Phagocytosis and intracellular killing of the contagious equine metritis organism by equine neutrophils in genital secretions.

Equine neutrophils were combined with contagious equine metritis organism (CEMO) or Escherichia coli in vitro in the presence of seminal plasma, uterine flushings, or Hank's balanced salt solution (HBSS). Phagocytosis and intracellular killing were estimated by bacterial culture and light and electron microscopy. With lysed neutrophils, the numbers of colony-forming units of CEMO and E coli increased in seminal plasma and uterine flushings. Numbers of CEMO decreased in HBSS. The numbers of CEMO increased more in the presence of seminal plasma than the other media. When neutrophils were in the various media, 29% to 32% of the CEMO were phagocytized by 120 minutes. At all sampling times and in all media types, more E coli than CEMO were observed to be associated with neutrophils. By 210 minutes' incubation in uterine flushings, seminal plasma, and HBSS, 60% to 75% of the intracellular CEMO were killed. Of the intracellular E coli in the various media, 85% to 90% were killed by 210 minutes. Seemingly, CEMO is an extracellular pathogenic bacteria and immunoglobulins in seminal plasma and uterine flushings from horses not previously infected with CEMO do not enhance CEMO phagocytosis or intracellular killing.