PHYLOGENETIC ANALYSIS OF ESCHERICHIA-COLI STRAINS CAUSING NEONATAL MENINGITIS SUGGESTS HORIZONTAL GENE-TRANSFER FROM A PREDOMINANT POOL OF HIGHLY VIRULENT B2 GROUP STRAINS

Phylogenetic relationships of 69 neonatal meningitis Escherichia coli strains isolated worldwide were studied, Restriction fragment length p olymorphism of rrn operons (rrn RFLP) in these isolates was compared w ith that of the 72 strains of the ECOR reference collection, Distribut ions of K1 antigen, of polymerase chain reaction-detected ibe10 gene, pap, afa, sfa/foc, hly, and aer operons, and of a 14.9-kb rrn-containi ng HindIII fragment previously associated with neonatal meningitis wer e compared. Oligoclonality was observed for the meningitis strains. Fa ctorial analysis of correspondence on the rm RFLP data showed a freque ncy gradient of meningitis strains from the phylogenetic B2 group (68% ) to the A group (6%), via the D and B1 groups (26%), The distribution of the virulence determinants argues for their horizontal transfer du ring the evolution of E. coli. Analysis of the status of some neonates further suggests that neonatal meningitis results from a balance betw een bacterial genes of virulence and host factors.