effect of meconium on the physical surface properties and morphology of exogenous pulmonary surfactant

The pathophysiology of meconium aspiration syndrome(MAS) is related to mechanical obstruction of the airways and to chemical pneumonitis. Meconium is also suggested to cause functional deterioration of pulmonary surfactant. Recent studies have reported that meconium inhibits the physical surface properties of pulmonary surfactant, and that administration of exogenous surfactant may provide therapeutic benefits in animal models or infants with respiratory distress due to MAS. To assess the effects of meconium on physical surface properties, especially the changes on the air-liquid interface and hypophase of pulmonary surfactant in vitro, we studied the following findings; a) the surface spreading rate(SSR) and the surface adsorption rate(SAR), b) the viscosity, c) the electron microscopic changes, on a series of mixtures with various concentrations of lyophilized human meconium and Surfactant-TA(SurfactenTM). The human meconium has significantly increased the surface tension of SSR and the viscosity of pulmonary surfactant, but had decreased the surface pressure of SAR of surfactant, and changed the electron microscopic findings of surfactant. We have concluded that these findings support the concept that meconium-induced surfactant dysfunction may play a role in the pathophysiology of MAS.

Repercussao neonatal do aspecto do liquido amniotico e das caracteristicas dos batimentos cardiacos fetais durante o trabalho de parto / Neonatal repercussion of the aspect of the amniotic fluid and the fetal heart rate characteristics during labor

Foram analisados 2741 partos ocorridos na Maternidade do Departamento de Tocoginecologia da UNICAMP, para estudo da repercussao neonatal do aspecto do liquido amniotico e das caracteristicas dos batimentos cardiacos fetais durante o trabalho de parto. O aspecto do liquido amniotico foi distribuido em cinco grupos: claro, ligeiramente tingido de meconio, tingido de meconio, com meconio espesso e com meconio antigo. A presenca de batimentos cardiacos fetais normais e anormais foi considerada em cada grupo, e as condicoes neonatais avaliadas pelos indices de Apgar no primeiro e quinto minuto. Concluiu-se que os resultados neonatais sao semelhantes nos casos com liquido amniotico claro, ligeiramente tingido e tingido de meconio, enquanto partos que evoluem com meconio espesso e antigo aumentam significativamente a incidencia de recem-nascidos deprimidos....