The Role of Pili and Capsule in Colonization and Bacteremia with Escherichia Coli K1 in Neonatal Rats
Escherichia coli K1 is a major cause of Gram-negative bacillary bacteremia and meningitis in neonates. If colonization of specific epithelial surfaces with Escherichia coli K1 is a prerequisite for bacterial invasion, it is possible that an understanding of the colonization process will permit prophylactic intervention before mucoid barriers have been breached. Pili are filamentous protein appendages found on the surface of many bacteria. A given bacterial strain may exist in both a piliated and nonpiliated phase. Escherichia coli express other types of pili which differ from mannose-sensitive pili in their chemical, physical, and serological properties. Colonization and bacteremia were determined at day five postchallenge. Colonization of the oropharynx was determined for each animal by gentle but thorough swabbing with a sterile cotton-tipped applicator and streaking onto one-half of a minimal glucose agar plate. Pilus vaccines have been effective against certain bacterial infections presumably because pilus-specific antibody blocks colonization.