Dynamics of Escherichia coli infection and meningitis in infant rats

Abstract

E. coli strains isolated from newborn infants were injected i.p. into infant rats. Strains possessing the K1 capsular polysaccharide antigen were significantly more virulent than strains lacking this antigen. When 5 day old animals were injected with 1.2 .times. 101 colony forming units of a K1 E. coli strain (serotype O18ac:K1:H7), about 80% had bacteria isolated from their blood. Of bacteremic animals, 48% had positive CSF of blood correlated with positive cultures of CSF. Some animals, studied with serial blood cultures, were able to clear bacteria spontaneously from their blood, whereas others succumbed to injection within 48 h of challenge. The susceptibility of infant rats to E. coli infection was age dependent and appeared related to the K1 antigen.