Meconium enhances the growth of perinatal bacterial pathogens.

OBJECTIVE

To demonstrate the effects of meconium on growth of bacterial pathogens, which are common causes of intra-amniotic infection and neonatal sepsis.

METHODS

Meconium collected from 9 healthy neonates was suspended as a 20% solution using sterile saline. In experiment 1, separate test tubes of meconium solution and sterile saline (the control) were individually inoculated with 10(6) colony-forming units of a single species of the following test pathogens: Escherichia coli, Enterococcus faecalis, Group B Streptococcus, Staphylococcus aureus, Pseudomonas aeruginosa, and Listeria monocytogenes. After incubation at 37 degree C for 24 hours, 1 L each of the bacterial-meconium and bacterial-saline solutions was inoculated onto 5% sheep blood agar. After 24 hours of incubation, the number of developing colonies was counted. In experiment 2, equal volumes of meconium and saline solutions were inoculated with 10(5) colony-forming units of either E. coli or Group B Streptococcus. At intervals of 6, 9, and 24 hours post-incubation, 1 L each of the bacterial-meconium and bacterial-saline solutions was inoculated onto 5% sheep blood agar plates, and colonies were counted after overnight incubation.

RESULTS

In the first experiment, 24 hours of incubation resulted in bacterial amplification in the meconium solution from an initial inoculum of 10(6) colony-forming units/mL to 10(9) colony-forming units/mL. In contrast, the same inoculation of saline solution (control) showed no increase in colony counts over the same time interval. For E. coli and Group B Streptococcus in experiment 2, growth enhancement in meconium was seen as early as 6 hours, as colony counts of a test species increased from 105 colony-forming units/mL to 10(9)-10(10) colony-forming units/mL.

CONCLUSION

Enhanced growth of perinatal pathogens in meconium was constantly observed, and can occur as early as 6 hours after bacterial interaction of meconium.